NEA COMMITTEE ON REACTOR PHYSICS...REACTOR PHYSICS ACTIVITIES IN OECD COUNTRIES This document is a compil.ation of national progress reports pre- sented to the Twentieth Meeting of

NEA COMMITTEE ON REACTOR PHYSICS

a

V REACTOR PHYSICS ACTIVITIES

IN OECD COUNTRIES

June 1976 - May 1977

OECD NUCLEAR ENERGY AGENCY 38, boulevard Suchet, 75016 Paris

NEA COMEITTEE ON REACTOR P R i S I C S

REACTOR P H Y S I C S A C T I V I T I E S I N

OECD COUNTRIES

June 1976 - May 1977

OECD NUCLEAR ENEFtGY AGENCY

38 B o u l e v a r d Suchet, 75016 P A R I S

REACTOR PHYSICS ACTIVITIES IN OECD COUNTRIES

This document is a compil.ation of national progress reports pre- sented to the Twentieth Meeting of the NEA Committee on Reactor Physics. held at ECN Petten. Netherlands. from 6th - 10th June 1977 .

Belgium .................... Canada .................... Denmark .................... Euratom .................... France .................... Germany .................... Netherlands .................... Italy .................... Japan .................... U.K. .................... Austria .................... Switzerland .................... Norway .................... Sweden ....................

................. United States Spain .................... Finland ....................

The Australian report (NEACRP-L-180a) will be sent out separately . Copies will be sent directly to all members and corresponding members of NEACRP: other recipients should request it from NEA Secretariat .

REACTOR PHYSICS ACTIVITIES I N BELGIUM

A r e p o r t t o t h e NEACHP. J u n e 1977.

Compiled by 3. DEBRUE, S.C.K./C.E.N., Mol

FAST REACTORS

The p a r t i c i p a t i o n o f S.C.K./C.E.N. a n d o f BELGONUCLEAIRE t o t h e DeBeNe f a s t

b r e e d e r programme w a s p u r s u e d i n d i f f e r e n t a r e a s . The a c t i v i t i e s i n t h e

r e a c t o r p h y s i c s a r e a are r e l a t e d t o t h e SNR-300 K k - I a and Mk-I1 c o r e d e s i g n

and t o t h e s t u d y o f p o s s i b l e c o r e l a y - o u t s f o r a c o m m e r c i a l b r e e d e r i n t h e

f r a m e o f t h e SNR-2 p r o j e c t .

1.1. An e v a l u a t i o n was made o f c r i t i c a l i t y a n d c o n t r o l r o d w o r t h m e a s u r e m e n t s

i n ZPPR-2 and -4 [I]. The m e a s u r e m e n t s c a n i n d e e d b e u s e d as a s u p p o r t o f t h e SNR-300 Mk-Ia c o r e d e s i g n , i n a d d i t i o n t o t h e e x p e r i m e n t s p e r -

fo rmed i n v a r i o u s SNEAK a s s e m b l i e s f o r t h i s p u r p o s e .

T y p i c a l k e f f v a l u e s o b t a i n e d w i t h t h e b e s t a v a i l a b l e methods o f c a l c u l a -

t i o n , i n c l u d i n g t r a n s p o r t c o r r e c t i o n s , a r e a b o u t 0.8% t o o h i g h f o r a c l e a n

c o r e and f o r a c o r e w i t h c o n t r o l r o d f o l i o w e r s . T h e s e r e s u l t s s u p p o r t

w e l l t h e t r e n d i n d i c a t e d by t h e SNEAK e v a l u a t i o n s . C o n s i s t e n c y b e t w e e n

t h e twu s e r i e s of e x p e r i m e n t s is a l s o r e l a t i v e l y good f o r c o r e s w i t h

a b s o r b e r r o d s i n s e r t e d b u t t h e o v e r e s t i m a t i o n d e c r e a s e s t o a b o u t 0.5% f o r

t h e ZPPR-4 c o r e s w i t h a n i n c r e a s i n g amount o f a b s o r b i n 8 m a t e r i a l s p r e s e n t

i n t h e c o r e r e g i o n .

A r e v i s i o n o f t h e u n c e r t a i n t i e s i n t h e p r e d i c t i o n o f k a n d k o n t r o l r o d e f f

w o r t h s f o r SNR-300 was p r e p a r e d b y BELGONUCLEAIKE, t o b e u s e d i n t h e d e t e r -

m i n a t i o n o f f u e l and a b s o r b e r e n r i c h m e n t s .

1.2. The d e s i g n work f o r a SNR-2 r e f e r e n c e c o r e is b e i n g c o n t i n u e d a t BELGO-

NUCLEAIRE, i n c o l l a b o r a t i o n w i t h GfK and INTERATOM. Two c o n c e p t s a r e

i n v e s t i g a t e d : t h e homogeneous ( o r c o n v e n t i o n a l ) c o r e and t h e h e t e r o g e n e o u s

one w i t h i n n e r f e r t i l e zones. The n e t e l e c t r i c power is now f i x e d a t

1300 MWe ( a b o u t 3900 ~ V t h ) , i n s t e a d o f 2000 MWe be fo re . The b a s i c d a t a

have been e s t a b l i s h e d f o r a n homogeneous c o r e o p e r a t i n g a t t h e now powor

l e v e l ; o p t i m i z a t i o n s t u d i e s were under t aken , e.g. w i th r e s p e c t t o c o n t r o l

r o d number and $ o s i t i o n s , t a k i n g i n t o accoun t r e v i s e d d a t a a b o u t t h e

s t r u c t u r a l p a r t of t h e f u e l a s s e m b l i e s . A s t o t h e he te rogeneoue c o n c e p t ,

t h e main p a r t of t h e work is c a r r i e d ou t a t INTEHATOM; a few c a l c u l a t i o n s

have h o i e v e r been made a t BLLGONUCLEAIHE: i n o r d e r t o s e l e c t c o r e l a y - o u t s

t o b e used i n p r e l i m i n a r y s a f e t y s t u d i e s . S e v e r a l ways t o d i s t r i b u t e

i n t e r n a l b l a n k e t s u b a s s e m b l i e s i n t h e f i a s i l e zone have been compared,

mainly w i 1.1) ruea rd t o power I'lutrrebs. A two-dimerieionnl (hexngona l ) model ,

is used and t h e i n f l u e n c e o f burn-up is t a k e n i n t o account . I n t h e s a f e t y

s t u d i e s , t h e b a s i s o f comparison between homogeneous and he te rogeneous

c o n c e p t s is a 1 6/s t r a n s i e n t overpower a c c i d e n t s t a r t i n g . from nominal c o n d i t i o n s i n each co re .

