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AI-AEC-MEMO-12717
REFERENCE ZIRCONIUM HYDRIDE REACTOR
THERMOELECTRIC SYSTEM
- L E G A L N O T I C E -Tliis report was prepared as an account of worlc sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of "their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.
ATOMICS INTERJIATIONAL A DIVISION OF NORTH AMERICAN ROCKWELL CORPORATION
JUNE 15, 1969 •»TSTRmUTTON OP THIS noCTTMKNT KS UNf IMTTEB
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
CONTENTS
P a g e
I. I n t roduc t i on 11
II. S u m m a r y 13
A. R e f e r e n c e S y s t e m 13
B. P o w e r p l a n t for O r b i t a l W o r k s h o p 15
C. L u n a r B a s e and Manned Orb i t i ng R e s e a r c h L a b o r a t o r y
(MORL) P o w e r p l a n t s 16
III. R e f e r e n c e S y s t e m , 17
A. S y s t e m D e s c r i p t i o n 17
B. S y s t e m P e r f o r m a n c e 22
1. R e f e r e n c e O p e r a t i n g Cond i t i ons 22
2. Of f -Des ign P e r f o r m a n c e 25
3. P a r t i a l - P o w e r P e r f o r m a n c e 29
C. S y s t e m O p e r a t i o n 29
1. S t a r t u p 30
2. Shutdown 35
D. R e l i a b i l i t y 35
1, S y s t e m R e l i a b i l i t y 37
2. B a s e s for E s t i m a t e s 37
E . S y s t e m T r a d e - o f f s 48
IV. S u b s y s t e m s 57
A. R e a c t o r / S h i e l d A s s e m b l y 57
1. T e c h n o l o g y Sta tus 57
2. R e a c t o r S u b s y s t e m D e s c r i p t i o n and P e r f o r m a n c e 57
B. T h e r m o e l e c t r i c C o n v e r t e r 63
1. TE Module Techno logy S ta tus 63
2. T u b u l a r Module 66
3. C o n v e r t e r Module 71
4. E l e c t r i c a l N e t w o r k and V o l t a g e - R e g u l a t i o n E q u i p m e n t 79
C. N a K - L o o p C o m p o n e n t s 91
1. P u m p S y s t e m 91
2. E x p a n s i o n C o m p e n s a t o r 101
A I - A E C - M E M O - 1 2 7 1 7 3
CONTENTS
P a g e
D. R a d i a t o r 107
1. C o n c e p t Se lec t ion 107
2. R a d i a t o r Des ign 109
M i s s i o n A d a p t a t i o n s 112
A. S a t u r n - V OWS P o w e r p l a n t 112
1. M i s s i o n R e q u i r e m e n t s and I n t e g r a t i o n C o n s i d e r a t i o n s 112
2 . S y s t e m D e s c r i p t i o n 115
3. O p e r a t i o n a l Mode 141
4 . F i n a l R e a c t o r Shutdown and D i s p o s a l 150
B. L u n a r B a s e P o w e r p l a n t 152
1. M i s s i o n R e q u i r e i n e n t s 152
2 . S y s t e m D e s c r i p t i o n and P e r f o r m a n c e 155
3. S u b s y s t e m D e s c r i p t i o n and P e r f o r m a n c e l o l
4 . O p e r a t i o n a l Mode 1^5
5. C o m p a r i s o n wi th P r e v i o u s Des ign 1°^
C. Manned Orb i t i ng R e s e a r c h L a b o r a t o r y P o w e r p l a n t 168
1. M i s s i o n R e q u i r e m e n t s 1"°
2. S y s t e m D e s c r i p t i o n and C o m p a r i s o n wi th P r e v i o u s D e s i g n 168
e r e n c e s 173
175 s s a r y
A I - A E C - M E M O - 1 2 7 1 7 4
TABLES
P a g e
I I - 1 , R e f e r e n c e R e a c t o r — T E S y s t e m Des ign and P e r f o r m a n c e
C h a r a c t e r i s t i c s 14
I I I - l . U n s h i e l d e d S y s t e m Weight B r e a k d o w n 22
I I I -2 . R e f e r e n c e P e r f o r m a n c e C h a r a c t e r i s t i c s 23
I I I - 3 . P a r t i a l - P o w e r P e r f o r m a n c e C h a r a c t e r i s t i c s
( T h r e e Loops O p e r a t i n g ) 28
I I I -4 . R e l i a b i l i t y E s t i m a t e s 39
I I I - 5 . T u b e - W e l d H i s t o r i e s 40
I I I -6 , P o w e r Diode " T h e r b l i g " F a i l u r e - R a t e s 47
I V - 1 . SNAP R e a c t o r O p e r a t i n g E x p e r i e n c e 56
I V - 2 . R e f e r e n c e Z r H R e a c t o r Des ign P a r a m e t e r s 64
I V - 3 . T u b u l a r Module T e s t E x p e r i e n c e 65
I V - 4 . C h a r a c t e r i s t i c s of R e f e r e n c e T u b u l a r Module 69
I V - 5 . C o n v e r t e r Module C h a r a c t e r i s t i c s 73
I V - 6 . P o w e r L o s s e s 90
I V - 7 . P u m p Module S u m m a r y 95
I V - 8 . NaK V o l u m e s 104
I V - 9 . E x p a n s i o n C o m p e n s a t o r C h a r a c t e r i s t i c s 104
I V - 1 0 . T u b e - a n d - F i n R a d i a t o r Des ign C r i t e r i a 108
I V - 1 1 . R e f e r e n c e R a d i a t o r C h a r a c t e r i s t i c s I l l
V - 1 . S a t u r n - V O r b i t a l W o r k s h o p M i s s i o n R e q u i r e m e n t s for N u c l e a r P o w e r S y s t e m 116
V - 2 . S a t u r n - V O r b i t a l W o r k s h o p P o w e r S y s t e m Weight
B r e a k d o w n 125
V - 3 . R a d i a t i o n Dose C r i t e r i a 126
V - 4 . D e n s i t y of Shie ld M a t e r i a l s 131
V - 5 . E s t i m a t e d R a d i a t i o n D o s e r a t e s a t S a t u r n - V O r b i t a l W o r k s h o p
C o m m a n d and C o n t r o l S ta t ion 132
V - 6 . L a u n c h Veh ic l e P a y l o a d E s t i m a t e s 144
V - 7 . Key P o w e r S y s t e m R e q u i r e m e n t s for L u n a r B a s e 153
V - 8 . B a s e l i n e L u n a r P o w e r p l a n t C h a r a c t e r i s t i c s 158
V - 9 . H i g h - P o w e r L u n a r P o w e r p l a n t C h a r a c t e r i s t i c s 162
A I - A E C - M E M O - 1 2 7 1 7 5
TABLES
Page
V-10. Doserate at 0.5 mi from Lunar Base Reactor 164
V-11. Design Compar i son 167
V-12. Key Manned Orbiting Resea rch Labora tory Mission and Reactor Power System Requirements 169
V-13. Mobile Orbiting Resea rch Labora tory System Charac te r i s t i c s . . 171
FIGURES
Front i sp iece . Manned Orbital Workshop with 25-kw Reactor — Thermoe lec t r i c Power System 10
I I I - l . Reference 25-kwe System Schematic 17
III-2. ZrH Reactor — Thermoelec t r i c System, Reac to r /Ga l l e ry Ar rangement 20
III-3, System Per fo rmance vs Load Voltage, Reactor-Out le t Tempera tu re = 1246°F 24
III-4. System Elec t r i ca l Cha rac t e r i s t i c s vs Reactor-Out le t Tempera tu re 26
III-5, Effect of Reactor-Out le t Tempera tu re on System Power ,
Voltage = 56 volts 27
III-6. SNAP lOA Startup in Orbit 32
III-7. System Shutdown Trans ien t s , NaK Tempera tu re s -24«^/min. . . . 34
III-8. System Shutdown Trans ien ts , Power and Rate of Tempera ture
Change -24^/min 34
III-9. System Reliabil i ty, 10,000-hr Duration 36
III-10. System Reliabil i ty, 20,000-hr Duration 38
III-11. Thermoelec t r i c Conver ter Full-and Par t i a l -Power
Reliabil i ty (Elect r ica l ) 46
III-12. Radiator Fin Effectiveness 50
III-13. 15-kwe System Weight and Area 50
III-14. 25-kwe System Weight and Area 51
III-15. 35-kwe System Weight and Area 51
III-16. 25-kwe System, 1250°F Reactor-Outlet Tempera tu re 52
III-17. 15-kwe System Weight and Area (Unshielded) 52
AI-AEC-MEMO-12717 6
FIGURES
9 Page
I I I - 1 8 . 2 5 - k w e S y s t e m Weight and A r e a (Unsh ie lded) 53
I I I - 1 9 . 35-kwe S y s t e m Weight and A r e a (Unsh ie lded) 53
I I I -20 . S y s t e m M i n i m u m Weight 54
I I I - 2 1 . S y s t e m R a d i a t o r A r e a , M i n i m u m - W e i g h t S y s t e m s 54
I I I -22 . R e a c t o r T h e r m a l P o w e r , M i n i m u m - W e i g h t S y s t e m s 55
I V - 1 . SNAP 8 D e v e l o p m e n t R e a c t o r G r o u n d T e s t A s s e m b l y 58
I V - 2 . Z i r c o n i u m H y d r i d e R e a c t o r , R e f e r e n c e Des ign 59
I V - 3 . P e r f o r m a n c e E n v e l o p e , R e f e r e n c e Z r H R e a c t o r 60
I V - 4 . Z r H R e a c t o r R e f e r e n c e Des ign 60
I V - 5 . T u b u l a r T h e r m o e l e c t r i c Module 65
I V - 6 . C o n v e r t e r Layout 67
I V - 7 . C o n v e r t e r Module C u t a w a y 72
I V - 8 . C o n v e r t e r Module Layout 75
I V - 9 . Double C o n t a i n m e n t of C o n v e r t e r Module H e a d e r 78
I V - 1 0 . C o n v e r t e r Module Of f -Des ign P o w e r 80
' I V - 1 1 . C o n v e r t e r Module Off -Des ign Ef f ic iency 81
I V - 1 2 . C o n v e r t e r Module Off -Des ign Vol tage 82
I V - 1 3 . C o n v e r t e r Module Off -Des ign F l o w r a t e s , Axia l A T ' S A s s u m e d C o n s t a n t a t 2 0 0 ° F 83
I V - 1 4 . C o n v e r t e r Module Of f -Des ign F l o w r a t e s , Axia l A T ' S
A s s u m e d C o n s t a n t a t 150°F 84
I V - 1 5 . C o n v e r t e r Module Ho t - and C o l d - S i d e P r e s s u r e D r o p s 85
I V - 1 6 . C o n v e r t e r - A s s e m b l y and P o w e r - C o n d i t i o n i n g C i r c u i t
D i a g r a m 86
I V - 1 7 . V o l t a g e - C u r r e n t P r o f i l e 87
I V - 1 8 . M e r c u r y - R a n k i n e P r o g r a m I n t e g r a l S o u r c e P u m p 92
I V - 1 9 . SNAP lOA I n t e g r a l S o u r c e P u m p 92
I V - 2 0 . P u m p C o n v e r t e r 94
I V - 2 1 . P r i m a r y and H e a t - R e j e c t i o n Loop E l e c t r o m a g n e t i c - P u m p
A s s e m b l y 96
I V - 2 2 . P u m p A s s e m b l y , S e p a r a t e S o u r c e , T h r e e - T h r o a t 99
I V - 2 3 . R e f e r e n c e P u m p P e r f o r m a n c e 102
I V - 2 4 . SNAP lOA E x p a n s i o n C o m p e n s a t o r 103
A I - A E C - M E M O - 1 2 7 1 7 7
FIGURES
P a g e
I V - 2 5 . E x p a n s i o n C o m p e n s a t o r , 2 5 - k w e N u c l e a r T h e r m o e l e c t r i c
P o w e r Supply 105
I V - 2 6 , E x p a n s i o n - C o m p e n s a t o r P r e s s u r e C h a r a c t e r i s t i c s 106
I V - 2 7 . C y l i n d r i c a l - R a d i a t o r Weight C h a r a c t e r i s t i c s 110
V - 1 . 2 5 - k w e N u c l e a r T h e r m o e l e c t r i c P o w e r Supply 117
V - 2 . S a t u r n - V O r b i t a l W o r k s h o p wi th 25 -kwe N u c l e a r T h e r m o e l e c t r i c P o w e r Supply 119
V - 3 . A c t u a t o r , N u c l e a r T h e r m o e l e c t r i c P o w e r Supply,
S a t u r n - I V B O r b i t a l W o r k s h o p 123
V-4 . R a d i a t i o n Shie ld Des ign C r i t e r i a 127
V - 5 . 477 Shie ld Out l ine , R e f e r e n c e Des ign 128
V - 6 . Shadow Shie ld Out l ine , R e f e r e n c e Des i gn 130
V - 7 . 25 -kwe N u c l e a r T h e r m o e l e c t r i c P o w e r Supply, T w o - L o o p S y s t e m 134
V - 8 . T h e r m o e l e c t r i c P o w e r P a c k a g e wi th Modif ied P o r t
L o c a t i o n s 135
V - 9 . P r e a s s e m b l e d R a d i a t o r A s s e m b l y I n t e g r a t i o n De ta i l s 138
V - 1 0 . P o w e r S y s t e m Loadpa th S c h e m a t i c 139 V - 1 1 . I n t e g r a l S a t u r n - V Launch C o n f i g u r a t i o n , N u c l e a r T h e r m o
e l e c t r i c P o w e r S y s t e m 140
V - 1 2 . S e p a r a t e Launch Conf igu ra t i on , S a t u r n - I B S e r v i c e Module 142
V - 1 3 . S e p a r a t e L a u n c h Conf igu ra t i on , T i t an III T r a n s t a g e 144
V - 1 4 . S a t u r n - I V B P o w e r S y s t e m C o n t r o l Logic 146
V - 1 5 . S a t u r n - I V B O r b i t a l W o r k s h o p P o w e r - S y s t e m S t a r t u p 148
V - 1 6 . 2 5 - k w e N u c l e a r T h e r m o e l e c t r i c P o w e r Supply L u n a r B a s e
A p p l i c a t i o n 156
V - 1 7 . L u n a r B a s e P o w e r Supply Des ign A l t e r n a t e s 157
V - 1 8 . R e a c t o r Shie ld ing and S t r u c t u r e , L u n a r B a s e Concep tua l 160 V - 1 9 . 25 -kwe N u c l e a r T h e r m o e l e c t r i c P o w e r Supply, Manned
O r b i t i n g R e s e a r c h L a b o r a t o r y 170
A I - A E C - M E M O - 1 2 7 1 7 8
• ''* , *,s* . •••• -1
- J 3 - 0 9 9 - 3 5
F r o n t i s p i e c e . Manned O r b i t a l W o r k s h o p wi th 25 -kw R e a c t o r — T h e r m o e l e c t r i c P o w e r S y s t e m
A I - A E C - M E M O - 1 2 7 1 7 10
I. INTRODUCTION
This r e p o r t p r e s e n t s the r e s u l t s of a n i n e - m o n t h e n g i n e e r i n g s tudy of n u
c l e a r r e a c t o r — t h e r m o e l e c t r i c (TE) power s y s t e m s . This g e n e r a l type of
s p a c e p o w e r s y s t e m i s not new; a 5 0 0 - w a t t (SNAP lOA) r e a c t o r — T E s y s t e m
w a s f l i g h t - t e s t e d in s p a c e in 1965. Since tha t t i m e s ign i f ican t t e c h n o l o g i c a l
a d v a n c e s have b e e n m a d e w i th SNAP ( z i r c o n i u m h y d r i d e type) r e a c t o r s and
wi th TE c o n v e r t e r s . A s of th i s w r i t i n g the l a t e s t of a s e r i e s of SNAP r e a c
t o r s (SNAP 8) h a s j u s t gone c r i t i c a l and i s e n t e r i n g a t e s t p r o g r a m a i m e d at
d e m o n s t r a t i n g o v e r 10,000 h r of o p e r a t i o n at 600 kwt, 1300°F . S i m i l a r l y the
t u b u l a r l e a d - t e l l u r i d e T E c o n v e r t e r s be ing deve loped for the AEC by W e s t i n g -
h o u s e A s t r o n u c l e a r L a b o r a t o r i e s (WANL) have d e m o n s t r a t e d e f f ic ienc ies 3 to
4 t i m e s h i g h e r than t h o s e u s e d in the SNAP lOA s y s t e m . The f ab r i ca t i on
p r o c e s s e s for t h i s c o n v e r t e r m o d u l e have a l s o been deve loped to y ie ld good
r e p r o d u c i b l e r e s u l t s , and e n d u r a n c e t e s t i n g h a s e x c e e d e d 20,000 h r .
T h e s e a d v a n c e s , t o g e t h e r wi th the r e s u l t s of s e v e r a l jo in t NASA/AEC a p
p l i ca t i on s t u d i e s , have m a d e it a p p a r e n t tha t r e a c t o r — TE power s y s t e m s u t i
l i z ing the c o m p o n e n t s deve loped to da te would be a t t r a c t i v e c a n d i d a t e s for
s p a c e m i s s i o n s in the 7 0 ' s r e q u i r i n g power l e v e l s up to a p p r o x i m a t e l y 40 kwe .
In l a t e 1967, t h e r e f o r e , the A t o m i c E n e r g y C o m m i s s i o n s t a r t e d t h i s r e a c t o r —
TE s y s t e m s tudy at A t o m i c s I n t e r n a t i o n a l (AI) to b e t t e r define the des ign and
p e r f o r m a n c e c h a r a c t e r i s t i c s of such a s y s t e m .
The g e n e r a l g u i d e l i n e s p r o v i d e d by the AEC for t h i s des ign effort w e r e tha t
the p o w e r s y s t e m shou ld u t i l i z e the r e f e r e n c e z i r c o n i u m h y d r i d e r e a c t o r coupled
to a p o w e r - c o n v e r s i o n s y s t e m (PCS) i n c o r p o r a t i n g l e a d - t e l l u r i d e t ubu l a r TE
m o d u l e s . WANL p e r f o r m e d the d e s i g n and a n a l y s i s w o r k on the TE c o n v e r t e r s
and p o w e r - c o n d i t i o n i n g e q u i p m e n t u n d e r s u b c o n t r a c t to AI.
Add i t i ona l o b j e c t i v e s se t for th i s s tudy a r e a s fo l lows:
1) E s t a b l i s h a c o n c e p t u a l d e s i g n of a r e f e r e n c e s y s t e m su i t ab le for
adap t ion to e i t h e r m a n n e d o r u n m a n n e d s p a c e m i s s i o n s wi th a n o m i n a l
power l e v e l of 25 kwe and a m i n i m u m l i f e t ime of 20,000 h r .
2) P r e p a r e p a r a m e t r i c p e r f o r m a n c e da ta o v e r a su i t ab le power r a n g e
above and be low 25 kwe to i l l u s t r a t e the t r a d e - o f f s ava i l ab l e b e t w e e n
p o w e r , we igh t , a r e a , t e m p e r a t u r e , e t c .
A I - A E C - M E M O - 1 2 7 1 7 11
3) E s t a b l i s h p r e l i m i n a r y d e s i g n and p e r f o r m a n c e r e q u i r e m e n t s for key
s y s t e m c o m p o n e n t s to s e r v e a s a guide for ongoing a n d / o r fu ture
d e v e l o p m e n t w o r k .
4) P r e p a r e o r u p d a t e c o n c e p t u a l d e s i g n s of r e a c t o r — TE p o w e r p l a n t s
a d a p t e d for spec i f i c s p a c e m i s s i o n s , inc lud ing m a n n e d o rb i t i ng w o r k
shops and m a n n e d l u n a r b a s e s .
The c o n c e p t u a l d e s i g n for a r e f e r e n c e z i r c o n i u m h y d r i d e r e a c t o r s u b s y s t e m
s u i t a b l e for u s e wi th T E or o t h e r P C S ' s w a s a l s o to be e s t a b l i s h e d p a r a l l e l wi th
the above s y s t e m e n g i n e e r i n g w o r k .
The r e s u l t s of the r e a c t o r — T E s y s t e m e n g i n e e r i n g effor t a r e p r e s e n t e d in
t h i s r e p o r t , in the s a m e o r d e r a s the o b j e c t i v e s l i s t e d a b o v e . De t a i l s of the
r e f e r e n c e z i r c o n i u m h y d r i d e r e a c t o r d e s i g n a r e g iven in a c o m p a n i o n docu-^ (1 )* m e n t .
The w o r k r e p o r t e d h e r e i n w a s p e r f o r m e d for the USAEC u n d e r C o n t r a c t No.
A T ( 0 4 - 3 ) - 7 0 1 , and w a s c o m p l e t e d in June 1968.
' ^Superscr ip t n u m b e r s in p a r e n t h e s e s a r e for R e f e r e n c e s a t the b a c k of th i s r e p o r t .
A I - A E C - M E M O - 1 2 7 1 7 12
II. SUMMARY
A. R E F E R E N C E SYSTEM
The r e f e r e n c e 2 5 - k w e r e a c t o r — TE s y s t e m d e s i g n evolved in th i s s tudy con
s i s t s of the z i r c o n i u m h y d r i d e r e a c t o r coupled by the p r i m a r y - c o o l a n t loop to
four p a r a l l e l p o w e r - c o n v e r s i o n s e c t i o n s . The r e a c t o r des ign i s s i m i l a r to the
SNAP 8 r e a c t o r but h a s a s l i gh t l y l a r g e r c o r e and an i n t e r n a l l y cooled BeO r e
f l e c t o r s u i t a b l e for o p e r a t i o n wi th in an e n c l o s e d sh ie ld . T h e s e mod i f i ca t i ons
a r e d e s i r a b l e for m a n n e d s p a c e a p p l i c a t i o n s .
E a c h of the four p o w e r - c o n v e r s i o n s e c t i o n s i nc ludes a TE c o n v e r t e r a s s e m
bly , a NaK p u m p , and a h e a t - r e j e c t i o n loop (HRL). E a c h c o n v e r t e r a s s e m b l y
c o n t a i n s 24 TE t u b u l a r m o d u l e s s t r u c t u r a l l y s u p p o r t e d wi th in a r e c t a n g u l a r box
and i n t e r c o n n e c t e d wi th coo lan t m a n i f o l d s for p r o p e r flow d i s t r i b u t i o n of the hot
p r i m a r y loop and the co ld H R L ' s . The t u b u l a r m o d u l e s a r e a r r a n g e d in p a r a l l e l
" 4 - p a c k s , " e a c h of w h i c h p r o v i d e s s l igh t ly m o r e than 1 kwe at 56 vo l t s , dc .
B lock ing d iodes a r e u s e d for e a c h 4 - p a c k to i s o l a t e p o s s i b l e s h o r t c i r c u i t s to
g r o u n d .
The NaK p u m p s a r e of the d c - c o n d u c t i o n e l e c t r o m a g n e t i c (EM) type . E a c h
p u m p h a s t h r e e t h r o a t s , two of which p u m p l / 4 t h of the to ta l p r i m a r y - l o o p flow
and the t h i r d t h r o a t p u m p s one of the H R L ' s . A s e p a r a t e TE power pack c o n
s i s t i n g of t h r e e h i g h - c u r r e n t m o d u l e s connec t ed in p a r a l l e l p r o v i d e s the dc
c u r r e n t to e a c h p u m p .
E a c h H R L c o n s i s t s of a r a d i a t o r s ec t i on , an expans ion c o m p e n s a t o r , and
i n t e r c o n n e c t i n g piping and m a n i f o l d s . The r a d i a t o r des ign s e l e c t e d as a r e f e r
ence i s of the c o n v e n t i o n a l f i n - a n d - t u b e t y p e , wi th s t a i n l e s s - s t e e l NaK tubes
d i f fus ion-bonded to a l u m i n u m fins and m e t e o r o i d a r m o r . A l t e r n a t e r a d i a t o r
m a t e r i a l s and c o n c e p t s of fer ing po t en t i a l p e r f o r m a n c e i m p r o v e m e n t s w e r e a l s o
iden t i f i ed . The p o s s i b l e u s e of h e a t - p i p e s for the h e a t - r e j e c t i o n s ide of the
P C S w a s a l s o s tud i ed , but i t i s not now r e c o m m e n d e d due to i n e x p e r i e n c e with
a s u i t a b l e work ing fluid for the t e m p e r a t u r e r a n g e of i n t e r e s t .
A r e f e r e n c e s t a r t u p and c o n t r o l s c h e m e w a s defined which u s e s r e a c t o r -
ou t l e t t e m p e r a t u r e a s the c o n t r o l p a r a m e t e r du r ing s t a r t u p and e l e c t r i c a l
A I - A E C - M E M O - 12717 13
cur ren t output during normal operation. No valves or moving par t s other than
the reac tor control drums a r e requi red . A shunt-type voltage regulator which
diss ipates excess power to space through h igh- t empera tu re r e s i s t ance e lements
was selected for voltage and load control .
The major design and per formance cha rac t e r i s t i c s for the reference r e a c
tor — TE sys tem a r e summar ized in Table I I - 1 . The reac tor the rmal power
and coolant-outlet t empera tu re a r e well within the capabil i t ies of the reference
ZrH reac to r , and provide adequate marg ins for rel iabi l i ty, power growth, and/o
compensation for possible sys tem degradation. The unshielded sys tem weight
and radia tor a r ea cor respond to a n e a r - m i n i m u m weight design; the a rea can
be reduced at the expense of inc reased weight. The specific weight of approxi-2
mate ly 280 Ib/kwe and specific a rea of 56 ft /kwe rep resen t a significant i m provement over previous des igns .
TABLE II-1
REFERENCE REACTOR - THERMOELECTRIC SYSTEM DESIGN AND PERFORMANCE CHARACTERISTICS
Elec t r i ca l power: (gross) (regulated)
Voltage
Reactor t he rma l power
Reac tor -ou t le t t empera tu re
Average rad ia tor t empera tu re
Net efficiency (system)
Unshielded weight
Specific weight
Radiator a r ea
Specific a r ea
Design lifetime
System degradation allowance
25.2 kwe 24.7 kwe
56 volts dc
5 83 kwt
1246°F
563°F
4.24%
7000 lb
280 Ib/kwe
1400 ft2
56 ft^/kwe
20,000 hr
10%
A number of sys t em and component optimization and trade-off studies were
made in the p roces s of a r r iv ing at the re fe rence design descr ibed briefly above.
AI-AEC-MEMO-12717 14
A m o n g t h e s e w e r e (1) the o p t i m i z a t i o n of the c o n v e r t e r m o d u l e d i m e n s i o n s ,
(2) s y s t e m w e i g h t - a r e a - a n d - t e m p e r a t u r e t r a d e - o f f s , (3) eva lua t ion of s e v e r a l
c o n v e r t e r - p a c k a g i n g a l t e r n a t e s , (4) s e v e r a l i t e r a t i o n s on the pump type and
c a p a c i t y , (5) c o m p a r i s o n of two vs t h r e e loops in s e r i e s , (6) r e l i a b i l i t y and
we igh t t r a d e - o f f s for two to e ight p a r a l l e l p o w e r - c o n v e r s i o n loops and H R L ' s ,
(7) d e t e r m i n a t i o n of n e a r - o p t i m u m p r e s s u r e d r o p and AT for both loops ,
(8) r a d i a t o r m a t e r i a l s , tube s i z e , and spac ing o p t i m i z a t i o n , and (9) o v e r a l l
s y s t e m r e l i a b i l i t y e s t i m a t e s for v a r i o u s s y s t e m con f igu ra t i ons and des ign
a l t e r n a t i v e s .
P a r a m e t r i c s t u d i e s w e r e a l s o p e r f o r m e d to d e t e r m i n e the s y s t e m c h a r
a c t e r i s t i c s at h i g h e r and l o w e r p o w e r l e v e l s , u s ing a c o m p u t e r code deve loped
for th i s p u r p o s e du r ing the s tudy . F r o m 15 to 35 kwe , the u n s h i e l d e d s y s t e m
spec i f i c weight r a n g e s f r o m a p p r o x i m a t e l y 320 to 250 I b / k w e , r e s p e c t i v e l y .
The spec i f i c a r e a for n e a r - m i n i m u m weigh t r e m a i n s in the r a n g e of 56 to 2
60 ft / k w e , and the r e a c t o r t h e r m a l power r a n g e s f r o m 350 to 800 kwt.
B . P O W E R P L A N T F O R O R B I T A L WORKSHOP
Majo r e m p h a s i s in a d a p t i n g the r e f e r e n c e s y s t e m for spec i f ic space m i s
s i o n s w a s p l a c e d on e s t a b l i s h i n g a c o n c e p t u a l p o w e r p l a n t des ign su i t ab le for
i n t e g r a t i o n wi th the S a t u r n - V O r b i t a l W o r k s h o p (OWS) concep t , which i s c u r
r e n t l y be ing s tud i ed by NASA u n d e r the Advanced Apol lo P r o g r a m . The power
s y s t e m des ign i s e s s e n t i a l l y i d e n t i c a l to the r e f e r e n c e s y s t e m excep t that the
r a d i a t o r a r e a h a s b e e n r e d u c e d s l igh t ly a t the e x p e n s e of a s m a l l weight p e n
a l t y , and r a d i a t i o n - s h i e l d d e s i g n s t a i l o r e d for the m i s s i o n have been inc luded .
The f r o n t i s p i e c e to t h i s r e p o r t i l l u s t r a t e s the p o w e r p l a n t - O W S i n t e g r a t i o n
c o n c e p t evo lved a f te r e x a m i n a t i o n of s e v e r a l a l t e r n a t e a p p r o a c h e s . The r e a c t o r
p o w e r s y s t e m i s shown e x t e n d e d in i t s o p e r a t i o n a l pos i t ion ; dur ing launch o r
shutdo'wn p e r i o d s i t v/ould be r e t r a c t e d wi th in the c y l i n d r i c a l s t r u c t u r e wh ich
s e r v e s a s an a e r o d y n a m i c s h r o u d , h e a t sh i e ld , s u p p o r t s t r u c t u r e , and docking
a d a p t o r . The p o w e r p l a n t p a c k a g e i s a t t a c h e d to (and can be d i s c o n n e c t e d f rom)
the f o r w a r d docking p o r t of the m u l t i p l e docking a d a p t o r . The power s y s t e m is
d e s i g n e d so t h a t wi th m i n i m a l m o d i f i c a t i o n s i t can be l aunched i n t e g r a l wi th the
OWS on a t w o - s t a g e S a t u r n - V , o r s e p a r a t e l y u s i n g e i t h e r a T i t a n - I I I F o r
A I - A E C - M E M O - 1 2 7 1 7 15
Saturn- IB/Serv ice Module combination. With the separa te launch an unmanned
rendezvous with the manned OWS would be requi red , using the Transtage or
Service Module for this maneuver .
Both shadow and 477 radia t ion-shie ld designs were examined for an assumed
dose l imit of 20 to 30 r e m / y r , which is small compared to the dose that is ex
pected from na tura l , space radiat ion. The power-convers ion equipment is
located in a compact gal lery within the shield. The shadow- and 477-shield
weight es t imates a r e approximate ly 14,300 and 16,500 lb respect ively, which
br ings the total powerplant weight (including power cables , deployment mech
an i sms , etc . ) to approximate ly 22,300 to 24,500 lb, depending on the shield
type. Thus the total , shielded power sys tem specific weight is approximately
885 to 975 Ib/kwe.
The es t imated payload marg ins available for the separa te launch and r en
dezvous mode (including al lowances for the shroud, rendezvous propellant , etc.)
a re 6700 to 8900 lb with the Ti tan-IIIF, and 1500 to 3800 lb with the Sa turn- IB/
service module. The marg in available for the in tegra l launch mode on a two-
stage Saturn-V depends strongly on the final weight es t imate for the OWS.
End-of-life (EOL) disposal of the r eac to r power sys tem, if requi red for
safety r ea sons , could be accomplished by undocking the powerplant and then
using the manned Command and Service Module's (CSM) propulsion and guid
ance capability to e i ther de-orb i t the reac tor into the ocean or park it in a
higher long-lived orbi t .
C, LUNAR BASE AND MANNED ORBITING RESEARCH LABORATORY (MORL) POWERPLANTS
Two reac tor — TE powerplant designs evolved in previous joint NASA/AEC (2 3) studies ' were updated to incorpora te the design and performance changes
available with the re fe rence sys tem. In both cases significant improvements
were obtained with respec t to sys tem simplification, specific weight, and
specific a r ea . Fo r the lunar base powerplant, for example, it now appears
possible to inc rease the net power from 20.4 to 35.5 kwe, using the same con
s t ra ints and c r i t e r i a es tabl ished in the previous joint study. For the MORL
powerplant the weight and a r ea reductions were 5 and 26% respect ively , the
total number of coolant loops was reduced from 22 to 5, and the r eac to r outlet-
t empera tu re was reduced approximately 50°F.
AI-AEC-MEMO-12717 16
III. REFERENCE SYSTEM
A. SYSTEM D E S C R I P T I O N
The r e f e r e n c e Z r H r e a c t o r - T E S y s t e m u t i l i z e s the n u c l e a r r e a c t o r d e
s c r i b e d in R e f e r e n c e 1 c o m b i n e d wi th a c o m p a c t P b T e TE c o n v e r t e r c u r r e n t l y
u n d e r d e v e l o p m e n t by W e s t i n g h o u s e to p r o d u c e 25 kw of e l e c t r i c a l p o w e r . The
d e s i g n u s e s two s e t s of h e a t - t r a n s f e r loops in s e r i e s , the p r i m a r y loops and
H R L ' s . A s o d i u m - p o t a s s i u m l i q u i d - m e t a l a l loy (NaK) i s u s e d in both l o o p s .
The a r r a n g e m e n t of loops and c o m p o n e n t s i s shown s c h e m a t i c a l l y in F i g u r e I I I - l ,
De ta i l ed d e s c r i p t i o n s of c o m p o n e n t s a r e p r o v i d e d in subsequen t s e c t i o n s of th i s
r e p o r t .
TO PARALLEL
LOOPS
RADIATOR Q = 138 kwt (551 kwt)
*NUMBERS IN PARENTHESES INDICATE FULL SYSTEM VALUES
' ELECTRICAL LINES 8-A30-075-1A
F i g u r e I I I - l . R e f e r e n c e 25 -kwe S y s t e m S c h e m a t i c
A I - A E C - M E M O - 1 2 7 1 7 17
T h r e e - l o o p s y s t e m s w e r e a l s o c o n s i d e r e d e a r l y i n t h e s tudy . In t h i s a r r a n g e
m e n t an i n t e r m e d i a t e s e t of l oops wi th h e a t e x c h a n g e r s is p l a c e d b e t w e e n the
p r i m a r y and H R L ' s . The i n t e r m e d i a t e h e a t e x c h a n g e r s ( IHX's) a r e s o m e w h a t
m o r e c o m p a c t than the c o m p a c t c o n v e r t e r s , and in o r b i t a l a p p l i c a t i o n s r e q u i r i n g
a sh i e lded g a l l e r y a s m a l l sh i e ld we igh t s av ings m a y thus be ob ta ined . F o r the
c u r r e n t 2 5 - k w e d e s i g n , h o w e v e r , the i n c r e a s e in we igh t c a u s e d by the i n t e r m e
d ia t e loops m o r e than of f se t s the s h i e l d - w e i g h t s a v i n g s . F o r t h e s e r e a s o n s and
b e c a u s e the t w o - l o o p a r r a n g e m e n t i s a l s o l e s s c o m p l e x and m o r e r e l i a b l e i t w a s
s e l e c t e d . Any f u r t h e r g r o w t h of the s y s t e m to u s e m o r e of the r e a c t o r ' s power
c a p a b i l i t y (>1200 kwt) , h o w e v e r , could r e s u l t in a t h r e e - l o o p a r r a n g e m e n t be ing
o p t i m u m .
The p r i m a r y loops t r a n s p o r t NaK, h e a t e d to 1246 °F in the r e a c t o r , to the
hot s ide of the TE t u b u l a r m o d u l e s . NaK c i r c u l a t i n g in the H R L ' s p r o v i d e s the
5 7 3 ° F a v e r a g e cold junc t ion of the m o d u l e s and t r a n s p o r t s the r e j e c t e d hea t to
r a d i a t o r s . The s a m e s c h e m a t i c a r r a n g e m e n t and s y s t e m c o m p o n e n t s a r e u s e d
in c o m m o n for s e v e r a l d i f f e ren t m i s s i o n a d a p t a t i o n s . As d e s c r i b e d l a t e r in th i s
r e p o r t , the m i s s i o n a d a p t a t i o n s , excep t for the r a d i a t o r and sh ie ld , a r e p r i
m a r i l y c o n f i g u r a t i o n a l c h a n g e s .
The P C S u t i l i z e s four c o m p a c t c o n v e r t e r s e a c h hav ing an independen t H R L .
F o u r p a r a l l e l loops a r e a l s o u s e d in the p r i m a r y s y s t e m to s impl i fy i n t e g r a t i o n .
The p r i m a r y loops a r e not h y d r a u l i c a l l y i ndependen t , a s they s h a r e the r e a c t o r
v e s s e l in c o m m o n .
The s e l e c t i o n of four p a r a l l e l loops w a s b a s e d on a t r a d e - o f f b e t w e e n weigh t ,
p a r t i a l - p o w e r (one loop out) p e r f o r m a n c e , c o m p l e x i t y , and r e l i a b i l i t y . The
p e n a l t y in going f r o m two to four loops w a s 150 lb; f r o m four to s ix w a s 200.
The p a r t i a l - p o w e r c a p a b i l i t y in a f o u r - l o o p s y s t e m is 80% of n o r m a l power a s
suming tha t the r e a c t o r - o u t l e t t e m p e r a t u r e is i n c r e a s e d to i t s full 1300°F c a p a
b i l i ty to p r o v i d e p a r t i a l c o m p e n s a t i o n for l o s s of the loop . Th i s i n c l u d e s the
p e n a l t y of flow r e v e r s a l t h r o u g h the i n a c t i v e NaK p u m p r e s u l t i n g f r o m the p o s t u
l a t ed loop f a i l u r e . (F low c h e c k v a l v e s for th i s a p p l i c a t i o n w e r e exc luded by r e
l i a b i l i t y c o n s i d e r a t i o n s . ) F o r l e s s than four i n s t a l l e d loops the p a r t i a l - p o w e r
c a p a b i l i t y fel l to a l e v e l c o n s i d e r e d to be u n a c c e p t a b l e for the p r o b a b l e r e q u i r e
m e n t s for m o s t m i s s i o n s . An i n c r e a s e to m a n y m o r e than four l o o p s , wi th the
A I - A E C - M E M O - 1 2 7 1 7 18
added c o m p l e x i t y and r e d u c e d r e l i a b i l i t y for fu l l -power o p e r a t i o n , could not be
j u s t i f i ed on the b a s i s of the s m a l l i n c r e a s e in p a r t i a l - p o w e r capab i l i t y . F o u r
loops w a s c o n s i d e r e d the b e s t c o m p r o m i s e for a t y p i c a l app l i ca t ion at the d e s i g
n a t e d p o w e r l e v e l . With the c o m p o n e n t s s i zed for th i s s y s t e m , c o n s i d e r a b l e
g r o w t h can be a c c o m p l i s h e d by adding p a r a l l e l loops wi thou t s e v e r e l y c o m p l i
ca t ing the s y s t e m .
E a c h of the four c o m p a c t c o n v e r t e r s c o n s i s t s of 24 t ubu l a r TE m o d u l e s .
They a r e p l aced in a f o u r - b y - s i x a r r a y ; each se t of four i s connec ted in s e r i e s
e l e c t r i c a l l y for a 56 -vdc e l e c t r i c a l ou tput . All m o d u l e s a r e h y d r a u l i c a l l y in
p a r a l l e l . In the r e f e r e n c e d e s i g n the o v e r a l l s y s t e m ef f ic iency i s 4.24%.
The NaK p u m p s u s e d in the r e f e r e n c e s y s t e m a r e the EM type u t i l i z ing a
s e p a r a t e T E p o w e r supp ly . One p u m p i s u s e d in e a c h of the four s y s t e m quad
r a n t s . E a c h p u m p h a s t h r e e t h r o a t s wi th in the s a m e m a g n e t f r a m e . Two t h r o a t s
a r e c o n n e c t e d h y d r a u l i c a l l y in s e r i e s to m e e t the p r i m a r y - l o o p flow r e q u i r e
m e n t . The t h i r d t h r o a t p r o v i d e s pumping of a H R L , The t h r e e pump t h r o a t s
a r e c o n n e c t e d in s e r i e s e l e c t r i c a l l y to a s p e c i a l t h r e e - m o d u l e TE power supply
hav ing a 2 2 0 - m v 1 5 0 0 - a m p output . The power supp l i e s a r e m o u n t e d d i r e c t l y
on the p u m p f r a m e s .
A to t a l of e ight NaK e x p a n s i o n c o m p e n s a t o r s is u s e d in the s y s t e m . F o u r
a r e u s e d in the p r i m a r y s y s t e m and one in e a c h of the four H R L ' s , All un i t s
a r e i d e n t i c a l , of the d o u b l e - s e a l e d g a s - b a c k e d be l lows type , wi th a vo lume 3
change c a p a c i t y of 0,15 ft , T h e y m a i n t a i n the s y s t e m p r e s s u r e s a t 20 p s i a
u n d e r n o m i n a l o p e r a t i n g c o n d i t i o n s .
The r a d i a t o r s t r u c t u r e and sh i e ld ing r e q u i r e m e n t s for the s y s t e m a r e d e
p e n d e n t to a c o n s i d e r a b l e ex t en t on the m i s s i o n a d a p t a t i o n . T r a d e s tud i e s con
s i d e r i n g h e a t - r e j e c t i o n t e m p e r a t u r e , TE p e r f o r m a n c e , r a d i a t o r a r e a , and s y s
t e m w e i g h t r e s u l t e d in the s e l e c t i o n of 5 7 0 ° F a v e r a g e h e a t - r e j e c t i o n t e m p e r a t u r e 2
and 1400 ft of r a d i a t o r a s n e a r - o p t i m u m v a l u e s .
The r a d i a t o r m a y be d e s i g n e d in a n u m b e r of ways inc luding finned tubes or
h e a t p i p e s . The r a d i a t o r s m a y a l s o be f ixed o r folding depending on v e h i c l e -
i n t e g r a t i o n c o n s t r a i n t s and o the r c o n s i d e r a t i o n s , A t y p i c a l des ign adopted for
the S a t u r n - V OWS a p p l i c a t i o n c o n s i s t s of a fixed 1 2 - f t - d i a m s t r u c t u r e to which
A I - A E C - M E M O - 1 2 7 1 7
19
REACTOR
PUMP TE CONVERTER
ELECTROMAGNETIC PUMP
CONTROL DRUM ACTUATORS
Lj.^MAIN TE CONVERTER
EXPANSION COMPENSATOR
j j PRIMARY LOOP ~~~.,
%^'^\ HEAT-REJECTION LOOP
Figure III-2. ZrH Reactor — Thermoe lec t r i c System, Reac to r /Ga l l e ry Ar rangement
8-MA21-07S-6
AI-AEC-MEMO- 12717 20
a r e a t t a c h e d 96 3 / 8 - i n . - d i a m NaK t u b e s . A l u m i n u m fins wi th i n t e g r a l m e t e o r o i d
a r m o r a r e d i f fus ion-bonded to the s t a i n l e s s - s t e e l t u b e s . E a c h H R L p r o v i d e s
NaK to one q u a d r a n t of the r a d i a t o r c y l i n d e r . E a c h q u a d r a n t in t u r n i s d iv ided
into t h r e e p a r a l l e l f lowpaths by m e a n s of h e a d e r s and i n t e r c o n n e c t i n g piping to
m a i n t a i n the r a d i a t o r p r e s s u r e d r o p to a low v a l u e . The s u p p o r t s t r u c t u r e for
the f inned t u b e s is a 0 . 0 1 0 - i n . - t h i c k Ti s h e l l - a n d - s t r i n g e r s t r u c t u r e wi th i n t e r
na l f r a m e s s p a c e d a t an a v e r a g e of 3-ft i n t e r v a l s . Th i s r a d i a t o r des ign concep t
i s u s e d for the we igh t s u m m a r y p r o v i d e d l a t e r .
The sh i e ld s t r u c t u r e , l i ke the r a d i a t o r , v a r i e s wi th m i s s i o n adap t a t i on .
F u n d a m e n t a l l y , the r e f e r e n c e d e s i g n c o n s i s t s of a m o I t e n - P b g a m m a sh ie ld
( e n c a p s u l a t e d in a s t e e l c o n t a i n e r ) i m m e d i a t e l y s u r r o u n d i n g the r e a c t o r , fol
lowed by a LiH n e u t r o n sh i e ld . I n t e r n a l h e a t g e n e r a t i o n in the Pb g a m m a sh ie ld
i s r a d i a t e d to the r e a c t o r v e s s e l . The p r i m a r y - l o o p c o m p o n e n t s conta in r a d i o
a c t i v e NaK and a r e s a n d w i c h e d b e t w e e n the p r i m a r y r e a c t o r sh ie ld and s e c o n d a r y
s h i e l d i n g . In a t y p i c a l m a n n e d a p p l i c a t i o n the s e c o n d a r y sh ie ld c o n s i s t s of a
d e p l e t e d u r a n i u m g a m m a sh i e ld followed by add i t iona l LiH n e u t r o n sh ie ld ing .
D e s c r i p t i o n s of d e s i g n s for spec i f i c m i s s i o n s a r e p r o v i d e d in Sec t ion V of th is
r e p o r t . G e n e r a l sh ie ld ing r e q u i r e m e n t s , r e a c t o r / s h i e l d i n t e g r a t i o n , and s h i e l d
ing t e c h n o l o g y s t a t u s a r e d i s c u s s e d in R e f e r e n c e 1.
The b a s i c r e a c t o r and g a l l e r y a r r a n g e m e n t i s shown in F i g u r e I I I -2 , The
p r i m a r y - l o o p e x p a n s i o n c o m p e n s a t o r s , the four s y s t e m p u m p s with power s u p
p l i e s , and the TE c o n v e r t e r s a r e l o c a t e d in the g a l l e r y r e g i o n be tween the p r i
m a r y and s e c o n d a r y s h i e l d s . The c o m p o n e n t s a r e a r r a n g e d s y m m e t r i c a l l y about
the s y s t e m c e n t e r l i n e . In the con f igu ra t i on shown, the r e a c t o r is sh ie lded on
a l l s i d e s to p r o v i d e sh i e ld ing for veh i c l e r e n d e z v o u s m a n e u v e r s . The r e a c t o r
c o n t r o l - d r u m a c t u a t o r s a r e l o c a t e d ou t s ide the r e a c t o r sh i e ld . In the lunar b a s e
a d a p t a t i o n the e q u i p m e n t a r r a n g e m e n t i s v e r y s i m i l a r . In th i s c a s e , h o w e v e r ,
it i s a d v a n t a g e o u s to i n v e r t the whole a s s e m b l y to p l a c e the c o n t r o l - d r u m d r i v e s
be low and the g a l l e r y c o m p o n e n t s above the r e a c t o r .
2 An u n s h i e l d e d s y s t e m we igh t b r e a k d o w n i s shown in Table I I I - l . The 1400 ft
f i x e d - f i n n e d - t u b e r a d i a t o r i s inc luded for i l l u s t r a t i o n . Shie lded s y s t e m we igh t s
a r e g iven in Sec t ion V for spec i f i c m i s s i o n a d a p t a t i o n s .
A I - A E C - M E M O - 1 2 7 1 7 21
TABLE III - l
UNSHIELDED SYSTEM WEIGHT BREAKDOWN
System Component
Reactor
P r i m a r y - l o o p piping
Pumps
Expansion compensa tors
Thermoe lec t r i c conver te r s
Gal lery s t ruc tu re
Instrumentat ion, control , and regulation
Subtotal
Radiator
Piping
Radiator and s t ruc ture
Subtotal
System Total
Weight (lb)
1422
100
440
208
1135
120
340
3765
661
2580
3241
7006
B. SYSTEM PERFORMANCE
The s teady-s ta te per formance of a r eac to r — TE sys tem is ext remely stable.
Because of the re la t ive ly high radia tor t e rape ra tu re , var ia t ions in the sink t em
pera tu re due to night and day variat ions a r e insignificant.
1. Reference Operating Conditions
Table II1-2 gives the performance cha rac t e r i s t i c s of this sys tem when
operating at the re fe rence conditions. The regulated power of 24.7 kwe is 2%
less than the gross power output due to losses in the voltage regulation equip
ment . The lifetime objective for the plant is 20,000 hr; however, the sys tem
has no cha rac t e r i s t i c s that definitely limit i ts l ifet ime. Operation well beyond
20,000 hr could be accomplished at only a slightly lower rel iabi l i ty level.
AI-AEC-MEMO-12717 22
TABLE III-2
REFERENCE PERFORMANCE CHARACTERISTICS
E l e c t r i c p o w e r , kwe:
G r o s s
R e g u l a t e d
V o l t a g e , v o l t s :
S y s t e m
T h e r m o e l e c t r i c t u b u l a r m o d u l e
L i f e t i m e , h r
T h e r m a l - p o w e r b a l a n c e , kwt:
R e a c t o r
P r i m a r y - l o o p l o s s e s
C o n v e r t e r s
P u m p c o n v e r t e r s
R a d i a t o r
G r o s s e l e c t r i c a l p o w e r
H y d r a u l i c power (adds to loop l o s s e s )
T e m p e r a t u r e s , ° F
R e a c t o r NaK
C o n v e r t e r , h o t - c l a d
C o n v e r t e r , c o l d - c l a d
R a d i a t o r NaK
E f f i c i e n c i e s , %
S y s t e m
C o n v e r t e r
C o n v e r t e r C a r n o t
H y d r a u l i c s
582.4
- 5 . 0
577.4
539.0
38,4
577,4
In le t A v e r a g e Out le t
P r i m a r y loops
H e a t - r e j e c t i o n loops
25,2
24.7
56.0
14.0
20,000
551.0
25.2
1.2
577.4
1044
1225
470
663
Total F lowra te , l b / s e c
13.0
12.4
1145 1246
1125 1025
570 670
563 463
P r e s s u r e Drop, psi
3,35
1,50
4.24
4.67
35.0
A I - A E C - M E M O - 1 2 7 1 7 23
32
1-13-69 UNC
48 64 80 LOAD VOLTAGE, volts
96 112
I I -
7759-5265
Figure III-3. System Per fo rmance vs Load Voltage, Reactor-Out le t Tempera tu re - 1246°F
AI-AEC -MEMO- 1 271 7 24
Figure III-3 shows how system performance var ies with changes in load
voltage, for a constant r eac to r -ou t l e t t empera tu re of 1246 °F, As the load
voltage inc reases the cu r r en t d e c r e a s e s , and because the effective thermal
conductance of the conver te r var ies with the cur ren t , the hot-to-cold-junction
A T i n c r e a s e s . The hot-junction t empera tu re i nc r ea se s and the cold junction's
d e c r e a s e s , with the la t ter resul t ing in reduced reac tor power.
These specific per formance curves resul ted because the sys tem was de
signed to produce power at nominally 56 vdc. For par t icu lar applications the
TE modules could be wired for any nominal load voltage that is a multiple of
14 vdc,
2, Off-Design Pe r fo rmance
It may be des i rab le to operate the powerplant at off-design conditions for
two r ea sons . F i r s t , degradation in the TE conver ter could be offset by rais ing
the operating t e m p e r a t u r e , or second, the plant could be operated at less than
i ts full power capabili ty if e lec t r ica l power requ i rements a r e projected at a
lower level for an extended period. Lowering the power level would tend to
inc rease the plant l ifetime and rel iabi l i ty because of the reduced t empera tu res
of all components , and would reduce the load requi red to be dumped by the volt
age regula tor . It is expected that changes in e lec t r ica l output of the plant would
be made only when the r equ i rement s were projected differently for a ma t t e r of
weeks.
F igure III-4 shows the e lec t r ica l power output of the system as a function
of load voltage for different reac tor -ou t le t t e m p e r a t u r e s . At the reference de
sign voltage of 56 volts this information can be c ross -p lo t ted to establ ish the
relat ionship between e lec t r i ca l power and outlet t empera tu re , as done in F ig
u re III-5. It should be noted that the the rmal power, also plotted on this figure,
does not vary proport ional ly to e lec t r ica l power. A 40% reduction in e lec t r ica l
power only reduces the the rma l power by 24%, from 5 82 to 440 kwt. An ext rapo
lation of this curve would show that the the rma l power required to obtain any
e lec t r ica l power at 56 volts is on the order of 300 kwt.
An important observat ion from Figure III-5 is that 27.2 kwe can be obtained
at a r eac to r -ou t le t t empe ra tu r e of 1300°F compared to the 24.7 kwt at 1246°F.
AI-AEC-MEMO-12717 25
32
28 -
24 -
20 -
LLl
O
16 -
12 -
1
-
Il -ll •
1
DESIGN
1-
1 1
^ ^
VOLTAGE \
_ J . . , . 1 .
1 1
\ \ REACTOR-OUTLET \ \ TEMPERATURE, "F
\ \ \ ^ 1 3 0 8
\ \ \ ^^ ^ ''
\\v\ ; \\v\-
1-13-69 UNCL
20 40 60 80
LOAD VOLTAGE, volts
100 120 140
7759-5266
Figure III-4. System Elec t r i ca l Cha rac t e r i s t i c s vs Reactor-Out le t Tempera tu re
AI-AEC-MEMO-12717 26
ELE
CT
RIC
AL
PO
WE
R,
kwe
c:
z o
> I—I > O
-J
W
O
ts)
-J
OQ
W
Ul
^ •
CO
S" M
R
^ (D
o
"*
'-i
p3
"*
(D
<?
0 r+
^2
-1
m
30
> c=
m
CD
NJ
OQ
'
(I
O
II &
I—
'
<:;?
o
2
^3
CO
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i-t
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i-i
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3
RE
AC
TOR
TH
ER
MA
L P
OW
ER
, kw
t
T A B L E I I I -3
470 .0
- 5 . 0
465 .0
435.0
30.0
465.0
P A R T I A L - P O W E R P E R F O R M A N C E C H A R A C T E R I S T I C S ( T h r e e Loops O p e r a t i n g )
R e g u l a t e d p o w e r , kwe
Vo l t age , vo l t s :
S y s t e m
T h e r m o e l e c t r i c t u b u l a r m o d u l e
T h e r m a l - p o w e r b a l a n c e , kwt:
R e a c t o r
P r i m a r y - l o o p l o s s e s
C o n v e r t e r s
P u m p c o n v e r t e r s
R a d i a t o r
G r o s s e l e c t r i c a l p o w e r
H y d r a u l i c power (adds to loop l o s s e s ^
T e m p e r a t u r e s , ° F
R e a c t o r NaK
C o n v e r t e r , h o t - c l a d
C o n v e r t e r , c o l d - c l a d
R a d i a t o r NaK
E f f i c i e n c i e s , %
S y s t e m
C o n v e r t e r
C o n v e r t e r C a r n o t
H y d r a u l i c s
O p e r a t i n g p r i m a r y loops (3)
N o n o p e r a t i n g p r i m a r y loop (1
H e a t - r e j e c t i o n loops (3)
To ta l F l o w r a t e , l b / s e c
12.9
- 2 . 3
9.5
19.8
56.0
14.0
Inle t
1104
1084
508
500
A v e r a g e
1184
1164
588
580
Out le t
1264
1244
668
660
444.0
20.2
0.8
465.0
4 .21
4 .57
35.5
A I - A E C - M E M O - 1 2 7 1 7
28
This means that the sys tem can accommodate as much as 10% degradation with
out the r eac to r -ou t l e t t empera tu re exceeding 1300°F. Operation at this t em
pe ra tu re level is believed to be acceptable for all components, but the reference
operating conditions a r e lower p r imar i l y to achieve t empera tu re margin to com
pensate for possible sys tem degradation.
3. P a r t i a l - P o w e r Pe r fo rmance
The e lec t r i ca l power capability of the sys tem is 19.8 kwe after loss of one
of the four H R L ' s . This a s sumes that all TE conver te rs in the three operating
loops a r e generat ing power and that the r eac to r core-out le t t empera ture is
r a i sed to 1300°F.
Since the pump on the nonoperating leg of the p r imary loop has no power,
this leg of the loop acts as a r eac to r bypass . Approximately 18% of the original
total flowrate goes through this loop while the flowrate in the other loops in
c r e a s e s to 33% of the original total f lowrate. This inc rease is due both to the
added bypass line and to the reduction in p r e s s u r e drop through the reac tor
co re . The bypass flow enters the r eac to r -ou t l e t plenum at the inlet t empe ra
ture so the t empera tu re exiting the plenum is only 1264°F when the core outlet
is 1300°F. Table III-3 s u m m a r i z e s the performance cha rac te r i s t i c s when
operating with only three quadrants .
C. SYSTEM OPERATION
Operation of the reac tor — TE powerplant is inherently simple because of
the pass ive na ture of TE power convers ion. Both the e lect r ica l power output
and the hydraulic power available from the pumps automatically increase as the
reac tor t empe ra tu r e and power a r e inc reased . The only par t s required to move,
for control of the powerplant, a r e the reac tor control d rums . The control drums
a r e rota ted slowly in d i sc re te steps of approximately 1 ° to change the radial
leakage of neutrons from the core and thus the neutron balance. Rotation of the
d rums in the direct ion to i nc rease the neutron level within the core causes the
reac tor power and t empera tu re to i nc rease until the inherent negative t empera
ture coefficient of the r eac to r s tabil izes the operation at a new power and t em
pera tu re level . A single drum step will change the operating tempera ture ap
proximate ly 5 to 15°F. The corresponding e lec t r ica l power change when operating
near the design point would be from 1/4 to 3/4 kwe.
AI-AEC-MEMO-12717 29
1. Startup
Severa l options a r e available for s tar tup that t rade off total t ime and stand
by power for s ta r tup against complexity of the electronic control c i r cu i t s . The
s imples t c i rcui t would involve rotating the reac tor control d rums at a constant
ra te until the des i red e lec t r ica l power is reached. The t ime for s tar tup in this
case would be on the o rder of 12 h r . By introducing s tepping-ra te changes into
the s tar tup sequence, the s tar tup t ime could be reduced to 2 to 3 h r . Fea tu re s
must be added to the control sys tem for this ; however, even in this case the
control sys tem logic is re la t ively s imple .
The sys tem s tar tup has four dist inct phases . The detai ls of a typical s tar tup
a r e descr ibed for the Saturn-IVB OWS power sys tem in Section V-A-4b. Since
these detai ls a r e miss ion-dependent , the following paragraphs will descr ibe only
the genera l na ture of each phase and the possible options.
a. Phase 1: Shutdown Margin Removal
For safe handling on the ground the reac to r is designed to be approximately
$4,75 subcr i t ica l at room t e m p e r a t u r e . The f i rs t step in the s tar tup, then, is
to remove this shutdown marg in . Normally a fast s tepping-ra te would be used
during this phase and it would be completed in about 30 min. If the single
s tepping- ra te , dictated by Phase 2 l imi ta t ions , were used throughout the s t a r t
up, this phase would requ i re approximate ly 10 hr .
The slowdown in s tepping-ra te at the end of Phase 1 would be signaled by
a con t ro l -d rum position indicator or step counter . The selected dr\am position
would cor respond to a 25 to 50« subcr i t ica l condition in the r eac to r . Since the
drum position at which the r eac to r is c r i t i ca l va r ies slowly throughout the life
of the r e a c t o r , it is anticipated that the selected drum position could be changed.
This could be coordinated routinely from the ground control center , since any
single adjustment would be usable for s tar tups during a period of at least one
month.
At leas t 5% flow will be requi red during this phase to a s s u r e that no local
NaK freezing occurs in the sys tem and that an acceptable t r ans ien t r esu l t s when
the rmal power is init iated. Though seve ra l ways of providing NaK flow a re
AI-AEC-MEMO-12717 30
p o s s i b l e , e a c h would r e q u i r e s o m e s t a n d b y e l e c t r i c a l p o w e r . One way i s
to p a s s 50 a m p t h r o u g h s m a l l s t a r t u p p u m p s a t t a c h e d to e a c h loop. This c u r
r e n t would p a s s t h r o u g h e a c h p u m p in s e r i e s , for a to ta l vo l t age d rop of about
2 v o l t s . T h u s the t o t a l p o w e r r e q u i r e m e n t would be about 100 w a t t s . It i s
a n t i c i p a t e d tha t th i s i s a r e l a t i v e l y low r e q u i r e m e n t c o m p a r e d to o the r power
r e q u i r e m e n t s d u r i n g s p a c e c r a f t d o r m a n t p e r i o d s or du r ing n o n o p e r a t i n g m a n n e d
p e r i o d s .
b . P h a s e 2: C r i t i c a l to S e n s i b l e Hea t
Dur ing t h i s p h a s e of the s t a r t u p the s t epp ing r a t e m u s t be r e d u c e d to the
m i n i m u m r a t e . Once the r e a c t o r goes c r i t i c a l the n e u t r o n flux o r power leve l
b e g i n s to i n c r e a s e f r o m s o m e low s o u r c e l e v e l , but no r e a c t i v i t y feedback due
to the n e g a t i v e t e m p e r a t u r e coef f ic ien t of the r e a c t o r i s i n t r o d u c e d unt i l the
power l e v e l r e a c h e s a l eve l of about 1 kwt . Th i s n o r m a l l y o c c u r s on the o r d e r
of 20 m i n a f t e r c r i t i c a l i t y , so the r e a c t o r is s u p e r c r i t i c a l by the a m o u n t of r e
a c t i v i t y i n s e r t e d du r ing t h i s 2 0 - m i n u t e p e r i o d . The d e g r e e of s u p e r c r i t i c a l i t y
d e t e r m i n e s the r a t e of i n c r e a s e of p o w e r , the m a g n i t u d e of the power s p i k e , and
the r e s u l t i n g t e m p e r a t u r e t r a n s i e n t tha t o c c u r s b e f o r e the i n h e r e n t r e a c t o r t e m
p e r a t u r e c h a r a c t e r i s t i c s s t a b i l i z e the o p e r a t i n g c o n d i t i o n s .
The d r u m s t e p p i n g - r a t e i s l i m i t e d so tha t the t e m p e r a t u r e t r a n s i e n t i s a c
c e p t a b l e . When the t i m e to r e m o v e the l a s t 25 to 50^ of the shutdown m a r g i n i s
i n c l u d e d , t h i s p h a s e of s t a r t u p t a k e s about 40 to 60 m i n . The end of P h a s e 2 i s
s i g n a l e d b y a t e m p e r a t u r e s e n s o r on the r e a c t o r ou t le t l ine s e t at a p p r o x i m a t e l y
3 0 0 ° F ,
An e s t i m a t e of the s t a r t u p t r a n s i e n t i s shown in Sect ion V - A - 4 b . The power
sp ike and t e m p e r a t u r e t r a n s i e n t wi th th i s r e a c t o r a r e g r e a t e r than wi th p r e v i o u s
SNAP r e a c t o r s b e c a u s e of the r e d u c t i o n in f u e l - t e m p e r a t u r e coeff ic ient c a u s e d
by the add i t i on of Gd p r e p o i s o n . The m a g n i t u d e of the t r a n s i e n t wi l l be r e d u c e d
a s the r e a c t o r i s o p e r a t e d , for two r e a s o n s . F i r s t , the Gd b u r n s out r e s u l t i n g
in an i n c r e a s e in fuel coef f ic ien t ; and s e c o n d , the s o u r c e power l eve l which af
f ec t s the t i m e b e t w e e n c r i t i c a l and s e n s i b l e hea t i s g r e a t l y i n c r e a s e d a f t e r o p e r a
t ion . In fac t if the r e a c t o r i s to be r e s t a r t e d within an h o u r a f t e r shutdown, the
s t e p p i n g - r a t e for t h i s p h a s e could be e a s i l y doubled.
A I - A E C - M E M O - 1 2 7 1 7
31
REA
CTO
R F
LUX
(n
vXlo
lf)
> n O
t\j
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hi
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ro ^ ho
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ro
to
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> 3>
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THERMAL POWER
(kw)
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c . P h a s e 3: Hea t Shield R e m o v a l
Once the t e m p e r a t u r e s e n s o r i n d i c a t e s tha t the r e a c t o r i s g e n e r a t i n g p o w e r ,
the h e a t s h i e l d s wh ich enve lope the r a d i a t o r dur ing n o n o p e r a t i n g p e r i o d s to p r o
t e c t a g a i n s t NaK f r e e z i n g can be r e m o v e d . This p h a s e of the s t a r t u p i s m o s t
a f fec ted by the d e s i g n of the p o w e r p l a n t and the m i s s i o n i n t e g r a t i o n c o n s t r a i n t s .
The t i m e for t h i s p h a s e can v a r y f r o m z e r o , w h e r e the hea t sh i e ld s a r e e j ec ted
o r r e m o v e d quick ly and no h e s i t a t i o n in the s t a r t u p i s r e q u i r e d , to about 30 m i n ,
w h e r e the r e m o v a l m u s t be a c c o m p l i s h e d m o r e s lowly . In the l a t t e r c a s e , which
m a y invo lve the d e p l o y m e n t of folded r a d i a t o r s , the r e a c t o r - o u t l e t t e m p e r a t u r e
would p r o b a b l y be l i m i t e d un t i l h e a t sh ie ld r e m o v a l is c o m p l e t e d ,
d. P h a s e 4: R a m p to P o w e r
Th i s p h a s e of the s t a r t u p i s r e s t r i c t e d only by the t r a n s i e n t t e m p e r a t u r e
l i m i t a t i o n on the s y s t e m . The r a m p could be a t a r a t e of t e m p e r a t u r e i n c r e a s e
of about 2 0 ° F / m i n and c o m p l e t e d in about 40 m i n . I t i s i m p o r t a n t to r e - e m p h a s i z e
tha t no c o n t r o l s a r e r e q u i r e d for the p o w e r p l a n t o the r than for the con t ro l d r u m s .
As the r e a c t o r t e m p e r a t u r e i n c r e a s e s , the t e m p e r a t u r e d i f fe rence a c r o s s the
T E m o d u l e s i n c r e a s e s and the NaK flow and e l e c t r i c a l power a u t o m a t i c a l l y in
c r e a s e . Once the o p e n - c i r c u i t vo l t age of the TE c o n v e r t e r e x c e e d s 56 v o l t s ,
u se fu l e l e c t r i c a l power a t the r e g u l a t e d 56-vdc l eve l b e c o m e s a v a i l a b l e .
P h a s e 4 of the s t a r t u p i s t e r m i n a t e d when e l e c t r i c a l c u r r e n t r e a c h e s a p r e
d e t e r m i n e d s e t t i n g . A r e a c t o r - o u t l e t t e m p e r a t u r e s igna l would be u sed to s top
d r u m i n s e r t i o n , should an a n o m a l y p r e v e n t r e a c h i n g full e l e c t r i c a l power wi thout
e x c e s s i v e t e m p e r a t u r e . Th i s cutoff would n o r m a l l y be se t a t about 1325°F . After
the end of th i s p h a s e of the s t a r t u p , wh ich c o m p l e t e s the s t a r t u p , the s y s t e m
would be c o n t r o l l e d wi th in a d e a d b a n d on e l e c t r i c a l c u r r e n t output .
A l though the vo l t age r e g u l a t i o n s y s t e m is de s igned to hand le e l e c t r i c a l load
f l u c t u a t i o n s , the e l e c t r i c a l c u r r e n t c o n t r o l point could be ad ju s t ab l e to t ake ad
van t age of long p e r i o d s (weeks ) when r e d u c e d power r e q u i r e m e n t s a r e p lanned .
Th i s could i n c r e a s e l ife o r r e l i a b i l i t y by a l lowing ex tended o p e r a t i o n at r e d u c e d
t e m p e r a t u r e s and r e d u c e d load on the vol tage r e g u l a t o r .
A b r i e f r e v i e w of the s t a r t u p of the SNAP lOA power s y s t e m in o rb i t , shown
in F i g u r e I I I -6 , i s helpful in u n d e r s t a n d i n g the s e q u e n c e . Th i s s t a r t u p s u c c e s s
fully a c c o m p l i s h e d a l l four p h a s e s a s d e s c r i b e d above . P h a s e 1, shutdown m a r g i n
A I - A E C - M E M O - 12717 33
1200
1000
800 -
600 -
400
200 -
0
1 ISG^UNC
1
-
-
1
1 1 1 1 I I 1 1 1 1 1 M M
AVERAGE PRIMARY LOOP ^ v NaK TEMPERATURE \
AVERAGE HEAT REJECTION TEMPERATURE
1 1 1 1 1 1 1 1 1 1 1 1 1 1 !
1 1 1 1 1 1 M
\ ;
\ \ -
1 1 1 1 1 1 I I 10 10 0
TIME mm
Figure III-7. System Shutdown Trans ien t s , NaK Tempera tu res -24«^/min
100 0
7759 5268
0 1
I 15 S9 UNC
Figure III-
600
„400
m o Q-
200
0
o
O a: < ^ 4 0 cn 13 1— <c ce
1 20 Ll_ O
< Q
1 1 1 1 1 1 r 1 * - F U L L POWER
- ^ ^ \
^
~
-
1 1 1 1 1 1 r 1
\
\ .
MISSION ^ ^ • ^ ^ ^ ^ POWER ^ ^ > ~ - - ^ ^ _
^ ^ ^ ^
HEAT REJECTIONv LOOP \ _
1 1 1
PRIMARY NaK LOOP
1 1 1 1
1 1 1 1
-
"
-
r ~ r 1 1 1
10 0 100 0
7759 5269
System Shutdown Trans i en t s , Power and Rate of Tempera tu re Change -24«^/min
AI-AEC-MEMO-12717 34
removal , was acce le ra ted by the immedia te inser t ion of two of the four control
drums immediate ly upon receipt of the s tar tup command. These were spr ing-
loaded. Phase 1 continued, however, for approximately 6 hr as the remaining
two drums were inse r ted at the single s tepping- ra te . Phase 2, the time from
cr i t i ca l to sensible heat , took approximately 25 min and culminated in the power
spike and t empera tu re t rans ien t shown. This important part of the s tar tup es tab
lished that the effective source power level in the SNAP lOA orbit was about as _ Q
predicted, 10 kw. Phase 3 was accomplished instantaneously by ejection of
the heat shields when the reac to r ou t le t - t empera tu re reached 325 °F, The r amp
to power, Phase 4, took about 2 h r . The control in this case was on r e a c t o r -
outlet t e m p e r a t u r e , 2. Shutdown
The sys tem is shut down simply by rotating the control drums to their least
react ive position. Again, e lec t r ica l generat ion and NaK flow follow automatically
as the r eac to r t empe ra tu r e drops . Normal ly the shutdown would be accom
plished using the same con t ro l -d rum s tepping-ra te as used during Phase 1 of
the s ta r tup . F igures III-7 and - 8 show the sys tem performance using a react iv i ty-
removal ra te of -24«^/min, typical of the ra te result ing from a Phase 1 stepping-
rate with the drum in the normal operation zone. The ra te of cooldown of the
sys tem is controlled by its heat capacity, and the t ime for cooldown therefore
is essent ia l ly independent of the reac t iv i ty - removal ra te in the range of in te res t .
For the ra te shown, the fission power is reduced to 1% in about 3.5 min. This
would probably be fast enough to mee t operat ional requ i rements ; however, the
reac t iv i ty - removal ra te could be inc reased to reduce the power to this level in
less than 1 min. The t empera tu re t rans ien t would not be appreciably different
for this la t ter ca se .
After approximately 1 hr , rep lacement of the heat shields around the r ad i
ator would have to be made to protect against NaK freezing.
D. RELIABILITY
The re l iabi l i ty of the sys tem has been calculated based on reasonable es t i
ma tes of that for the components . These es t imates r ep resen t s t a t e -o f - the -a r t
rel iabi l i ty for s imi la r c l a s ses of equipment where possible , and in other a r eas
AI-AEC-MEMO-12717 35
o
> t-H I
> O
M
O
u asaa
0 9998
0 9994
0 999
0 998
0 994
0 990
0 98
0 94
0 90
08
04
n
1 1
-
„
-
-
-
-
-
-
1 L_
1 1 1 1 1 1 1 1
1 1 1
HEAT-REJECTION SYSTEM 1
1 1 1
I I I 1 1
1
'CONVERTER 'ELECTRICAL 1 ,
1
REACTOR AND PRIMARY
LOOP'
1 _ _ . _ _ „
TOTAL SYSTEM
1 ,
T"
1
1
1 1 1
-
~
-
-
-
-
-
-:
-
12 14 16
ELECTRICAL POWER kwe
20 22 24 26
Figure III-9. System Reliability, 10,000-hr Duration
they a r e based on demonstrable object ives. The calculated resu l t s a re not to
be taken as p rec i se values of the sys tem rel iabi l i ty, but as good indicators of
the o rder of magnitude of that expected, the t rend of rel iabi l i ty with par t ia l
power leve ls , and a reasonable apport ionment of it to the system components.
1. System Reliabil i ty
F igures III-9 and -10 show a s u m m a r y of system rel iabil i ty es t imates for
various power l eve l s . The calculated figures show that the system has very
high re l iabi l i ty for delivering a la rge percentage of the design power. The gross
sys tem power capabili ty is 25.2 kwe and the rel iabil i ty for producing this power
for 20,000 hr is 64%. The rel iabi l i ty figures inc rease significantly fronn. this
level to 95% at 23 kwe and over 99% at about 18 kwe for the same period. At
10,000 hr , the t rend is the same; however, the full-power rel iabi l i ty is in
c reased to 80%, the 23-kwe value is over 97,5%, and the 18-kwe value is over
99.7%, It should be noted that these par t ia l -power rel iabi l i t ies do not imply
that the sys tem mus t be operated at reduced power in order to achieve them.
The sys tem can be operated continuously at its maximum capability with little
or no effect on the par t ia l -power re l iab i l i t i es .
The major subsys tem values a r e also shown in Figures III-9 and -10. It
can be seen that the f i rs t s t ep - inc reases in rel iabil i ty occur when the e lec t r ica l
output of individual conver ter 4-packs can be lost due to open or short c i rcu i t s .
Below 75% po^wer a large incrementa l change in rel iabil i ty is gained by allowing
an ent i re HRL to fail. The rel iabi l i ty of the reac tor and p r imary hea t - t ransfe r
loop is the final l imiting value. With the exception of insignificant gain which
might be rea l ized by lower s t r e s s on the fuel and more allowable combinations
of con t ro l -d rum fa i lures , the probabil i ty of successful operation for this portion
of the sys tem rema ins essent ia l ly constant r egard less of the power level for the
sys tem,
2, Bases for Es t ima tes
The var ious component re l iabi l i ty values used to calculate subsystem and
sys tem re l iabi l i ty a r e best es t imates of expected rel iabil i ty for developed equip
ment . The re l iabi l i ty analysis of the sys tem is thus based on values judged to
be reasonably at tainable. The following paragraphs contain the bases for the
rel iabi l i ty e s t ima tes of major component classif icat ions, A summary of these
es t imates is shown in Table III-4 for the entire system.