I n s u p p o r t t o t h e computa t ion methods and F&O development f o r SNH-2,

S.C.K./C.E.N. and BELGONUCLEAIRE have been a s s o c i a t e d t o t h e d i s c u s s i o n

o f G f K w i t h UKAEA on common e x p e r i m e n t s i n t h e ZEBRA f a c i l i t y a t Winf r i th .

Three s e r i e s of e x p e r i m e n t s have been d e f i n e d i n t h e s o - c a l l e d BIZET

programme i n o r d e r t o s i m u l a t e c o r e f e a t u r e s o f l a r g e b r e e d e r s . The first

c o r e (BZ-A) was made c r i t i c a l a t t h e end of November 1976. C o n t r o l rod

wor th measurements were performed by S.C.K./C.E.N. i n t h i s c o r e u s i n g t h e

p u l s e d n e u t r o n t echn ique . F i v e c o n t r o l rod p a t t e r n s were s t u d i e d ; t h e

r e a c t i v i t y v a l u e s ranged from -1.5 $ t o -26 $ . D e t e c t o r and n e u t r o n s o u r c e l o c a t i o n s were o p t i m i z e d i n o r d e r t o minimize harmonlc e f f e c t s .

1.3. Concerning t h e s a f e t y s t u d i e s f o r f a s t r e a c t o r s i n g e n e r a l , s e v e r a l a c t i -

v i t i e s have t o b e p o i n t e d o u t :

- p a r t i c i p a t i o n t o European code comparison e x e r c i s e s i n t h e frame o f t h e Working of ECC

- development of a p r e d i s a s s e m b l y phase code CASSANDHE which w i l l be i n t e g r a t e d i n t o a common eu ropean a c c i d e n t code system.

1.4. The p r e s e n t s t a t u s of t h e work performed i n benchmark n e u t r o n f i e l d s

used f o r r e a c t o r d o s i m e t r y a p p l i c a t i o n s h a s been reviewed and p r e s e n t e d

a t t h e IAEA Meeting on I n t e g r a l Cross -Sec t ion Measurements i n S t a n d a r d

Neut ron F i e l d s (Vienna , November 1976) . Updated e x p e r i m e n t a l r e a c t i o n

r a t e s have been compared w i t h c a l c u l a t e d v a l u e s u s i n e t h e ENDF/B-IV

d o s i m e t r y c r o s s s e c t i o n f i l e . Very s i m i l a r t r e n d s i n t h e i n c o n s i s t e n c i e s

a r e obse rved f o r t h e fundamenta l f i s s i o n r a t e s i n f i v e n e u t r o n f i e l d s

a ' x s z $5. E, CFRMF, Big Ten). The o v e r a l l c o n s i s t e n c y , i n c l u d i n g t h e b e s t known c a t e g o r y I1 t h r e s h o l d r e a c t i o n s , is a b o u t 5 5% ( 1 0). For

o t h e r t h r e s h o l d r e a c t i o n s of t h i s c a t e g o r y , t h e r e s u l t s o b t a i n e d c o n s t i t u t e

a good b a s i s f o r f u t u r e e v a l u a t i o n work [ 2 ] [ 3 ] .

A t t h e same I A E A mee t ing , i n t e r l a b o r a t o r y measurements i n t y p e n e u t r o n

f i e l d s have been r e p o r t e d [4][5]. Two rev iew p a p e r s r e l a t e d t o s p e c t r a l

c h a r a c t e r i z a t i o n methods have t o b e mentioned a l s o [6]r7].

Dosimetry a p p l i c a t i o n s , i n t h e f rame of t h e DeBeNe f u e l and m a t e r i a l

development programme conce rn i r r a d i a t i o n e x p e r i m e n t s i n BR2 (MOL 7D :

SNR p i n b u n d l e ) , RAPSODIE ( s t e e l c l a d d i n g m a t e r i a l s ) and PFR (SNR Mk-I1

f u e l a s sembly ) .

THERMAL REACTORS

The main p a r t of t h e work c a r r i e d o u t by t h e S.C.K./C.E.N. - BELGONUCLEAIRE A s s o c i a t i o n is r e l a t e d t o p lu ton ium r e c y c l i n g i n l i g h t w a t e r r e a c t o r s :

- The BR3 r e a c t o r is o p e r a t e d s i n c e J u n e 1976 w i t h a c o r e l o a d i n g c o n t a i n i n g one t h i r d of p lu ton ium a s s e m b l i e s . A number o f o p e r a t i n g and P.I.E. d a t a

a r e c o l l e c t e d t o back up t h e R and D programme on p lu ton ium r e c y c l e

s u p p o r t e d by t h e European C o m p n i t y [8]

- I n SENA (PUR), f o u r p lu ton ium i s l a n d a s s e m b l i e s a r e under i r r a d i a t i o n s i n c e December 1974; t h e TRILUX noda l code sys tem is used t o f o l l o w t h e c o r r e s -

ponding o p e r a t i o n c y c l e s

- Similar calculations are being performed for TIHANGE I (PWR), in the frame of the evaluation of various plutonium recycle strategies

- A review of the work performed in connection with the irradiation of two plutonium assemblies in the DODEWAARD reactor (BWR) has been reported [9].