AI-AEC-MEMO-12717 37
>
O
w E 00 ^
O
DO - J
0 9999
0 9998 -
0 9994
0 999
0 998
0 994 -
: 0 99
0 94
0 90
08
04
0
1 1 1 1 1 I I I 1 1
; HEAT REJECTION SYSTEM 1 _,
REACTOR AND PRIMARY LOOP
1
-
-
1 1 1 1 L . _ ,
[CONVERTER |_ELECTRICAL
1 1 1 1 1
1 1 J
1
1 1
__ __ - -
-
1 1 1 _ ] 1 . 1 1 1 . J 1 1
-
1 1 •
L
1
0 2
I 15-69 UNC
10 12 14 16
ELECTRICAL POWER kwe
18 20 22 24
Figure 111-10. System Reliabil i ty, 20,000-hr Duration
TABLE III-4
RELIABILITY ESTIMATES
Component
P r i m a r y sys tem
Reactor
Vessel
Fuel
Control drums and actuator
Piping
Pumps and conver ter piping
Pump and conver ter e lec t r ica l
Expansion compensator
Main conver ter piping
Heat - re jec t ion loop (4 per
Piping
unit (4)
system)
Pump and conver ter piping
Pump and conver ter e lec t r ica l
Expansion compensator
Main conver ter piping
Radiator
Function
Meteoroid
Conver ter e lec t r ica l
24 of 24 (4-packs)
23 of 24 (4-packs)
22 of 24 (4-packs)
unit
Ful l -power sys tem re l iabi l i ty
Est imated R
10,000 hr
0,9979
0,99900
0.999
0,999999
0,999999
0.9997
0,99968
0,99986
0,99992
0,99968
0.9949
0,99984
0,99985
0,99994
0,99998
0,9986
0.998
0.9987
0.820
0.983
0.9989
0.802
eliability, R
20,000 hr
0,9953
0.9978
0.998
0.9999
0,99987
0,9994
0.99936
0,99962
0.9996
0.99935
0,990
0,99968
0,99969
0,99988
0,9999
0.9971
0.996
0.9975
0.673
0.941
0.9927
0.643
AI-AEC-MEMO-12717 39
a. Welds
B a s e d on s u r v e y s of f lu id - loop e x p e r i e n c e , a weld f a i l u r e - r a t e of l e s s than
one f a i l u r e in 10 h r / t u b e - w e l d h a s b e e n e s t i m a t e d . This i s s u p p o r t e d by da ta
ob ta ined 3 y e a r s ago f r o m ORNL c o n c e r n i n g r e a c t o r f u e l - e l e m e n t we ld i n t e g r i t y
and m o r e r e c e n t s u r v e y s of l a r g e r e a c t o r h e a t - t r a n s f e r loops and h e a t e x c h a n g e r
conduc t ed by AI,
As of O c t o b e r 1965, W e s t i n g h o u s e w a t e r r e a c t o r fuel e l e m e n t s had a c c u m u -9
l a t ed in e x c e s s of 10 w e l d - o p e r a t i n g h o u r s wi thout a f a i l u r e . M o r e r e c e n t e x p e r i e n c e wi th h e a t e x c h a n g e r s in p r e s s u r i z e d - w a t e r - r e a c t o r (PWR) p l a n t s h a s
9 d e m o n s t r a t e d 1.5 x 10 t u b e - h o u r s w i th 11 f a i l u r e s , none of w h i c h w e r e i d e n t i fied as we ld f a i l u r e s ,
A s u r v e y of t u b e - w e l d p e r f o r m a n c e in s o d i u m s e r v i c e a l s o s u p p o r t s the
weld f a i l u r e - r a t e e s t i m a t e . E x a m i n a t i o n of s o m e of the s o d i u m s y s t e m s which
have a c c u m u l a t e d an i m p r e s s i v e a m o u n t of o p e r a t i n g e x p e r i e n c e g ives the v a l u e s
in Tab le I I I - 5 , C o n s i d e r i n g the s t e a m - g e n e r a t o r e x p e r i e n c e a lone g ives a b e s t - 8
e s t i m a t e f a i l u r e r a t e of 1.3 x 10 f a i l u r e s p e r w e l d - h o u r . If the h e a t e x c h a n g e r
and D o u n r e a y p r i m a r y - l o o p e x p e r i e n c e i s added to the s t e a m - g e n e r a t o r e x p e r i -_9
e n c e , the f a i l u r e - r a t e d r o p s a f ac to r of five to 2,6 x 10 f a i l u r e s p e r w e l d - h o u r .
T A B L E III-5
T U B E - W E L D HISTORIES
F a c i l i t y
H a l l a m N u c l e a r P o w e r F a c i l i t y ( H N P F )
Sodium R e a c t o r E x p e r i m e n t (SRE)
D o u n r e a y
E x p e r i m e n t a l B r e e d e r R e a c t o r II (EBR II)
R a p s o d i e
MSAR (Model S t e a m G e n e r a t o r )
A s s e m b l y
S t e a m g e n e r a t o r Hea t e x c h a n g e r
S t e a m g e n e r a t o r Hea t e x c h a n g e r
P r i m a r y loop
S t e a m g e n e r a t o r Hea t e x c h a n g e r
Hea t e x c h a n g e r
S t e a m g e n e r a t o r No, 1 S t e a m g e n e r a t o r No, 2 H e a t e x c h a n g e r
Tubes
3,720 8,400
2 0 0 316
-
730 3,026
8 8 8
59 38
2 7 3
Tube Welds
7,440 16,800
4 0 0 632
8,000
1,460 6,052
1,776
118 76
546
H o u r s
7,194 7,194
37,000 37,000
60 ,000
4 ,360 4 ,360
17,400
3,615 4,926 8,541
F a i l u r e s
0 0
0 0
0
1 0
0
0 0 1
A I - A E C - M E M O - 12717 40
Considering the above data and all of the additional tes t - loop experience and -9
faci l i t ies , the weld f a i lu re - ra t e of 1 x 10 failures per weld-hour appears to be
a reasonable es t ima te . This f a i lu re - ra te has been applied to all NaK-loop tube
joints in the sys tem. Where large weldments a r e involved, an es t imate of the
equivalent number of welds has been used,
b . Reactor Vessel
-7 The reac tor vesse l f a i lu re - r a t e of 10 failures per hour r ep resen t s an es t i
mate that the vesse l is equivalent to 100 tube welds in complexity,
c. Reactor Fuel
The reac to r fuel re l iabi l i ty is determined analytically by margin co r r e l a
t ions . These cor re la t ions for fuel growth and phase change were a major resu l t
of the SNAP 8 Exper imenta l Reactor (S8ER) test analysis and SNAP 8 Develop
mental Reactor (S8DR) design p rogram. The fuel e lements a re designed to p ro
vide a mean life of 36,000 hr to phase change with a deviation of 4115 hr. They
also have a calculated mean life of 156,000 hr to cladding rupture with a devia
tion of 31,250 h r . These dis tr ibut ions resu l t in a probability of failure for an -6 -5
element of 1.3 x 10 in 10,000 hr or 5,5 x 10 in 20,000. Combining these
probabi l i t ies in a Poisson expansion for the 295 elements in the core resu l t s in
a 0.99984 probabili ty of no m o r e than one failure in 10,000 hr and 0.99997 proba
bility of no more than two fai lures in 20,000, A rel iabi l i ty of 0.9999 is used as
the es t imated value under the assumption that loss of one or two elements late
in the sys tem life would be of no consequence. This is ext remely conservative
since S8ER operated successfully with 80% of i ts fuel elements cracked. By the
same reasoning the core re l iabi l i ty for 10,000 hr is est imated to be > 0.99999 or
essent ia l ly 1.0, d. Control Drums and Actuators
Each control drum and actuator is es t imated to have a failure ra te of 1 x
10 fai lures per hour. This is broken down to 0.6 x 10 for the actuator and
0.4 X 10 for the bea r ings . These es t imates a re from the tabulation of "Fa i lu re
Ra te s" published by AVCO for equipment judged to be s imi la r in design and appli
cation. In these tab les , s tepper moto r s a re es t imated to have a generic fai lure-- 6 -6 6
ra te between 0,22 x 10 and 0,71 x lO" and bearings range from 0,02 x 10 to 5,5 X 10 . Because of the redundant nature of the bearing it appears reasonable
AI-AEC-MEMO-12717 41
to a s s i g n a va lue of 0,4 x 10 to the two s e t s of b e a r i n g s for e a c h d r u m . The
d r u m s t h e m s e l v e s a r e not c o n s i d e r e d to have a f a i l u r e - r a t e which would be a
s ign i f i can t add i t ion to a 1 x 10 f a i l u r e - r a t e for the d r i v e c o m p o n e n t .
A f a i l u r e - m o d e and effects s tudy of the ten c o n t r o l d r u m s can b e s u m m a r i z e d
a s fo l lows:
1) Two d r u m s c a n r e m a i n in the shu tdown p o s i t i o n at the beg inn ing-o f -
life (BOL) wi th the r e s u l t be ing a life l i m i t of a p p r o x i m a t e l y 42 m o
for r e a c t o r o p e r a t i o n .
2) T h r e e d r u m s can r e m a i n s e i z e d in any o p e r a t i n g pos i t i on a f t e r hot
B O L and not affect the 2 0 , 0 0 0 - h r o p e r a t i o n .
3) T h r e e d r u m s s e i z e d in the cold c r i t i c a l pos i t i on be fo re hot B O L wi l l
l i m i t r e a c t o r o p e r a t i o n to about 54 m o .
4) T h r e e d r u m s s e i z e d in the h o t - B O L pos i t i on wi l l m a k e the r e a c t o r
shutdown l i m i t e d in a p p r o x i m a t e l y 20 m o .
5) C o n t r o l i s a s s u m e d to b e e i t h e r s i m u l t a n e o u s on a l l ten d r u m s or
s e q u e n t i a l in s u c h a m a n n e r tha t u n d e r n o r m a l o p e r a t i n g cond i t i ons
a l l d r u m s wi l l be in r e l a t i v e l y the s a m e pos i t i on at any g iven t i m e .
The r e l i a b i l i t y of the r e a c t i v i t y c o n t r o l - d r u m s y s t e m i s c a l c u l a t e d by a
b i n o m i a l e x p a n s i o n a l lowing t h r e e out of t en d r u m s to fail a t any t i m e . T h i s
a p p e a r s to be a r e a s o n a b l e a p p r o x i m a t i o n to the c o n d i t i o n s ; the only c r i t i c a l
c o m b i n a t i o n of e v e n t s -which i s i g n o r e d i s t he s i m u l t a n e o u s f a i l u r e of t h r e e
d r u m s a t hot B O L . The p r o b a b i l i t y of t h i s o c c u r r e n c e i s i n s ign i f i can t . The
r e s u l t i n g e s t i m a t e d r e l i a b i l i t y for the c o n t r o l d r u m s i s 0.999999 for 10,000 h r
and 0.99987 for 20 ,000 h r .
e . P r i m a r y P i p i n g
This p o r t i o n of the s y s t e m inc l udes a l l i n t e r c o n n e c t i n g piping of the p r i m a r y
N a K - l o o p wi th the e x c e p t i o n of the c o n v e r t e r m a n i f o l d s and p u m p m a n i f o l d s , A - 8
f a i l u r e - r a t e of 3 x 10 f a i l u r e s p e r hou r i s a s s i g n e d on the b a s i s of an e s t i m a t e d
30 t u b e - w e l d s .
A I - A E C - M E M O - 12717 42
f. P u m p s
E a c h of the four p u m p a s s e m b l i e s c o n t a i n s t h r e e t h r o a t s ; two a r e in s e r i e s
for the p r i m a r y s y s t e m and one i s for the r e s p e c t i v e H R L . Coupled to t h e p u m p
a r e t h r e e T E m o d u l e s . The m o d u l e s a r e e l e c t r i c a l l y p a r a l l e l e d to the pump bus
b a r s . The p u m p t h r o a t s a r e e l e c t r i c a l l y in s e r i e s . The p r i m a r y piping to the
pump c o n v e r t e r i s c o n s i d e r e d to be d o u b l e - c o n t a i n e d .
P o r t i o n s of the p u m p and c o n v e r t e r p ip ing c o n s i d e r e d for the p r i m a r y loop
inc lude eight p u m p w e l d s p e r p u m p and 23 c o n v e r t e r - p i p i n g we lds d o u b l e -_9
con ta ined p e r p u m p . Us ing the t u b e - w e l d f a i l u r e - r a t e of 10 f a i l u r e s p e r hour
r e s u l t s in a r e l i a b i l i t y of 0 .99968 for 10,000 h r , or 0.99936 for 20,000 hr con
s i d e r i n g a l l four p u m p a s s e m b l i e s .
The r e l i a b i l i t y for the p u m p c o n v e r t e r e l e c t r i c a l p e r f o r m a n c e c o n s i d e r s a l l
twe lve c o n v e r t e r m o d u l e s . A s h o r t - c i r c u i t condi t ion in the m o d u l e s is of no
c o n s e q u e n c e s i n c e the bus b a r s to the p u m p p r o v i d e a m u c h b e t t e r s h o r t to
g round than any o t h e r c r e d i b l e p o s t u l a t e d s h o r t f r o m a f a i lu re condi t ion . An
o p e n - c i r c u i t in one m o d u l e out of the twe lve m o d u l e s would r e d u c e the to ta l s y s -_7
tern e l e c t r i c a l p o w e r c a p a b i l i t y about 1% o r 250 w a t t s . A f a i l u r e - r a t e of 1 x 10
f a i l u r e s p e r h o u r p e r m o d u l e i s a s s i g n e d for th i s m o d e . This i s one -ha l f of the
f a i l u r e - r a t e a s s i g n e d to the m a i n c o n v e r t e r m o d u l e s for both sho r t i ng and o p e n -
c i r c u i t m o d e s . The b a s i s for th i s f a i l u r e - r a t e i s d e s c r i b e d in the p a r a g r a p h s
c o v e r i n g the m a i n c o n v e r t e r r e l i a b i l i t y e s t i m a t e s . It i s a s s u m e d that one pump
c o n v e r t e r out of the twe lve can fail wi th no s ign i f ican t effect on the s y s t e m . Using
a b i n o m i a l expans ion for t h i s c r i t e r i o n r e s u l t s in a p u m p c o n v e r t e r e l e c t r i c a l r e
l i ab i l i t y of 0.99986 for 10,000 h r o r 0.99962 for 20,000 h r . This r e l i a b i l i t y is
c h a r g e d to the p r i m a r y s y s t e m . V a r i o u s c o m b i n a t i o n s of p u m p - m o d u l e f a i l u r e s
could r e s u l t in f u r t h e r l o s s of s y s t e m p o w e r wi thout c o m p l e t e power l o s s , but
th i s p o s s i b i l i t y h a s b e e n i g n o r e d for the p r e s e n t a n a l y s i s .
P o r t i o n s of the p u m p and c o n v e r t e r p iping c o n s i d e r e d for e a c h H R L inc lude
four e a c h of p u m p and t u b e - w e l d s , and 7,5 equ iva l en t tube-welds for the c o n t a i n
m e n t j a c k e t s u r r o u n d i n g the m o d u l e s , for a to ta l of 15.5 . Using the t u b e - w e l d _9
f a i l u r e - r a t e of 10 f a i l u r e s p e r hour r e s u l t s in a r e l i a b i l i t y of 0.99985 for
10,000 h r or 0,99969 for 20 ,000 , A f a i l u r e in th i s c a t e g o r y wil l fail only the
H R L invo lved .
A I - A E C - M E M O - 12717 43
The p u m p and c o n v e r t e r e l e c t r i c a l r e l i a b i l i t y w h i c h in f luences e a c h H R L
IS d e t e r m i n e d by the e l e c t r i c a l - b u s bond a r e a s . E a c h p u m p h a s the equ iva len t
of 6 bond a r e a s m s e r i e s . A f a i l u r e of any bond wi l l r e s u l t m the l o s s e q u i v a
len t of the r e s p e c t i v e H R L . The f a i l u r e - r a t e for an e l e c t r i c a l bond i s a s s u m e d _9
to be 10 f a i l u r e s p e r h o u r , on the a s s u m p t i o n tha t an e l e c t r i c a l bond i s about
the s a m e a s a t u b e - w e l d for f a i l u r e - r a t e c o n s i d e r a t i o n s . The r e s u l t i n g r e l i a
b i l i ty IS 0,99994 for 10,000 h r o r 0 .99988 for 20,000 h r for e a c h p u m p .
g. E x p a n s i o n C o m p e n s a t o r Unit (ECU)
B e c a u s e the p r i m a r y f a i l u r e m o d e c o n s i d e r e d for the ECU is l e a k a g e t h r o u g h
the b e l l o w s a s s e m b l y , e a c h un i t h a s r e d u n d a n t b e l l o w s . A p r i m a r y c o n t a i n m e n t
be l l ows funct ions n o r m a l l y con ta in ing the NaK t h r o u g h o u t the expans ion c y c l e ,
and a s e c o n d a r y i s p r o v i d e d to con ta in the NaK and a l low u n i n t e r r u p t e d function
of the un i t m even t of a l eak t h r o u g h the p r i m a r y . P r e v i o u s a n a l y s i s of the b e l
lows for the SNAP lOA c o m p e n s a t o r i n d i c a t e d a s t r e s s - m a r g i n r e l i a b i l i t y of e s
s e n t i a l l y un i ty , A w e l d - f l a w f r e q u e n c y a n a l y s i s of the SNAP lOA b e l l o w s e x
p e r i e n c e i n d i c a t e d r e l i a b i l i t y for f r e e d o m f r o m f laws of a p p r o x i m a t e l y 0.997 p e r
a s s e m b l y . In add i t ion it i s c o n s e r v a t i v e l y e s t i m a t e d tha t e a c h a s s e m b l y wi l l
have a t i m e - d e p e n d e n t f a i l u r e - r a t e equ iva l en t to 180 t u b e - w e l d s . T h e s e v a l u e s
r e s u l t in r e d u n d a n t b e l l o w s p r o v i d i n g a r e l i a b i l i t y of 0 ,99998 for 10,000 h r o r
0.9999 for 20,000 h r for one c o m p e n s a t o r un i t . F o u r c o m p e n s a t o r s a r e r e q u i r e d
for the p r i m a r y s y s t e m and one c o m p e n s a t o r i s r e q u i r e d for e a c h H R L .
h. M a m C o n v e r t e r P i p i n g
The c o n v e r t e r c o n s i s t s of 24 4 - p a c k a s s e m b l i e s . The man i fo ld ing of the
p r i m a r y H R L into and out of the 4 - p a c k s wi l l be d o u b l e - c o n t a i n e d , a l though
th i s f e a t u r e w a s not i n c o r p o r a t e d in to the d e s i g n m t h i s s tudy , f ea s ib l e m e t h o d s
of d o u b l e - c o n t a i n m e n t w e r e r e v i e w e d and one wi l l be i n c o r p o r a t e d a s the c o n
v e r t e r d e s i g n evo lves m the nex t p h a s e of the p r o g r a m . The H R L mani fo ld ing
on the co ld s ide of the c o n v e r t e r s i s m a n i f o l d e d into the four i s o l a t e d l o o p s .
E a c h loop p r o v i d e s the h e a t r e j e c t i o n for s ix 4 - p a c k a s s e m b l i e s . The r e l i a b i l i t y
e s t i m a t e s a r e b a s e d on weld jo in t s a s fol lows
P r i m a r y Manifolding
32 h e a d e r s , e a c h wi th 17 d o u b l e - c o n t a i n e d w e l d s a s fol lows
7 m o d u l e p ipe w e l d s ,
A I - A E C - M E M O - 1 2 7 1 7 44
1 c a p weld ;
9 s e a m weld on h e a d e r (4 i n . / w e l d equ iva len t ) ; and
1 p i p e - t o - h e a d e r weld (not d o u b l e - c o n t a i n e d ) .
H R L Manifo ld ing;
6 4 - p a c k s p e r loop wi th 24 w e l d s p e r 4 - p a c k as fol lows:
8 m o d u l e ;
6 p a c k - t o - h e a d e r ; and
10 s e a m - w e l d equ iva l en t , m a k i n g a to t a l of 144 we lds p e r loop .
_9 A s s i g n e d a we ld f a i l u r e - r a t e of 10 p e r we ld and accoun t ing for the r e d u n d a n c y
of the d o u b l e - c o n t a i n e d p ip ing g ives a r e l i a b i l i t y for the p r i m a r y mani fo ld ing of
0,99968 for 10,000 h r o r 0,99935 for 20,000 h r .
F o r the H R L ' s the r e l i a b i l i t y of the mani fo ld ing for e a c h loop i s c a l c u l a t e d
to be 0.9986 for 10,000 h r o r 0,9971 for 20,000 h r ,
i . H R L P i p i n g
This p o r t i o n of the s y s t e m i nc ludes a l l of the i n t e r c o n n e c t i n g piping of the
H R L ' s wh ich c o n n e c t the c o n v e r t e r 4 - p a c k s , p u m p s , r a d i a t o r s , and E C U ' s
into four i s o l a t e d l o o p s . An e s t i m a t e d t u b e - w e l d c o m p l e x i t y equ iva len t to 16 - 8
w e l d s p e r loop g i v e s an a s s i g n e d f a i l u r e - r a t e of 1,6 x 10 f a i l u r e s p e r hour p e r
H R L . Any l e a k in the p iping fa i ls only the H R L involved ,
j . R a d i a t o r
The r a d i a t o r i s s e g m e n t e d into four p a r t s wi th e a c h s e g m e n t be ing an i s o
l a t ed p o r t i o n of the r e s p e c t i v e H R L . The funct ional f a i l u r e - r a t e for each s e g -_7
m e n t is e s t i m a t e d on the b a s i s of a p p r o x i m a t e l y 200 t u b e - w e l d s to be 2 x 10
f a i l u r e s p e r h o u r . In add i t ion to t h i s f a i l u r e - r a t e is the m e t e o r o i d - p u n c t u r e _7
h a z a r d wh ich i s s e t at 1.25 x 10 p u n c t u r e s p e r hour for the p r e s e n t de s ign .
Th i s r a t e i s e s t a b l i s h e d by the m e t e o r o i d - i n f l u x c r i t e r i a and the a r m o r t h i c k n e s s
s e l e c t e d .
k. C o n v e r t e r E l e c t r i c a l
Two f a i l u r e m o d e s a r e c o n s i d e r e d in the eva lua t ion of the c o n v e r t e r . An
open c i r c u i t in any c o n v e r t e r m o d u l e could c a u s e r educ t i on in to t a l power
A I - A E C - M E M O - 1 2 7 1 7 45
T 1 1 I I
22 OUT OF 24 4-PACKS
AT LEAST / ^ 23 OUT OF 24 4-PACKS
DIODE SHORT PROTECTION MODULE FAILRATE ASSUME 50/50 FOR
SHORT TO GROUND OR OPEN DIODE FAILURE RATES:
OPEN 2.6 X 10-8 LOSS OF SHORT PROTECTION, 1.14 x lO ' '
, ALL 24 4-PACKS
J I I I I I I 10-°
1-13-69 UNC
10' CONVERTER MODULE FAILURE RATE (4 modules '4-pack)
Figure I I I - l l . The rmoe lec t r i c Conver ter Full-and Pa r t i a l -Power Reliabil i ty (Elect r ica l )
AI-AEC -MEMO-1 2717 46
c a p a b i l i t y . A s h o r t - c i r c u i t to g round wi th in any c o n v e r t e r m o d u l e could c a u s e
a l m o s t t o t a l l o s s of power c a p a b i l i t y wi thout s o m e m e a n s of i s o l a t i n g the faul t .
To p r o t e c t a g a i n s t the s h o r t - c i r c u i t cond i t ion , each 4 - p a c k a s s e m b l y i s d i o d e -
p r o t e c t e d so tha t a s h o r t to g r o u n d wi l l only c a u s e the l o s s of the r e s p e c t i v e 4 -
pack . The add i t ion of d iodes c a u s e s a s l igh t i n c r e a s e in o p e n - c i r c u i t h a z a r d
due to the p o s s i b i l i t y of a d iode f a i l u r e . In m a n n e d s y s t e m s the d iodes would
be r e a d i l y a c c e s s i b l e for r e p l a c e m e n t , but the p o s s i b i l i t y h a s not been con
s i d e r e d in t h i s a n a l y s i s .
In a p a p e r p r e s e n t e d at WESCON in Augus t 1962 by D, R. E a r l e s and M. F .
E d d i n s t i t l e d " F a i l u r e T h e r b l i g F a i l u r e R a t e s " it i s e s t i m a t e d tha t power d iodes
have the m o d e f a i l u r e - r a t e s shown in Tab le I1I-6,
T A B L E III-6
P O W E R DIODE " T H E R B L I G " F A I L U R E - R A T E S
Mode F a i l u r e - R a t e x 10 / h r
Open
Dri f t
Leak
Sho r t
U n s t a b l e
0,026
0,02
0,005
0,021
0,068
a s s u m e d l o s s of s h o r t - c i r c u i t p r o t e c t i o n
0,140
The f a i l u r e - r a t e of a diode which r e s u l t s in an open c i r c u i t i s a s s u m e d to - 8
be 2,6 X 10 f a i l u r e s p e r h o u r , and the f a i l u r e - r a t e which r e s u l t s in l o s s of _7
s h o r t - c i r c u i t p r o t e c t i o n i s a s s u m e d to be 1,14 x 10 f a i l u r e s p e r h o u r .
A s s u m p t i o n of f a i l u r e - r a t e s for the c o n v e r t e r e l e m e n t s i s c r i t i c a l to the
p o w e r r a t i n g v e r s u s r e l i a b i l i t y for the s y s t e m ; for t h i s r e a s o n the c o n v e r t e r
r e l i a b i l i t y h a s b e e n s tud ied p a r a m e t r i c a l l y . F o r s tudy p u r p o s e s i t w a s a s s u m e d
tha t the c o n v e r t e r m o d u l e f a i l u r e - r a t e s for both s h o r t i n g to g round and o p e n --7
c i r c u i t a r e equa l ; a to ta l f a i l u r e - r a t e for a m o d u l e of 2 x 10 f a i l u r e s p e r hour -7 -7
i n d i c a t e s f a i l u r e - r a t e s of 1 x 10 for s h o r t i n g and 1 x 10 for o p e n - c i r c u i t .
T h e s e f a i l u r e - r a t e s w e r e v a r i e d o v e r a r a n g e of s e v e r a l o r d e r s of m a g n i t u d e
for c a l c u l a t i n g c o n v e r t e r s y s t e m r e l i a b i l i t y . The r e s u l t s a r e shown in F i g u r e I I I - 1 1 .
A I - A E C - M E M O - 1 2 7 1 7 47
The p r e s e n t d e m o n s t r a t i o n l eve l of m o d u l e f a i l u r e - r a t e s i s in the r a n g e of _ 5
5 x 1 0 f a i l u r e s p e r h o u r . Th i s r e s u l t s f r o m l i m i t e d t e s t e x p e r i e n c e and by
no m e a n s r e p r e s e n t s an e x p e c t e d l o w e r l i m i t . It a p p e a r s r e a s o n a b l e to a s s u m e
tha t c o m p o n e n t t e s t i n g of m o d u l e s could d e m o n s t r a t e a m o d u l e f a i l u r e - r a t e to
b e , a t m o s t , 10 f a i l u r e s p e r h o u r t h r o u g h a c c e l e r a t e d o r m a r g i n t e s t s a s we l l
a s p e r f o r m a n c e e n d u r a n c e t e s t s . It i s a s s u m e d tha t s y s t e m d e v e l o p m e n t and _7
qua l i f i ca t ion t e s t s cou ld f u r t h e r r e d u c e t h i s l i m i t e s t i m a t e to abou t 2 x 1 0 f a i l u r e s p e r h o u r . The r e s u l t i n g c o n v e r t e r r e l i a b i l i t i e s shown in F i g u r e I I I - l l for
_7 a m o d u l e f a i l u r e - r a t e of 2 x 10 a r e the full-and p a r t i a l - p o w e r v a l u e s u s e d for
c a l c u l a t i n g s y s t e m r e l i a b i l i t y ,
E , SYSTEM T R A D E - O F F S
The r e f e r e n c e s y s t e m d e s c r i b e d above h a s b e e n s tud ied in d e t a i l for a
spec i f ic o p e r a t i n g poin t , but the s a m e d e s i g n c o n c e p t could be u s e d o v e r a wide
r a n g e of p o w e r r e q u i r e m e n t s . The r e s u l t s of a p a r a m e t r i c a n a l y s i s a r e p r e
sen t ed in th i s s e c t i o n for the a n t i c i p a t e d p o w e r r a n g e of i n t e r e s t for the 1 9 7 0 ' s .
In th i s s tudy the key c o m p o n e n t s (the r e a c t o r and the TE t u b u l a r m o d u l e s ) a r e
unchanged o v e r the e n t i r e r a n g e , and the o t h e r c o m p o n e n t s , e, g, p u m p s , e x
pans ion c o m p e n s a t o r s , and r a d i a t o r , a r e s i m i l a r in des ign bu t r e s i z e d for the
a p p r o p r i a t e p e r f o r m a n c e .
To f ac i l i t a t e the s y s t e m p a r a m e t r i c a n a l y s e s , a r e a c t o r — T E s y s t e m c o m
p u t e r code w a s d e v e l o p e d . The code input r e q u i r e m e n t s a r e c o n v e r t e r c l ad t e m
p e r a t u r e s , e l e c t r i c a l p o w e r l e v e l , c o n v e r t e r t u b u l a r m o d u l e c h a r a c t e r i s t i c s ,
and g e n e r a l s y s t e m g e o m e t r i c c o n s t r a i n t s . The c a l c u l a t e d r e s u l t s a r e the
t h e r m a l - p o w e r d i s t r i b u t i o n , s y s t e m o p e r a t i n g t e m p e r a t u r e s , r a d i a t o r a r e a ,
e f f i c i e n c i e s , f l o w r a t e s , p r e s s u r e d r o p s , and w e i g h t s . This code w a s u s e d to
d e t e r m i n e s y s t e m weigh t and a r e a c h a r a c t e r i s t i c s for power l e v e l s of 15, 25 ,
and 35 kwe a t r e a c t o r o u t l e t - t e m p e r a t u r e s of 1200, 1250, and 1300°F ; r e a c t o r
coo lan t A T ' S of 200, 250, and 3 0 0 ° F ; C a r n o t e f f i c i enc ies of 25 , 30, 35 , 40 , and
45%; and two r a d i a t o r d e s i g n s .
The two r a d i a t o r d e s i g n s w e r e s e l e c t e d a s a r e s u l t of d e t a i l e d r a d i a t o r
a n a l y s e s . T h e s e a n a l y s e s , d e s c r i b e d f u r t h e r in Sec t ion I V - D - 1 , d e t e r m i n e d
the r a d i a t o r we igh t vs a r e a t r a d e - o f f for the t h e r m a l cond i t ions of the r e f e r e n c e
A I - A E C - M E M O - 1 2 7 1 7 48
25-kwe s y s t e m . The r e f e r e n c e d e s i g n r a d i a t o r w a s p icked a t the m i n i m u m 2
we igh t point , which w a s found to o c c u r at about 1400 ft . This r a d i a t o r h a s a
fin e f f e c t i v e n e s s of 0,80 a t the r e f e r e n c e t e m p e r a t u r e s and a weight , inc luding 2
s t r u c t u r e , of 1.84 l b / f t , The o t h e r point on the c u r v e s e l e c t e d c o r r e s p o n d e d 2
to the a r e a , 1287 ft , a v a i l a b l e for the S a t u r n - I V B W o r k s h o p r a d i a t o r and r e p r e s e n t e d a h e a v i e r d e s i g n tha t could be bene f i c i a l w h e r e an a r e a l im i t a t i on w a s
invo lved . This r a d i a t o r had a fin e f f ec t i venes s of 0.87 at the r e f e r e n c e t e m p e r a -2
t u r e s and a we igh t of 2.19 lb / f t , By ana lyz ing s y s t e m s wi th both r a d i a t o r d e
s i g n s , a t r u e a r e a - w e i g h t t r a d e - o f f a t a given power l eve l can be ob ta ined . F i g
u r e I I I -12 shows how the fin e f f e c t i v e n e s s of the two d e s i g n s v a r i e s with co ld -
c lad t e m p e r a t u r e s a t the TE m o d u l e s .
F i g u r e s I I I - 1 3 , - 1 4 , and -15 show the r e s u l t s of the c o m p u t e r c a l c u l a t i o n s
for 15, 25 , and 35 kwe wi th the h e a v i e r r a d i a t o r . At e a c h C a r n o t eff ic iency
poin t , s y s t e m c h a r a c t e r i s t i c s w e r e d e t e r m i n e d for r e a c t o r coo lan t A T ' S of 200,
250, and 3 0 0 ° F . The AT t h a t r e s u l t e d in m i n i m u m weight was s e l e c t e d and is
shown on the f i g u r e s . In a l l c a s e s the r e f e r e n c e c o n v e r t e r t ubu l a r modu le d e s i g n
w a s he ld fixed wi th the n u m b e r of t u b u l a r m o d u l e s and o p e r a t i n g t e m p e r a t u r e s
v a r y i n g . As C a r n o t e f f ic iency d e c r e a s e s , the r a d i a t o r t e m p e r a t u r e i n c r e a s e s
and r a d i a t o r fin e f f e c t i v e n e s s d e c r e a s e s . Th i s effect , coupled with an a s s o c i a t e d
d e c r e a s e in c o n v e r t e r dev i ce e f f ic iency , r e s u l t s in m i n i m u m r a d i a t o r a r e a o c
c u r r i n g a t C a r n o t e f f i c i enc i e s above the u s u a l 20%.
As C a r n o t e f f ic iency i n c r e a s e s , the coo lan t AT a s s o c i a t e d wi th m i n i m u m
we igh t d e c r e a s e s b e c a u s e the r e a c t o r t h e r m a l - p o w e r d e c r e a s e s ; th i s r e s u l t s
in l ower f l o w r a t e s and p r e s s u r e d r o p , and r e d u c e d p u m p i n g - s y s t e m weigh t .
S i m i l a r c u r v e s w e r e g e n e r a t e d for the l i g h t e r - w e i g h t r a d i a t o r de s ign . The
two s e t s of c u r v e s w e r e c o m b i n e d , a s i l l u s t r a t e d in F i g u r e I I I -16 , and the
enve lope of m i n i m u m we igh t e s t a b l i s h e d . F i g u r e s I I I -17 , - 1 8 , and -19 show
t h e s e m i n i m u m - w e i g h t e n v e l o p e s a t power l e v e l s of 15, 25 , and 35 kwe.
F i g u r e s I I I -20 , - 2 1 , and -22 show how s y s t e m weight , a r e a , and t h e r m a l
po-wer v a r y wi th e l e c t r i c a l power for m i n i m u m - w e i g h t s y s t e m s . T h e s e c u r v e s
w e r e e s t a b l i s h e d by s e l e c t i n g the m i n i m u m - w e i g h t point for e a c h r e a c t o r o u t l e t -
t e m p e r a t u r e on F i g u r e s I I I -17 , - 1 8 , and -19 and t abu la t ing the a s s o c i a t e d r a d i a t o r
A I - A E C - M E M O - 12717 49
100 200 300 400 500 600 700 COLD-JUNCTION TEMPERATURE "F
1 15 69 UNC 7759-5273
Figure III-12, Radiator F m Effectiveness
1
CARNOT EFFICIENCY %s
T -r
Mr
REACTOR OUTLET TEMPERATURE °F
'25
REACTOR COOLANT AT 2 5 0 ° F - H 200° F = A
X J . X 600 800 1000
RADIATOR AREA, ft2
1200 1400
7759-5274
Figure III-13. 15-kwe System Weight and Area
AI-AEC-MEMO-12717 50
I J -
45 CARNOT EFFICIENCY, %
REACTOR COOLANT A T • = 300"F • = 250''F A = 200''F
1000 1200 1400 1600 1800 2000
RADIATOR AREA, ft^
2200 2400
1-13-69 UNC 7759-5275
Figure III-14. 25-kwe System Weight and Area
1 1 1 r
_-CARN0T EFFICIENCY, %
Lu-L n » 101
REACTOR COOLANT AT
• 300OF
• 250°F
A 200°F
J - J . 0 ' 1800 2000 2200
1-15-69 UNC
2400 2600 2800
RADIATOR AREA, ft2
3000 3200 3400
7759-5276
Figure III- 15. 35-kwe System Weight and Area
AI-AEC-MEMO-12 717 51
1 1 r
, CARNOT EFFICIENCY,".
4^r
• = 300°F • = 250° F A = 200°F
J - J -1200 1400 1600 1800
RADIATOR AREA, ft^
2000 2200
Figure III-16. 25-kwe System, 1250°F Reactor Out le t -Temperature
6 -
5 -
REACTOR OUTLET TEMPERATURE, OF
o ^ r J . _L J -400 600 800 1000
RADIATOR AREA, ft^
1200 1400
Figure III-17. 15-kwe System Weight and Area (Unshielded)
AI-AEC-MEMO-12717 52
10
REACTOR OUTLET TEMPERATURE (op)
360
320 |_ X
o LU
280 I
240
2400
RADIATOR AREA (fr)
Figure III-18.
8-JY25-119-42
25-kwe System Weight and Area (Unshielded)
10
oV/J _L J_ 0 1600
1 14 69 UNC
1800 2000 2200 2400 2600 2800 F.2
3000 3200 3400 3600
7759 5280 RADIATOR AREA ft
Figure III-19. 35-kwe System Weight and Area (Unshielded)
AI-AEC-MEMO-12717 53
9 -
REACTOR OUTLET TEMPERATURE, °F
20 25 30 35 ELECTRICAL POWER kwe
1 14 69 UNC 7759-5281
Figure III-20. System Minimum Weight
1-14-69 UNC
20 25 ELECTRICAL POWER, kwe
30 35
7759 5282
Figure I I I -21 . System Radiator Area , Minimum-Weight Systems
AI-AEC-MEMO-12717 54
° 5
3 -
20 25 ELECTRICAL POWER, kwe
1-14-69 UNC
30 35
7759-5283
Figure III-22. Reactor Thermal Power, Minimum-Weight Systems
a rea and r eac to r the rmal power. Thermal power in Figure III-22 is shown as
a band because of the scat ter in the calculated points and the small variation
with t e m p e r a t u r e . It should be noted that slight differences in the minimum-
weight values shown on the p a r a m e t r i c curves and the weight es t imates for the
re ference sys tem a re due to c loser definition and refinement of the la t ter .
The inherent modular i ty of the r eac to r — TE sys tem and its adaptability
to any po'wer level over a wide range of in te res t is c lear ly shown by the resu l t s
of this ana lys is .
AI-AEC-MEMO-12717 55
TABLE IV-1
SNAP REACTOR OPERATING EXPERIENCE
R e a c t o r Date C r i t i c a l /
Shutdown
T h e r m a l P o u ' e r (kwt)
T e m p e r a t u r e (°F)
T h e r m a l E n e r g y
(kwt -h r )
T i m e at P o w e r and T e m p e r a t u r e
> I
>
O
o
-J
S N A P E x p e r i m e n t a l R e a c t o r (SER)
SNAP D e v e l o p m e n t a l R e a c t o r (SDR)
SNAP 8 E x p e r i m e n t a l R e a c t o r (S8ER)
SNAP lOA F l i gh t S y s t e m No. 3 (S lOA-FS-3 )
SNAP lOA F l i g h t Systemi No. 4 (S lOA-FS-4 )
S e p t e m b e r 1959/ D e c e m b e r I960
A p r i l 1 9 6 1 / D e c e m b e r 1962
May 1963 / A p r i l 1965
J a n u a r y 1965 / M a r c h 1966
A p r i l 1965 / May 1965
50
65
600
43
1200
1200
1300
1000
1000
225,000
273,000
5,100,000
382,944
41 ,000
1800 h r a t 1 2 0 0 ° F 3500 h r above 9 0 0 ° F
2800 h r at 1 2 0 0 ° F 7700 h r above 9 0 0 " F
1 y r a t 1 3 0 0 ° F and 400 to 600 kwt
10,005 h r
43 days
IV. SUBSYSTEMS
A. R E A C T O R / S H I E L D ASSEMBLY
1. T e c h n o l o g y S ta tu s
The r e a c t o r d e s i g n u s e d for t h i s s y s t e m s tudy i s b a s e d l a r g e l y on the t e c h
nology deve loped o v e r the p a s t 10 y e a r s in the SNAP R e a c t o r P r o g r a m . Dur ing
th i s t i m e 15 r e a c t o r s h a v e b e e n bu i l t for d e v e l o p m e n t , qua l i f i ca t ion , and flight
t e s t s ; f ive h a v e b e e n o p e r a t e d in s u s t a i n e d n u c l e a r power t e s t s , and the o the r
t en w e r e u s e d for n o n - n u c l e a r d e v e l o p m e n t and qua l i f i ca t ion t e s t s . In addi t ion ,
m a n y h u n d r e d s of t h o u s a n d s of t e s t h o u r s h a v e been a c c u m u l a t e d on r e a c t o r
c o m p o n e n t s . T a b l e IV-1 s u m m a r i z e s the n u c l e a r t e s t o p e r a t i o n e x p e r i e n c e ,
which t o t a l s about 3 5,000 h r to d a t e . The one y e a r of o p e r a t i o n of the SNAP 8
E x p e r i m e n t a l R e a c t o r (S8ER) a t power l e v e l s b e t w e e n 400 and 600 kwt at 1300°F
NaK ou t l e t t e m p e r a t u r e and the con t inuous 10 ,000-hour o p e r a t i o n of the SNAP
1 OA r e a c t o r a s a p a r t of a c o m p l e t e r e a c t o r — T E s y s t e m t e s t a r e c o n s i d e r e d to
be of p a r t i c u l a r s i g n i f i c a n c e .
The s ix th r e a c t o r t e s t i s c u r r e n t l y be ing s t a r t e d on the SNAP 8 D e v e l o p
m e n t a l R e a c t o r (S8DR) shown wi th o n e - h a l f the r e f l e c t o r r e m o v e d in F i g u r e I V - 1 .
The t e s t ob j ec t ives inc lude 10,000 h r of h i g h - p o w e r o p e r a t i o n , 500 h r of which i s
a t 1000 kwt, 1 1 0 0 ° F , and the r e m a i n i n g 9500 h r at 600 kwt, 1 3 0 0 ° F . In add i t ion ,
s e v e r a l shutdown and r e s t a r t t e s t s a r e s c h e d u l e d .
A s a r e s u l t of the d e v e l o p m e n t and t e s t e x p e r i e n c e ga ined fronn the SNAP
p r o g r a m s , the t echno logy s t a t u s of the z i r c o n i u m h y d r i d e type r e a c t o r i s c o n s i d
e r e d to be s\ifficiently a d v a n c e d to a s s u r e i t s a v a i l a b i l i t y for space m i s s i o n s in
the e a r l y to m i d - 1 9 7 0 ' s ,
2. R e a c t o r S u b s y s t e m D e s c r i p t i o n and P e r f o r m a n c e
P r e l i m i n a r y d e s i g n and d e v e l o p m e n t w o r k con t inues on the r e f e r e n c e z i r
c o n i u m h y d r i d e r e a c t o r . I ts d e s i g n h a s b e e n u s e d for a l l of the r e a c t o r — T E
s y s t e m s s tud ied and p r e s e n t e d in th i s r e p o r t .
The r e f e r e n c e z i r c o n i u m h y d r i d e r e a c t o r des ign , i l l u s t r a t e d in F i g u r e I V - 2 ,
i s s i m i l a r to the S8DR, e x c e p t for m o d i f i c a t i o n s i n c o r p o r a t e d to m a n r a t e the
s y s t e m and p e r m i t o p e r a t i o n wi th in an e n c l o s e d sh i e ld . F o r e x a m p l e , the n u m
b e r of f u e l - m o d e r a t o r e l e m e n t s h a s been i n c r e a s e d f r o m 211 to 295 and the
A I - A E C - M E M O - 1 2 7 1 7 57
F i g u r e I V - 1 , SNAP 8 D e v e l o p m e n t R e a c t o r Ground T e s t A s s e m b l y
n u m b e r of c o n t r o l drumis h a s been i n c r e a s e d f r o m 6 to 10 to p r o v i d e h i g h e r d e -
d e s i g n m a r g i n s and a w i d e r r a n g e of power and l i f e t i m e c a p a b i l i t i e s . In a d d i
t ion, the r e f l e c t o r / c o n t r o l - d r u m d e s i g n h a s been changed to p c r i n i t cool ing by
the l i q u i d - m e t a l coo lan t e n t e r i n g the r e a c t o r , s i nce the r e f l e c t o r cannot be
cooled by d i r e c t r a d i a t i o n to s p a c e a s h a s b e e n the c a s e with p r e v i o u s SNAP
r e a c t o r s .
The rninimiumL p e r f o r m a n c e ob jec t ive for the r e a c t o r i s to p r o v i d e 600 kw of
t h e r m a l power a t a coolant o u t l e t - t e m p e r a t u r e of 1300° F for 20,000 h r . The
c a l c u l a t e d p e r f o r m a n c e enve lope i s shown in F i g u r e I V - 3 .
The r e a c t o r con f igu ra t ion is shown in F i g u r e I V - 4 . Th i s r e a c t o r , l ike a l l
p r e c e d i n g z i r c o n i u m h y d r i d e r e a c t o r s , u s e s the s o d i u m - p o t a s s i u m i e u t e c t i c
N a K - 7 8 a s the coo lan t . The NaK e n t e r s the b a s e of the r e a c t o r v e s s e l at 1100°F
and flows a r o u n d d r y w e l l s which con ta in the l e f l e c t o r c o n t r o l d r u m s . The
A I - A E C - M E M O - 1 2 7 1 7
58
REFLECTOR COOLING PASSAGE
FUEL ELEMENT
FIXED REFLEQOR
CONTROL DRUM ACTUATOR
BEARING
BeO-POISON CONTROL DRUM
DIMENSIONS
HEIGHT-36 1/4 m DIAM - 21 5/8 m
OUTLET PIPE (TYPICAL)
Figure IV-2. Zirconium Hydride Reactor , Reference Design
AI-AEC-MEMO-12717 59
IbUU
1200
900
600
300
0
-
. _ /
-
-
—
-
1 ' 1 ' ,1800 F MAXIMUM BeO
/ / J...^
1
S. FUEL GROWTH ANON. X REACTIVITY LIMITS \ .
REFERENCE ^ v THERMOELECTRIC Q X>, SYSTEM DESIGN ^
REACTOR PERFORMANCE EVALUATION AREA
t
1 ' 1 '
x
1100 1300
1000°F INLET 1200°F OUTLET
°F INLET "F OUTLET
FUEL PERFORMANCE
• S8DR GROWTH MODEL • S8DR PREPRODUCTION H2 LOSS
1
-
—
-
-
10 000 20 000 30,000
OPERATING TIME hr
40 000 50 0 0 0
8 M21 048 12A
Figure IV-3 . Per formance Envelope, Reference ZrH Reactor
SECTION
295 FUEL ELEMENTS
COOLANT PASSAGE
FIXED REFLECTORS (BeO or Be)
tLEVATION
22 00 DIA-
Figure IV-4. ZrH Reactor Reference Design
8 A30 075 2
AI-AEC-MEMO-12717 60
y
coo l an t flow i s t u r n e d 180° , p a s s e s o v e r the fuel e l e m e n t s , and l e a v e s the r e a c
to r v e s s e l at 1 3 0 0 ° F . The fuel e l e m e n t s in the c o r e a r e spaced in a nonun i fo rm
h e x a g o n a l a r r a y to p r o v i d e each e l e m e n t with a coolan t flow a p p r o x i m a t e l y p r o
p o r t i o n a l to the pov/er g e n e r a t e d in the e l e m e n t . The n o z z l e - t o - n o z z l e p r e s s u r e -
d r o p of the r e a c t o r i s 0.65 p s i a t the n o r m a l f l owra t e of 13.0 l b / s e c . Type 316
s t a i n l e s s s t e e l is u s e d a s a s t r u c t u r a l m a t e r i a l for the r e a c t o r v e s s e l and
i n t e r n a l s .
The r e a c t o r fuel m a t e r i a l i s a z i r c o n i u m - u r a n i u m a l loy which h a s b e e n h y -22 3
d r i d e d to a h y d r o g e n con ten t of 6,3 x 10 a t o m s / c m (the H^ content in cold 22
w a t e r i s about 6.6 x 10 ). T h i s fuel m a t e r i a l i s qui te s t ab le in the expec t ed
t e m p e r a t u r e and r a d i a t i o n e n v i r o n m e n t and i t s p e r f o r m a n c e h a s been wel l c h a r
a c t e r i z e d a s a r e s u l t of the o p e r a t i o n of five SNAP r e a c t o r s p lus m a n y i n - p i l e
i r r a d i a t i o n e x p e r i m e n t s . The fuel i s con ta ined in a H a s t e l l o y - N c ladding tube
which i s coa ted on the i n s i d e with a c e r a m i c m a t e r i a l to inhibi t the l o s s of H^
m o d e r a t o r f r o m the fuel r o d .
The m a j o r change f r o m p r e v i o u s Z r H r e a c t o r s l i e s in the d e s i g n of the r e
f l e c t o r c o n t r o l s y s t e m . The SNAP 1 OA and SNAP 8 r e a c t o r s w e r e des igned to
o p e r a t e in a s h a d o w - s h i e l d e d con f igu ra t i on . The c o n t r o l d r u m s w e r e s e m i c y l i n -
d e r s of b e r y l l i u m s u r r o u n d i n g the c o r e which could be r o t a t e d to i n c r e a s e or d e
c r e a s e the n e u t r o n l e a k a g e f r o m the s y s t e m . The r e f e r e n c e con t ro l s y s t e m for
th i s r e a c t o r i s d e s i g n e d to o p e r a t e i n s i d e a sh ie ld which c o m p l e t e l y s u r r o u n d s
the r e a c t o r . T e n c y l i n d r i c a l r e f l e c t o r po i son c o n t r o l d r u m s a r e moun ted in
d r y w e l l s cooled by the i n l e t NaK. N e u t r o n - l e a k a g e c o n t r o l i s a c c o m p l i s h e d in
th i s c a s e by r o t a t i n g the d r u m f r o m p o s i t i o n s w h e r e n e u t r o n - r e f l e c t o r m a t e r i a l
i s ad j acen t to the c o r e to p o s i t i o n s w h e r e n e u t r o n - a b s o r p t i o n m a t e r i a l (poison)
i s a d j a c e n t .
The c o n t r o l d r u m s wi l l o p e r a t e a t r e l a t i v e l y h igh t e m p e r a t u r e s (1500 to
1800°F) b e c a u s e the i n t e r n a l n u c l e a r h e a t g e n e r a t e d m u s t be t r a n s f e r r e d by r a d
i a t i on to the w a l l s of the d r y w e l l , which a r e cooled by 1100°F NaK. B e r y l l i u m
oxide i s u s e d a s the r e f l e c t o r m a t e r i a l in th i s h i g h - t e m p e r a t u r e e n v i r o n m e n t .
The s e l e c t e d po i son m a t e r i a l i s e u r o p i u m - o x i d e d i s p e r s e d in n i cke l and h igh-
s t r e n g t h n i o b i u m a l l o y s a r e p lanned for s t r u c t u r a l u s e .
A I - A E C - M E M O - 1 2 7 1 7
61
The c o n t r o l d r u m r o t a t e s on a s e t of b a l l - a n d - s o c k e t b e a r i n g s . L ike the
S8DR, an a l u m i n u m - o x i d e - c o a t e d shaft r o t a t e s in a c a r b o n - g r a p h i t e ba l l
moun ted in a s o c k e t coa t ed with a l u m i n u m ox ide . The m a x i m u m b e a r i n g t e m
p e r a t u r e i s e x p e c t e d to be b e l o w 1 3 5 0 ° F , T e s t i n g of th i s type of b e a r i n g h a s
b e e n conduc ted a t t e m p e r a t u r e s up to 1 5 0 0 ° F . The c o n t r o l d r u m wil l be r o
ta ted by a n S8DR a c t u a t o r which h a s been modi f ied s l i gh t ly for th i s a p p l i c a t i o n .
The a c t u a t o r o p e r a t i n g t e m p e r a t u r e wil l be l e s s than tha t e x p e c t e d on the S8DR,
due to i t s l o c a t i o n ou t s ide the s h i e l d .
F o r c o n t r o l and m o n i t o r i n g p u r p o s e s a d r u m p o s i t i o n i n d i c a t o r wil l be in
c o r p o r a t e d in to the s y s t e m . Th i s v/ill be l o c a t e d in a cool p a r t of the s p a c e
c ra f t and v/ill ob ta in i t s r e a d i n g by count ing p u l s e s to the a c t u a t o r s . A s ing le
l i m i t s'witch on e a c h d r u m , a c t u a t e d v/hen the d r u m i s in the l e a s t r e a c t i v e
pos i t i on , -will p r o v i d e a s e c o n d a r y check on the pos i t i on i n d i c a t o r and wil l s a t
is fy the p r o b a b l e l aunch pad r e q u i r e m e n t of hav ing a p o s i t i v e i nd i ca t i on that the
r e a c t o r i s in a safe cond i t ion .
The sh ie ld con f igu ra t i on wi l l be dependen t upon the p a r t i c u l a r m i s s i o n for
which the r e a c t o r i s to be u s e d . In g e n e r a l , the r e a c t o r v e s s e l wi l l be s u r
rounded by a g a m m a sh i e ld of e i t h e r t u n g s t e n or m o l t e n l ead e n c a p s u l a t e d in
s t e e l . A th ick l a y e r of i n s u l a t i o n -will s e p a r a t e the h i g h - t e m p e r a t u r e Pb f r o m
a r e g i o n of LiH n e u t r o n s h i e l d i n g . Th i s type of t w o - r e g i o n sh ie ld i s a d e q u a t e
for a p p l i c a t i o n s w h e r e the a l l o w a b l e d o s e r a t e s a r e h igh o r the s e p a r a t i o n d i s
t ance f r o m the p e r s o n n e l i s l a r g e (e. g, m a n n e d l u n a r b a s e ) . In the c a s e of a
shaped 47r sh ie ld for a m a n n e d s p a c e s t a t i on , the sh i e ld ing wil l be m u c h t h i c k e r
in the d i r e c t i o n of the s t a t i o n . N o r m a l l y the f i r s t two r e g i o n s wil l be followed
by a g a l l e r y conta in ing the p o w e r - c o n v e r s i o n s y s t e m (PCS) . Aft of the g a l l e r y
wi l l be a s econd g a m m a sh ie ld of d e p l e t e d U and a s e c o n d LiH n e u t r o n sh i e ld .
The LiH s h i e l d s a r e c a s t in s t a i n l e s s - s t e e l c o n t a i n e r s s t r e n g t h e n e d by in
t e r n a l s h e l l s and s t r i n g e r s . The sh ie ld a s s e m b l y i s n o r m a l l y the h e a v i e s t uni t
in the r e a c t o r s y s t e m and p r o v i d e s p r i m a r y s t r u c t u r e for the e n t i r e s y s t e m .
The weigh t of the r e a c t o r , P C S , and sh ie ld i s c a r r i e d t h r o u g h the sh ie ld to a
load r ing which i s m a t e d to the v e h i c l e . T y p i c a l s h i e l d s a r e d e s c r i b e d in S e c
t ion V for spec i f i c m i s s i o n a d a p t a t i o n s of the s y s t e m .
A I - A E C - M E M O - 1 2 7 1 7
62
Some of the more significant design p a r a m e t e r s for the reac tor subsystems
a r e given in Table IV-2, In general the design involves very few deviations from
the s t a t e -o f - the -a r t as exemplified by the S8DR. In a r ea s where conditions a r e
more severe than S8DR, development p rograms a r e underway to establ ish the
required capabi l i t ies ,
B, THERMOELECTRIC CONVERTER
1. TE Module Technology Status
The objective of the Compact TE Converter P r o g r a m begun by the AEC in
mid-1965 is to develop a h igh-per formance re l iable long-life conver ter module
for application to space s y s t e m s . The basic element in the p rogram being con
ducted for the AEC by Westinghouse is the tubular TE module shown schemat
ically in Figure IV-5 . It has a TE circui t encapsulated between its inner and
outer clads in a completely compact void-free design that is s t ructura l ly rugged.
Because of the unique design of the tubular module, radial heat flows from the
inner to the outer surface without the requi rement of bonded joints . The TE
circui t is completed through a se r i e s of washers and r ings . The a l te rna te P -
and N-type washers a r e separa ted by thin washers of natural mica for e lec t r ica l
insulation. Hot- and cold-conductor r ings span adjacent PbTe washers to form
a serpentine cur ren t flowpath. The c i rcui t is e lect r ical ly isolated from the
s t ruc tura l claddings by thin s leeves of boron nitr ide that provide good thermal
contact between the r ings and the c lads .
Table IV-3 s u m m a r i z e s the test experience accumulated through mid-1968
with the tubular modules . Since the p rog ram began in mid-1965 approximately
eighty tubular modules have been fabricated, and fifty have been life-tested.
The remainder were subjected to special dest ruct ive examination, s h o r t - t e r m
performance t e s t s , and special ones such as cyclic t empera tu re and vibration
t e s t s . To maximize the benefits from each module life-tested an average hot-
clad t empera tu re of 1000°F was chosen at the beginning of the p rogram as the
basic test condition. There a r e axial t empera tu re gradients in the inner clad,
however, because of end effects. In a typical test setup an e lec t r ica l heater is
inser ted into the bore of the module and heat is t r ans fe r red to the inner clad
through NaK fluid which fills the cavity between the hea te r and module. Because
AI-AEC-MEMO-12717 63
TABLE IV-2
REFERENCE ZrH REACTOR DESIGN PARAMETERS
1. Gene ra l P e r f o r m a n c e
Design t h e r m a l power
Design o u t l e t - t e m p e r a t u r e
T e m p e r a t u r e r i s e
Design l i fe t ime
Coolant f lowrate
P r e s s u r e d rop
Operat ing p r e s s u r e capabi l i ty
2. Fuel and Core In te rna ls
Number of fuel e lements
ZrH hydrogen content
Uran ium content
H y d r o g e n - b a r r i e r m a t e r i a l
Cladding m a t e r i a l
Cladding th ickness
Burnable poison m a t e r i a l
Active fuel length
Overa l l (f lat- to-flat) e l ement length
Outside d i ame te r of fuel e lement
F u e l - e l e m e n t spacing (variable for flow control)
In ternal re f lec tor m a t e r i a l
In ternal r e f l ec to r cladding
Gr idp la te m a t e r i a l
Core shel l , ins ide d i ame te r
Core shell th ickness
Core shell m a t e r i a l
Reac tor coolant m a t e r i a l
600 kwt
1300°F
200°F
26,000 h r
49,000 I b / h r
0.65 psi
35 ps ia
295 22
6.3 X 10^" a t o m s / c m
10.5 wt%
SCB-1
Has te l loy -N
0.015 in.
Gd-155
16.8 in.
17.5 in.
0.570 in.
0.025 to 0.045 in.
BeO
316 SS
316 SS
11.4 in.
0.030 in.
316 SS
NaK-78
3. Reac to r V e s s e l
Outside d i a m e t e r
Ves se l wall th ickness
Inside d i a m e t e r of d r y wells
Drywell wall th ickness
Number of inlet and outlet nozzles
4. Reflector Control S y s t e m
Con t ro l -d rum type
Number of control d r u m s
Reflector m a t e r i a l
Poison m a t e r i a l
S t ruc tu re m a t e r i a l
Cladding m a t e r i a l
Drum d i a m e t e r
Drum length
S t ruc tu ra l s t rongback th ickness
c ladding th ickness
Drum bear ing shaft m a t e r i a l
C o n t r o l - d r u m ac tua to r
C o n t r o l - d r u m bea r ings
5. Shield
H i g h - t e m p e r a t u r e g a m m a shield
Lead conta iner m a t e r i a l
L o w - t e m p e r a t u r e g a m m a shield
Neu t ron-sh ie ld m a t e r i a l
LiH conta iner m a t e r i a l
22.0 in.
3 /16 in.
4.62 in.
0.065 in.
4 ea
Ref lec to r -po i son
10
BeO
60% Eu^Oj in Ni
Nb-10 W
Nb-1 Zr
4.5 in.
19.0 in.
0.25 in.
0.030 in.
Ta -10 W
Modified S8DR
Modified S8DR
Molten Lead
Croloy 2 - 1 / 4
Uran ium
LiH
316 SS
AI-AEC-MEMO-12717 64
DESIGN FEATURES
FULLY ENCAPSULATED
FULLY COMPACTED-VOID FREE
STRUCTURALLY RUGGED
NO BONDED JOINTS
USES PbTe AT HIGH TEMPERATURE
MECHANICALLY AND ELECTRICALLY ADAPTABLE
LONGEVITY- SHELF AND OPERATING
OUTER CLADDING
ELECTRICAL CONDUCTOR
THERMOELECTRIC MATERIAL
ELECTRICAL INSULATION
INNER CLADDING 612249-4C
Figure IV-5 . Tubular Thermoelec t r ic Module
TABLE IV-3
TUBULAR MODULE TEST EXPERIENCE
T e m p e r a t u r e , H o t ( ° F )
1000
1100
1125
1150
1200
1250
1300
T e m p e r a t u r e , M a x i m u m
( ° F )
1050
1150
1175
1200
1270
1340
1350
N u m b e r of M o d u l e s
58
9
4
2
12
1
2
T o t a l T i m e ( h r )
2 1 7 , 1 0 0
2 5 , 8 0 0
5 ,500
6 , 0 0 0
1 0 , 3 0 0
1,200
5 ,900
2 7 1 , 2 0 0
M a x i m u m T i m e ( h r )
2 4 , 6 0 0
9 , 5 0 0
2 , 0 0 0
4 , 0 0 0
1,700
1,200
4 , 2 0 0
AI-AEC-MEMO-12717 65
of end l o s s e s , peak t e m p e r a t u r e s a r e about 5 0 ° F h i g h e r than a v e r a g e t e m p e r a
t u r e s .
2. T u b u l a r Module
The r e f e r e n c e t u b u l a r T E m o d u l e s e l e c t e d for the r e a c t o r — T E s y s t e m is
shown in F i g u r e I V - 6 . A s u m m a r y of i t s p e r f o r m a n c e and d e s i g n c h a r a c t e r i s
t i c s i s g iven in T a b l e I V - 4 . The m o d u l e h a s an ID of 0,75 in, , an OD of 1.50 in . ,
and an a c t i v e T E c i r c u i t l eng th of 15,07 in . I ts o v e r a l l l eng th inc luding i n n e r -
c lad e x t e n s i o n s i s 19.0 in .
The r e f e r e n c e m o d u l e -was c h o s e n a f t e r a de t a i l ed p a r a m e t r i c s y s t e m s tudy .
Befo re a n a l y z i n g the s y s t e m t r a d e - o f f s , s e v e r a l m o d u l e d e s i g n c r i t e r i a w e r e
fixed b a s e d on the p r e s e n t s t a t e - o f - t h e - a r t and r e a l i s t i c p r o j e c t i o n s of the t e c h
nology which could be m a d e •with a h igh d e g r e e of con f idence . Th i s was n e c e s
s a r y b e c a u s e the ex i s t ing d e v e l o p m e n t p r o g r a m for t u b u l a r m o d u l e s h a s b e e n a
b r o a d l y b a s e d t echno logy effor t not spec i f i ca l l y o r i e n t e d t o w a r d m o d u l e s t a i l o r e d
for r e a c t o r s y s t e m a p p l i c a t i o n s , A s u m m a r y of the c r i t e r i a a s s t a t ed for the
s tudy fo l lows :
1) TE M a t e r i a l s , S i n g l e - p i e c e 2P and t w o - p i e c e 2N-3N w a s h e r s wil l be
the b a s i s for m o d u l e p e r f o r m a n c e c a l c u l a t i o n s .
2) Cladding M a t e r i a l s . H i g h - s t r e n g t h Incone l or i t s m e c h a n i c a l e q u i v a
len t ( c o n s i s t e n t wi th m i n i m u m - w e i g h t m o d u l e s ) wi l l be c o n s i d e r e d for
modu le i n n e r and o u t e r c l add ing . F o r p a r a m e t r i c c a l c u l a t i o n s the
c ladding wi l l be s i zed p r o p e r l y to e n s u r e suff ic ient con tac t p r e s s u r e s
u n d e r o p e r a t i n g c o n d i t i o n s .
3) End C l o s u r e s , The r e f e r e n c e m o d u l e v/ill be b a s e d on an e n d - c l o s u r e
d e s i g n that y i e l d s n o m i n a l h e a t l o s s e s of 100 w a t t s p e r end.
4) Module Ac t ive Leng th and V o l t a g e . F o r p a r a m e t r i c c a l c u l a t i o n s of
m o d u l e p e r f o r m a n c e and w e i g h t s , a fixed a c t i v e length of 15.0 in ,
and c o r r e s p o n d i n g 14.0 vo l t s at m a t c h e d - l o a d wil l be u s e d . The r a t i o
of t h e s e two v a l u e s is r e p r e s e n t a t i v e of n e a r - m a x i m u m vol t s p e r uni t
a x i a l l eng th tha t can be a t t a i n e d •within the c u r r e n t s t a t e - o f - t h e - a r t .
A I - A E C - M E M O - 1 2 7 1 7
66
O U T E R CLA>D
I NSULATINQ 5UEEVE
CONDUCTOR RING,
THeRMOEUECTRlC W A S H E R
— E L E : C T R I C A . L I N 5 U L ^ T O R
CONDUCTOR RINC,
- — I N S U L A T I N G , S L E E V E
N E R C L A D
- 8 T U R N S @ 1 SO P ITCH —
Figure IV-6. Converter Layout (Drawing No. 914E163)
AI-AEC-MEMO-1Z71 7
67
TABLE IV-4
CHARACTERISTICS OF REFERENCE TUBULAR MODULE
Power output, watts e lec t r ic
Efficiency, %
Voltage to matched-load, vdc
Internal r e s i s t ance , XI
Current , amp
Heat input, kwt
Mean hot-c lad t empera tu re , °F
Mean cold-clad t empera tu re , °F
Dry weight, lb
Envelope Dimensions (in. )
Inner d iameter
Outer d iameter
Total length
Active length
Radial Thickness (in. )
Cladding
Insulator
Conductor
Thermoe lec t r i c ma te r i a l
Inner
0.090
0.040
0.025
262
4.67
14.0
0.74J
18.7
5.61
1125
570
5.75
0.75
1.50
19.0
15.07
Outer
0.020
0.037
0.020
0.143
AI-AEC-MEMO-12717 69
5) Module D i a m e t e r s . I D ' s f r o m 3 / 8 to 3 /4 in . wi l l be c o n s i d e r e d d u r
ing p a r a m e t r i c s t u d i e s . The c o r r e s p o n d i n g r a n g e for O D ' s -will be
f r o m 1.2 to 2.5 in .
6) Module D e g r a d a t i o n . It w a s a s s u m e d that by the e a r l y 1970 ' s h i g h -
t e m p e r a t u r e (1200 to 1250°F) m o d u l e s with l i t t l e or no d e g r a d a t i o n
wi l l be d e m o n s t r a t e d for l i f e t i m e s in e x c e s s of 10,000 h r . T h e r e f o r e
no spec i f i c v a l u e s of m o d u l e d e g r a d a t i o n w e r e u s e d in the s tudy . In
s t e a d , n o r m a l s y s t e m o p e r a t i n g t e m p e r a t u r e s w e r e e s t a b l i s h e d so
tha t s o m e d e g r a d a t i o n can be r e c o v e r e d by r a i s i n g the t e m p e r a t u r e s
•without e x c e e d i n g c o m p o n e n t l i m i t s .
Al though the c o n v e r t e r h o t - c l a d a v e r a g e t e m p e r a t u r e ob jec t ive i s 1 2 0 0 ° F ,
an a v e r a g e t e m p e r a t u r e of 1125°F w a s s e l e c t e d to a l low s o m e d e s i g n m a r g i n
and to a l low for d e g r a d a t i o n r e c o v e r y .
One c o n c l u s i o n of the s tudy w a s tha t a m i n i m u m OD for a g iven ID, or m i n -
imuna p r a c t i c a l T E e l e m e n t t h i c k n e s s , w a s d e s i r a b l e . T h i s r e s u l t e d in m i n i
m u m s y s t e m we igh t and r a d i a t o r a r e a , p r i m a r i l y b e c a u s e of the h i g h e r h e a t -
r e j e c t i o n t e m p e r a t u r e , and f ewer m o d u l e s b e c a u s e of g r e a t e r e l e c t r i c a l output
p e r m o d u l e . Ef f ic iency v/as m i n i m u m for th i s condi t ion , bu t s i n c e the r e a c t o r
i s not t h e r m a l - p o w e r - l i m i t e d th i s w a s not c r i t i c a l .
S y s t e m we igh t , r a d i a t o r a r e a , and e f f ic iency did not v a r y s ign i f i can t ly -with
c h a n g e s in ID when the e l e m e n t t h i c k n e s s w a s m a i n t a i n e d , bu t the p o w e r output
p e r m o d u l e i n c r e a s e d wi th i n c r e a s i n g ID. To m i n i m i z e the n u m b e r of m o d u l e s ,
then , the l a r g e s t ID a l l owab le wi th in the s tudy c r i t e r i a , 0.75 in . , was c h o s e n .
M i n i m i z i n g the n u m b e r of m o d u l e s i n c r e a s e s r e l i a b i l i t y by r e d u c i n g the n u m b e r
of we lds and the s y s t e m c o m p l e x i t y , bu t i t c an h a v e an a d v e r s e effect on p a r t i a l -
power r e l i a b i l i t y by i n c r e a s i n g the power l o s s with one m o d u l e f a i l u r e . F o r the
r a n g e of m o d u l e s i z e s s tud ied th i s w a s not ye t judged to be a p r o b l e m ; h o w e v e r ,
r e v i e w of the p a r t i a l - p o w e r r e l i a b i l i t y c u r v e s in Sec t ion I I I -D shows tha t f u r t h e r
s ign i f i can t r e d u c t i o n in the n u m b e r of m o d u l e s m a y not be d e s i r a b l e .
With the ID e s t a b l i s h e d , the m i n i m u m p r a c t i c a l OD of 1.5 in . and the a v e r
age c o l d - c l a d t e m p e r a t u r e of 5 7 0 ° F w e r e f ixed.
A I - A E C - M E M O - 1 2 7 1 7
70
3. Converter Module
a. Descript ion and Per formance
The re ference TE conver ter module consis ts of an assembly of 24 tubular
modules a r ranged into six subassembl ies of four tubular modules each. Each
4-pack is enclosed in a single metal jacket that provides containment for all
cold NaK flowing around the four modules . This a r rangement simplifies mani
folding and header r equ i rements for del ivery and removal of cold NaK to the in
dividual tubular modules . Cross-coupl ing of the hot- and cold-NaK manifolding
provides for the differential t he rmal expansion that occurs during startup and
other the rmal t r ans ien t s , and minimizes the rmal s t r e s s e s on the piping
assembly .
A cutaway of the converter module is shown in Figure lV-7 ( isometric) ;
for this orientat ion the tubular modules a r e standing on end with ver t ical cen ter -
l ines . The tubular modules provide the conver ter module s t ruc ture in the ve r
tical direct ion, the hot manifolds provide the longitudinal s t ruc tu re , and the
cold manifolds provide the t r a n s v e r s e s t ruc tu re . For specific applications the
orientation of the conver ter module and the layout of the inlet and outlet mani
folds can be modified to satisfy any unique requ i rement s . Discussion of the
present design, ho'wever, is predicated on the nominal orientation defined above.
The hot- loop NaK enters one end of each longitudinal manifold at the top
and flows to the other end. A portion of the flow exits downward from the man
ifold through each tubular module to the lo^wer longitudinal manifold where it is
collected and re turned to the r eac to r . The cold-loop NaK en te r s the bottom of
the divided outer can which c lus te r s each t r ansve r se group of modules into a
4-pack. Cold NaK then flows into annuli that surround each tubular module,
removes the waste heat from the modules , and is then collected in an exit man
ifold and pumped to the rad ia to r .
Each of the 24 tubular modules in the converter module contains a 0.5-in.-
diam rod that channels the hot NaK into an annular flowpath. A spiral-wound
wire centers the rod in the tubular module and provides a flowpath that ensures
c i rcumferent ia l distr ibution of the flow. Use of the 0.5-in. rod and spira l wire
se rves two purposes . F i r s t , it provides sufficient hydraul ic impedance within
the tubular module to ensure good flow distribution among the tubular modules.
AI-AEC-MEMO-12717 71
COLD
CONVERTER MODULE 6.3 KWE
Figure IV-7. Converter Module Cutaway
AI-AEC-MEMO-12717 72
TABLE IV-5
CONVERTER MODULE CHARACTERISTICS
Power output, kwe
Efficiency, %
Matched-load voltage, volts
Number of tubular modules
Number of modules e lec t r ica l ly in s e r i e s
Current per 4-pack, amp
Wet weight, lb 3
Volume, ft
Envelope d imensions , in.
Tempera tu re s (°F)
Inlet clad
Outlet clad
Mean clad
NaK flowrate, l b / s e c
P r e s s u r e drop, ps i
Energy Balance
Heat into conver ter module, kwt
P r i m a r y - h e a t l o s s e s , kwt
Heat del ivered to tubular modules , kwt
E lec t r i ca l power, kwe
Heat removed from conver ter module, kwt
6.3
4.6
56.0
24
4
18.7
284
3.4
12.5 X 19.5 X 24.0
Hot Loop
1225
1025
1125
3.03
0.28
Cold Loop
470
670
570
2.88
0.26
136,1
1.3
134.8
6.3
128.5
Second, it improves the convective heat t ransfer between the NaK and the mod
ule cladding. The calculated AT between bulk NaK and clad is 20°F with the
rod inse r t . Without the rod inser t the AT would be ~ 5 0 ° F and would impose a
significant t empera tu re penalty on the sys tem.
A summary of the conver ter module design and performance cha rac te r i s t i c s
is given in Table IV-5. For the selected sys tem operating t empera tu res each
converter module produces 6.3 kwe at a matched-load voltage of 56 volts. Four
AI-AEC-MEMO- 1 2717 73
tubular modules a r e a r ranged e lec t r ica l ly in se r i e s to yield 56 vol ts , and the
six 4-packs a r e connected e lec t r ica l ly in para l le l . The e lec t r i ca l network that
connects the four conver ter modules and the associa ted voltage regulation eqxiip-
ment is descr ibed in Section IV-B-4 .
The overal l efficiency of the conver ter module operating at 1125 and 570°F
mean hot - and cold-clad t e m p e r a t u r e s , respect ively , is 4.6%. This includes
heat los ses of 1,3 kwt in the p r imary - loop manifolding based on thermal i n t e r
change between the manifolds and the box that surrounds the conver ter module.
The heat balance of the module is given in Table IV-5 .
b . Mechanical Design
An engineering dra^wing of the reference converter module is sho-wn in F ig
u r e IV-8. A fundamental mechanical design requi rement is to provide for dif
ferential thermal expansion because the NaK loops operate at t empera tu re lev
els that differ by more than 500°F. The components must be carefully a r ranged
to allow for the result ing differential expansions.
The hot clads of the tubular modules a r e welded direct ly to the hot mani
folds which a r e free to expand in the longitudinal direct ion and space the 4-packs
as requi red . The hot clads separa te the upper and lower hot manifolds and a re
free to move these inanifolds as requi red by their thermal expansions. The 4-
pack cans operate at cold-loop t empera tu re and a r e attached direct ly to the cold
clads of the tubular modules . The t r a n s v e r s e spacing is thus freely adjusted by
the the rmal expansion of these cans . Suitable flexible connections a r e provided
to join the four hot- in le t manifolds to the common inlet header and the four hot-
exit manifolds to the exit heade r . Likewise, flexibility is provided in the con
nections to the cold-loop inlet and exit h e a d e r s .
Perhaps the most c r i t ica l design requi rement of the sys tem is absolute
containment of NaK in the loops. All loop connections a r e welded and emphasis
is placed on minimizing the number of welds and maximizing the quality of the
required welds. Some weight sacr i f ices were made to reduce the number of
welds such as using the coraplete can around each 4-pack r a the r than individual
tubes with t r a n s v e r s e h e a d e r s at top and bottom. The •weld quality was maxi
mized by providing for p r e - a s s e m b l e d components as much as possible before
genera tor inser t ion. Thus s t r e s s relief, aging, inspect ion, and p r e s s u r e t e s t
ing a r e possible and prac t ica l in most of the welds.
AI-AEC-MEMO-12717 74
HTT
Figure IV-8. Converter Module Layout
(Drawing No. 939J385)
AI-AEC-MEMO-12717
75
The oval-shaped can w^hich surrounds the 4-pack is the basic building unit.
It is rolled and welded Inconel 718 with a nominal thickness of 0.100 in. This
h igh-s t rength m a t e r i a l is required to prevent bulging of the la rge flat s ides .
The top and bottom dividers and the baffle tubes a r e inser ted in these cans f i rs t .
Then the perforated cover -p la tes a r e seal-welded in place. These units can
then be s t r e s s - r e l i e v e d , aged, inspected, e tc . without fear of damaging gener
a to rs which have not yet been assembled into the pack.
At this point in the assembly sequence the tubular modules can be inser ted
and the tips of the cold clads welded to the can cover-p la tes to form a complete
4-pack. A possible a l te rna t ive would be to assemble the entire cold loop with
out g e n e r a t o r s . This would include the manifolds and the longitudinally flexible
shear m e m b e r s between cans . The assembled cold loop (without tubular mod
ules) could again be s t r e s s - r e l i e v e d , e tc . without fear of generator damage,
thereby maximizing weld quality in the cold loop.