This publication describes the design calculations, the mock-up experiments

in the VENUS critical facility, the burn-up calculations and open-vessel

experiments performed in DODEWAARD in the initial cold conditions (sub-

stitution experiments and gamma scanning of individual fuel rods). The

results of this extensive experimental programme have confirmed the ade-

quacy of design calculation methods.

A subject of increasing interest is the behaviour of light water pressure

vessels under irradiation. The vessel surveillance programme for the first

large power plants is now starting on a concrete basis : the first surveillance

specimens have been unloaded. The belgian manufacturing industry is directly

interested in this programme and in vessel design improvement. On the other

hand, the BR3 vessel, put into service in 1961, requires most attention.

From the neutronic point of view, irradiation analysis involves characteriza-

tion of the irradiation environment, correlation of surveillance data and

projection of such data to vessel operating conditions ['lo]. S.C.K./C.E.N. participated to the PWH shielding benchmark exercise proposed by NEA [II].

A joint EPRI (Electric Power Research Institute)/NRC (Nuclear Regulatory

CommiSsion)/S.C.K.-C.E.N. programme has been extensively specified.

From the belgian side, neutron fluence measurements at different locations in

BH3, combined with steel sample irradiations, are being prepared; reference

steel specimens from the U.S. HSST programme will be irradiated together with

belgian steels. An overview of the world-wide effort directed towards a better

characterization of the neutron environment in pressure vessel applications is

gj.ven in [12].

MATERIALS TESTING REACTOR BR2

An important safety experiment, the first one of a series of three, took place

in the reactor in May 1977. The aim of these tests, made in collaboration with

GfK, is to investigate fuel pin behaviour under off-normal cooling conditions.

A t h i r t y SNR-type f u e l p i n bund le is i r r a d i a t e d i n a sodium loop . A f t e r a

few d a y s a t s t e a d y power, l o c a l b lockage of t h e sodium f low is provoked i n

t h e c e n t r a l r e g i o n of t h e bundle . The l o o p i s equipped w i t h i n s t r u m e n t a t i o n f o r

r e c o r d i n g f a s t t r a n s i e n t phenomena; f u e l p i n f a i l u r e is d e t e c t e d by p r e s s i o n

c o n t r o l on i n d i v i d u a l p i n s and by de layed n e u t r o n c o u n t i n g .

The pu rpose of t h e p h y s i c s work r e l a t e d t o t h i s expe r imen t c a l l e d MOL-7C was

t o a c h i e v e p r o p e r i r r a d i a t i o n c o n d i t i o n s i . e . a f l a t r a d i a l power d e n s i t y d i s -

t r i b u t i o n i n t h e b u n d l e a t a power o f 380 W/cm i n t h e h o t p l a n e . under a c y l i n -

d r i c a l cadmium s c r e e n . Three f u e l e n r i c h m e n t s were s e l e c t e d f o r t h e p i n s of

t h e bund le and a s p e c i a l 200 mm O.D. d r i v e r f u e l e l emen t a round t h e l o o p was

, @ d e s i g n e d . The c o r e o p e r a t i n g c o n d i t i o n s were d e f i n e d : i n agreement w i t h t h e

p r e d i c t i o n , a r e a c t o r power of 100 M W was r e q u i r e d t o f u l f i l l t h e s p e c i f i c a t i o n s

It was t h e f i r s t t i m e t h a t t h e r e a c t o r was o p e r a t e d a t t h i s power l e v e l .

The l o a d i n g of a he l ium g a s c o o l e d l o o p i n a new c o r e c o n f i g u r a t i o n is b e i n g

p r e p a r e d . The i r r a d i a t i o n s h o u l d s tart b e f o r e t h e end of June . T h i s l o o p w i l l

b e used f o r t e s t i n g GCFR f u e l p i n s , i n c l u d i n g t h ? f u e l p i n v e n t i n g sys t em, a t

t h e r e q u e s t o f KFA-Jiilich. An e x t e n s i v e e x p e r i m e n t a l proe;rscme was c a r r i e d o u t

i n BH02, combined wi.th. c a l c u l a t i o n , t o a s s e s s t h e power d i s t r i b u t i o n i n t h e

f u e l b u n d l e and t h e gamma h e a t i n g i n t h e s t r u c t u r a l m a t e r i a l s o f t h e loop .

The BR02 r e a c t o r , which w a s l o c a t e d i n t h e Technology b u i l d i n g s i n c e i t s

.start-up i n 1959, was moved t o be i n s t a l l e d i n one o f t h e a u x i l i a r y b u i l d i n g s

of t h e BR2 complex.

REACTOR CALCULATION

Mathemat i ca l s t u d i e s r e l a t e d t o t h e development o f r e a c t o r computa t ion methods

were p u b l i s h e d by t h e U n i v e r s i t y of B r u s s e l s [13].

R e f e r e n c e s

S. PILATE, R. d e WOUTERS ( B e l g o n u c l 6 a i r e ) , U. WEHMANN (Interatom-Germany),

F. HELM, W. SCHOLTYSSEK (GfK-Karlsruhe) , "Use o f ZPPR Measurements as a

Suppor t of C r i t i c a l i t y P r e d i c t i o n f o r SNR-300". Trans . Am. Nucl. Soc.,

1976 I n t e r n a t i o n a l Meet ing , Washington D.C., November 14-19 (1976).

A. FABRY (SCK/CEN) , W.N. McELROY , L.S. KELLOGG, E.P. LIPPINCOTT (HEDL) , J.A. GRUNDL, D.M. GILLIAM (NBS), G.E. HANSEN (LASL), "Review of Microscopic

I n t e g r a l C r o s s S e c t i o n Data i n Fundamental R e a c t o r Dosimetry Benchmark

Neutron F i e l d s " , C o n s u l t a n t s ' Meeting on I n t e g r a l Cross-Sect ion Measure-

ments i n S t a n d a r d Neutron F i e l d s , IAEA, Vienna, November 13-39 (1976).