For ei ther a s sembly method the ent i re cold-loop and generator assembly
will be built before the hot manifolds a r e welded on. The hot clads of the tubu
la r modules will be long enough to reach the hot manifolds without any in te r
mediate welds being requi red . The hot manifolds will be channel-shaped •with
one open side so that the clads can be welded to the inside of the manifold. This
is the only way that sa t is factory clad-weld accessibi l i ty can be obtained. Fin
ally the hot manifold cover -p la tes will be seal-welded to the open manifold sides
The assembly , as shown in F igure IV-8, has 202 cr i t ica l welds. Many of these
welds, however, can essent ia l ly be eliminated as potential problem a r ea s by the
use of manufacturing and inspection procedures which will guarantee their qual
ity to be near ly the same as the parent ma te r i a l .
Three mounting lugs a r e shown in the reference design. These lugs a r e
rigidly attached to the 4-pack cans . They will penetrate the cover at each end
and must move thermal ly re la t ive to the cover . One lug can be seal-welded to
the cover , but a sliding seal (or bellows) will be used at the other penetra t ions .
A suitable support linkage •will be requi red to proper ly mount the unit to the
spacecraft and allow for the rmal movement of the support lugs . This method of
support is p re l iminary and •will likely be changed as the constraints of specific
sys tem adaptations and the r e su l t s of further studies become available.
AI-AEC-MEMO-12717 77
The stiffened shell which covers the ent i re conver te r module provides con
tainment of NaK in the event of a leak, thus avoiding subsequent e lec t r ica l shor t
ing of other conver ter modules . The cover cannot withstand significant in ternal
or external p r e s s u r e ; therefore , a vent has been provided for p r e s s u r e equali
zation during launch and to allow NaK vapor, in the event of a leak, to vent over
board or to a safe a r e a .
Because a tv/o-loop reac to r sys tem was selected for the reference configu
rat ion, an additional provis ion for containing the hot NaK in the converter mod
ule was briefly invest igated. Redundancy in containing the hot NaK is needed
because all four conver ter modules in the sys tem v/ill sha re a common hydraul ic
loop with the r eac to r . Therefore a single hydraul ic leak anywhere in the p r i
m a r y loop will cause fai lure of the complete sys tem. Over 80% of the p r i m a r y -
loop containment v/elds a r e associa ted •with these hot h e a d e r s . A conceptual
sketch shown in F igure IV-9 shows provisions for providing double containment
of the hot- loop h e a d e r s . The bello'ws sho^wn is to allow differential expansion
bet^ween the p r i m a r y and secondary containment. A conclusion of the brief in
vestigation is that double containment of these h e a d e r s is feasible, and can be
incorporated into the conver ter design.
F igure IV-9. Double Containment of Converter Module Header
1-13-69 UNC 7759-5284
AI-AEC-MEMO-12717 78
c. Off-Design Pe r fo rmance
If the reference conver te r module is operated at t empera tu res other than
those selected for the sys tem design points, the power output, efficiency, and
voltage will vary .
F igure IV-10 shows the calculated variat ions in power output for mean hot-
clad t empera tu re s ranging from 1000 to 1225°F and for mean cold-clad t empera
tures from 400 to 700°F. Similar ly , for the same ranges of t empe ra tu r e s , off-
design values for efficiency and voltage a r e shown in F igures IV-11 and IV-12,
respect ive ly .
Although the final selection of axial-NaK AT in the converter module was
200°F, the design analys is was made , based on a tentative selection of 150°F.
By increas ing the AT in each loop from 150 to 200°F, the e lec t r ica l pe r fo rm
ance cha rac te r i s t i c s change by a negligible amount. Hydraulic p a r a m e t e r s ,
however, a r e significantly affected. F igure IV-13 shows the off-design var ia
tions in hot- and cold-NaK flowrates for the final selection of 200°F, while
Figure IV-14 indicates the values for the ea r l i e r 150°F AT. The p r e s s u r e -
drop variat ions a r e shown in Figure IV-15 as functions of flowrate with the
200°F A T design point indicated,
4. E lec t r ica l Network and Voltage-Regulation Equipment
The e lec t r ica l network for the re ference power sys tem provides shunt-
voltage regulation of the nominal 56.0 vdc output of the TE conver ter . A sche
mat ic d iagram of the network is shown in F igure IV-16. The 24 TE 4-packs
a r e connected to a common negative bus . The positive lead of each 4-pack is
routed individually to the power-conditioning equipment, all of which is located
in a low- tempera tu re environment . Each of the 24 4-packs has an open-circui t
voltage of 11 2 vdc at the re ference operating conditions. Based on the test ex
per ience of the compact conver ter development p rogram, this no-load voltage
will be near ly constant throughout the miss ion l i fet ime.
Shunt-voltage regulat ion was selected since the TE converter attains its
maximum rel iabi l i ty and inninimum degradation when it is operated at constant
t empera tu re conditions, i . e. without thermal t r ans ien t s . This operation is
attained when the e l ec t r i ca l load is held constant. Constant thermal- load oper
ation also simplifies the r eac to r controls , thereby improving overall sys tem
rel iabi l i ty and reducing weight.
AI-AEC-MEMO-12717
79
13 -
l400"F
24 TUBULAR MODULES WEIGHT: 284 lb AXIAL A T : 150°F
MEAN COLD-CLAD TEMPERATURE
l l - ^ I I 1000 1100 1200
HEAN HOT-CLAD TEMPERATURE, °F 1-13-69 UNC
1300
7759-5285
Figure IV-10. Conver ter Module Off-Design Power
AI-AEC -MEMO- 1 271 7 80
2l->V-1000
400OF
24 TUBULAR MODULES WEIGHT: 284 lb AXIAL AT: ISO^F
MEAN COLD-CLAD TEMPERATURE
1-13-69 UNC
1100 1200 MEAN HOT-CLAD TEMPERATURE, °F
7759-5286
Figure IV-11. Conver ter Module Off-Design Efficiency
AI-AEC-MEMO-12717 81
400°F
500'JF
570°F
600°F
^EAN COLD-CLAD FEMPERATURE
24 TUBULAR MODULES WEIGHT: 284 lb AXIAL AT- 150"F
30 U ^ _L 1000 1300 1100 1200
MEAN HOT-CLAD TEMPERATURE,°F
1-13-69 UNC 7759-5287
Figure IV-12. Conver ter Module Off-Design Voltage
AI-AEC -MEMO-1 2717 82
5 0
4 0
< 30
o
2 0
1 0
I I MEAN COLO-SIDE WEIGHT OF 24 TUBULAR MODULES-284 lb TEMPERATURE °F
HOT-SIDE FLOWRATE COLD-SIDE FLOWRATE
J L 1000
1-13-69 UNC
1100 1200 MEAN HOT-CLAD TEMPERATURE, °F
1300
7759-5288
Figure IV-13. Conver ter Module Off-Design F lowra tes , Axial AT's Assumed Constant at 200° F
AI-AEC-MEMO-12717 83
6 0
5 0
40
3 0
2 0
/ 700"F
MEAN COLD-SIDE TEMPERATURE
HOT-SIDE FLOWRATE COLD-SIDE FLOWRATE
^ 1000 1100 1200
MEAN HOT-CLAD TEMPERATURE "P
1-13-69 UNC
1300
7759-5289
Figure IV-14. Conver te r Module Off-Design Flowrates , Axial AT's Assumed Constant at 150° F
AI-AEC -MEMO- 12717 84
10
09
08 -
07
05 -
fc 05 -
04 -
03
02 -
01 -
•HOT SIDE COLD SIDE
A T - 200° F
2 3 4 NaK FLOWRATE, lb/sec
- L 6 7
7759-5290
Figure IV-15. Conver ter Module Hot- and Cold-Side P r e s s u r e Drops
AI-AEC-MEMO-12717 85
POWER-GENERATION
24 FOUR-PACK
SUBASSEMBLIES
INTERNAL FAULT
PROTECTION 24 BLOCKING DIODES
ROUGH CURRENT CONTROL
22 SHUNT RESISTORS
WITH TRANSISTOR SWITCHES
POSITIVE BUS
CURRENT-SENSING TRANSISTOR CONTROL
4: J
^ ^
NEGATIVE BUS
FINE CURRENT CONTROL
ONE SHUNT RESISTOR
WITH LINEAR TRANSISTOR
VOLTAGE-SENSING TRANSISTOR CONTROL
METER SHUNT
tr
FILTER CAPACITOR
*9 1
- < 5 — 6
1-13-69 UNC 7759-5291
Figure IV-16. Conver t e r -Assembly and Power-Condit ioning Circui t Diagram
Figure IV-17. Vol tage-Current Profile
LOAD CURRENT, amp 1-13-69 UNC 7759-5292
It is an inherent cha rac t e r i s t i c of each independent 4-pack that a direct
sho r t - c i r cu i t may be placed a c r o s s i ts t e rmina ls indefinitely without damage.
This means that any value of load r e s i s t ance from zero to infinity may be ap
plied. When the load r e s i s t ance is infinity, i. e. the 4-pack is operating as an
open-c i rcui t , the te rminal voltage is a maximum. When the load res i s tance is
ze ro , i, e. a shor t -c i rcu i t ex i s t s , the output voltage is zero . When the load
r e s i s t ance equals the in ternal r e s i s t a n c e , the terminal voltage is one-half the
open-c i rcu i t voltage, as i l lus t ra ted in Figure IV-17. Thus, the terminal volt
age can be adjusted by controlling the res i s t ance of the load.
Power is del ivered to the po^wer conditioner on 24 independent positive
leads and one common negative lead. Because the load may consist of a la rge
number of power-consuming devices that will be switched on and off in a r an
dom fashion, the total power consumption may vary over a wide range. To
design the sys tem with wide flexibility it was assumed that the load could go all
the way to ze ro .
The total load is further assumed to be made up of two subloads; a single
dc load of approximately 56 volts requir ing a regulation of ±2%, and an inver te r
load which requ i res approximately 56 volts input. It was also assumed that
these loads will be applied as step functions and that they will draw high-
frequency cur ren t s -which must be supplied without the introduction of high-
AI-AEC-MEMO- 12717 87
f r e q u e n c y o u t p u t - v o l t a g e v a r i a t i o n s . The p o w e r - c o n d i t i o n i n g c o m p o n e n t s shown
in F i g u r e I V - 1 6 p r o v i d e a r e g u l a t i o n vo l t age of 56.0 vdc ±1%. T h e s e c o m p o n e n t s
a r e d e s c r i b e d in the fol lowing p a r a g r a p h s .
a. P r o t e c t i o n D iodes
A b lock ing d iode i s p l aced in s e r i e s wi th e a c h of the 4 - p a c k l e a d s to d e
couple the s u b a s s e m b l y f r o m the output bus if the 4 - p a c k or i t s l ead should b e
c o m e faul ted to g r o u n d . A s long a s the output t e r m i n a l vo l tage of a 4 - p a c k i s
g r e a t e r than 56 v o l t s , the diode wil l conduc t and supply c u r r e n t to the output
b u s . If the t e r m i n a l vo l t age d r o p s be low 56 v o l t s , a s i t would if s h o r t e d to
g round , a r e v e r s e vo l t age would a p p e a r a c r o s s the diode and no c u r r e n t would
flow. Without the d iode a fault on any 4 - p a c k o r l e ad would take c u r r e n t f r o m
the output bus and t h e r e b y r e d u c e the c u r r e n t a v a i l a b l e for the l o a d . If the fault
c u r r e n t e x c e e d e d the r a t e d load c u r r e n t , the output vo l t age of 56 vol t s could not
be m a i n t a i n e d . The b lock ing d iodes thus p r o t e c t the c o n v e r t e r a s s e m b l y a g a i n s t
i n t e r n a l f a u l t s .
b . Shunt V o l t a g e R e g u l a t o r
Under a n o - l o a d cond i t ion , i. e. no po^wer be ing u s e d by the s p a c e c r a f t , the
p o w e r - d i s s i p a t i o n r e s i s t o r s of a s h o r t e d r e g u l a t o r m u s t be ab le to c a r r y the e n
t i r e r a t e d c u r r e n t of the p o w e r s y s t e m , or 446 a m p . Since no t r a n s i s t o r s with
th i s c u r r e n t r a t i n g a r e a v a i l a b l e , a l a r g e n u m b e r of l o w - c u r r e n t t r a n s i s t o r s
m u s t be u s e d . Th i s i s not a d i s a d v a n t a g e , h o w e v e r , s i nce it p e r m i t s the c i r c u i t
to be des igned with h i g h e r r e l i a b i l i t y and with a r e d u c t i o n in the power tha t m u s t
be d i s s i p a t e d a t low t e m p e r a t u r e .
In the c i r c u i t of F i g u r e I V - 1 6 , 22 of the t r a n s i s t o r s a r e o p e r a t e d a s s w i t c h e s ,
in which c a s e the m a x i m u m t r a n s i s t o r d i s s i p a t i o n i s 660 w a t t s . T h i s o c c u r s
only in the r a r e c a s e when the e n t i r e load c u r r e n t i s be ing d u m p e d . With t h i s
c i r c u i t p r a c t i c a l l y a l l of the e x c e s s power i s d i s s i p a t e d in the r a d i a t i n g shunt
r e s i s t o r s , which can o p e r a t e at v e r y h igh t e m p e r a t u r e s and d u m p l a r g e a m o u n t s
of power wi th v e r y l i t t l e s p a c e and we igh t .
Each of the 22 swi tch ing t r a n s i s t o r s of F i g u r e IV-16 c a r r i e s a m a x i m u m of
20 a m p . Since the i n t e r n a l r e s i s t a n c e of the 24 4 - p a c k s u b a s s e m b l i e s in p a r a l
l e l i s a p p r o x i m a t e l y 0.125 o h m s , the vo l t age on the output bus wi l l d r o p 2.5 vo l t s
each t i m e a t r a n s i s t o r i s s w i t c h e d - o n . The t r a n s i s t o r s could be s w i t c h e d - o n
A I - A E C - M E M O - 1 2 7 1 7
88
when the b u s vo l t age r e a c h e s 56 plus 1.25 vol t s so that the vol tage would d r o p
to 56 m i n u s 1.25 v o l t s . The output vo l t age would thus be he ld within ±2.2% by
the rough c u r r e n t c o n t r o l . In the c i r c u i t of F i g u r e I V - 1 6 t h e s e s t e p - v o l t a g e
c h a n g e s a r e e l i m i n a t e d and the r e g u l a t i o n i m p r o v e d by us ing one t r a n s i s t o r
o p e r a t i n g l i n e a r l y so tha t it c a r r i e s the c u r r e n t which i s i n t e r m e d i a t e to the 20-
a m p s t e p s . The m a x i m u m d i s s i p a t i o n of th i s s ing le l i n e a r l y o p e r a t e d t r a n s i s t o r
wi l l be only 250 w a t t s , a va lue which can be a c c e p t e d by the l o w - t e m p e r a t u r e
e n v i r o n m e n t .
The o p e r a t i o n of the swi tch ing t r a n s i s t o r s is con t ro l l ed by a logic c i r c u i t
•which s e n s e s the load c u r r e n t . The n u m b e r of t r a n s i s t o r swi t ches open i s
p r o p o r t i o n a l to the load c u r r e n t . The c u r r e n t d r a w n by the l i n e a r t r a n s i s t o r i s
c o n t r o l l e d by s e n s i n g the output bus v o l t a g e . A f i l t e r c a p a c i t o r p r o v i d e s low
i n t e r n a l i m p e d a n c e of the p o w e r s o u r c e s to h i g h - f r e q u e n c y load c u r r e n t s . Since
the v o l t a g e - r e g u l a t i n g c i r c u i t s a r e v e r y f a s t th i s c a p a c i t o r i s not v e r y l a r g e .
c . C h a r a c t e r i s t i c s of the Po^wer-Condi t ioning C i r c u i t
(1) Ef f ic iency
The e f f ic iency of the po^wer-condi t ioning e q u i p m e n t at r a t e d load i s i m p o r t
ant s i n c e the p o w e r - c o n d i t i o n i n g l o s s e s wi l l s u b t r a c t f r o m the m a x i m u m power
which i s a v a i l a b l e f r o m a f i x e d - c o n v e r t e r a s s e m b l y . The eff ic iency of the
p o w e r - c o n d i t i o n i n g e q u i p m e n t a t p a r t i a l load i s not i m p o r t a n t s ince it does not
affect the m a x i m u m a v a i l a b l e p o w e r .
The ef f ic iency of the p r o p o s e d c i r c u i t a t full load i s 98%, inc luding the l o s s
due to the 1-volt d r o p a c r o s s the b locking d i o d e s . The l o s s e s in the v o l t a g e -
r e g u l a t i o n c o m p o n e n t s a r e neg l ig ib l e at r a t e d load b e c a u s e a l l of the t r a n s i s t o r
s w i t c h e s would be open and no c u r r e n t would be flowing in the l i n e a r t r a n s i s t o r .
The power r e q u i r e d to o p e r a t e the c o n t r o l c i r c u i t r y i s a l s o neg l ig ib l e .
(2) Cooling R e q u i r e m e n t s
The e s t i m a t e d p o w e r - c o n d i t i o n i n g e q u i p m e n t power l o s s e s which m u s t be
p icked up by the e n v i r o n m e n t a l c o n t r o l s y s t e m a t a t e m p e r a t u r e not ove r IOO°C
a r e a s in T a b l e I V - 6 .
A I - A E C - M E M O - 1 2 7 1 7
89
T A B L E I V - 6
P O W E R LOSSES
Source of Loss
Blocking diodes
Switching t r a n s i s t o r s
Linear t r ans i s to r
Control c i rcui ts
Wiring l o s se s
Total;
Loss at Ze ro -Load Conditions
(watts)
447
660
250
10
20
1387
Loss at Rated-Load Conditions
(watts)
447
0
0
10
20
477
(3) P e r f o r m a n c e
The r e g u l a t i n g c a p a b i l i t y of the c i r c u i t i s l i m i t e d only by the e l e c t r i c a l
t i m e c o n s t a n t of the c o n v e r t e r a s s e m b l y and the po-wer-condi t ion ing c o m p o n e n t s .
It is v e r y p r o b a b l e tha t the vo l t age can be r e g u l a t e d to ±1% or b e t t e r so tha t
add i t i ona l dc r e g u l a t o r s for c r i t i c a l dc l o a d s wi l l not be r e q u i r e d .
The r e f e r e n c e power s y s t e m h a s no o v e r l o a d c a p a c i t y , s i n c e the load i s
m a t c h e d to the i n t e r n a l r e s i s t a n c e of the c o n v e r t e r a s s e m b l y . Any a t t e m p t to
d r a w m o r e than r a t e d c u r r e n t wi l l c a u s e the output vo l t age to d r o p i n s t a n t l y and
the to ta l power wil l go down. T h i s i s an a d v a n t a g e when des ign ing p r o t e c t i o n
for the p o w e r - d i s t r i b u t i o n s y s t e m s i n c e the s h o r t - c i r c u i t c u r r e n t cannot be
m o r e than twice the r a t e d c u r r e n t .
(4) Size
The c o n s t r u c t i o n of the p o w e r - c o n d i t i o n i n g p a c k a g e wil l fol low p r a c t i c e s
s i m i l a r to t hose u s e d in the Apol lo i n v e r t e r . The cool ing of the d iodes and
t r a n s i s t o r s wi l l be by conduc t ion to the power c o n d i t i o n e r b a s e - p l a t e o r by i n
t e r n a l c i r c u l a t i o n of cool ing l iquid or g a s .
The m i n i m u m v o l u m e r e q u i r e m e n t s for the p o w e r - c o n d i t i o n i n g c h a s s i s (not
inc lud ing the r a d i a t i n g r e s i s t o r s ) wi l l be a p p r o x i m a t e l y a s fo l lows :
A I - A E C - M E M O - 1 2 7 1 7
90
24 diodes at 6 in. /diode 3
23 t r a n s i s t o r s at 16 in. / t r a n s i s t o r 3 2 printed circui t boards at 50 in.
3 1 capaci tor at 27 in.
Termina l s
Enclosure s t ruc ture
Total Volume
Detail design will be requi red to establ ish prec ise dimensions for this
component.
(5) Weight
The weight of the power-conditioning equipment (not including the radiating
r e s i s t o r s ) will be a lmost exclusively the weight of the s t ruc ture since the r ec t i
f iers weigh only 0.65 oz each and the t r a n s i s t o r s only 1 oz each.
Assuming that the packaging density would be the same as attained for the 3
Apollo inver te r at 0.0288 lb / in . , the weight will be approximately 28 pounds.
C. NaK-LOOP COMPONENTS
1. Pump System
The pumps selected for this sys tem a r e of the dc conduction EM type pow
ered by special low-voltage TE modules . As with the e lec t r ica l generation in
this sys tem, the pump packages have no moving par ts and their hydraul ic
power output i nc r ea se s automatical ly as the reac tor operating t empera tu re in
c r e a s e s . The advantages of this type pump a re simplicity of operation and high
rel iabi l i ty . The one disadvantage is that the p r e s s u r e - d r o p within the loops
must be kept low. However, in the design of a TE sys tem this is not par t icu
lar ly r e s t r i c t i ve .
a. Technology Status
Due to the compatibili ty of TE power sources with dc pumps, most of the
pump developnnent has been devoted to in tegral source dc pumps. In this type
the TE genera tor is int imately attached to the throat of the pump and the need
for h igh-cur ren t buses is vir tually el iminated.
144 in.
3 68
100
27
68
250
957 in.3
AI-AEC-MEMO-12717 91
- ' ' * - te>' . - , : ' , i ' - ' ".?-.•
1-22-64 7636-5402CN
F i g u r e I V - 1 8 . M e r c u r y - R a n k i n e P r o g r a m I n t e g r a l S o u r c e P u m p
P
•V;-"';T-?:'
^•1^'tSli.T
•?.''-tl>i"-i' . •?'.-l'^ 'i^
1 0 - 2 6 - 6 2 7561-5471
F i g u r e I V - 1 9 . SNAP 1 OA I n t e g r a l S o u r c e P u m p
A I - A E C - M E M O - 12717
92
The SNAP 2 Mercury-Rankine P r o g r a m (MRP) developed a dc conduction
pump which used chromel -cons tan tan for the TE power genera tor . The pump
throat consisted of a Type 316 s t a in l e s s - s t ee l tube having a wall thickness of
0.020 in. The active throat length •was 10 in. The MRP pump is shown in F ig
ure IV-18. This pump was designed to operate in a vacuum environment at
1200°F. Over 20,000 h r of test exper ience were accumulated on this pump.
The SNAP lOA pump, shown in Figure IV-19, was a dc conduction pump
powered by a l ead- te l lu r ide TE genera to r . The pump operated at 1000°F in a
space environment and met all shock and vibration requ i rements for launch into
an Ear th orbit . More than 150,000 hr of test operation were logged by this
pump including over 20,000 hr by a single pump. Moreover , the pump was suc
cessfully operated in space during the SNAP lOA space flight.
In addition to these in tegral source pump designs which in general impose
the mos t severe r e s t r i c t i ons on pump design, over 50 dc conduction pumps have
been fabricated at AI for use in ground test faci l i t ies . These pumps have been
po^wered by remote power supplies and have been used for various component
t e s t s . They have operated without a single failure for over 200,000 h r . The
design concepts and fabrication methods used in them a re those specified for the
pump to be used in the ZrH reac to r — TE sys tem.
A t r i p l e -pa s s pump s imi la r to the reference design pump has been fabr i
cated and was pe r fo rmance- t e s t ed . The measured performance was within 5%
of that predic ted.
All fabricat ion steps of the selected pump a re s t a t e -o f - the -a r t and no new
p r o c e s s e s a r e involved.
b. Pump Power Source
To maximize the use of existing tubular TE module experience and to mini
mize the different types of ha rdware development required for the program, a
separa te pump power source , consisting of modules s imi lar to the power-
generat ion modules , was chosen for the reference design.
The bas ic design problem that had to be overcome was to obtain a high cur
rent at a low enough voltage to match the impedance in the pump throa ts . P r e
l iminary studies showed that a p rac t ica l mul t ipass pump, one in which the e lec
t r i ca l cu r ren t flo-ws through more than one throat in s e r i e s , could be designed
AI-AEC-MEMO-12717 93
I
>
n
o
INNER CLAD,
OUTER CLAD
COLLECTOR RING
ELECTRICAL PIN
RETAINING RING
Figure IV-20. FHimp Converter (Drawing No. 939J386)
if a tubular module could be developed to provide 500 amp at a nominal voltage
of 0.22 volts. The design of such a special purpose module was evaluated and
fo\md to be feasible.
The TE-pump module has an active length of 7 in. , consisting of four t h e r
mocouples in se r i e s that produce an open-c i rcui t voltage of 0.54 volt at the nom
inal mean hot- and cold-clad t e m p e r a t u r e s , 1125 and 570°F, respect ive ly . A
layout of the reference module is shown in Figure IV-20 and a summary of i ts
cha rac te r i s t i c s is given in Table IV-7.
TABLE IV-7
PUMP MODULE SUMMARY
Nominal Load Requirements
Power, watts e lec t r ica l
Current , amp
Voltage, volts
Res is tance , mil l iohms
Module Charac te r i s t i c s
Mean hot-c lad t e m p e r a t u r e , °F
Mean cold-clad t e m p e r a t u r e , °F
Efficiency, %
Internal r e s i s t ance , mil l iohms
Elec t r ica l pin r e s i s t a n c e , mil l iohms
Inner d iameter , in.
Outer d iameter , in.
Open-circui t voltage, volts
Active length, in.
Number of couples
Weight, lb
Heat required, kwt
110
500
0.22
0.44
1125
570
3.46
0.54
0.10
0.75
2.24
0.54
7
4
7.4
3.2
AI-AEC-MEMO-12717 95
TE POWER SOURCE
>
O
O I 1—'
-J I — '
MAGNET YOKE
PRIMARY LOOP'
HEAT REJECTION LOOP"
OS*
POWER SUPPLY (TUBULAR TE MODULES)
VOLTAGE (mv)
CURRENT (amps)
MAGNETIC FLUXdmes/in.^)
PRIMARY
NO. COOLANT PASSES 2
AP(psi) 3.35
FLOWRATE (lb/sec) 3.25
WEIGHT (lb)
• POWER SUPPLY
• PUMP
• BUS
TOTAL
HYDRAULIC POWER ( watts)
THERMAL POWER (kwO
NET EFFICIENCY (%)
3
220
1500 (500 each)
11,500
HRL
1
1.5
3.10
30
30
50
110
65
9.6
0.68
Figure IV-21 . P r i m a r y and Heat-Reject ion Loop E lec t romagne t i c -Pump Assembly 8-J1-099-12
Because the high cu r ren t and low-voltage output requi res the pump module
to have a low internal r e s i s t a n c e , its e lec t r ica l conductors a r e relat ively thick.
The radial and axial th icknesses of the conductors and the TE washers were
sized so that the module in ternal r e s i s t ance would equal the effective load r e
s i s tance , 0.54 mil l iohm. Design trade-offs were a lso made to satisfy the load
requ i rements without imposing significant thermal-power or •weight penalties on
the sys tem.
Although the pump module design differs from that of the tubular modules
in the main conver te r , s t r e s s calculations and consideration of the manufactur
ing process indicate that fabrication of this design concept is feasible.
c. Pump System Descript ion
Several a l te rna te pump designs were considered before an a t t ract ive pack
age was designed based on the cha rac te r i s t i c s of the tubular TE modules de
scr ibed above. The best design using these modules was found to resul t when
the pumping requ i rements for both the p r i m a r y loop and HRL's were combined
at one location so that th ree modules could be operated in paral le l to provide
high cur ren t at the location v/ithout a penalty due to inefficient use of thermal
power. In this vi ay 1500 amp was available to the pumps at 0.22 volts.
The cha rac t e r i s t i c s of the sys tem dictated that the optimum configuration
would be as shown in F igure IV-21, where the e lec t r ica l current is passed
through two throats on the p r i m a r y loop and one on the HRL. With this config
urat ion the hydraul ic po^wer available to the p r imary would be approximately
twice that available to the HRL. Also it was determined that the pr imary- loop
throats should be in the cooler portion of the loop (1044°F) and the heat - re jec t ion
throat should be in the hot ter portion of its loop (663 °F) . This would minimize
the the rmal shunting between loops.
A sys tem optimization •was performed, trading off NaK-system weight
against pump weight •with p r e s s u r e drop as the var iable . On the basis of the
optimization, p r e s s u r e drops of 3.35 psi in the p r imary loop and 1.5 psi in the
HRL's were selected.
F igure IV-22 sho^ws the reference design pump package. The three-module
power source is designed s imi la r to the 4-packs in the main TE conver ter . One
AI-AEC-MEMO-12717 97
THERMOLLLCTRIC COMVtRTER KAODULE
MAGMET
YOK.E
S E - C T I O M fK- f\ 7759-5293
Figure IV-22. F^amp Assembly, Separate Source,
Three -Throa t
AI-AEC-MEMO-12717 99
of these pump packages is used in each quadrant of the sys tem. The power sup
ply weighs 30 lb, the pump also 3 0, and the e lec t r ica l bus 50 for a total of
110 lb.
Figure IV-23 shows the predicted performance of the pump as designed.
Note that at the reference flowrates the p r imary - loop p r e s s u r e - d r o p is 3.45 psi
and that at the HRL is 1.65. These values a r e g r ea t e r than those in the sys tem
design, to provide a design marg in for meeting the pumping requ i rement . F u r
ther margin also exists since the calculated p r e s s u r e - d r o p s for both loops a r e
well below the l imit . The total t he rmal power required to run the four-pump
system is 38.4 kwt or 6.6% of the reac tor power.
Thermal and s t r e s s analyses were conducted to evaluate the pump, and no
ser ious problems were determined for ei ther s teady-s ta te or t rans ien t opera
tion. The differential expansion between the hot and cold throats is bas ica l ly
alleviated by sli ts in the connecting bus bar which allows it to bend more freely.
The maximum magnet t empera tu re , even when operating at 1150°F in the p r i
m a r y loop and 650 in the HRL is 790°F. This is well within the allowable t em
pera ture range for the magnet ma te r i a l .
2. Expansion Compensator
The p r imary loop and HRL a r e designed to be void-free at all t imes . Ex
pansion compensators a r e used in the loops to accommodate the expansion of
the NaK from the cold shutdown condition to the hot operating condition, and to
maintain the sys tem at the operating p r e s s u r e .
a. Technology Status
More than 50 expansion compensators of the type shown in F igure rV-24
were built under the SNAP lOA development p rog ram for development, qualifi
cation, and sys tem t e s t s . This unit is a spring-loaded bellows with a latch
mechanism to prevent deformation due to hydraul ic loads experienced during
launch. A position indicator was also included to provide a measu remen t of
the NaK-loop status during operation. More than 100,000 h r of testing were
accomplished on the SNAP lOA expansion compensator ; the longest single tes t
was 10,000 hr as a par t of a complete nuclear sys tem tes t .
AI-AEC-MEMO-12717 101
CURRENT = 1500 amp MAGNETIC FLUX = 11,500 lines/in
PRIMARY-LOOP PASSES •(TOTAL)
2
•HEAT-REJECTION PASS —
0 1
1-14-69 UNC
2 3 4 5 NaK FLOWRATE, lb/sec
6 7
7759-5294
Figure IV-23. Reference Pump Pe r fo rmance
AI-AEC-MEMO-12717 102
F i g u r e I V - 2 4 . SNAP 1 0A E x p a n s i o n C o m p e n s a t o r
b . Des ign D e s c r i p t i o n
The s i ze and weight of the c o m p e n s a t o r s a r e a funct ion of loop NaK vo l
u m e s , the o p e r a t i n g t e m p e r a t u r e s , and o p e r a t i n g p r e s s u r e s . T a b l e IV-8 p r e
s e n t s the NaK v o l u m e s for the r e f e r e n c e s y s t e m . At the r e f e r e n c e o p e r a t i n g 3 3
t e m p e r a t u r e the e x p a n s i o n vo lume of the p r i m a r y loop i s 0.161 ft p e r ft of 3 3
NaK v o l u m e , and 0.061 ft p e r ft of NaK vo lume for the H R L ' s . Using the vo l -3
u m e s in Tab le I V - 8 the to ta l p r i m a r y - l o o p e x p a n s i o n r e q u i r e m e n t i s 0.59 ft and that for the H R L i s 0.44 ft'^.
F o u r e x p a n s i o n c o m p e n s a t o r s a r e r e q u i r e d for the H R L , one for each quad
r a n t . It is a l s o conven ien t to h a v e four c o m p e n s a t o r s in the p r i m a r y l oop . 3
T h u s , the p r i m a r y loop would r e q u i r e four 0.15-ft c o m p e n s a t o r s and the H R L 3
four 0.11-ft c o m p e n s a t o r s . To p r o v i d e c o m m o n a l i t y of d e s i g n , a s ing le c o m -3 .
p e n s a t o r s i z e was s e l e c t e d (0.15 ft ), which r e s u l t s in a s l igh t o v e r d e s i g n in the
H R L . A d o u b l e - s e a l e d g a s - b a c k e d c o m p e n s a t o r af fording s e c o n d a r y NaK con
t a i n m e n t w a s s e l e c t e d to m e e t t h e s e e x p a n s i o n r e q u i r e m e n t s . The c h a r a c t e r i s t i
A I - A E C - M E M O - 1 2 7 1 7
103
TABLE IV-8
NaK VOLUMES
P r i m a r y Loop
Reactor
Converter
Piping
Total :
Heat-Reject ion Loop
Converter
Gal lery piping
Radiator
Total :
1.75 ft^
1.07
0.82
3.64 ft^
1.59 ft^
0.63
4.95
7.17 ft"
TABLE IV-9 EXPANSION COMPENSATOR
CHARACTERISTICS
Type
Expansion volume
P r e s s u r i z a t i o n
Size:
Diameter
Height
Weight
Number requi red
Double-bellows s e r i e s
0.15 ft^
Inert gas
11 in.
9.65 in.
26 lb
8
of such a compensator a r e summar ized in Table IV-9 and a conceptual drawing
of it is shown in F igure IV-25.
The principle of operation of the compensator involves two bellows assem
bled in s e r i e s as shown in F igure IV-25. Two sets of s e r i e s - s t a c k e d bellows
a r e mutually opposed. The inner surface of the p r imary bellows and the
bel lows-top cups of the compensator provide containment for the NaK. The
AI-AEC-MEMO-12717 104
SECONDARY VOLUME EVACUATION TUBE 2 PLACES
H 00 DIAM
ALTERNATE GAS TUBE CONFIGURATION
FULL VOLUME POSITION
NaK SUPPLY TUBE 0 375 ODx 0 049 WALL
PRIMARY BELLOWS 10 50 OD X 9 00 ID
SECONDARY BELLOWS 10 50 ODx 9 00 ID
8-JY25 119-38
Figure rV-25. Expansion Compensator , 25-kwe Nuclear The rmoe lec t r i c Power Supply
space between the bellows outer surface and the cyl indrical sect ions inner su r
face is evacuated and const i tutes the secondary containment in event of a NaK
leak through the p r i m a r y bel lows. The volume of the inner surface of the s e c
ondary bellows is closed with a dome to facilitate gas fill for sys tem p r e s s u r i
zation. The opposed bellow design provides par t ia l sys tem pressur iza t ion in
the event of the loss of p r e s s u r e from one gas chamber . The null point of the
bellows (heat- t reat position) is at about 2/3 of the maximum s t roke , to allow the
bellows to operate at a low s t r e s s at the operational and launch volumes.
With inc rease of sys tem t e m p e r a t u r e , the NaK volume change is displaced
by the p r i m a r y bellows and the initial p r e s s u r e within the secondary bellows is
increased proport ional to the PVT ( p r e s s u r e / v o l u m e / t e m p e r a t u r e ) re la t ion
ship. This gas p r e s s u r e , in addition to the stiffness of the bel lows, es tabl ishes
the sys tem operating p r e s s u r e . F igure IV-26 shows this p r e s s u r e as a function
of average NaK t empera tu re for the two loops. The normal operating p r e s s u r e
for both loops is 20 psia while p r e s s u r e within the loops at launch, when non-
operat ing, is approximately 6 ps ia . The curves in Figure IV-26 also show that
T 1 1 1 r
0 i 1 I I i I I 0 200 400 600 800 1000 1200
AVERAGE NaK TEMPERATURE (°F)
8-JY19-119-5
Figure IV-26. Expansion-Compensator P r e s s u r e Charac te r i s t i c s
AI-AEC-MEMO-12717 106
even with one chamber vented to space, both loops would maintain adequate
p r e s s u r e during a shutdo^vn.
At operating t empera tu re both bellows a r e at minimum ex tens ion-s t ress
and maximum p r e s s u r e - s t r e s s leve ls . The tempera ture limitation on the bel
lows is approximately 725 °F . At this t empera tu re the bellows maintain their
s p r i n g - r a t e , a s s i s t in maintaining sys tem p r e s s u r e , and a r e safely below the
normal h e a t - t r e a t t empera tu re of 800°F. The t empera tu re of the bellows will
be maintained at this level by design of the gal lery. However, no NaK-contain-
ment failure of the bellows would be expected until a t empera ture of at least
900 to 1000°F is exceeded.
The expansion compensa tors will be located near the high point of their
loop during launch. The actual attach point for the compensator supply line
will be at the high point so that as the launch acce lera t ion i nc r ea se s , the line
will drain down into the compensator eliminating large static head forces .
D. RADIATOR
1. Concept Selection
The rad ia tor for the HRL is one of the most mission-dependent subsystems
in the powerplant. Integration const ra in ts associated with launch package size,
operat ional cycle, and rel iabi l i ty , all affect the choice of a radiator type.
Several radia tor design variat ions were considered during this study, in
cluding heat -p ipe designs and relat ively standard fin-and-tube rad ia to r s with
ei ther fixed or folding NaK joints . Although final selection of a radiator design
concept would depend strongly on miss ion and integrat ion const ra in ts , a fixed,
cylindrical tube-and-fin type radia tor was tentatively selected for the reference
power sys tem design in o rder to more completely define its design and pe r
formance c h a r a c t e r i s t i c s . Several rad ia tor ma te r i a l combinations were ana
lyzed, including a luminum-bery l l ium alloy (Lockalloy) and pyrolytic graphite
for the radia tor fin and meteoroid a r m o r ; however , aluminum fins diffusion-
bonded to s t a in l e s s - s t ee l tubes were selected, due to the relat ive simplicity
and technology available for this comibination. A semimonocoque ti tanium sup
port s t ruc ture s imi la r to that used in the SNAP lOA system was also selected
for the same r e a s o n s .
AI-AEC-MEMO- 12717 107
TABLE IV-10
TUBE-AND-FIN RADIATOR DESIGN CRITERIA
The rma l power
Inlet t empera tu re
Outlet t empera tu re
NaK flow (total)
The rma l -con t ro l coating:
Emiss iv i ty
Solar absorpt ivi ty
Meteoroid nonpuncture pr
Tube d iameter
obabiT Lty"~
551 kwt
663°F
463°F
12.4 l b / s e c
0.90
0.30
0.990
3/8 in.
CONFIGURATION
CYLINDRICAL RADIATOR
H * 1.5 X D-
ti w^\s •ALUMINUM FIN
^ALUMINUM ARMOR
SS TUBE (Wall thickness = 0.020 in.)
11.5 ft-diam CYLINDER
RADIATING FROM ONE SIDE
STRUCTURE WEIGHT= 0.75 Ib/ft^
'^Reference for meteoroid a r m o r calculat ions: H. D. Hal ler and S. Lieblein, NASA LERC, Analytical Comparison of Rankine Cycle Space Radiators Constructed of Central Double and Block-Vapor-Chamber Fin-Tube Geomet r i e s , " NASA T N D - 4 4 1 1 , F e b r u a r y 1968
AI-AEC-MEMO- 12717 108
Several feasible designs for folding NaK joints which would make possible
the use of deployable rad ia tor panels were evolved. Although such a design is
not specifically incorpora ted in the reference sys tem, the concept may be of
sufficient in te res t for applications requir ing compact powerplant packaging to
justify further investigation and development. The heat -p ipe radiator concept
was not selected due to the lack of a des i rab le working fluid for the 500 to 600°F
t empera tu re range of in t e re s t for this sys tem.
2. Radiator Design
The assumpt ions , configurations, and c r i t e r i a used for the radia tor design
a r e shown in Table IV-10. The the rmal power and t empera tu res l isted a re
those w^hich •were determined to be nea r -op t imum for the reference system on
the bas is of overal l sys tem weight.
F igure IV-27 shov/s the total r a d i a t o r - p l u s - s t r u c t u r e weight as a function of
rad ia tor a rea for different numbers of tubes. The minimum-weight envelope is
a lso plotted. The weight includes the tube, fin, a r m o r , s t ruc ture , and NaK 2
holdup. A s t ruc ture weight of 0.75 lb/ft , determined by a separa te design
study, was used. This plot shows that as the a rea is increased from 1250 to 2
1400 ft , the optimum number of tubes for minimum weight d e c r e a s e s . The 2
min imum radia tor -weight point exists at about 1450 ft with approximately 100
tubes; however, it is c lear that an a rea /weigh t trade-off can be made for the 2
re fe rence sys tem over a rad ia tor a rea range from 1200 to 1450 ft .
Another considerat ion in the radia tor design is the NaK p r e s s u r e - d r o p in
the tubes. P r e l i m i n a r y analys is showed that the tube size should be small to
minimize radia tor weight and a r e a , but the minimum size was res t r i c t ed to
3 /8- in . diam based on potential NaK-plugging considerat ions . Calculations in
dicated that even for this tube size the p r e s s u r e - d r o p was excessive for r ad i
ator a r ea s of in te res t when the NaK was allowed to flow the complete length of
the tube. This excess ive p r e s s u r e - d r o p was alleviated by breaking the flow
into two to three para l le l paths . This also provides some advantage in system
assembly; however, such an a r rangement r equ i res additional headers feeding
the individual NaK tubes.
Thermal per formance for the radia tor was calculated for the worst case
where the projected a r ea is normal to the sunlight. Per formance of the radia tor
AI-AEC-MEMO-1271 7 109
4000 -
C3
LJ
o ZD
h-
+
3000 -
P 2000
< a:
1000 1000
NO. OF NaK TUBES
220
SATURN-V OWS DESIGN
J t
LOCUS OF MINIMUM WEIGHT
REFERENCE DESIGN
± 1200 1400 1600
RADIATOR AREA ( f r ) 8-J26-119-73A
Figure IV-27. Cyl indr ica l -Radia tor Weight Charac te r i s t i c s
AI-AEC-MEMO-12717 110
in the full shade or with sun reflection and d i rec t radiat ion from the earth will
be increased by a maximum of about 2.5%. 2
Table IV-11 p resen t s the cha rac t e r i s t i c s of the 1400 ft cylindrical radia tor 2
selected for the re ference sys tem. An a r ea of 1450 ft would resul t in a slight •weight reduction but not enough to war ran t the l a rge r a r ea . Areas below 1400 ft
resu l t in rapidly increas ing weight c h a r a c t e r i s t i c s . A drawing sho^wing the
c ross - sec t iona l design of a typical radiator is shown in Figure V-9 .
TABLE IV-11
REFERENCE RADIATOR CHARACTERISTICS
Radiator a r e a , ft
Geometry
Number of tubes
A r m o r th ickness , in.
Fin th ickness , in.
Fin and a r m o r m a t e r i a l
Tube outside d iamete r , in.
Tube th ickness , in.
Tube ma te r i a l
S t ructure
Total weight, lb""
1400
Cylindrical
94
0.19
0.035
6061 Aluminum
3 / 8
0.020
347 Stainless steel
Titanium alloy
2580
-''Includes tube, NaK fin, a r m o r , and s t ruc ture
AI-AEC-MEMO-12717 111
V. MISSION ADAPTATIONS
The re fe rence 25-kwe reac to r — TE sys tem descr ibed in the preceding sec
tions of this repor t provides a general design bas is from which powerplants can
be configured for specific space applicat ions. Mission and integration cons ide r
ations a r e par t icu la r ly important when concerned with the radiation shield and
heat - re jec t ion rad ia tor design, which in turn affects the design and performance
cha rac t e r i s t i c s of the power sys tem. To i l lus t ra te severa l typical integration
concepts and corresponding powerplant c h a r a c t e r i s t i c s , designs for three m i s
sions for which r eac to r — TE sys tems have been and a r e being considered a r e
presented in this section. The f i rs t design is ta i lored to the Saturn-V OWS m i s
sion cur ren t ly under study by NASA as a par t of the Apollo Applications P r o g r a m
(AAP). The second is an update of a powerplant concept evolved in a recent
NASA/AEC study of r eac to r power sys tems for manned lunar ba se s . The third
updates an ea r l i e r design developed in a joint NASA/AEC study of reac tor power
sys tems for the MORL. In the la t ter two cases the bas ic integration concepts
and constra ints es tabl ished in previous studies were maintained, whereas the
OWS powerplant design and integrat ion concept were evolved in this study.
A. SATURN-V OWS POWERPLANT
1. Mission Requi rements and Integration Considerat ions
The Saturn-V OWS concept being studied by NASA is a d i rect , generic evolu
tion from the Saturn-I Workshop which is cur ren t ly under development as par t of
the AAP, As cur ren t ly conceived, the Saturn-V OWS would consist of a dry
Saturn-IVB stage s t ruc tu re fitted with docking por t s , a i r locks , power and life-
support equipment, exper iments , and other subsys tems requi red to function as
a manned OWS. The Saturn-V OWS would be launched (fully equipped) using the
f irs t two stages of the Saturn-V launch vehicle. The planned launch date is cu r
rently est imated to be in the 1973 to 1975 t ime period. The nominal orbit altitude
and inclination a r e 270 n, mi (nautical mi les ) , 50°,
One of several possible Saturn-V OWS configurations is shown on the front
ispiece of this r epor t with a nuclear power sys tem attached to the forward docking
port . This concept would provide accommodations for a s ix-man crew with
AI-AEC-MEMO-12717 112
g r o w t h c a p a b i l i t y to n i n e . The d e s i g n goal for the o p e r a t i o n a l l i f e t ime of the
OWS i s 2 y r , a l though the c r e w would be r o t a t e d s e v e r a l t i m e s p e r y e a r , u s ing
a modi f i ed v e r s i o n of the Apol lo C o m m a n d and S e r v i c e Module (CSM).
The o r b i t a l a v e r a g e cond i t i oned power r e q u i r e m e n t s for the S a t u r n - V OWS (2) a r e c u r r e n t l y e s t i m a t e d to be f r o m 12 to 16 kwe. C o n s i d e r i n g power cond i
t ion ing l o s s e s , t he g r o s s dc power r e q u i r e m e n t s would thus be in the r a n g e of
14 to 18 kwe . A p o w e r g r o w t h m a r g i n i s a l s o d e s i r e d and the m i n i m u m r a n g e
of i n t e r e s t for the n u c l e a r p o w e r s y s t e m h a s t h e r e f o r e been a s s u m e d to be f rom
15 to 20 k^we. Uncond i t i oned vo l t age r e q u i r e m e n t s a r e 28 vdc o r h i g h e r .
No spec i f i c r e l i a b i l i t y r e q u i r e m e n t s for the power s y s t e m have been e s t a b
l i s h e d , but it i s known tha t a m i s s i o n - s u c c e s s p r o b a b i l i t y for the e n t i r e OWS of
0,95 o r b e t t e r would be d e s i r e d . Thus the r e l i a b i l i t y of the power s y s t e m p r o
duc ing 15 to 20 kwe for the 2 - y r d u r a t i o n would p r o b a b l y have to be ^^0.99, a s
s u m i n g tha t th i s l eve l of po^wer is r e q u i r e d for m i s s i o n s u c c e s s . Surv iva l r e l i
a b i l i t y r e q u i r e m e n t s in e x c e s s of 0,99 for the e n t i r e OWS a r e a l s o d e s i r e d but
diff icult to p r o j e c t , m u c h l e s s d e m o n s t r a t e . P r e v i o u s s t u d i e s of r e a c t o r power
s y s t e m s for the M O R L have conc luded tha t a backup power s y s t e m c a p a b l e of
p r o d u c i n g suff ic ient p o w e r for m i n i m u m s ta t ion and o r b i t - k e e p i n g for a p e r i o d
of about 42 days would be n e c e s s a r y to p r o v i d e such a s s u r a n c e .
In add i t ion to the g e n e r a l p o w e r s y s t e m r e q u i r e m e n t s d i s c u s s e d above , a
n u m b e r of i m p o r t a n t i n t e g r a t i o n f a c t o r s m u s t be c o n s i d e r e d . Among t h e s e a r e :
1) P o w e r s y s t e m c o n f i g u r a t i o n and loca t ion .
2) R a d i a t i o n - s h i e l d we igh t and d o s e p ro f i l e .
3) Launch and deplo^yment m o d e s ,
4) E O L d i s p o s a l p r o v i s i o n s .
All of the above c o n s i d e r a t i o n s a r e i n t e r r e l a t e d , p a r t i c u l a r l y the f i r s t two.
F o r e x a m p l e , it i s d e s i r a b l e t ha t the po^wer s y s t e m i n t e g r a t i o n i m p o s e m i n i m a l
m o d i f i c a t i o n s to the OWS c o n f i g u r a t i o n o r c o m p r o m i s e s in i t s o p e r a t i o n . The
l oca t i on of the t e l e s c o p e w i th i t s r a d i a t i o n - s e n s i t i v e f i lm and o the r e x p e r i m e n t a l
s e n s o r s in the aft end of the OWS m a k e the i n t e g r a t i o n of the n u c l e a r s y s t e m in
tha t r e g i o n difficult and u n d e s i r a b l e . S i m i l a r l y , a t t a c h m e n t of the powerp l an t to
A I - A E C - M E M O - 1 2 7 1 7
113
the sides of the workshop would requi re the use of long deployment boomis to
obtain acceptable radia t ion-shie ld weights, due to the length of the OWS, which
is about 120 ft (including a docked CSM in the forward docking port) . Thus by
a p rocess of el imination it appears that the most favorable location for the
nuclear power sys tem for the OWS as now conceived would be attached to the
forward docking port , as shown on the front ispiece. The side docking por ts
would then be used for docking the CSM's.
The basic radiat ion shielding requ i rements a r e that the total radiation dose
received by the crew during normal operat ion, rendezvous, and ext ravehicular
act ivi t ies (EVA) should not exceed prede termined allowable levels . An allowable (3) whole-body dose of 100 r e m / y r has been proposed for this miss ion . The ex
pected annual whole-body dose due to natura l radiation (electrons and protons)
for the specified orbit is approximately 56 r e m . Thus an allowable annual
whole-body dose of 44 r e m or less from the nuclear power sys tem would ap
pear to be an acceptable and reasonable requ i rement . For the present study
a shield dosera te r equ i rement in the range of 20 to 30 r e m / y r within the Work
shop and a rendezvous dose of l ess than 5 r e m were assumed.
Launch and deplo-yment considerat ions r equ i re that the power sys tem con
figuration, s ize, and weight be compatible with available launch vehicles appro
priate for the miss ion . An objective for this study has been to evolve a power-
plant design which, with minor modifications, could be compatible with any of
the following launch options:
1) Integral launch with the OWS on the two-stage Saturn-V,
2) Separate launch on a Saturn-IB,
3) Separate launch on a Ti tan-3 ,
The la t ter two cases would requ i re an unmanned rendezvous with the OWS,
using the Apollo serv ice module, or Titan Trans tage , Additional details on pay-
load capabili t ies and proposed launch configurations a r e discussed in Sec
tion V-A-3 .
The EOL-disposal r equ i rement is based on nuclear safety considera t ions .
Previous studies made under the AEC Aerospace Nuclear Safety (ANS) P r o g r a m
AI-AEC-MEMO- 12717 114
have shown that it will be des i rab le to provide rel iable means for disposing of
the r eac to r after sustained operation in the orbit altitude range of in te res t for
the OWS, Two general approaches toward satisfying this requi rement con
s idered to be acceptable a r e to:
1) Boost the r eac to r up to a higher orbit (^-450 mi les ) , or
2) Deboost the r eac to r into deep ocean a r e a s .
In the f i rs t approach the f iss ion-produce activity will decay to safe levels
before eventual random r e - e n t r y . Recovery is not required in the second
approach.
Table V-1 summar i ze s the miss ion and power -sys tem requi rements which
have been specified, derived, or a s sumed for this study,
2, System Description
In adapting the re ference r eac to r — TE system to the Saturn-V OWS there
a re no changes in per formance , and all of the foregoing miss ion requirements
a r e met . At full power the sys tem produces 24,7 kwe at 56 volts dc ± 1%, The
rel iabi l i ty requ i rement of 0,99 is exceeded at a par t ia l -power level of about
18 kwe. All performance p a r a m e t e r s and rel iabil i ty es t imates a re as descr ibed
in Section HI. The only difference frona the reference system descr ibed in that 2
section is that the radia tor a r e a is reduced fromi 1400 to 1287 ft at a weight
penalty of 320 lb.
The radiat ion environment imposed by the operating reactor will be p r e
sented la ter in Subsection a, with the discussion of the two shield options,
A layout of the complete plant as adapted for the Saturn-V OWS is shown
in Figure V - 1 , It is designed to mount in line with the Workshop on the Multiple
Docking Adapter (MDA) as depicted in F igure V-2,
During launch the power sys tem is housed •within the heat shield shroud (or
power-supply adapter) , which acts as an aerodynamic fairing and s t ruc ture .
This shroud is coated to provide a re la t ively high solar absorptivity and low
emiss iv i ty so that the equi l ibr ium t empera tu re within it, when the powerplant
is not operat ing in space, is about 100°F, This technique, proven during the
SNAP lOA flight tes t , a s s u r e s that NaK freezing does not occur . When inside the
shroud the overal l plant length is 47.3 ft and the shroud diameter is 12.8 ft.
AI-AEC-MEMO-12717 115
T A B L E V - 1
S A T U R N - V O R B I T A L WORKSHOP MISSION R E Q U I R E M E N T S F O R NUCLEAR P O W E R SYSTEM
Uncond i t ioned power l eve l :
U n r e g u l a t e d v o l t a g e :
Des ign l i f e t i m e :
R e l i a b i l i t y :
R a d i a t i o n d o s e (wholebody) :
T o t a l , inc lud ing n a t u r a l r a d i a t i o n
R e a c t o r ( n o r m a l o p e r a t i o n )
R e a c t o r ( r e n d e z v o u s )
Spec i a l n u c l e a r s a fe ty p r o v i s i o n s :
Launch o p t i o n s :
P r o b a b l e l a u n c h d a t e :
G e n e r a l i n t e g r a t i o n c o n s t r a i n t :
P r e f e r r e d p o w e r s y s t e m loca t ion :
15 to 20 kwe
> 28 vdc
2: 2 y r
^ 0 , 9 9
100 r e m / y r
20 to 30 r e m / y r
-^5 r e m
E n d - o f - l i f e d i s p o s a l
(Orb i t boos t to ^-450 m i o r d e b o o s t in to ocean)
I n t e g r a l wi th t w o - s t a g e S a t u r n - V
S e p a r a t e wi th S a t u r n - I B / C o m m a n d and S e r v i c e Module or T i t a n - I I I / T r a n s t a g e
1973 to 1975
M i n i m a l mod i f i ca t i on to O r b i t a l W o r k s h o p or l a u n c h v e h i c l e s
Docked to f o r w a r d p o r t of Mul t ip le Docking A d a p t e r
A I - A E C - M E M O - 12717 116
-APOLLO COMMA/^£> ^££rPV/C£ MODOL£ (P^p)
D*TE ykrCBOVtD
SATURN V WORKSHOP
£5/<r\^e NOCLEAP THCRMOeLECTP/C P'OWER 5C/PPL y
PReSSCR/ZED EXPER/ME/Vr CA/^/STER
POWER £a/='PL YADAPrER
- A^^L T/PLE DOCMAJG /IZ^APTE/?
O 5 10 I I I i I M I I I
IS
I 20 2S
_L_ 30 35 40 45
_ L _ 50
rcET Figure V-2, Saturn-V Orbital Workshop with 25-kwe
Nuclear Thermoelec t r ic Power Supply
AI-AEC-MEMO-127 17 119
Dur ing o p e r a t i o n the s y s t e m i s ex t ended out f r o m wi th in the sh roud to e x
p o s e the r a d i a t o r . Th i s p r o v i d e s the added a d v a n t a g e of i n c r e a s i n g the s e p a r a
t ion d i s t a n c e to o v e r 100 ft b e t w e e n the r e a c t o r and the p r i m a r y a r e a s of the
W o r k s h o p w h e r e p e r s o n s a r e l o c a t e d . The m e t h o d of ex tending and r e t r a c t i n g
the p o w e r p l a n t w a s s tud ied only enough to e s t a b l i s h f ea s ib i l i t y . With the m e t h o d
evo lved , the p l an t i s guided by r a i l s i n c o r p o r a t e d into the r a d i a t o r moving on
r o l l e r s a t t a c h e d to the s h r o u d , and i s m o v e d by a s c r e w j a c k a r r a n g e m e n t , A
c o n c e p t u a l d e s i g n of the d e p l o y m e n t m e c h a n i s m is shown in F i g u r e V - 3 . The
m o t i v e f o r c e i s p r o v i d e d by a d r i v e m o t o r o p e r a t i n g t h r o u g h a g e a r t r a i n on a
ba l l s c r e w - a n d - n u t c o m b i n a t i o n . A m a g n e t i c b r a k e i s emp loyed for pos i t i ve
l ock ing . The d e s i g n i s s i z e d to ex tend the s y s t e m in about 15 m i n .
The r e a c t o r c o n t r o l e q u i p m e n t , TE c o n v e r t e r p r o t e c t i v e d i o d e s , and the
v o l t a g e - r e g u l a t i o n e q u i p m e n t would be l o c a t e d in the space s t a t ion , a c c e s s i b l e
for e q u i p m e n t r e p l a c e m e n t o r r e p a i r d u r i n g o p e r a t i o n .
Tab le V-2 g i v e s a we igh t b r e a k d o w n for the power s y s t e m excluding the h e a t -
sh i e ld s h r o u d . Inc luded a r e the we igh t s for the t w o - s h i e l d opt ions d i s c u s s e d in
the fol lowing s u b s e c t i o n .
The c o m p o n e n t s for the s y s t e m a r e d e s c r i b e d in Sect ion IV. In the fol lowing
p a r a g r a p h s the spec i f i c c o m p o n e n t a r r a n g e m e n t s a r e d e s c r i b e d for th i s a d a p t a
t ion of the p lan t ,
a . R a d i a t i o n Shie ld Des ign
The r a d i a t i o n sh i e ld r e q u i r e m e n t s and concep t s h a v e an i m p o r t a n t effect on
the o v e r a l l c h a r a c t e r i s t i c s of r e a c t o r p o w e r p l a n t s for the S a t u r n - V OWS m i s s i o n .
The m o s t i m p o r t a n t sh i e ld c o n s i d e r a t i o n s a r e the dose c r i t e r i a , the g e o m e t r y
of bo th the r e a c t o r and the s p a c e c r a f t , and the sh ie ld m a t e r i a l s . The a s s u m p t i o n s
and g e n e r a l a p p r o a c h t a k e n t o w a r d s evolv ing a c o n c e p t u a l sh ie ld des ign for th i s
i n i s s i o n a r e d i s c u s s e d in t h i s s e c t i o n a long wi th the r e s u l t s ob ta ined .
The sh i e ld ing a n a l y s i s r e q u i r e d to evolve an o p t i m u m m i n i m u m - w e i g h t
sh i e ld des ign for th i s type of m a n n e d s p a c e m i s s i o n i s qui te c o m p l e x and the
r e s u l t s in the p r e s e n t s tudy , t h e r e f o r e , m u s t be c o n s i d e r e d a s p r e l i m i n a r y
e s t i m a t e s . R e f i n e m e n t s in e s t i m a t e s of the r a d i a t i o n - s o u r c e t e r m s and the
p o s s i b l e sh i e ld g a l l e r y d i m e n s i o n s which have been m a d e s ince the sh ie ld ing
a n a l y s i s t a s k w a s c o m p l e t e d , h o w e v e r , i n d i c a t e tha t the r e s u l t s p r e s e n t e d should
be c o n s e r v a t i v e .
A I - A E C - M E M O - 1 2 7 1 7 121
12 11 10 H DATt I A^PRO^'E•D
S-a D£. T t ^ ^ C K .
v i t vy c SCALE l / z
12 11 10
^ , > ATOMjTS ,1^^TLR\ U l O V a
C - (JflNO 0 9 9 7 ^ ^ IfFlAVE
"" iHttT
f ^ $ $ $ $ ^
vV
4 PITCH Dl(\ SALL SCeE.W - 3 0 F r u& )• LEflO
- *£ / iKHEf lD MOroe
-AMG/V£r/C SRA/<£:
-BCAR/NS PH£-i?tcflL "SOLL f? -^rtieusT t^es-
VILW B
• INSTtJUMeKJTATlOW LOCltEF?
-L lWMT ^vjl-TCHe.=S
C^ ATOMICS ^1>1LU>^VTI0N a CA 'OC4 Mite ctu o»e>
ccocicc Tfig Q99 74~ltaAve
5E.CTIOM ^ • A
Figure V-3 , Actuator , Nuclear Thermoelec t r ic Power
Supply, Saturn-IVB Orbital Workshop
AI-AEC-MEMO-12717 123
A
'i 7 1
TABLE V-2 SATURN-V ORBITAL WORKSHOP POWER SYSTEM
WEIGHT BREAKDOWN
Component Weight
(lb)
Reactor
Thermoe lec t r i c conver ters
Pumps
Expansion compensators
Piping
Gallery s t ruc tu re
Instrumentat ion and controls
Radiator and s t ruc ture
Power cable
Deployment mechan i sm
Total Unshielded Weight
Shadow
Radiation Shield Weight 14,330
Total Shielded Weight 22,280 24,450
(1) Dose Cr i t e r i a
The radiat ion dose c r i t e r i a assumed for this miss ion were derived from
data presented in a recen t study of Ear ly Orbital Space Stations (EOSS) by (4) McDonnell-Douglas Corporat ion, Table V-3 shows the maximum-al lowable
dose proposed for this type miss ion , the expected dose due to natural space
radiation, and (by subtraction) the maximum dose allowed from the reac to r .
Different values a r e shown for the allowable and expected dose to the whole
body and blood-forming organs , the lens of the eye and skin. The expected
space radiat ion dose is based on the same orbi t altitude and inclination as the
OWS and allows for s t ruc tu re and body self-shielding.
1,422
1,135
440
208
761
120
340
2,900
214
410
7,950
477
16,500
AI-AEC-MEMO-127 17 125
TABLE V-3
RADIATION DOSE CRITERIA
D u r a t i o n (days )
W h o l e b o d y and b l o o d - f o r m i n g o r g a n s
L e n s of e y e
Sk in of -whole b o d y
Sk in of e x t r e m i t i e s
M a x i m u n n A l l o w a b l e D o s e ( r e m )
60
50
200
275
600
90
60
225
300
650
180
80
240
350
750
360
100
270
4 0 0
900
S p a c e R a d i a t i o n ( r e m )
60
9
40
40
40
90
14
59
59
59
180
28
118
118
118
360
56
238
238
238
M a x i m u m Allo-wable D o s e f r o m R e a c t o r
( r e m )
60
41
160
23 5
560
90
4 6
166
241
591
180
52
122
232
632
360
44
32
162
662
The las t column in Table V-3 shows that the allowable reac tor dose to the
lens of the eye is the smal les t and therefore controls the shield design. For
miss ions up to one year the r eac to r dosera te should therefore not exceed approxi
mately 32 r e m / y r . In the shielding calculations per formed for this study a
maximum-al lowable operating dose from the reac to r was establ ished in the
range of 20 to 30 r e m / y r ,
(2) Geometry and Operational Mode
Figure V-4 shows the proposed integration a r r angemen t for the nuclear
power sys tem and the OWS. The shaded zones super imposed on this a r r a n g e
ment identify general regions with different radiation dose c r i t e r i a . The p r imary
shielded zone cor responds to a cone with a 10° half-angle which includes the
basic Workshop s t ruc tu re where approximately 99% of the c r ew ' s t ime will be
spent, the p r e s su r i zed exper iment canis te r which would contain radiat ion-
sensit ive film, and approximately a 10-ft radia l c lea rance around the Workshop
for possible EVA or other external ly mounted exper iments . The design dose
point shown is located at the control station for the Workshop, which is the
c loses t point to the reac tor which would be occupied routinely. Dosera tes
c loser to the reac tor and further back into the Workshop would vary approxi
mately as the inverse square of the distance from the r e a c t o r .
AI-AEC-MEMO-12717 126
r - APOLLO COMMAND AND SERVICE MODULE
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PRESSURIZED r-EXPERIMENT \ CANISTER
FEET
8-JY22-099-37A
Figure V-4. Radiation Shield Design Cr i t e r i a
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Figure V-5, 477 Shield Outline, Reference Design 8-J1-099-1
The s h a d e d con i ca l r e g i o n ex tend ing f r o m the p r i m a r y sh i e lded zone out to
a half ang le of 24° i s the s c a t t e r sh ie ld z o n e . The m a j o r c o n s i d e r a t i o n s in th i s
r e g i o n a r e s c a t t e r i n g of n e u t r o n s and g a m m a s f rom p a r k e d C S M ' s and f rom the
s m a l l p o r t i o n of the r a d i a t o r wh ich e x t e n d s ou t s ide the p r i m a r y sh ie lded zone .
In g e n e r a l the d o s e r a t e s in the s c a t t e r s h i e ld zone can be one or two d e c a d e s
h i g h e r than in the p r i m a r y zone b e f o r e s c a t t e r e d r a d i a t i o n into the w o r k s h o p
b e c o m e s i m p o r t a n t .
The t h i r d zone of i n t e r e s t c o v e r s the path tha t m i g h t be t aken by a m a n n e d
CSM a p p r o a c h i n g the w o r k s h o p for r e n d e z v o u s and docking . Al lowable d o s e
r a t e s in t h i s r e g i o n d e t e r m i n e the a m o u n t of sh ie ld ing which m u s t be p l aced on
the s ide of the r e a c t o r if i t i s o p e r a t i n g du r ing the r e n d e z v o u s m a n e u v e r . If
such sh i e ld ing i s p r o v i d e d , the sh i e ld i s c l a s s i f i e d a s a 477 sh ie ld even though
the s h i e l d i n g i s not s p h e r i c a l l y s y m m e t r i c a l . Without s ide sh ie ld ing the sh ie ld
i s r e f e r r e d to a s a shadow sh i e ld . With a shadow sh ie ld the r e a c t o r would have
to be shut down s h o r t l y b e f o r e the r e n d e z v o u s m a n e u v e r i s p e r f o r m e d . Both 477
and s h a d o w - s h i e l d d e s i g n s w e r e evo lved in th i s s tudy.
If the p r i m a r y s h i e l d e d - z o n e ang le w e r e ex tended to inc lude the p a r k e d
C S M ' s wi th the s a m e dose c r i t e r i a a s a r e u s e d wi th in the o r b i t a l w o r k s h o p ,
e x c e s s i v e sh i e ld w e i g h t s would r e s u l t . Thus the p r o p o s e d m u l t i z o n e dose m o d e l
r e p r e s e n t s a r e f i n e m e n t w h i c h m o r e a c c u r a t e l y r e p r e s e n t s the e x p e c t e d o p e r a t i n g
cond i t i ons and r e s u l t s in r e d u c e d sh i e ld we igh t s whi le p r e s e r v i n g a feas ib le i n t e
g r a t i o n c o n f i g u r a t i o n and o p e r a t i o n a l e n v i r o n m e n t ,
(3) R e a c t o r P C S G e o m e t r y
The r e a c t o r d e s i g n shown in Sec t ion IV-A can be u s e d wi th e i t he r a 477 o r
s h a d o w - s h i e l d con f igu ra t i on . In e i t h e r c a s e the g e o m e t r y of the sh ie ld i s a l s o
af fec ted by the l ayout of the p o w e r - c o n v e r s i o n e q u i p m e n t in the sh ie ld g a l l e r y .
F i g u r e V-5 shows the 477-shield g e o m e t r y for the p r o p o s e d i n t e g r a t i o n a r r a n g e
m e n t , r e a c t o r d e s i g n , and m i n i m u m g a l l e r y d i m e n s i o n s . The 10° cone half-
ang le c o m b i n e d wi th the g a l l e r y d i m e n s i o n s d e t e r m i n e the d i a m e t e r of the l o w e r
g a m m a and n e u t r o n s h i e l d s . The g e o m e t r y of the u p p e r n e u t r o n sh ie ld s u r r o u n d
ing the r e a c t o r i s d e s i g n e d to l i m i t the s c a t t e r e d r a d i a t i o n f r o m the p a r k e d C S M ' s
to t o l e r a b l e v a l u e s . N e u t r o n s s c a t t e r e d f r o m the C S M ' s a r e p r i m a r i l y t h o s e tha t
e m e r g e f r o m the s u r f a c e of the 477 sh i e ld a t g r a z i n g a n g l e s be tween 10 and 2 4 ° .
A I - A E C - M E M O - 12717
129
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8-JV22-099-38A
F i g u r e V - 6 , Shadow Shie ld Out l ine , R e f e r e n c e Des ign
F i g u r e V-6 shows the con f igu ra t i on of the shadow sh ie ld . The lower sh ie ld
d i a m e t e r i s the s a m e a s tha t of the 477 s h i e l d , s ince bo th d e s i g n s have the s a m e
g a l l e r y a r r a n g e m e n t . The u p p e r s h i e ld in t h i s c a s e is de s igned to p r o t e c t the
s e r v i c e m o d u l e s f r o m r e a c t o r d i r e c t r a d i a t i o n ,
(4) M a t e r i a l s
Shie ld ing m a t e r i a l s s e l e c t e d for bo th the shadow and 477 sh ie ld d e s i g n s a r e
P b , U, and LiH, P b i s u s e d for the f i r s t g a m m a sh ie ld i m m e d i a t e l y ad j acen t to
the r e a c t o r b e c a u s e of i t s low s e c o n d a r y g a m m a p roduc t ion r a t e s and i ts r e l a
t i v e l y h igh d e n s i t y . Dep le t ed U i s u s e d for the s econd g a m m a sh i e ld l oca t ed at
the b o t t o m of the g a l l e r y w h e r e the n e u t r o n flux h a s been d e c r e a s e d s e v e r a l
o r d e r s of m a g n i t u d e , LiH i s u s e d for bo th n e u t r o n sh i e ld s due to i t s h igh
n e u t r o n - s h i e l d i n g e f f e c t i v e n e s s , good p h y s i c a l and m e c h a n i c a l p r o p e r t i e s , and
a d v a n c e d t e c h n o l o g i c a l s t a t u s . Tab le V - 4 shows the effect ive d e n s i t i e s of the
sh i e ld m a t e r i a l s u s e d . In the c a s e of LiH the d e n s i t y h a s been i n c r e a s e d 30%
to a c c o u n t for cann ing and i n t e r n a l s t r u c t u r e ,
T A B L E V - 4
DENSITY O F SHIELD MATERIALS
M a t e r i a l Dens i t ( Ib / in .^) %
Lead
Uranium
Lithium hydride
0.410
0.676
0.03 5*
'=An a d d i t i o n a l 3 0% is inc luded to a c c o u n t for cann ing .
(5) R e s u l t s
Us ing the b a s i c dose c r i t e r i a , g e o m e t r y , and m a t e r i a l s d i s c u s s e d above , a
n u m b e r of i t e r a t i o n s w e r e m a d e b e t w e e n sh ie ld t h i c k n e s s e s and d o s e r a t e e s t i
m a t e s . The b a s i c tool u s e d for t h i s a n a l y s i s was the Dup lex -2 sh ie ld o p t i m i z a
t ion code wh ich d e t e r m i n e s a n e a r - o p t i m u m d i s t r i b u t i o n of t h i c k n e s s e s for the
v a r i o u s sh i e ld l a m i n a t i o n s . In add i t i on , the DOT and ANISN codes w e r e u s e d
A I - A E C - M E M O - 1 2 7 1 7 131
to d e t e r m i n e n e u t r o n l e a k a g e flux f r o m the u n s h i e l d e d r e a c t o r . The s o u r c e s of
r a d i a t i o n inc luded m the a x i a l ( shadow) d i r e c t i o n w e r e c o r e n e u t r o n s , c o r e g a m m a
r a y s , g a m m a r a y s f r o m r a d i o a c t i v e s o d i u m - 2 4 m the p r i m a r y loop , and s e c o n d
a r y gammia r a y s f r o m bo th g a m m a s h i e l d s . In the r a d i a l d i r e c t i o n only, t h r e e
s o u r c e s w e r e c o n s i d e r e d , n a m e l y , c o r e n e u t r o n s , g a m m a r a y s , and s e c o n d a r y
g a m m a r a y s f r o m the l ead sh ie ld , S o d i u m - 2 4 g a m m a r a y s w e r e not i nc luded m
the r a d i a l d i r e c t i o n s ince t h e i r d o s e c o n t r i b u t i o n i s s m a l l c o m p a r e d to the r a d i a l -
d o s e c r i t e r i a .
The sh i e ld d e s i g n i t e r a t i o n s n a r r o w e d down to the 477 and s h a d o w - s h i e l d d e
s igns shown on F i g u r e s V-5 and - 6 , r e s p e c t i v e l y . The t o t a l we igh t of the shadow
sh ie ld ( inc luding s t r u c t u r e ) i s e s t i m a t e d to be 14,330 lb . The we igh t of the 477
sh i e ld IS e s t i m a t e d to be 16,500 lb . Thus for the spec i f ic c r i t e r i a and c o n s t r a i n t s
u s e d the 477 sh i e ld i s only 15% h e a v i e r than the shadow sh i e ld .
F o r the 477 sh i e ld the i n t e g r a t e d d o s e to the a s t r o n a u t s d u r i n g r e n d e z v o u s
has b e e n c a l c u l a t e d to be l e s s than 5 r e m wi th the r e a c t o r a t full p o w e r , a s s u m
ing they a p p r o a c h the W o r k s h o p f r o m one m i l e out a t 1 m i / h r m a d i r e c t i o n
n o r m a l to the OWS c e n t e r l i n e .
The e s t i m a t e d r a d i a t i o n d o s e r a t e s a t the c o m m a n d and c o n t r o l s t a t ion w i t h m
the OWS a r e shown on Tab le V - 5 , for both sh ie ld t y p e s . The d i r e c t d o s e is the
T A B L E V - 5
E S T I M A T E D RADIATION D O S E R A T E S AT SATURN-V O R B I T A L WORKSHOP COMMAND AND CONTROL STATION
Number of Parked CSM's
Direct Dose, m r e m / h r
Command and Service Module Scattered Dose, m r e m / h r
Radiator Scattered Dose, m r e m / h r
Total, m r e m / h r
Annual Dose, r em
47r Shield
1
1.56
0.53
0.08
2.17
19.0
2
1.56
1.06
0.08
2.70
23.7
Shadow Shield
1
1.56
0.88
0.08
2.52
22.1
2
1.56
1.76
0.08
3.40
29.8
A I - A E C - M E M O - 12717 132
same in both cases but the sca t te red dose from the parked CSM's is slightly
higher for the shadow-shield design and depends on how many CSM's a re parked.
Thus the total annual dosera te es t imate from all sources ranges from 19 to
slightly l e s s than 30 r e m per year , which is within the dose c r i t e r i a assumed
for the study. It should be mentioned that the amount of t ime spent by any
single crew m e m b e r in the command and control station has been est imated to (4) be approximately 17%. The dosera tes in the aft portions of the OWS where
the crew will be spending a l a rge r fraction of their total t ime will be lower than
the values shown. Thus the dosera tes and shield-weight es t imates a re believed
to be conservat ive . Additional more -de ta i l ed shield design and analysis beyond
the scope of the p resen t study a re requi red , however, to obtain more accurate
dose or weight e s t ima t e s .
b, PCS Instal lat ion
The TE PCS along with the pumps, p r imary- loop expansion compensa tors ,
and interconnecting piping a r e located in a gal lery between the two shield sections
as shown in F igure V-7, The components were ar ranged to minimize the d iam
eter and height of the gal lery since both of these have a relat ively strong effect
on the shield weight. The gal lery height is 20 in. and all components fit within
the 10° shield cone having a d iameter of 68 in. at the bottom of the gal lery. An
i somet r i c view of the r eac to r and ga l le ry a r rangement that provides a c l ea re r
understanding of the pipe routing is shown in Figure III-2.