A. FABRY (SCK/CEN), " F u r t h e r Phase I1 t e s t i n g d a t a of t h e ENDF/B-IV

Dosimetry Cross S e c t i o n F i l e and comments r e l a t i v e t o t h e e l a b o r a t i o n

o f Vers ion V", Memorandum, Task f o r c e on R e a c t o r Dosimetry f o r ENDF/B-V

March 25, 26, and 28 Meet ing , March 27 (1977) .

A. FABRY (SCK/CEN), J . G . WILLIAMS, A.H.M.A. HANNAN, D. AZIMI-GARAKANI

(Univ. o f London R e a c t o r C e n t r e ) , " In te rcompar i son o f t h e I n t e r m e d i a t e

Energy S t a n d a r d Neutron F i e l d s a t t h e NISUS and MOL-z F a c i l i t i e s by

means of A b s o l u t e F i s s i o n Chambers", C o n s u l t a n t s ' Meeting on I n t e g r a l

Cross-Sect ion Measurements i n S tandard Neutron F i e l d s , IAEA, Vienna,

November 15-19 (1976).

A. FABRY (SCK/CEN), I. GIXLEA (ITN), " Q u a l i t y C o n t r o l and C a l i b r a t i o n

o f M i n i a t u r e F i s s i o n Chambers by exposure t o S t a n d a r d Neutron F i e l d s .

A p p l i c a t i o n t o t h e Measurement o f Fundamental I n t e g r a l Cross S e c t i o n

Ra t ios" , C o n s u l t a n t s ' Meeting on I n t e g r a l Cross -Sec t ion Measurements i n

S t a n d a r d Neutron F i e l d s , IAEA, Vienna, November 15-19 (1976) .

W.N. McELROY, R. GOLD and E.P. LIPPINCOTT (HEDL) , A. FABRY (SCK/CEN), J.H. ROBERTS ( M a c a l e s t e r C o l l e g e S t . P a u l ) , " S p e c t r a l C h a r a c t e r i z a t i o n by

combining Neutron S p e c t r o s c o p y , A n a l y t i c a l c a l c u l a t i o n s , and I n t e g r a l

Measurements", C o n s u l t a n t s ' Meeting on I n t e g r a l Cross-Sect ion Measurements

i n S t a n d a r d Neutron F i e l d s , IAEA, Vienna, November 75-19 (1976).

G. DE LEEUW-GIERTS, S. DE LEEUW (SCK/CEN), " I n - p i l e Neutron Spec t romet ry :

S t a t u s u l , C o n s u l t a n t s ' Meeting on I n t e g r a l Cross -Sec t ion Measurements i n

S t a n d a r d Neutron F i e l d s , IAEA, Vienna, November 15-19 (1976).

"Programme d e Recherche e t d e D6veloppement c o n c e r n a n t l e Hecyclage

du Plu tonium d a n s l e s C e n t r a l e s 6 eau ikgkre" , S c i e n c e e t Techno log ie

N u c l h a i r e s , EUR 5780 d /e / f / i / n (1977).

H. BAIRIOT, P. DERAMAIX, and C. VANDENBERG ( B e l g o n u c l & a i r e ) , L. LEENDERS

(SCK/CEN), P. MOSTERT (GKN, N e d e r l a n d ) , "Plutonium Assembl ies i n Reload 1

of t h e DODEWAARD R e a c t o r " , Nucl. Techn.,Vol. 2, A p r i l (1977).

R. ODETTE (Univ. of C a l i f . ) , N. DUDEY (ANL), W.N. McELROY (HEDL),

l l . WULLAERT ( F C C , C a l i f . ) , A. FABRY (SCK/CEN), " A p p l i c a t i o n of Advanced

I r r a d i a t i o n A n a l y s i s Methods t o L i g h t Water R e a c t o r P r e s s u r e Vesse l T e s t

and S u r v e i l l a n c e Programs", ASTM 8 t h I n t e r n a t i o n a l Symposium on t h e

E f f e c t s of R a d i a t i o n on S t r u c t u r a l M a t e r i a l s , S t . L o u i s , May (1976).

G. MINSART (SCK/CEN), C. VAN BOSSTRAETEN (CORAPRO), f f C o n t r i b u t i o n t o t h e

S tudy of t h e R e a c t o r S h i e l d i n g Benchmark no 2 (PWR) proposed by t h e NEA",

J o i n t T e c h n i c a l Meeting on " D i f f e r e n t i a l and I n t e g r a l Data Requi rements

f o r S h i e l d i n g C a l c u l a t i o n s " , Vienna, October 12-15 (1976).

F.J. RAHN (EPRI) , "Power R e a c t o r P r e s s u r e Vesse l Benchmarks. An overview"

C o n s u l t a n t s ' Meeting on I n t e g r a l Cross -Sec t ion Measurements i n S t a n d a r d

Neutron F i e l d s , I A E A , Vienna, November 15-19 (1976).

J.P. HENNART (Univ. Mexico) , E.H. MUND (ULB), " S i n g u l a r i t i e s i n t h e F i n i t e

Element Approximat ion of Two-Dimensional D i f f u s i o n Problems", Nucl. Sc.Eng

Vol. - 6 2 , 55-68 (1977) .

J. DEVOOGHT (ULB), "Spectrum of t h e Mul t ig roup-Mul t ipo in t D i f f u s i o n

O p e r a t o r w i t h Delayed Neut rons" , Trans . ANS, Vol. 2, 473 (1976).