For this design the main TE conver ter assembly is r ea r ranged as shown in
Figure V-8 . The basic s t ruc tu re of the assembly is the same as descr ibed in
Section IV-B-3 ; however, the a t tachments to the main manifolds a r e changed.
Also the unit is placed in the ga l le ry with the 4-packs in the horizontal plane.
This orientat ion presen ts no par t icu la r problem, however, since the la te ra l
design load factors a r e approximately two- th i rds of the longitudinal load factors
and the unit mus t be designed with about the same strength in all d i rect ions .
In the assembly sequence the ga l lery components a re mounted on top of the
secondary shield before mating to the top shield. Such an a r rangement allows
for c lear access to all piping runs and components during assembly . After ins ta l
lation and checkout of the PCS components , the bottom shield and the gal lery
AI-AEC-MEMO-127 17 133
r - ^ A
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NaK EXAPNSION COMPENSATOR (PRIMARY LOOP)
THERMOELECTRIC CONVERTER (MAIN)
-SECONDARY SHIELD
SECTION A " A Ul-A
HEAT REJECTION LOOP NaK
THERMOELECTRIC CONVERTER (PUMP)
ELECTROMAGNETIC PUMPS
IMCHES
0 10 20 30 40 50 60 70 80 ^O 100 110 120
I I ' I ' - r^-T^ \ V ' I ' I ' i' 1 0 I 2 3 4 5 6 7 8 9 10
FEET
8-JY25-119-40
F i g u r e V - 7 , 25 -kwe N u c l e a r T h e r m o e l e c t r i c P o w e r Supply, T w o - L o o p S y s t e m
-19.50
< } UP
e Si
(\ r\ r\
-/2.50-
H-
7
23.sa c —-
Lim
// J.5
• • Figure V-8 . Thermoelec t r i c Power
Package with Modified Po r t Locations
AI-AEC-MEMO-127 17 135
a s s e m b l y a r e m a t e d to the top sh ie ld and r e a c t o r . The r e a c t o r coolan t p ipes
a r e t hen c o n n e c t e d p r o v i d i n g a c o m p l e t e l y s e a l e d p r i m a r y loop. The r a d i a t o r
i s nex t m a t e d to the l ower p o r t i o n of the s e c o n d a r y sh ie ld and the h e a t - r e j e c t i o n
p ip ing c o n n e c t e d .
The c o n v e r t e r a s s e m b l y and p u m p yoke a s s e m b l y a r e m o u n t e d to the lower
s h i e l d . P i p e a n c h o r s wi l l be i n c o r p o r a t e d a t each point w h e r e l i ne s p e n e t r a t e
the m a i n c o n v e r t e r box and n e a r the p u m p m o u n t s . C a l c u l a t i o n s of the piping
l o a d s for the w o r s t c a s e , in which the NaK s y s t e m has h e a t e d to o p e r a t i n g t e m
p e r a t u r e bu t the s h i e l d s a r e s t i l l a t about 100°F , showed tha t the m a x i m u m
s t r e s s o c c u r r e d a t the point w h e r e the l i n e s bend downward a f te r coming out
r a d i a l l y f r o m the r e a c t o r . E v e n t h e s e s t r e s s e s w e r e below the a l lowable of
24,000 p s i ; h o w e v e r , t h e y could be r e d u c e d with a m o r e g e n e r o u s elbow so tha t
a l l s t r e s s e s would be be low about 16,000 p s i .
The e x p a n s i o n c o m p e n s a t o r s for the p r i m a r y loop a r e a t t a c h e d to the n e a r e s t
p r i m a r y - l o o p l ine by a 3 / 8 - i n . - d i a m fill l i n e . Th i s l ine would run to the high
poin t of the loop d u r i n g l aunch , a d i f fe ren t loca t ion depending on the s y s t e m
o r i e n t a t i o n du r ing l aunch , and would be i n s i d e the m a i n l ine o r w r a p p e d wi th it
to p r e v e n t NaK f r e e z i n g .
c . R a d i a t o r
2 The fixed f i nned - tube r a d i a t o r h a s 1287 ft of u s a b l e r a d i a t i n g a r e a . A
c r o s s - s e c t i o n of a t y p i c a l r a d i a t o r pane l i s shown in F i g u r e V - 9 . In it a r e
96 ind iv idua l NaK t u b e s of 3 / 8 - i n . - d i a m 347 s t a i n l e s s s t e e l wi th a 0.020-in. wa l l
t h i c k n e s s . E x t r u s i o n s of 6016 a l u m i n u m , wh ich p r o v i d e bo th the fin and m e t e -
o r o i d a r m o r , a r e d i f fus ion -bonded to t h e s e t u b e s . The ind iv idua l tube- f in p i e c e s
a r e a s s e m b l e d into p a n e l s by we ld ing the NaK tubes to h e a d e r s a t e i t h e r end.
E a c h q u a d r a n t c o n t a i n s s ix i nd iv idua l p a n e l s . The t h r e e longi tud ina l p a n e l s a r e
r e q u i r e d to m i n i m i z e the NaK p r e s s u r e - d r o p a s we l l a s for e a s e of f ab r i ca t i on .
The two c i r c u m f e r e n t i a l p a n e l s on e a c h q u a d r a n t a r e for e a s e of a s s e m b l y . The
NaK supp ly and r e t u r n l i n e s a r e r o u t e d to a l low for d i f f e ren t i a l expans ion .
The p a n e l s a r e a t t a c h e d to a t i t a n i u m s e m i m o n o c o q u e s t r u c t u r e by c l i p s tha t
a l low d i f f e r en t i a l e x p a n s i o n b e t w e e n the tubes and the s t r u c t u r e . The s t r u c t u r e
i s d e s i g n e d to s u p p o r t the r a d i a t o r du r ing l aunch and a c c o m m o d a t e docking and
m a n e u v e r i n g loads when the p lan t i s ex tended in o r b i t . The r a d i a t o r s t r u c t u r e
A I - A E C - M E M O - 12717 137
I
>
o
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o I
MANIFOLD (CRES TUBE)
RADIATOR TUBE (CRES)
SUPPORT (Ti ALLOY)
RADIATOR FIN AND ARMOR (ALUMINUM)
STRUCTURE SKIN (TITANIUM)
CORRUGATED STIFFENER (TITANIUM)
NaK SUPPLY LINE (CRES TUBE)
STRUCTURE FRAME (TITANIUM)
1-14-69 UNC 7759-52100
Figure V-9. P r e a s s e m b l e d Radiator Assembly Integration Details
is not required to support the r eac to r shield weight during launch. The 0.010-in.-
thick corrugated stiffeners and s t ruc tura l skin and the frames a r e all made of
t i tanium since the maximum operating t empera tu re of the s t ruc ture will be be
tween 650 and 700°F.
d. St ructure
The p r i m a r y loadpaths for the sys tem a r e shown in Figure V-10. The LiH
upper shield is re la t ively light and will be supported by i ts own shell . It will
1. UPPER LiH SHIELD
INTERMEDIATE LiH SHIELD
REACTOR
477 GAMMA SHIELD
STRUCTURE
STRUCTURAL PANEL
ATTACHMENT RING
LOWER LiH SHIELD
RADIATOR
1-13-69 UNCI 7759-52101
Figure V-10. Power System Loadpath Schematic
AI-AEC-MEMO-12717 139
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o
- v j
134 4 ft
3.0 ft
MSEC NOSE FAIRING
REACTOR
LAUNCH SUPPORT STRUCTURE
SHROUD/ADAPTOR
RADIATOR
DOCKING SUPPORT STRUCTURE
MDA
SLA
INSTRUMENTATION UNIT
SATURN V WORKSHOP
PRESSURIZED ATM CANNISTER
INTERSTAGE STRUCTURE
S-ll STAGE
143 5 ft
LAUNCH ESCAPE SYSTEM
COMMAND MODULE
SERVICE MODULE
SIVB
S-ll STAGE (REFl
DRY S-V WORKSHOP WITH NUCLEAR POWER SYSTEM STANDARD APOLLO SATURN V
8-JI4-099-64
Figure V - I l . Integral Saturn-V Launch Configuration, Nuclear Thermoelec t r ic Power System
be r e m o v a b l e wi th a bo l t r i n g on i t s l o w e r ou t e r p e r i p h e r y . Its loadpa th wi l l
follow down the o u t e r she l l of the i n t e r m e d i a t e LiH sh i e ld . The r e a c t o r and the
477 g a m m a sh i e ld wi l l be s u p p o r t e d on a c o m m o n c o n i c a l she l l wi th in the i n t e r
m e d i a t e LiH sh ie ld and wh ich i n t e r s e c t s the ou t e r she l l at the lower o u t e r
p e r i p h e r y .
To p r o v i d e m a x i m u m v o l u m e and a c c e s s to the g a l l e r y du r ing s y s t e m fab
r i c a t i o n , the s t r u c t u r e ad j acen t to the g a l l e r y i s a t the ou te r l im i t of the sh ie ld
a r e a . A s e r i e s of p e r m a n e n t p o s t s wi l l f o r m the b a s i s of th i s s t r u c t u r e . T h e s e
wi l l be g iven t o r s i o n a l r i g i d i t y by s t r u c t u r a l p a n e l s t ha t can be r e m o v e d for
a c c e s s to the g a l l e r y on the g round .
The s t r u c t u r e of the l o w e r sh i e ld wi l l be the ou te r she l l wi th a t t a c h m e n t
r i n g s at both the l o w e r and u p p e r o u t e r e d g e . The s e l e c t i o n of the a t t a c h m e n t
r i n g wi l l depend on the l aunch m o d e , a s the power s y s t e m is des igned to be
l a u n c h e d in e i t h e r d i r e c t i o n . The r a d i a t o r s t r u c t u r e i s t ied into the l ower a t
t a c h m e n t r i n g and i s r e q u i r e d to s u p p o r t only the r a d i a t o r .
The p r i m a r y r e a c t o r and s h i e ld s t r u c t u r e is 316 s t a i n l e s s s t e e l . Se lec t ion
of th i s m a t e r i a l is d i c t a t e d by c o m p a t i b i l i t y with LiH and s h i e l d - c a s t i n g -
t e m p e r a t u r e c o n s i d e r a t i o n s .
3. O p e r a t i o n a l Mode
a. Launch Opt ions
S e v e r a l op t ions a r e a v a i l a b l e for l aunch ing the n u c l e a r powerp l an t into o r b i t
and m a t i n g it to the S a t u r n - V OWS. If the OWS i s l aunched u n m a n n e d (which i s
be ing c o n s i d e r e d ) the p o w e r p l a n t could be m o u n t e d on top of the s t ack a t t a c h e d
to the f o r w a r d end of the MDA, a s shown in F i g u r e V - I I . In th i s c a s e the p o w e r -
p lan t would be a l r e a d y l o c a t e d in i t s o p e r a t i o n a l pos i t i on , r e a d y for subsequen t
s t a r t u p , e x t e n s i o n , and o p e r a t i o n a f te r the OWS is m a n n e d .
The o v e r a l l he igh t of the S a t u r n - V OWS s t ack wi th the n u c l e a r power s y s t e m
m o u n t e d a s shown on F i g u r e V-11 i s about 9 ft l e s s than tha t of the s t a n d a r d
A p o l l o / S a t u r n - V inc lud ing the l aunch e s c a p e s y s t e m . The n u c l e a r power s y s
t e m s h r o u d , i nc lud ing the s t a n d a r d M a r s h a l l Space F l i gh t C e n t e r (MSEC) nose
f a i r i n g , i s about 20 ft l o n g e r t han the Apol lo CSM, h o w e v e r , and the c e n t e r of
A I - A E C - M E M O - 1 2 7 1 7 141
NOSE FAIRING
46.3 ft
28 ft
22 ft
DOCKING PROBE
SHROUD/ADAPTOR
RADIATOR 82.1 ft
REACTOR
SERVICE MODULE
SLA
^NSTRUMENTATION UNIT
SIVB
52.6 ft
STANDARD APOLLO
SATURN IB
A 1
1 J
8-J14-099-63
u re V-12. Separate Launch Configuration, Saturn-IB Service Module
AI-AEC-MEMO-12717 142
gravity of the power sys tem is near the top. Therefore, this configuration
would requ i re further analysis to de termine whether the aerodynamic and
s t ruc tura l cha rac t e r i s t i c s a r e acceptable .
F igure V-12 shows the launch configuration for a separa te unmanned launch
of the nuclear power sys tem using the Saturn-IB/Service Module (SIB/SM). The
SIB/SM combination has been studied and proposed as an unmanned launch vehicle
combination by North American Rockwell, Space Systems Division, For the
p resen t application, the service module would serve both as a mu l t i p l e - r e s t a r t
third stage to reach the parking orbit and final orbit, and as a maneuverable
rendezvous vehicle. The power sys tem would be supported from the service
module with the r eac to r / sh i e ld assembly at the lower end and a docking adaptor
at the upper end. After rendezvous with the manned OWS and docking have been
achieved, the se rv ice module would be disconnected from the power sys tem and
discarded. F igure V-13 shows a s imi lar launch configuration for a separate
unmanned launch using the Titan-III Trans tage . In this case the Transtage
se rves the same function as the serv ice module in the SIB/SM vehicle. In
ei ther case some modifications would be required for the unmanned rendezvous
maneuver . These modifications have been studied by the vehicle cont rac tors
and found to be reasonable and feasible .
The available payloads and marg ins for the designated orbit , launch vehicles,
and modes d iscussed above a r e summar ized in Table V-6. The payload infor
mation was obtained from personnel at the Martin Mariet ta Corporation, Denver,
Colorado, North Amer ican Rockwell 's Space Systems Division, Downey, Cali
fornia, and NASA-MSFC, Huntsvil le , Alabama.
The g ross payload for an unmanned launch of the OWS on a two-stage
Saturn-V is 186,000 lb. A d i rec t ascent to the 270 n. mi , 50° orbit is neces
sa ry in this c a s e , since multiple burn of the S-2 stage is not feasible with the
p resen t engines due to the short burn t ime that would be required for a Hohmann
t ransfe r from a parking orbi t . This payload capability is about 65,000 lb l ess
than that achievable with the manned launch, where the CSM propulsion system
can be used to t r ans fe r the OWS to the des i red orbit .
The cu r r en t Saturn-V OWS weight es t imate is in the range of 156,000 lb for
a t h r e e - m a n vers ion to 188,000 lb for a s ix-man design, including supplies.
AI-AEC-MEMO- 12717 143
NOSE FAIRING
DOCKING PROBE
SHROUD/ADAPTOR
RADIATOR
REACTOR
TITAN III TRANSTAGE
Figure V-13. Separate Launch Configuration, Titan-III
Transtage
8-J14-099-62
TABLE V-6
LAUNCH VEHICLE PAYLOAD ESTIMATES''
Launch Mode
I^aunch veh ic le
G r o s s pay load , lb
Orb i ta l Workshop weight , t h r e e - m a n / s i x - m a n , lb
Net payload ava i l ab l e for n u c l e a r power s y s t e m , lb
Nuc lea r power s y s t e m we igh t , ! lb:
wi th 477 sh ie ld
with shadow sh ie ld
Pay load m a r g i n , lb; with 477 shie ld
with shadow sh ie ld
In t eg ra l Unmanned D i r e c t A s c e n t
T w o - s t a g e S a t u r n - V
186,000
156,000/188,000
30 ,000 / ( -2 ,000)
27,000
24,800
+3 ,000 / ( -29 ,000)
- f5 ,200/( -26,800)
S e p a r a t e Unmanned, wi th Hohmann T r a n s f e r and Rendezvous
T i t a n - m C ( T r a n s t a g e )
23,000
22,700
27,000
24,800
(-4,300)
(-2,100)
T i t an - I I IF ( T r a n s t a g e )
34,000
33,700
27,000
24,800
+6,700
+ 8,900
S a t u r n - I B / S M
28,800
28,500
27,000
24,800
+ 1,500
+3,700
*Orbi t a l t i tude = 270 n. m i Orbi t inc l ina t ion = 50°
t i n c l u d e s 2 ,500- lb s h r o u d / a d a p t o r
AI-AEC-MEMO- 12717 144
e x p e r i m e n t a l e q u i p m e n t , and a 12 .5 -kwe s o l a r - p a n e l b a t t e r y power s y s t e m .
Thus the pay load a v a i l a b l e for the n u c l e a r power s y s t e m r a n g e s f r o m about
+ 30,000 to -2 ,000 lb for the t h r e e - and s i x - m a n OWS c o n c e p t s , r e s p e c t i v e l y .
The we igh t s shown for the n u c l e a r power s y s t e m inc lude e i t h e r 47T o r
shadow sh i e ld ing , a s no ted , and a 2 ,500 - lb a l l owance for the s h r o u d and dock
ing a d a p t o r . ( T h e s e n u m b e r s have b e e n rounded u p w a r d s to the n e a r e s t 100 lb . )
C o m p a r i s o n of the pay load w e i g h t s wi th da ta a v a i l a b l e shows tha t the i n t e g r a l
l a u n c h would be f e a s i b l e only wi th the t h r e e - m a n OWS, in which c a s e the m a r g i n
would be f r o m 3,000 to 5,200 lb depend ing on w h e t h e r a 477 o r shadow sh ie ld i s
u s e d . If t h e po'wer l e v e l of the s o l a r - c e l l b a t t e r y s y s t e m w e r e cut in half the
pay load m a r g i n could be i n c r e a s e d by a p p r o x i m a t e l y 11,000 lb . N o n e t h e l e s s ,
wi th the i n t e g r a l l aunch m o d e i t i s a p p a r e n t tha t the pay loads a v a i l a b l e for the
n u c l e a r p o w e r s y s t e m would be i n a d e q u a t e for the s i x - m a n OWS, which is the
one t h a t could m o s t p r o f i t a b l y u s e the add i t iona l p o w e r .
The p a y l o a d s a v a i l a b l e for the s e p a r a t e l aunch c a s e s a r e a l l b a s e d on an
i n i t i a l l aunch ang le of a p p r o x i m a t e l y 44.5 o r 135.5° to a c h i e v e a 100-mi p a r k i n g
o r b i t in the c o r r e c t i n c l i n a t i o n for the f inal o r b i t . Two b u r n s of the Ti tan
T r a n s t a g e o r the s e r v i c e m o d u l e a r e u s e d for the Hohmann t r a n s f e r . F u e l
w e i g h t r e q u i r e d for the r e n d e z v o u s wi th the OWS i s e s t i m a t e d to be a p p r o x i
m a t e l y 300 lb , which r e d u c e s the ne t pay load a v a i l a b l e for the n u c l e a r power
s y s t e m to the v a l u e s shown. It c a n be s e e n tha t a s e p a r a t e l aunch with the
T i t an - I I IC does not a p p e a r to be f e a s i b l e , but e i t h e r the T i t a n - I I I F or the
S a t u r n - I B / S M v e h i c l e s could be u s e d for t h i s m i s s i o n . (The T i t a n - I I I F i s the
d e s i g n a t i o n g iven to the l a u n c h v e h i c l e be ing deve loped for the Manned O r b i t a l
L a b o r a t o r y (MOL) p r o g r a m , bu t wi th the T r a n s t a g e r e p l a c i n g the MOL and
G e m i n i c a p s u l e . ) The e s t i m a t e d pay load m a r g i n s a v a i l a b l e wi th t h e s e v e h i c l e s
in the s e p a r a t e l aunch m o d e r a n g e s f r o m about 5 to 36%, depending on which
v e h i c l e and sh ie ld ing opt ion i s u l t i m a t e l y s e l e c t e d .
F r o m th i s p r e l i m i n a r y e v a l u a t i o n of l aunch o p t i o n s , it i s conc luded tha t the
s e p a r a t e u n m a n n e d l aunch and r e n d e z v o u s wi th a m a n n e d OWS u s i n g e i t h e r the
S a t u r n - I B / S M or the T i t a n - I I I F v e h i c l e a p p e a r s to be the m o s t p r o m i s i n g a p
p r o a c h . Add i t iona l m o r e - d e t a i l e d s t u d i e s beyond the s cope of the p r e s e n t s tudy
wi l l be r e q u i r e d , h o w e v e r , b e f o r e a f inal s e l e c t i o n can be m a d e .
A I - A E C - M E M O - 1 2 7 1 7 145
> l-H I
O
O I
I—I
- J I—'
"PLANT-EXTENDED" SWITCH
DRUM-POSITION INDICATOR
EXTENDED < 3 1 0 0 F
REACTOR-OUTLET TEMPERATURE SWITCH
(NO SIGNAL WHEN TEMPERATURE >1325°F)
STARTUP' SHUTDOWN SWITCH
ELECTRICAL POWER CONTROL SWITCH
1-13-69 UNC TO DRUM-CONTROL CIRCUITS
(NO SIGNAL WITHIN DEADBAND AT25kwe)
7759-52105
F i g u r e V - 1 4 . S a t u r n - I V B P o w e r S y s t e m C o n t r o l Log ic
b . S y s t e m O p e r a t i o n
In Sec t ion I I I -C the g e n e r a l r e q u i r e m e n t s for s y s t e m c o n t r o l w e r e d i s c u s s e d
a long wi th the c h a r a c t e r i s t i c s of the four p h a s e s of a s t a r t u p . The d e t a i l s of a
c o n t r o l s y s t e m have b e e n f u r t h e r def ined for the spec i f ic c a s e of the S a t u r n - I V B
OWS power s y s t e m . F i g u r e V-14 shows the logic d i a g r a m for th i s c o n t r o l s y s
t e m and V- 15 s u m m a r i z e s the f e a t u r e s of the s t a r t u p inc lud ing the r e s u l t s of
p r e l i m i n a r y c a l c u l a t i o n s of the s t a r t u p t r a n s i e n t . In the logic d i a g r a m the
s t a n d a r d def in i t ion i s u s e d w h e r e both s i g n a l s to an "AND" box a r e r e q u i r e d
to p a s s a s i g n a l , whi le only one of the s i g n a l s to an "OR" box is r e q u i r e d .
In the following p a r a g r a p h s each p h a s e of the s t a r t u p wi l l be d e s c r i b e d .
(1) P h a s e 1, Shutdown M a r g i n R e m o v a l
All d r u m s a r e m o v e d s i m u l t a n e o u s l y a t a r a t e of one s t e p / 1 5 sec un t i l the
d r u m pos i t i on i n d i c a t o r shows they a r e a t 105° . At th i s t i m e , the d r u m s have
e a c h m o v e d 75° and the e l a p s e d t i m e i s 31 m i n . The d e g r e e of s u b c r i t i c a l i t y
at th i s point is d e p e n d e n t upon NaK t e m p e r a t u r e but would v a r y f rom 25^ at
7 5 ° F to 35« a t 1 5 0 ° F .
As the g a d o l i n i u m in the r e a c t o r c o r e i s b u r n e d out, the d r u m pos i t i on w h e r e
t h i s p h a s e i s t e r m i n a t e d would m o v e o u t w a r d , and l a t e r in l i fe , when hyd rogen
l e a k a g e o v e r c o m e s the b u r n o u t effect , i t would m o v e i n w a r d . The pos i t ion s e t
t ing in the c o n t r o l s y s t e m would be a d j u s t a b l e and could a lways be se t for a
p e r i o d of a t l e a s t one m o n t h wi th a c h a n g e .
(2) P h a s e 2, C r i t i c a l to S e n s i b l e H e a t
As s e e n in F i g u r e V - 1 4 , when the c o n t r o l d r u m s a r e r o t a t e d p a s t the 105°
pos i t i on the s t epp ing p e r i o d i n c r e a s e s to 30 s ec and only one d r u m i s m o v e d at
a t i m e . A s s u m i n g the r e a c t o r i s a t 100°F , it would go c r i t i c a l 24 m i n in to th i s
p h a s e , and the s e n s i b l e - h e a t t r a n s i e n t would o c c u r in a n o t h e r 17 m i n . A power
sp ike of a p p r o x i m a t e l y 180 kwt wi l l o c c u r a t th i s t i m e r e s u l t i n g in a m a x i m u m
r a t e of change of t e m p e r a t u r e of 1 2 0 ° F / m i n . The r e a c t o r would a u t o m a t i c a l l y
s t a b i l i z e a t a p p r o x i m a t e l y 2 7 0 ° F wi thou t f u r t h e r r e a c t i v i t y i n s e r t i o n ; h o w e v e r ,
the c o n t r o l s y s t e m wi l l c a u s e the d r u m s to r o t a t e f u r t h e r un t i l the r e a c t o r i s
at 3 I 0 ° F .
A I - A E C - M E M O - 12717 147
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(3) P h a s e 3, P o w e r p l a n t E x t e n s i o n
The e x t e n s i o n of the p o w e r p l a n t f r o m wi th in the sh roud would be a c c o m
p l i s h e d a t a r a t e of about 1 to 2 f t / m i n . In th i s d i s c u s s i o n it i s a s s u m e d tha t
full e x t e n s i o n r e q u i r e s 30 m i n .
A s the p o w e r p l a n t is ex tended the a v e r a g e r e a c t o r t e m p e r a t u r e t ends to
r e m a i n c o n s t a n t and the t h e r m a l power s t a r t s to i n c r e a s e as the r a d i a t o r is
g r a d u a l l y e x p o s e d . As th i s o c c u r s , p u m p power i n c r e a s e s and the s u p p l e m e n t a l
pumping u s e d d u r i n g the shutdown p e r i o d can be t e r m i n a t e d . As the AT in the
p r i m a r y loop i n c r e a s e s and the a v e r a g e r e a c t o r t e m p e r a t u r e r e m a i n s c o n s t a n t ,
the r e a c t o r o u t l e t - t e m p e r a t u r e d r i f t s u p w a r d , so no fu r the r r e a c t i v i t y is added
du r ing th i s p h a s e .
The m i n i m u m r a d i a t o r t e m p e r a t u r e o c c u r s when the u p p e r con i ca l s ec t ion
i s f i r s t e x p o s e d s i n c e the flow is s t i l l qui te low. The 310°F t e m p e r a t u r e l imi t
w a s s e l e c t e d so tha t t h i s m i n i m u m t e m p e r a t u r e would be about 150°F .
(4) P h a s e 4, R a m p to P o w e r
When the " p l a n t - e x t e n d e d " s w i t c h shows the s y s t e m is fully ex tended , the
r e a c t o r o u t l e t - t e m p e r a t u r e l i m i t is r a i s e d to 1325 °F and the s tepping p e r i o d is
r e t u r n e d to 15 s e c . R e a c t i v i t y i s then i n s e r t e d at a r a t e tha t r e s u l t s in a
p r i m a r y - l o o p h e a t i n g r a t e of about 2 0 ° F / m i n . As th i s hea t ing o c c u r s , a l l
p lan t funct ions a u t o m a t i c a l l y i n c r e a s e t o w a r d t h e i r o p e r a t i n g point , and in
a p p r o x i m a t e l y 43 m i n the n o r m a l o p e r a t i n g cond i t ions a r e r e a c h e d . Af te r
about 14 m i n of the r a m p the o p e n - c i r c u i t vo l t age of the c o n v e r t e r e x c e e d s
56 vo l t s and use fu l power b e c o m e s a v a i l a b l e .
The p a r a m e t e r u s e d to c o n t r o l t he p lan t and to t e r m i n a t e the r a m p to power
is e l e c t r i c a l c u r r e n t f r o m the T E c o n v e r t e r . This c u r r e n t i s u s e d to o p e r a t e
the e l e c t r i c p o w e r c o n t r o l swi t ch which a d d s o r s u b t r a c t s r e a c t i v i t y a s n e c e s
s a r y to m a i n t a i n the e l e c t r i c power wi th in a deadband about the s e l e c t e d power
l e v e l . As p r e v i o u s l y s t a t ed , t h i s se t t ing could be ad jus ted if o p e r a t i o n for a
p e r i o d of w e e k s w e r e p r o j e c t e d wi th p o w e r r e q u i r e m e n t s s ign i f i can t ly d i f ferent
than 25 k w e .
If for s o m e r e a s o n the power output i s not adequa t e when the r e a c t o r ou t l e t -
t e m p e r a t u r e r e a c h e s 1325 ° F , the i n s e r t i o n of r e a c t i v i t y is s topped , a s no ted in
A I - A E C - M E M O - 1 2 7 1 7 149
the c o n t r o l s y s t e m logic d i a g r a m . Th i s t e m p e r a t u r e l e v e l i s s t i l l we l l wi th in the
r a n g e w h e r e s e r i o u s d a m a g e or r a p i d d e g r a d a t i o n of the s y s t e m would not r e s u l t .
The above s t a r t u p s e q u e n c e would t a k e a p p r o x i m a t e l y 2 h r and 25 m i n f r o m
beg inn ing to f u l l - p o w e r .
To shut down, the s t a r t u p - s h u t d o w n s w i t c h i s m o v e d f r o m the " o p e r a t e " to
the " s h u t d o w n " p o s i t i o n . As s e e n in F i g u r e V-14 , th i s c a u s e s a l l d r u m s to s t ep
out t o g e t h e r and , s i n c e the p lan t would be ex tended , it would be at a 1 5 - s e c s t e p
ping r a t e . With the d r u r a s in the n o r m a l o p e r a t i n g pos i t i on , t h i s r e s u l t s in a
r e a c t i v i t y r e m o v a l r a t e of about 24{^/min. The r e s u l t i n g shutdown t r a n s i e n t w a s
shown in F i g u r e s I I I -7 and I I I -8 of Sec t ion I I I - C . The r a d i a t i o n flux f r o m f i s s i o n
ing would be r e d u c e d to about 1% in 3.5 m i n .
In abou t 1 h r the h e a t - r e j e c t i o n NaK t e m p e r a t u r e s would be n e a r 150°F and
r e t r a c t i o n of the s y s t e m into the s h r o u d would have to be s t a r t e d to p r e v e n t NaK
f r e e z i n g . The r e t r a c t i o n r a t e would be s low enough tha t suff ic ient r a d i a t o r would
be e x p o s e d to r e j e c t the r e a c t o r d e c a y h e a t wi thout e x c e s s i v e t e m p e r a t u r e s , but
fas t enough to m a i n t a i n the m i n i m u m r a d i a t o r t e m p e r a t u r e above about 1 0 0 ° F .
A r e s t a r t of the s y s t e m would be a c c o m p l i s h e d e x a c t l y a s the in i t i a l s t a r t .
H o w e v e r , b e c a u s e of an i n c r e a s e d r a d i a t i o n s o u r c e l eve l wi th in the r e a c t o r and
an i n c r e a s e d f u e l - t e m p e r a t u r e coef f ic ien t a f t e r a long p e r i o d of o p e r a t i o n , the
s e n s i b l e hea t t r a n s i e n t would be s ign i f i can t ly r e d u c e d . In fac t , if the r e s t a r t i s
u n d e r t a k e n b e f o r e r e t r a c t i o n of the s y s t e m into the s h r o u d , the c r i t i c a l - t o -
s e n s i b l e - h e a t p h a s e of the s t a r t u p would be a c c o m p l i s h e d wi th a 1 5 - s e c s t epp ing
r a t e , s i n c e the s o u r c e l eve l would s t i l l be n e a r the s e n s i b l e h e a t p o w e r l e v e l .
4. F i n a l R e a c t o r Shutdown and D i s p o s a l
At the end of the n u c l e a r p o w e r s y s t e m o p e r a t i o n a l l i f e t ime the r e a c t o r
would be shu t down, u s i n g the n o r m a l c o n t r o l s y s t e m , and d i s p o s e d of in a m a n
n e r wh ich wi l l m i n i m i z e the p o s s i b i l i t y of r a d i o l o g i c a l h a z a r d s .
N u m e r o u s s t u d i e s and e x p e r i m e n t s p e r f o r m e d in the A E C ' s ANS p r o g r a m
and the e x p e r i e n c e in the SNAP lOA fl ight t e s t p r o g r a m have p r o v i d e d a p r a c t i c a l
b a s i s for e s t a b l i s h i n g p r e l i m i n a r y n u c l e a r sa fe ty gu ide l ine s for SNAP r e a c t o r s .
The sa fe ty d e v i c e s and p r o c e d u r e s for the f a c t o r y - t h r o u g h - l a u n c h and o r b i t a l
A I - A E C - M E M O - 1 2 7 1 7
150
s tar tup phases of the miss ion would be s imi la r to and perform the same func
tions as those used for SNAP lOA flight. The lOA flight was completely reviewed
and approved by all government agencies affected. The fact that the reac tor is
not radioact ive until after it has been operated at power great ly simplifies the
nuclear safety r equ i remen t s for this par t of the miss ion .
The orbit altitude range of in te res t for the OWS mission is from 200 to
300 n . m i , for which e s t ima tes of the orbi tal lifetime of an abandoned space
station range from approximately 1 to 10 yr . If the reac tor power system
randomly r e - e n t e r e d 1 to 10 yr after shutdown, survived r e - e n t ry without burn-
up (which is quite probable with a 477' shield), and impacted on land, a small but
finite possibi l i ty of ser ious radiation exposure to anyone coming in close contact
with the debr is ex i s t s . To further reduce the r i sk of this situation occurr ing,
a l ternate means for safe disposal of the r eac to r have been proposed and analyzed (7) in detail . The two most promising disposal techniques a re : (a) boost the r e
actor to a higher orbit or , (b) deboost the reac tor into deep ocean a r e a s .
If the f i rs t option is used, an altitude of about 450 n . m i would provide orbital
s torage for seve ra l hundred y e a r s , after which t ime the f ission-product activity
would have decayed to safe leve ls . If the r eac to r is deboosted into deep ocean
a r e a s , radiat ion from the fission products would not pose a significant hazard .
References 7 and 8 presen t the re la t ive haza rds , rel iabil i ty es t imates , a t t i
tude control and propulsion r equ i r emen t s , etc , for the above disposal options.
If a separa te communicat ion, control , and propulsion package is used to auto
mat ica l ly boost or deboost the reac tor sys tem, the weight penalty would be ap
proximate ly 12 to 22%, depending on the alti tude and other var iables . The r e l i
abili ty of this equipment after extended s torage in space was est imated to be
from 0.85 to 0.95, and the r i sk of radiation injuries could thus be reduced by
about one o rde r of magnitude relat ive to that which would exist from random (9) r e - e n t r y . In the SNAP lOA Safeguards Report it was shown that the individual
r i sk probabil i ty due to random r e - e n t r y of a reac tor after sustained operation - 7 - 8
would be l ess than 10 for radiation injury and less than 10" for lethal rad ia
tion exposure . These hazards a re at least 6 o rde r s of magnitude lower than the
a l ready existing injury or death potential from all other accidental causes .
AI-AEC-MEMO-12717 151
F o r the S a t u r n - V OWS m i s s i o n i t i s p r o p o s e d tha t the CSM u s e d for r o u t i n e
c r e w r o t a t i o n be u s e d to p r o v i d e the c o n t r o l and p r o p u l s i o n c a p a b i l i t y n e e d e d for
r e a c t o r d i s p o s a l . The r e l i a b i l i t y of the m a n n e d CSM for t h i s p u r p o s e should be
g r e a t e r than 0.99, the s e r v i c e m o d u l e ' s c o n t r o l and p r o p u l s i o n s y s t e m s should
be m o r e than a d e q u a t e for t h i s t a s k , and an e x t r a l aunch would not be r e q u i r e d .
B a s i c a l l y the p r o p o s e d d i s p o s a l t e c h n i q u e would be to decoup le the CSM and the
r e a c t o r p o w e r s y s t e m f r o m t h e i r r e s p e c t i v e docking p o r t s , couple t h e m t o g e t h e r ,
and then u s e the CSM to push the p o w e r s y s t e m up to a h i g h e r o r b i t or to deboos t
i t into the o c e a n . If r e q u i r e d , a s e p a r a t e , a u t o m a t e d d i s p o s a l s y s t e m ( c o n t r o l l e d
f r o m the g round or the OWS) could be i n c o r p o r a t e d in the p o w e r p l a n t p a c k a g e a s
a b a c k u p , in which c a s e the to t a l r e l i a b i l i t y for safe d i s p o s a l should exceed 0 .999.
The ind iv idua l r a d i a t i o n i n j u r y o r d e a t h p r o b a b i l i t y cou ld thus be r e d u c e d to l e s s
than 10 and 10 r e s p e c t i v e l y , w h i c h i s b e l i e v e d to be t e c h n i c a l l y and p o l i t i
c a l l y a c c e p t a b l e .
Al though the fo rego ing d i s c u s s i o n i s of n e c e s s i t y an o v e r s i m p l i f i e d s u m m a r y
of a c o m p l e x p r o b l e m , the s u g g e s t e d a p p r o a c h t o w a r d s a s s u r i n g a d e q u a t e n u c l e a r
sa fe ty m a r g i n s for t h i s m i s s i o n i s thought to be r e a s o n a b l e . Add i t iona l m o r e -
de t a i l ed s t u d i e s of the p r o p o s e d d i s p o s a l t e c h n i q u e s and h a z a r d a n a l y s e s s i m i l a r
to t h o s e m a d e b e f o r e ob ta in ing a p p r o v a l for the SNAP lOA flight t e s t wi l l be
r e q u i r e d ,
B . LUNAR BASE P O W E R P L A N T
1. M i s s i o n R e q u i r e m e n t s
R e a c t o r power s y s t e m s for m a n n e d l u n a r b a s e s w e r e s tud ied r e c e n t l y in a
(3 5)
jo in t NASA-AEC s tudy ' to d e t e r m i n e the d e s i g n and d e v e l o p m e n t r e q u i r e
m e n t s and the p e r f o r m a n c e c h a r a c t e r i s t i c s of th i s type p o w e r p l a n t for such a
m i s s i o n . The b a s i c r e q u i r e m e n t s and r e s u l t s r e g a r d i n g i n t e g r a t i o n , d e p l o y
m e n t , and o p e r a t i n g m o d e ob t a ined f r o m tha t s tudy a r e thought to be s t i l l val id
and have been r e t a i n e d , t h e r e f o r e , in the p r e s e n t s tudy for the p u r p o s e of u p
dat ing the r e a c t o r — T E s y s t e m d e s i g n and p e r f o r m a n c e c h a r a c t e r i s t i c s .
The key power s y s t e m r e q u i r e m e n t s for a l u n a r b a s e p o w e r p l a n t de s igned
to s u p p o r t ex t ended m a n n e d l u n a r e x p l o r a t i o n a r e s u m m a r i z e d on Tab le V - 7 .