REACTOR PHYSICS ACTIVITIES I N CANADA

M.F. Duret & W.H. Walker

1. Fuel Fabr ica t ion , Reprocessing and Waste Disposal

1.1 Pu Fuel Fabr ica t ion

The p i l o t f a b r i c a t i o n l i n e has been commissioned us ing

n a t u r a l uranium. Twenty of 40 bundles f o r i r r a d i a t i o n i n the Douglas

Poin t power r e a c t o r a r e f in i shed and the remainder w i l l be ready by t h e

end of summer.

S in t e r ing furnaces a r e being r e b u i l t . When t h i s work is

completed i n the f a l l the l i n e w i l l s t a r t f a b r i c a t i n g Pu/nat U f u e l .

These w i l l be used i n r e a c t o r physics t e s t s a t CRNL before being shipped

t o Douglas Point .

1.2 Spent Fuel Handling

A group has been s e t up wi th in AECL to s e l e c t a s i t e s u i t a b l e

f o r cons t ruc t ing a p i l o t reprocessing p l a n t and p i l o t permanent s to rage

f a c i l i t y f o r r ad ioac t ive waste. Seven a r e a s a r e being considered.

Reactor physics support f o r t h i s p r o j e c t c o n s i s t s of computer

s t u d i e s of f i s s i o n product and a c t i n i d e contents of spent f u e l and of

the c o s t of t h e reprocessing and s to rage f a c i l i t i e s .

2. Reactor Assessment

Most work i n t h e p a s t year has been on Th-U f u e l and on f u e l

management.

The e f f e c t on f u e l burnup of using laser -separa ted Z r

i so topes ("2.r o r "2.r) has been ca l cu la t ed . S u b s t a n t i a l savings of

uranium could be achieved but i t is n o t c e r t a i n whether the va lue of f u e l

saved would be l e s s than the c o s t of i so tope separa t ion .

Some Z r i so tope c r o s s sec t ions a r e poorly known and ERDA has

been asked t o loan samples of separa ted i so topes . These a r e expected

t h i s year. Cross s e c t i o n measurements w i l l be made both by p i l e o s c i l l a t o r

and counting of capture y-rays.

3. S t a t u s of Reactors

3.1 Power Reactors

NPD. Douglas Point and the four Pickering A r e a c t o r s have

a l l performed r e l i a b l y .

Bruce-1 and -2 went c r i t i c a l on December 17 and Ju ly 28, 1976

r e spec t ive ly , and a r e now supplying 625 MW and 725 MW t o the Ontario g r id .

Power is cu r ren t ly l imi t ed i n both r e a c t o r s by main steam l i n e v ib ra t ions .

Fuel loading i n t o Bruce-3 w i l l s t a r t i n t h e near f u t u r e .

I 3.2 Research Reactors

i 3.2.1 SLOWPOKE Four r e a c t o r s have now been commissioned a t Canadian u n i v e r s i t i e s

and a r e i n r egu la r use.

Licensing hear ings f o r the Universi ty of Cologne SLOWPOKE

were he ld on Flarch 3 , 1977.

3.2.2 AECL Research Reactors -

I n Z E D - I 1 the 7-channel hot pressur ized loop and two-phase

absorber have been commissioned. 'Experimental work using the l a t t e r , a

con t ro l l ed mixture of borated water and gas, has s t a r t e d and should be

completed by the end of the year .

I n NRX a 3 ~ e v a r i a b l e shroud f o r the X-6 loop has been completed.

Inc reas ing 3 ~ e pressure from 6 ps ig t o 177 ps ig decreases power by a f a c t o r

of 1.8 with only a smal l d is turbance a t nearby s i t e s .

A formal proposal f o r rep lac ing n a t u r a l uranium f u e l i n WR-1

with Pu-enriched Th i s under cons idera t ion .

4. Reactor Kine t i c s

4 .1 Hybrid Computer

The major e f f o r t i n the p a s t year has been on the hydrodynamic

s t a b i l i t y of the G 1 steam supply t o the LaPrade heavy water p l a n t . This

work i s done mainly on the CDC-6600.

The 8-node l-dimensional model. f o r s tudying s p a t i a l e f f e c t s

i n loss-of-coolant acc idents is working and has Keen augmented by a

16-node l-dimensional model. Work i s nearing completion on a 2-dimensional

8x8 node model.

4.2 NEACRP/Benchmarks

No f u r t h e r work is planned.

4.3 CERBERUSICERKIN

CERKIN i s a n improved ve r s ion of CERBERUS. Both codes have

been completed and a r e being t e s t e d a g a i n s t o t h e r codes and a l s o experiment.

So f a r agreement has been s a t i s f a c t o r y .

4.4 Experiments

Trans ient measurements where an absorber is dropped i n t o one

ha l f of a s p l i t core l a t t i c e i n ZED-2 have been made. The experiments were

s imulated us ing the code CERKIN which gave very good agreement with the

measurements. The work i s being w r i t t e n up.

Ris0 National Laboratory

Department of Reactor Technology

May 24, 1977

Recent Reactor Physics Pctivities in Denmark

by

Hans Neltrup

1. Fission product and activide inventory

As part of a general study of the consequences of a core

melt down or a similar accident of the Barsebzck power reactor

a program has been devel-oped calculating the fissionproduct

and actinide inventory in a LWR fuel box as function of burn-

UP. The program may also follow the long term development of

the post irradiation activity as shown in Fig. 1. The fission

product inventory comprises 380 nuclides and the actinide

inventory 140 nuclides with mass numbers between 80 and 100. . 2. Fission product decay heat

Fissionsproducts have also been treated from the aspect

of decay heat. 563 nuclides, partly very short lifed, have

been considered. Since the decay schemes are known only for

roughly half of these nuclides the decay schemes for the re-

maining have been postulated based on simplifying assumptions

involving a B-strength function known from nuclear reaction

theory. Preliminary calculations show agreement within 10%

with measured values in the one-second range as illustrated

in Fig. 2.

3. Management an economy of the fuel cycle

A program treating the management and economy of the fuel

cycle has been developed. The fundamental features 02,t?;i,s; ., L J I i i 1 4

multicycle fuel management program is a simplified reactor

physics treatment of the burn-up combined with a rather ex-

tensive treatment of the economic aspects of the fuel cycle.

The reactor physics- and economic parameters are brought on

a form suitable for optimization by linear programming tech-

nique. Apart from complete fuel cycle optimization the pro-

gram can be used for just economic calculations or it can be

used as a burn-up program coupled with economical analysis

but leaving out the optimization.

4. Core follow up studies

A major project concerned with practicing core follow up

calculations on a running power BWR has been going on during

the preceeding year in collaboration with a reactor vendor.

The work has been slowed somewhat down by the very com-

plicated loading patern used in the first fuel cycle of this

reactor. 3-dimensional calculations of a number of critical

configurations in the cold clean condition as well as some

power shape pictures including thermohydraulics in the clean

60, 80 and 100% power condition have been carried through with

reasonable success.

5. Poison effect of hetorogenuously distributed Gadolinium

As a preparation for core follow up calculations on a second power BWR a program calculating poison effect and

poison burnup of Gadolineum containing fuel pellets hetero-

genuously distributed in axial direction, has been developed

and tested against measurements. The program uses a Monte

Carlo superposition principle with starters derived from the

2-dimensional angular flux distribution on the pellet surface

in the regular unpoissoned case.

FIG. 1 Radiation intenslty of the spent fuel from the production of 1000 eMW years in a LMR.

10-I 1 10 lo2

1. Total activity of the fuel.

2. Activity of all fission products.

3. Activity of all actinides (and their daughters). 4. ?.ctivity of Np 239 (Half life= 2.35 days ) . 5. Activity of Pu 241 (Half life=14.0 years) . 6. Activity of Sr 90 (Half life=29.0 years) . 7. Activity of Kr " (Half life=10.7 vears) . - 8. Activity of cs 13' (Ealf life=2.3~1.0~ vears) .

1 I I -

Calculations

0 o Measurements by Perry

TIME AFTER SHUT DOWN (sec)

Fig. 2. Decay vs. time a f t e r s h u t down of a reactor

Reactor Physics A c t i v i t i e s a t JRC-EURATOM/Ispra

June 1976 - June 1977 11. RIEF --

i. RADIATION SHIELDING STUDIES -

I. 1. NUCLEAR DATA F3R SIIILLDING -

Evalua t ion -- of t h e Reaction Cross S e c t i o r d f o r t h e F ive I so topes Ba 134-138.

The e v a l u a t i o n of t h e Ba 134-138 has been alniost completed. The r e s u l t s a r e a t p r e s e n t being updated i n ENDF/B4 format .

The Coupled Sh ie ld inq Standard L ib ra ry EURLID 3. -.---

I n c o l l a b o r a t i o n w i t h t h e I K E S t i ~ t t q a r t , t h e neu t ron s h i e l d i n g l i b r a r y EURLTB (ESIS Xewsle t te r 12, January 1975) was extended. 2 6 gamma groups were added t o t h e 100 neu t ron groups; t h e i r group s t r u c t u r e c o c s i s t s o f i 8 gamma groups of CASK, t o wh ic i~ two f ~ r t h e r groups between 1 0 and 1 4 MeV wcze added. Thus f u s i o n problems can a l s o be t r e a t e ? . Coupled l i b r a r i e s gendra ted i r o n ENDF/B-4 d a t a f i l e s have been ob ta ined by %e new v e r s i o n AMPX-1. A main e f f o r t has beer, devoted t o t h e impr0vemer.t of t h e f l . ~ x wei.ght.ing f o r bo th neutron and gamma r a d i a - t i o n s . For neu t rons , i n t h i c k l a y e r s OF r e a c t o r s t e e l narrow resonance wciah t ing i s necessary and a weinht- i n 9 f u n c t i o n 1/0j E has been llsed (p rev ious ly f o r a l l elelltents 1 / E weigh t ing was ap,;li.ed below 0.825 "lev an2 f i s s i o n spectrum weight inq above) . For t h e qamma r a y s one d i f f i c u l t y had t o be overcome : t h e t h r e c lowest group? (enerqy 1i.mLts 2 0 keV - 50 k e V - 100 keV - 2 0 0 keV) aye r a t h e r l a r g e , and i n m a t e r i a l s w i t h medium and high Z t h e qamma f i u x is no lonqer f l a t a t low e n e r g i e s bu t dec reases by o r d e r s of maqnjtude. There, a r e a l i s t i c weiqht Zunction i s t h e resonaqce e s - cape p r o b a b i l i t y p ( E ) ! t h i s cdn be proved hy ge?era- l i s i n y t h e neutron slowing down theo ry f o r t h e qamma c a s e ) . p ( E ) was approximated a s t h e produc t of t h e sdr - v i v a 1 p r o b a b i l i t i e s f o r succes s ive averaa: scat ter ;nc:s . This wc igh t in3 was a p p l i e d helow 1 0 0 keV f o r e l e a c ~ , t s from C r ( 2 - 2 4 ) t o Z r ( ' 4=40) , and below 200 keV f o r t h e two uraniui11. i s o t o p e s . I n i t i a l l y tlie yamma-gamma p a r t of ZLMPX' d i d n o t work f o r a non- f l a t weight ino fur.-tion, and GAMLEG r e s u l t s were t r m s - c r i h e d i x t o EURLIB 3. Then t h e i n c o n s i s t e n c i e s i n AnPX-1 were c o r r e c t e d {ESIS Newsle t te r 2 1 ~ 1 , an? t h e l a t e r CVRI,I~-?

c a l c u l a t i o n s were done w i t h TJPX-1 on ly . The e le -. ments and i s o t o p e s now covered a r e : :!,Be, LiG, i i 7 , B10, B l l , O, C , Ma, A l , S i , Ca, C r , Mn, Fe, M i , Cu, Zr, U235, and U238. He, 12, B, and Cu were processed i n F 5 zpproxirnation, t h e o t h e r s i n P3. I f p o s s i b l e , XNDF/B4 d a t a were used; b u t some ( n , namma) d a t a had t o be taken from e l sewhere , for i n s t a n c e POPOP and ENDL.