A I - A E C - M E M O - 1 2 7 1 7 152
This m i s s i o n i s e n v i s i o n e d a s a l og i ca l ou tg rowth of the Apol lo and Advanced
Apol lo p r o g r a m s , w h e r e i n the l e v e l of e x p l o r a t i o n , c r e w s i z e , and s t ay t i m e s
would g r a d u a l l y i n c r e a s e in a step-wise fash ion . One o r two p e r s o n n e l s h e l t e r s
c a p a b l e of s u p p o r t i n g up to s ix m e n e a c h for s ix m o n t h s wi thout r e supply would
c o n s t i t u t e the l u n a r b a s e .
T A B L E V-7
KEY P O W E R SYSTEM R E Q U I R E M E N T S F O R LUNAR BASE
P o w e r l e v e l r a n g e of i n t e r e s t , kwe 10 to 30
N u m b e r of m e n 6 to 12
M i n i m u m l i f e t i m e , y r 1
P r e - o p e r a t i o n a l s t o r a g e on m o o n , m o ^6
A v a i l a b i l i t y 1975-1980
Al lowab le d o s e to a s t r o n a u t f r o m r e a c t o r , r e m 70
A l lowab le s e p a r a t i o n d i s t a n c e , m i ^ 1 2
A v a i l a b l e r a d i a t o r a r e a , ft 1500 to 2500
A l lowab le p o w e r p l a n t we igh t , lb 29,475
Shie ld c o n c e p t s a) I n t e g r a l 47T b) Lunar soi l
The b a s i c h o u s e k e e p i n g power r e q u i r e m e n t s have b e e n e s t i m a t e d to be
'~1 kwe p e r m a n , so the m i n i m u m luna r b a s e p o w e r p l a n t c a p a c i t y , t h e r e f o r e ,
would be in the r a n g e of 6 to 12 kwe , depend ing on the a c t u a l b a s e s i z e . Add i
t iona l p o w e r would be r e q u i r e d for e x p e r i m e n t s , r e c h a r g i n g m o b i l e v e h i c l e s ,
and s i m i l a r func t ions . The m a x i m u m p o w e r l eve l of i n t e r e s t would thus depend
on the s c o p e and n a t u r e of the e x p l o r a t i o n p r o g r a m , and would p r o b a b l y c o r r e
spond to the m a x i m u m c a p a b i l i t y t ha t could be p rov ided wi th in the payload l i m i t s
of the d e s i g n a t e d l aunch and landing v e h i c l e s . Up to two w e e k s e m e r g e n c y power
would a l s o be supp l i ed by fuel c e l l s .
The S a t u r n - V b o o s t e r c o m b i n e d wi th a Luna r Landing Vehic le (LLV) having
a ne t pay load c a p a c i t y of s l igh t ly l e s s than 30,000 lb ( landed on the luna r su r f ace )
w a s s e l e c t e d by NASA as the s t a n d a r d l o g i s t i c s s y s t e m for t h i s m i s s i o n . The
A I - A E C - M E M O - 1 2 7 1 7 153
a r e a a v a i l a b l e for fixed r a d i a t o r s wi th in the s t a n d a r d s h r o u d w a s abou t 1500 ft . 2
This can be i n c r e a s e d to a p p r o x i m a t e l y 2500 ft u s ing a l a r g e r s h r o u d of the
s i z e d e s i g n e d for the Voyage r m i s s i o n , o r by u s ing folding r a d i a t o r p a n e l s .
The n u c l e a r p o w e r p l a n t would be l anded a s a s e p a r a t e u n m a n n e d pay load in
the v i c in i t y of the l u n a r b a s e , m o u n t e d on the LLV. As long a s 6 m o of p r e
o p e r a t i o n a l s t o r a g e in the moon m i g h t be r e q u i r e d b e f o r e b a s e m a n n i n g and ful l -
power o p e r a t i o n .
T h r e e p o s s i b l e d e p l o y m e n t m o d e s and a s s o c i a t e d p lant c o n c e p t s w e r e c o n
s i d e r e d in the r e f e r e n c e d s tudy:
1) An o f f - loaded a r r a n g e m e n t w h e r e i n the r e a c t o r a s s e m b l y would be
b u r i e d in a hold in the l u n a r so i l and the p lan t would then be a s s e m
b led , c h e c k e d out , and s t a r t e d up on the l u n a r s u r f a c e ,
2) An i n t e g r a l p o w e r p l a n t u s i n g 47T sh ie ld ing and fixed r a d i a t o r s , a l l of
wh ich would be a s s e m b l e d and c h e c k e d out on E a r t h b e f o r e l aunch , and
3) An i n t e g r a l , 477 s h i e l d e d concep t s i m i l a r to 2) wi th dep loyab l e r a d i a t o r s
wh ich would be a s s e m b l e d on the m o o n .
The i n t e g r a l ( p r e - a s s e m b l e d ) p o w e r p l a n t concep t wi th a 477 sh i e ld w a s
s e l e c t e d , to r e d u c e a s t r o n a u t l a b o r and avo id t e c h n i c a l p r o b l e m s a s s o c i a t e d
with the o t h e r c o n c e p t s . C o n s e q u e n t l y in the p r e s e n t s tudy, c o n s i d e r a t i o n w a s
l i m i t e d to the i n t e g r a l de s ign a p p r o a c h u s i n g a 477 sh ie ld to r e d u c e the annua l
dose to the a s t r o n a u t s to the p r e v i o u s l y spec i f i ed v a l u e , 70 r e m . The a l l owab le
s e p a r a t i o n d i s t a n c e b e t w e e n the p o w e r p l a n t and the l u n a r s h e l t e r s w a s a l s o d e
t e r m i n e d to be u p to 1 m i l e , b a s e d on p o w e r t r a n s m i s s i o n and o p e r a t i o n a l c o n
s i d e r a t i o n s .
A n o t h e r i m p o r t a n t g e n e r a l c r i t e r i o n w a s tha t a s s e m b l y , s t a r t u p , and o p e r a
t ion of the p lan t should r e q u i r e a m i n i m u m of a s t r o n a u t l abo r o r a t t e n t i o n , s i nce
the p r i m a r y m i s s i o n o b j e c t i v e s a r e no t to w o r k on p o w e r p l a n t s but to e x p l o r e
the m o o n . Thus a p r e m i u m would be p l a c e d on p o w e r p l a n t s i m p l i c i t y and r e l i
ab i l i t y .
A I - A E C - M E M O - 12717 154
2. System Descript ion and Pe r fo rmance
The updated basel ine lunar powerplant design consis ts of the reference
25-kwe sys tem presented in Section III of this repor t , packaged in a configura
tion suitable for this miss ion . F igure V-16 shows the powerplant a r rangement ,
which is designed to be mounted on the top of the LLV. The reac to r , shield,
and PCS assembly is mounted along the center l ine , inside the radiator at the
base of the powerplant to maintain a low center of gravity. The r eac to r / sh i e ld
a s sembly is supported by s t ru t s attached to a mounting ring. The conver te r s ,
pumps, and p r imary- loop expansion compensators a re located atop the shield.
Each of the four radia tor sections consis ts of cylindrical and conical quadrants
connected in para l le l hydraul ical ly. The expansion compensators for the HRL's
a r e mounted within and near the top of the radia tor .
The electronic package used for remote s tar tup, control , and monitoring
of the sys tem from Ear th during low-power operation on the moon is located at
the top of the sys tem. The electronic package is thermal ly insulated from the
r e s t of the sys tem and is exposed to space for proper the rmal control .
A the rma l shroud covers the radia tor to reduce heat losses during storage
and periods -when the reac tor is shut down. When the sys tem is at full power,
the shroud is deployed, as shown in F igure V-17.
The reac to r con t ro l -d rum d r ive -moto r s and e lec t r ica l connectors a re lo
cated at the base of the sys tem where they a r e access ible to the as t ronauts
during r eac to r shutdown for possible maintenance.
Table V-8 summar i zes basel ine lunar power sys tem cha rac t e r i s t i c s . The
g ross e lec t r i ca l power is 27.0 kwe; los ses in t r ansmiss ion and power condition
ing reduce the power available at the lunar shelter to 22.9 kwe. The converter
power output is inverted to ac , t ransformed to 4160 volts, and t ransmit ted via
cable to the lunar she l te r .
The conver te r modules a r e identical with those of the reference sys tem de
sign and the Saturn-IVB Workshop design. The higher power output is due to
the l a rge r available radia tor a rea and consequent lower conver ter cold-clad
t e m p e r a t u r e .
AI-AEC-MEMO-12717 155
26 9 ft
15 4 ft
PREOPERATIONAL REACTOR CONTROL AND COMM EQUIPMENT
EXPANSION COMPENSATOR
NaK MANIFOLD
SHROUD ENVELOPE
RADIATOR (1500f|2)
INTERFACE LOAD RING
SUPPORT STRUT
NaK SUPPLY AND RETURN PIPES
REACTOR CONTROL MOTOR
POWER CONVERSION EQUIPMENT
REACTOR CONTROL MOTOR
REACTOR AND SHIELDING
8 JH 099 60
F i g u r e V - 1 6 . 25 -kwe N u c l e a r T h e r m o e l e c t r i c P o w e r Supply L u n a r B a s e A p p l i c a t i o n
SHROUD ENVELOPE
> l-H
>
n
O
-
48.8 ft (REF)
FIXED RADIATOR WITH STANDARD SHROUD
RADIATOR AREA = 1,500 ft^
NET POWER = 22.9 kwe
FIXED RADIATOR WITH LARGE SHROUD
RADIATOR AREA = 2,500 ft^ NET POWER = 35.5 kwe
FIXED AND FOLDING RADIATOR
RADIATOR AREA = 2,500 ft^
NET POWER = 35.5 kwe
FLEXIBLE NaK JOINT
FOLDING RADIATOR
HEAT SHIELD
LUNAR SURFACE
F i g u r e V - 1 7 . L u n a r B a s e P o w e r Supply Des ign A l t e r n a t e s
8-J14-099-58
T A B L E V - 8
BASELINE LUNAR P O W E R P L A N T CHARACTERISTICS (Sheet 1 of 2)
G r o s s p o w e r output , kwe
L o s s in c o n v e r s i o n and t r a n s m i s s i o n , kwe
Net power to s h e l t e r , kwe
T h e r m a l p o w e r , kwt:
R e a c t o r
C o n v e r t e r
P u m p c o n v e r t e r
( P r i m a r y loop
( H e a t - r e j e c t i o n loop)
R a d i a t o r
P r i m a r y - l o o p l o s s e s
T e m p e r a t u r e , ° F :
R e a c t o r
C o n v e r t e r , h o t - c l a d
C o n v e r t e r , c o l d - c l a d
R a d i a t o r
E f f i c i e n c i e s , %:
S y s t e m 3.74
C o n v e r t e r 4 .74
C o n v e r t e r C a r n o t 35.9
V o l t a g e s , vo l t s
S h e l t e r h i g h - v o l t a g e bus 4160.0
C o n v e r t e r :
T u b u l a r m o d u l e 14.4
C o n v e r t e r m o d u l e 57.6
Inle t
1045
1225
456
648
Out le t
1247
1025
656
448
27.0
4.1
22.9
613.4
570,0
38.4
25.6)
12.8)
581.4
5.0
A v e r a g e
1146
1125
556
548
A I - A E C - M E M O - 1 2 7 1 7 158
TABLE V-8
BASELINE LUNAR POWERPLANT CHARACTERISTICS (Sheet 2 of 2)
F lowra tes , l b / s e c ;
P r i m a r y loop 13,7
Heat - re jec t ion loop 13,1
P r e s s u r e - d r o p , psi :
P r i m a r y loop 3.0
Heat- re jec t ion loop 1,4
,2 Radiator a rea , ft
Weights, lb:
Reactor
Conver ter
R a d i a t o r / s t r u c t u r e
Pumps
Expansion compensa tors
Piping
Instrumentat ion and control equipment
Power conditioning
Subtotal
Nuclear shield
Reactor and power-conversion sys tem support s t ruc ture
Thermal shield
Direct cu r ren t t r ansmis s ion cable
Alternating cu r r en t t r ansmis s ion cable
Subtotal
Total sys tem weight
Allowable payload
Design miargin
7,525
14,000
1,575
23,100
29,475
6,375
1500
1,422
1,135
2,'760
440
210
518
240
800
525
500
300
250
AI-AEC-MEMO-12717 159
TE CONVERTER
EXPANSION COMPENSATOR
> n
O
- J
PUMP ASSEMBLY
REACTOR INLET NaK FLOW
INTERFACE LOAD RING
CONTROL DRUM DRIVE MOTOR 8-J14-099-59
F i g u r e V - 1 8 . R e a c t o r Shie ld ing and S t r u c t u r e , L u n a r B a s e C o n c e p t u a l
The total es t imated sys tem weight is 23,100 lb (including the 14,000-lb shield,
power-condit ioning equipment, and t r ansmi s s ion cables) which is 6,375 lb less
than the 29,475-lb payload l imit for the designated launch vehicle sys tem. This
marg in provides the possibi l i ty for increas ing the design power output by adding
TE conver te r s and rad ia tor a r ea .
The n e c e s s a r y inc rease in radia tor a r e a can be obtained by using radia tors
which can be deployed with the the rmal shroud, as shown in Figure V- 17, using
flexible NaK joints at the hinge points. An a l te rna te approach is to use fixed
rad ia to r s and a l a rge r shroud. The Voyager shroud design, for example, is the
same diameter and same general configuration as the standard shroud, except 2
that its cyl indrical section is long enough to accommodate an additional 1000 ft
of rad ia to r . These two a l te rna te configurations a r e shown on Figure V-17, along
with the basel ine sys tem. 2
As shown in Table V-9, with 2500 ft of radia tor available the e lec t r ic power output inc reased to 42,9 kwe gross and 35.5 kwe net. The reac tor power and
ou t l e t - t empera tu res a r e 962.4 kwt and 125 1°F still within the reference ZrH
reac to r per formance capabili ty. The shield weight was held constant at 14,000 1b
and the min imum separat ion distance would thus be increased to approximately
3250 ft for the same dosera te at the higher reac tor power level, A coolant A T
of 300°F is used to minimize pumping-power r equ i rement s . The total sys tem
weight is 27,675 lb; the allowable weight l imit is 28,775 lb (700 less than the
29,475 because of the use of the heavier Voyager shroud), which still leaves a
design marg in of 1100 lb. This marg in , while probably adequate, could be in
c reased by approximately 3200 lb by t ranspor t ing the power-conditioning equip
ment and t r ansmi s s ion cables to the moon in the lunar shel ter or other logist ics
vehic les .
Thus reac to r — TE lunar powerplants with net capacit ies up to 35 kwe appear
feasible within the cons t ra in ts and guidelines established for this miss ion ,
3, Subsystem Descr ipt ion and Per fo rmance
a. Reactor /Shie ld Assembly
The heat source cons is t s of the re ference ZrH reac tor surrounded by a 477
shield, A drawing of the r eac to r and shield is shown in Figure V-18. The reac tor
AI-AEC-MEMO- 12717 161
T A B L E V-9
H I G H - P O W E R LUNAR P O W E R P L A N T C H A R A C T E R I S T I C S (Sheet 1 of 2)
G r o s s p o w e r output , kwe 42.9
L o s s to c o n v e r s i o n and t r a n s m i s s i o n , kwe 7.4
Net power to s h e l t e r , kwe 35.5
T h e r m a l p o w e r , kwt:
R e a c t o r
C o n v e r t e r
P u m p c o n v e r t e r
( P r i m a r y loop
( H e a t - r e j e c t i o n loop
R a d i a t o r
P r i m a r y - l o o p l o s s
T e m p e r a t u r e , ° F :
R e a c t o r
C o n v e r t e r , h o t - c l a d
C o n v e r t e r , c o l d - c l a d
R a d i a t o r
E f f i c i e n c i e s , %
S y s t e m 3.78
C o n v e r t e r 4.67
C o n v e r t e r C a r n o t 35.0
V o l t a g e s , v o l t s :
S h e l t e r h i g h - v o l t a g e bus 4160
C o n v e r t e r :
T u b u l a r m o d u l e 14.0
C o n v e r t e r m o d u l e 56.0
In le t
949
1230
390
384
Out le t
1251
930
690
684
962.4
919
38.4
25.6)
12.8)
914.4
5.0
A v e r a g e
1100
1080
540
5 34
A I - A E C - M E M O - 1 2 7 1 7
162
TABLE V-9
HIGH-POWER LUNAR POWERPLANT CHARACTERISTICS (Sheet 2 of 2)
F lowra te , l b / s e c :
P r i m a r y loop 14.4
Heat - re jec t ion loop 13.7
P r e s s u r e - d r o p , psi
P r i m a r y loop 3.3
Heat - re jec t ion loop 1,5
Weights, lb
Reactor 1,422
Conver ter 1,928
R a d i a t o r / s t r u c t u r e 4,600
Pump s 530
Expansion compensa tors 310
Piping 900
Inst rumentat ion and control equipment 300
Power conditioning 1,600
Radiation shield 14,000
Reactor and power-conversion sys tem support s t ruc ture 630
Thermal shield 835
Direct cu r r en t t r ansmis s ion cable 300
Alternat ing cu r ren t t r ansmis s ion cable 320
Total sys tem weight 27,675
Allowable payload 28,775
Design marg in 1,100
AI-AEC-MEMO-127 17 163
i s the s a m e a s tha t d e s c r i b e d in Sec t ion IV-A wi th the excep t ion tha t i t i s o p e r
a t ed in an i n v e r t e d pos i t i on . The c o n t r o l - d r u m d r i v e - s h a f t s p a s s downward
t h r o u g h the l o w e r end of the sh i e ld in to a r i g h t - a n g l e g e a r and then to the d r i v e -
m o t o r s . The l a t t e r a r e l o c a t e d n e a r the l ower p e r i p h e r y of the r a d i a t o r to p r o
vide a c c e s s for p o s s i b l e m a i n t e n a n c e when the r e a c t o r i s shut down.
The r e a c t o r sh i e ld i s c o m p o s e d of an i n n e r P b g a m m a s h i e l d s u r r o u n d e d by
a canned LiH n e u t r o n sh i e ld . A l a y e r of i n s u l a t i o n s e p a r a t e s the two s h i e l d s to
avoid o v e r h e a t i n g the LiH, The n e u t r o n s h i e ld i s cooled b y r a d i a t i o n to the inne r
s u r f a c e of the power s y s t e m r a d i a t o r . The sh i e ld enve lope i s 68 in . in d i a m by
68.5 in . h igh , and the to ta l sh i e ld we igh t i s a p p r o x i m a t e l y 14,000 lb . The sh ie ld
t h i c k n e s s e s shown on F i g u r e V - 1 8 a r e s i z e d to l i m i t the annua l r a d i a t i o n dose to
70 r e m / y e a r (8 m r e m / h r ) at the l u n a r s h e l t e r , wh ich i s l o c a t e d a t a d i s t a n c e of
a p p r o x i m a t e l y 1/2 m i . In add i t i on , the i n t e g r a t e d d o s e to the p r e - o p e r a t i o n a l 12
c o n t r o l e q u i p m e n t l o c a t e d above the r e a c t o r w a s l i m i t e d to 5 x 10 nvt in 6 m o
of o p e r a t i o n a t 10% p o w e r . No sh i e ld i s p l a c e d a r o u n d the p o w e r - c o n v e r s i o n
e q u i p m e n t , and the d o s e r a t e f r o m the a c t i v a t e d NaK in the e x p o s e d p a r t of the
p r i m a r y loop i s i n c l u d e d a s a s o u r c e in the c a l c u l a t i o n of e x p e c t e d d o s e r a t e s .
Tab le V-10 p r e s e n t s the d o s e r a t e c o n t r i b u t i o n s f r o m n e u t r o n s and g a m m a s at a
s e p a r a t i o n d i s t a n c e of 0.5 m i .
T A B L E V-10
D O S E R A T E A T 0.5 m i F R O M LUNAR BASE R E A C T O R
Neutrons
Gamma rays (p r imary and secondary)
24 Na in power-convers ion sys tem
Total
Dosera te ( m r e m / h r )
1.57
3.66
2.32
7.55
A I - A E C - M E M O - 1 2 7 1 7
164
b , PCS Ar rangement
The TE PCS including the conve r t e r s , pumps, and pr imary- loop expansion
compensa to r s a r e located above the r eac to r / sh i e ld as shown in F igures V-16
and -18 , The a r r angemen t is essent ia l ly the same as that in the gallery of the
Saturn-V OWS (see F igure V-7), Pump power r equ i remen t s , conver ter s ize ,
and expansion compensator size a r e the same for both plants . Detailed de sc r ip
t ions of each of the PCS components a r e given in other sections of this repor t .
For the 35.5-kwe plant the r eac to r AT has been increased, result ing in
nea r ly the same pump power r equ i r emen t s . The conver ter packages will be
l a r g e r , however, requir ing a somewhat expanded a r rangement of the power-
convers ion equipment shown previously .
c . Rad ia to r /S t ruc tu re
The r a d i a t o r / s t r u c t u r e is s imi la r to that on the Saturn-V OWS plant (see
F igure V-9). The radia tor consis ts of a 6061 aluminum fin and a r m o r which
is diffusion-bonded to a s t a i n l e s s - s t e e l NaK tube. The individual tube-fin pieces
a r e a s sembled into panels by welding the NaK tubes to headers at either end.
The panels a r e then assembled to the s t ruc ture through supports to provide dif
ferent ia l t h e r m a l expansion between the s t ruc ture and the tube-fin panels. The
NaK heade r s a r e connected to the supply and re turn l ines .
The radia tor s t ruc tu re is of the semimonocoque type, consisting of c o r r u
gated s t i f feners , skin, and f r ames . Titanium is used as the s t ruc tura l m a t e r i a l
because during power - sy s t em operat ion, the maximum tenaperature is between
650 and 700°F,
The rad ia tor s t ruc tu re is at tached to a load ring located at the base of the
rad ia to r . The r e a c t o r / s h i e l d is supported off this same load ring through spar
beams attached to the outside of the shield s t ruc tu re .
4. Operat ional Mode
The methods and p rocedures proposed for deployment of the powerplant on
the lunar surface , p re -opera t iona l s torage, s tar tup, and operation, a re the
same as those identified in the previous study of reac tor power sys tems for (3 5) this mis s ion . ' Briefly, the planned operational mode is as follows:
AI-AEC-MEMO-12717 165
1) The power sys tem will be launched using the Sa tu rn-V/LLV booster
and landing vehicle, and landed on the lunar surface at a p r e d e t e r
mined position located approximately 1/2 to 1 mi from the position
of the lunar she l t e r s .
2) The reac tor will be s tar ted up by a command signal from Ear th , and
the reac tor power level r a i sed to approximately 5 to 10% of its design
full-power operating point. The the rmal shields will then be opened
to expose approximately 10% of the rad ia to r a r ea (again by control
from Ear th) . Under these conditions severa l hundred watts of e lec
t r i ca l power will be generated, sufficient to power the communicat ions
and control equipment at the top of the powerplant. Its operabil i ty can
thus be confirmed on Ear th before the as t ronauts a r e committed to the
lunar base . In addition the powerplant can be kept w a r m through the
lunar the rmal cycles thus avoiding freezing of the l iquid-metal loops.
3) The as t ronauts will land somet ime during the two-week lunar day at
which t ime the reac tor powerplant will be shut down by remote com
mand. The as t ronauts then will deploy the power - t r ansmis s ion cables
between the lunar shelter and the powerplant, and set up the operat ional
control and power-conditioning equipment, on the lunar surface within
about 100 ft of the powerplant.
4) After the as t ronauts have re turned to the lunar she l t e r s , the heat
shields will be lowered and the sys tem s tar ted up and brought to the
des i red operating power level . (The operat ional control sys t em will
be of the type discussed under the re ference power sys tem in this
repor t . )
5) In the event of sys tem shutdown (planned or unplanned), the heat
shields will be ra i sed back into position to avoid eventual freezing
of the l iquid-metal loops. Maintenance and repa i r will be possible
on the con t ro l -d rum actuator m o t o r s , located at the outer surface
of the powerplant, and on the e lec t r i ca l control and power-conditioning
equipment located on the lunar sur face .
AI-AEC-MEMO-12717 166
6) At the end of the miss ion the powerplant will be shut down using the
normal control sys tem and abandoned in position. If des i red , the
power level can be reduced to 5 to 10% of i ts des ign-power level and
left on the moon in this condition, ready for subsequent r e s t a r t and
operation.
Nuclear safety requ i rements for this miss ion can be me t quite easi ly since
the power sys tem would not be s ta r ted up until it has been safely landed on the
moon.
5. Comparison With Previous Design
The cu r ren t lunar base powerplant design r e p r e s e n t s a considerable im
provement over that repor ted in Reference 3. Table V-11 is a compar ison of
the more significant features of the cu r r en t and previous des igns . The new
TABLE V-11 DESIGN COMPARISON
Elec t r ica l power del ivered to Degradation allowance, % Reactor power, kwt Reactor ou t l e t - t empera tu re , Converter clad average tempe
System efficiency, % Radiator a rea , ft^ Number of tubular modules Total number of loops Weight, lb:
Power-conversion sys tem . Nuclear shield Support s t ruc ture Thermal shield Transmiss ion cable
Total
Allowable payload
Design margin
she l te r .
° F
sra ture .
kwe
"F: hot cold
ind r eac to r
Cur ren t
22.9 10
613.4 1247 1125 556 3.74 1500 96
5
7,525 14,000
525 500 550
23,100
29,475
6,375
Previous
20.4 14.0 541
1229 1100 500 3.77 1500 256
17
11,195 13,900
525 500 500
26,620
29,475
2,855
AI-AEC-MEMO-12717 167
s y s t e m h a s a h i g h e r n e t power p r i m a r i l y b e c a u s e of i m p r o v e m e n t s in the T E
c o n v e r t e r and s y s t e m d e s i g n . The r e a c t o r t h e r m a l power i s h i g h e r for the
new s y s t e m b e c a u s e of the h i g h e r e l e c t r i c a l p o w e r output . The s y s t e m effi
c i e n c i e s a r e n e a r l y the s a m e .
The p r e v i o u s d e s i g n u s e d 256 c o n v e r t e r t u b u l a r m o d u l e s wh ich -were s m a l l e r
than the c u r r e n t r e f e r e n c e t u b u l a r m o d u l e d e s i g n . Th i s c h a n g e in c o n v e r t e r
de s ign not only d r a s t i c a l l y r e d u c e d the n u m b e r of t u b u l a r m o d u l e s r e q u i r e d , but
a l s o r e d u c e d c o n v e r t e r we igh t by o v e r 2400 lb . Th i s a c c o u n t s for m o s t of the
weigh t d i f f e r e n c e s b e t w e e n the c u r r e n t and p r e v i o u s d e s i g n s . A n o t h e r 1000- lb
r e d u c t i o n w a s a c h i e v e d by u s i n g i m p r o v e d r a d i a t o r des ign , u s i n g f ewer p a r a l l e l
l o o p s , and e l i m i n a t i n g the i n t e r m e d i a t e loops e n t i r e l y . Th i s g r e a t l y s i m p l i f i e s
the s y s t e m d e s i g n and should i n c r e a s e the r e l i a b i l i t y . The c u r r e n t d e s i g n h a s
twice the we igh t d e s i g n m a r g i n a s the p r e v i o u s d e s i g n .
C. M O R L P O W E R P L A N T
1. M i s s i o n R e q u i r e m e n t s
The M O R L i s a p r e l i m i n a r y d e s i g n for an advanced s p a c e s t a t i on tha t h a s
been s tud i ed e x t e n s i v e l y o v e r the p a s t s e v e r a l y e a r s by the M c D o n n e l l - D o u g l a s
C o r p . for NASA. A jo in t NASA/AEC s tudy to d e t e r m i n e the d e s i g n r e q u i r e m e n t s
and c h a r a c t e r i s t i c s of s e v e r a l t y p e s of r e a c t o r power s y s t e m s for the M O R L
w a s conduc t ed in 1966. ' One of the power s y s t e m s s tud i ed w a s a 2 2 . 5 - k w e
r e a c t o r — T E s y s t e m b a s e d on the P b T e t u b u l a r co rapac t c o n v e r t e r . Al though
the M O R L d e s i g n h a s now been s u p e r s e d e d by the OWS s e r i e s , upda t ing of the
r e a c t o r — T E po-wer s y s t e m d e s i g n for the s a m e i n t e g r a t i o n c o n s t r a i n t s u s e d
p r e v i o u s l y i s of i n t e r e s t .
The m a j o r p o w e r s y s t e m r e q u i r e m e n t s and i n t e g r a t i o n c o n s t r a i n t s e s t a b
l i s h e d for the M O R L m i s s i o n a r e shown in Tab le V - 1 2 .
2. S y s t e m D e s c r i p t i o n and C o m p a r i s o n wi th P r e v i o u s D e s i g n
The g e n e r a l con f igu ra t i on and p e r f o r m a n c e c h a r a c t e r i s t i c s of the u p d a t e d
M O R L r e a c t o r — TE s y s t e m a r e the s a m e a s t h o s e of the r e f e r e n c e 25 -kwe s y s
t e m d e s c r i b e d in Sec t ion III of t h i s r e p o r t . The p o w e r p l a n t l ayout and d i m e n s i o n s
A I - A E C - M E M O - 1 2 7 1 7
168
TABLE V-12
KEY MANNED ORBITING RESEARCH LABORATORY MISSION AND REACTOR POWER SYSTEM REQUIREMENTS
Elec t r i ca l power range , kwe 10 to 30
Lifetime objective, yr 5
Allowable radiat ion dosera te from r e a c t o r , r e m / y r 20
Reactor — Manned Orbiting Resea rch
Labora to ry separat ion dis tance, ft 125
Doseplane d iame te r , ft 80
Shield type Shadow
Available payload for power sys tem, lb
Initial launch 41,000
Replacement 18,110
shown on F igure V-19 a r e set p r imar i l y by the 17° shield half-angle which r e
sults from the doseplane d iameter and separat ion distance requ i rement s . A
shadoAV shield is used, consis tent with the previous requ i rements for this appli
cation. This po-wer-conversion equipment is located in the shield gal lery.
Table V-13 i s a brief summary of the cu r ren t MORL system cha rac te r i s t i c s (2) and a compar i son with the previously published sys tem design. That had an
e lec t r ica l power output of 22.5 kwe and the cu r ren t design power level is 21.9 kwe.
These a re net conditioned powers based on a conditioning efficiency of 0.87.
The r e a c t o r t he rma l powers and efficiencies a r e approximately the same
for the two s y s t e m s . As was the case with the lunar base sys tem, the cur ren t
design u se s the improved conver te r module design which reduces the number of
modules r equ i r ed by 70%. The cu r ren t design does not use an intermediate loop,
thereby el iminating heat exchangers , in te rmedia te loop pumps, compensa tors ,
and piping.
The previous design used 12 active and 2 standby redundant loops with NaK
valves . The cu r r en t design has four active HRL's and no standby redundant loops
Any sy s t em degradat ion which might occur is compensated for by adjusting r e
actor ou t l e t - t empe ra tu r e , which has been reduced 54°F in the cu r ren t design.
AI-AEC-MEMO-12717 169
TABLE V-13 MOBILE ORBITING RESEARCH LABORATORY
SYSTEM CHARACTERISTICS
Regulated e lec t r ica l power, kwe
Reactor thermal power, kwt
Reactor ou t le t - tempera ture , °F
Converter clad average t e m p e r a t u r e .
" F : hot
cold
System efficiency, % 9
Radiator a rea , ft Number of tubular modules
Number of loops in s e r i e s
Number of hea t - re jec t ion loops in para l le l
Total number of hydraul ic loops
Weights, lb:
Reactor
P r i m a r y loop
Heat exchangers
Converters
Expansion compensators
Pumps
Piping
Support s t ruc ture
Radiator / s t ruc ture / piping
Subtotal
Radiation shield
Total
Current
21.9
582
1,246
1,125
570
3.77
1,400
96
2
4
5
1,422
515
-
1,135
285
440
100
113
2,990
7,000
12,300
19 300
Previous
22.5
622
1,300
1,150
550
3.62
1,891
336
3
14
22
755
503
147
5,082
693
280
200
-
3,573
11,233
9,315
20,548
AI-AEC-MEMO-12717 171
The cur ren t sys tem has a total of five hydraul ic loops, i, e. one p r i raa ry and
four HRL's , whereas the previous design had 22 hydraulic loops, i, e. one p r i
m a r y , seven in te rmedia te , and 14 HRL's 2
The radia tor a r ea has been reduced by 49 1 ft , which reduces the overal l
package height approximately 7 ft.
The weights shown in Table V-13 a r e a r r anged to provide a consis tent com
par ison and do not include integrat ion penalt ies in e i ther ca se .
The cu r ren t design uses the 477'-shieldable 295-element r eac to r , and the
previous design used a 349-element r eac to r concept with a Be ref lector de
signed for use with a shadow-shield. The conver te r weight is reduced near ly
4000 lb by use of the cu r r en t module design. Other weight differences except
for the nuclear shield a r e a r esu l t of the different hydraul ic a r r angemen t s .
The cur ren t shield design is significantly heavier at 12,300 lb than the p r e
vious weight of 9,315 lb . This difference is caused by the use of a l a rge r gal lery
to accommodate the pumps, conver t e r s , and expansion compensa to r s . The p r e
vious design used compact heat exchangers to reduce gal lery size and shield
weight. However, the cu r r en t study has shown that it is n e c e s s a r y to use l a r g e r
heat exchangers with fewer tubes to improve re l iabi l i ty . Heat exchangers of
this type resu l t in ga l l e r ies a s la rge as those requ i red for the two-loop design
and resu l t in shield weights near ly as heavy as the c u r r e n t design. Without a
significant weight advantage there is no reason to use an in te rmedia te loop,
especial ly since the additional components in the loop reduce overal l sys tem
rel iabi l i ty .
Thus the major improvements in the updated powerplant for the MORL are
considered to be the simplification in the sys tem design which should enhance
the rel iabi l i ty , a 26% reduction in radia tor a r e a , a 50°F reduction in r eac to r
out le t4:emperature , and a 5% reduction in shielded sys tem weight.
AI-AEC-MEMO-12717 172
• REFERENCES
1. AI-AEC-MEMO-12715, "Reference ZrH Reactor , " December 1, 1968
2. DAC-57950, "Final Report on the Design Requi rements for Reactor Power Systems for Manned Ear th Orbital Applications, " January 1967, Douglas Miss i les and Space Division
3. LMSC-677879, Vol. II, "Design Requi rements for Reactor Power Systems for Lunar Exploration, " September 1967, Lockheed Miss i les and Space Company
4. DAC-56550, "Ear ly Orbital Space Station, " Douglas Miss i le and Space Systems Division, November 1967
5. NAA-SR-12374, "Reactor Power Plants for Lunar Base Applications, " (CRD), June 30, 1967, Atomics Internat ional
6. J . D. Gylfe, NAA-SR-MEMO-12373, Vol. I, "Reactor /Shie ld Subsystems for Manned Orbiting Resea rch Labora tor ies (MORL), " June 15, 1967
7. D. K. Nelson and R. L. Det terman, "Evaluation of SNAP Reactor Disposal Techniques, " Pape r presented at the Amer ican Nuclear Society Annual Winter Meeting, Chicago, 111., November 6-9, 1967
8. SID 65-1552, "Propuls ion Systems for Enhancing SNAP Reactor Safety {Contract A T ( l l - l ) - G E N - 8 ) (U), December 21 , 1965
9. R. S, Hart and W. T. Harper , E d s . , "Final SNAPSHOT Safeguards Report , NAA-SR-10022, Rev. (CRD), March 20, 1965
10. H. C. Haller and S. Lieblein, NASA LERC, "Analytical Comparison of Rankine Cycle Space Radia tors Constructed of Central Double and Block-Vapor-Chamber Fin-Tube G e o m e t r i e s , " NASA TN D-4411, Feb rua ry 1968
11. J . Mil ler , Pe r sona l Communication, NASA, MSFC
AI-AEC-MEMO-12717 173
GLOSSARY
A A P
a c
AI
ANS
B O L
GSM
dc
E B R
E C U
E M
E O L
EOSS
EVA
H N P F
H R L
ID
IHX
kwe
kwt
L L V
MDA
M O L
M O R L
M R P
Apol lo A p p l i c a t i o n s P r o g r a m
a l t e r n a t i n g c u r r e n t
A t o m i c s I n t e r n a t i o n a l
A e r o s p a c e N u c l e a r Safety
B e ginning -of- Life
C o m m a n d and S e r v i c e Module
d i r e c t c u r r e n t
E x p e r i m e n t a l B r e e d e r R e a c t o r
E x p a n s i o n C o m p e n s a t o r Unit
e l e c t r o m a g n e t i c
E n d - o f - L i f e
E a r l y O r b i t a l Space Sta t ion
E x t r a v e h i c u l a r a c t i v i t i e s
H a l l a m N u c l e a r P o w e r F a c i l i t y
H e a t - r e j e c t i o n loop
i n s i d e d i a m e t e r
I n t e r m e d i a t e h e a t e x c h a n g e r
k i l o w a t t s e l e c t r i c
k i l o w a t t s t h e r m a l
L u n a r Landing Veh ic l e
Mul t ip l e Docking A d a p t o r
M a n n e d O r b i t a l L a b o r a t o r y
M a n n e d O r b i t i n g R e s e a r c h L a b o r a t o :
M e r c u r y - R a n k i n e P r o g r a m
ry
A I - A E C - M E M O - 1 2 7 1 7 175
MSEC
n. m i
NPS
OD
OWS
P C S
P V T
P W R
SRE
S I B / S M
S8DR
S8ER
TE
T E M
WANE
M a r s h a l l Space F l i gh t C e n t e r
n a u t i c a l m i l e s
n u c l e a r power s y s t e m
o u t s i d e d i a m e t e r
O r b i t a l W o r k s h o p
p o w e r - c o n v e r s i o n s y s t e m
p r e s s u r e / v o l u m e / t e m p e r a t u r e
P r e s s u r i z e d W a t e r R e a c t o r
Sod ium R e a c t o r E x p e r i m e n t
S a t u r n - I B S e r v i c e Module
SNAP 8 D e v e l o p m e n t a l R e a c t o r
SNAP 8 E x p e r i m e n t a l R e a c t o r
t h e r m o e l e c t r i c
t h e r m o e l e c t r i c m o d u l e
W e s t i n g h o u s e A s t r o n u c l e a r L a b o r a t o r i e s
A I - A E C - M E M O - 1 2 7 1 7 176
Recommended