I n t e r p _ ~ e t a t j o n of t h e Winf r i t h i r o n measurements -

I n t h e ASPIS experiment tire s o u r c s i s a 60 c m r a d i u s c o n v e r t e r , and t h e s h i e l d mock-up c o n s i s t s of 24 i r o n p l a t e s each 183x191 c m wide and 5 c m t h i c k .

Neutron speckra have been measured by !fc C a r t e r & Pzckwood a t dep ths of 20,51, 76 and 102 c m i n i r o n , f r o = 5 ?ley? t n 7 keV.

During 1976, DOT-3 t r a n s p o r t c a l ~ u l a t i o n s have been performed on t h i s c o n f i g u r a t i o n us ing t h e EURLIE c r o s s s e c t i o n l i b r a r y , based on ENDF/E-111, and EURLIB-3, based cn ENDF/E-IV.

I n g e n e r a l , t h e r e i s good. agreement betweer1 c a l - c u l a t i o n and measurement, however t h e c a l c u l a t e d f l ~ > . e s are much lower than t h e measured f l u x e s a t 76 and 102 cm dep ths above C . 3 NeV.

The d i f f e r e n c e between t h e EURLIB and ZURLIB-3 s p e c t r a is r e l a t i v e l y sma l l .

Work has cont inued t o a s c e r t a i n t h e cause o f t h e s e d i s c r e p a n c i e s .

Po e s t i m a t e t h e i n f l u e n c e of t h e angula r quadra- t u r e o r d e r t h r i n i t l a 1 S4 s e t has been changed i n t o S g agd t h e EURLIB c a l c u l a t i o n r epea t ed dciwn t o 2 . 4 6 MeV : t h e f l u x e s a t 102 cm inc reased by 10-IS%, ar.3 by up t o 4 0 2 above 10MeV.

The a x i a l i n t e r v a l width i n i r o n , was t hen reduced from 1. i n c t o 0.5 i nches . The f l u x e s i nc reased by 20-30s. These two i n c r e z s e s a r e t o o sma l l t o improve

s i g n i f i c a n t l y t h e ag reemen t .

A l s o A N I S M ( 1 - d i m e n s i s n a l ) c a l c u l a t i o n s have been done t o e s t i m a t e t h e a p p r o x i m a t i o n o f t h e r educ - t i o n t o 2 -d imens iona l DOT geometry . Thc ANISN geo- m e t r y and s o u r c e d e n s i t y have been set e n u a l t o t h a t e x i s t i n g on t h e a x i s o f t h e DOT c a s e : t h r e e s i m i l a r c a l c u l a t i o n s ( S /i", S /I", S / O . 5") have been clone u s i n g EURLIB, b u t t h e Anisn/Dot f a c t o r h a s r e s u l t e d iower t h e n e a p c c t e d , b e i n g a b o u t 1 . 5 between 1 5 f4eV and 1 ?.lev, and i n c r e d s i n g t o 3 by 10 kell (below t h i s e n e r g y t h e t h r e e AhISEJ f l u x e s d i f f e r by less t h a n I % ) . I t i s conc luded t h a t n e i t h e r t h e s p a c e / a n q l e di;- c r e t i z a t i o n s , n o r t h e reducLion t o r - Z (DOT) geo- m e t r y , a r e t h e main c a u s e s f o r t h e d i s c r e p a n c y a t . h i g h e n e r g y be tween measurement and c a l c u l a t i o n o f n e u t r o n s p e c t r a a t ?/4m - 1 m d e p t h i n i r o n . I t i s p n s s i b l e t h a t a s y s t e m a t i c e r r o r i n b o t h EURLIB and EURLID 3 c o u l d b e t h e c a u s e .

B e f o r e c o n s i d e r i n g r x p c r i m e n t a l e r r o r s ( o r nurneii- c a l errors c o r r e c t e z w i t h u n f o l d i n q o f experimental d a t a ) , t h e c r o s s s z c t i o n l i b r a r y c o u l d LC e x t e n d e d t o h i g h e r Legendre terms t h a n t h r P3 used h e r e : t h e f a c t t h a t d i s c r e p a n c i e s i n c r e a s e w i t h i n c r e a - s i n g e n e r g y , a s d o Pn t e r m s , i s an argument f o r i h i s a p p r o a c h ,

REF. : K . Burn, U . C a n a l i , and R . N icks , "100-qroup. 2-D C a l c u l a t i o n o f t h e W i n f r i t h I r o n Rcnchmark Exper imen t" , p a p e r p r e s e n t e d a t t h e J o i n t Tech- n i c a l Committee Mcet ing on D i f f e r e n t ; - a 1 and I n t e g r a l . Data Requi rements f o r S h i e l d i n q C a ? - c u l a t i o n s , NEA-OECD-IAEA, Vienna , 1 2 t h - 1 6 t h O r - t o b e r 197G.

Neutron transport calculations in 3 - D geometries are almost exclusively done by Monte Carlo techniaues. For this reason the associated sensitivity studies require the appl.ication of the same methods.

.a rather detailed description cf this a~proach has been presei-.tcd at the Meeting G I Sensitivity Studies and Shielding Benchmarks (paris, Oct.19'75) and is a- vailable ic the proceedings of that Conference. Since then the proposed methods ha-te been proqrammed, tested and incarporated into the Monte Carlo pronra:.: TIMOC-72 . At present the program allows for the calculation of energy intenrated sensitivity factors in multiqroup, 3-D multimedia geometries and of energy dependent sensitivity profiles in 3-D single media geomet-' ies . As a typical example of interpreting a three-dimensional benchmark experiment, the neutron transmission neasurements at the fast source reactor "YAYOI" were chosen. In one of these experiments a narrow col limated neutron beam penztrates a 9.6 cm or a 13.2 cm thich iron slab.

The spectra are measured at two positions, both at G distance of 100 cm from the surface of the iron slab. One detector is located on the beam axis (0' position) and the other at 36' off the beam axis. The calculations were performed agzin by the use of the previously mentioned 55 group cross-section set.

In the cslculations the source was represented by a monodirectional beam of 20 cm diameter. The energy spectrum of the emitted neutrons was measured at the 0' position in the absence cf the iron slab, and it was this spectrum which was used in the calculations. Unfortunately the spatial source distribution on the iron slab and the degree of colli- mation is not well known. lor this reasoc the calculated spectra were normalized to the experimental

o n e s . F o r b o t h s l a b s t h e r e i s a n e x c e l l e n t aqreement i n t h e O 0 g o s i t i o n be tween measurements and c a l c u - l a t i o n s up t o 1 3 MeV. The same h o l d s o v e r t h e whole e n e r g y r a n q e f o r t h e c a l c u l a t e d and measured v a l u e s i n t h e 30'. p o s i t i o n w i t h o n e e s c e p t i o n . T h i s i s t h e e n e r g y band f rcm a p p r o x i m a t e l y 5 t o 7 MeV i n t h e 19 .2 clci i r ~ a s l a b .

The s e n s i t i v i t y p r o f i l e s which c o r r e s p o n d t o t h e f o u r measzrements d e s c r i b e d a b ~ v e ,

show an a p p x x i m a t e p r o p o r t i o n a l i t y w i t h t h - f i u x - s p e c t r a and t h e r e a r n , a t l e a s t f o r t h e g r o u p s t r u c t u r e c o n s i d e r e d , no g r o u p cross s e c t i o n s o f v e r y pronounced i m p o r l a n c e . F l u x e s i n t h e r a n g e 1-3 XeV and above 1.0 MeV a r e most s e n s i t i v e t o t o t a l cross s e c t i o n changes i n t h e 19 .2 c m i r o n p l a t e d i r e c t t r z n s m i s s i o n ( i . e . 0') e x p e r i m e n t . The 9 . 6 c m p l a t e d i r e c t t r a n s m i s s i o n e x p e r i m e n t and t h e 1 9 . 2 cin expe r i r r en t w i t h a d c t e c t o r p o s i t i o n 30' o f f t h e beam a x i s show a v e r y s i m i l a r b e h a v i o u r . The l e + s t s e n s i t i v e m e a s u r e m ~ c t i s t h e 30' p o s i t L o n i n t h e 9 . 6 c m p l a t c e x p e r i m e n t .

REF. : I:. R i e f , P r o c , o f t h e FlFTIl INTERNATIONAL CONFRRENCC ON REACTOR SIIIELUIXG, K n o x v i l l e , Tennessee .

I. 2 CODE .ASSESSMENT -- MODESTY, a Program for the Calculation of Reaction Cross Sections 1mportznt for Reactor Shieldinq and CTK ~pplications.

The code MODESTY was designed to calculate all energe- tically possible reactlon cross-sections and particle spectra within a possible decay chai;~ initiated by a nuclear resction.

The code is based on the statistical model for nuclear reactions, s6 that the results will be of sense only within the limitations of this model; about 2 MeV tc 25 MeV. This energy is important for shielding in fission reactors and in particular in fusion technology.

The partial width's for particle decay are calculated using the optical model, for &--decay the Rlatt-Weiss- -kopf single particle model. The programme was made to simplify the evaluation of cross-section data by giving maximum output infornation for minimum input. All necessary nuclear data are au- to~natically sparcher? irom an external library of fundamental data.

The outpct of the programme contains the : reaction cross sections, particle spectra, level activation cross sections, production cross sections for dijcrete 5 -Lines. For further cross-section data evaluation some modifications of the code are however still desirable (e.9. addition of the pre-equilibrium model, refine- ments in the interpolation of transnission coefficieiits, a more flexible treatment of the 6 -deczy by including the Brink-Axel model for the & -ray strength fuctions). To simplify such modifications the code is writteii in the "Structured Programming" style that means, the code is linearly unfolded and contains no explicit "GO-TO" statements.

The computer - t ime T needed t o sweep t h r o u q h a whole c a s c a d e depends s t r o n g l y on t h e e n e r g y E o f t h e i n - c0mir.g p r o j e c t i l e . C a l c u l a t i o n s (Ii3M 370/75) q i v e r o u g h l y t h e f o l l o w i n g t i g u r e s :

E=lO (MeV) T a b o u t l ' , E = l F (MeV) T a b o u t 1 0 ' and E=20 (MeV) T a b o u t 20 ' . Th? comple te programme, i n c l u d i n g a t e s t example and JOB-Control c a r d s , i s a v a i l a b l e from t h e FFA-proqram l i b r a r y .

REF. : W . MaLthes, EUR-5722e (1977) (MODESTY Code hlanual )

I . 3 . SHIELDING EXPERIMENTS -

F i r s t mezsurements a t EURACOS I1

The WRrICOS I1 i n s t a l l z t i o n , a t t h e LENA TRIG?\ r e a c t o r ( P a v i a ) , was comple ted and a s e r i e s 02 measurements t o test t h e c o n v e r t e r power have been c x c c u t e a . Ac te rwards t h e f i r s t s h i e l . d i n g mock-up (dn i ro l ; b l o c k o f l . f ,Ox1.5Ox~.00m) h a s been Cns ta l l . ed . I t i s composed o f c o n s e c u t i v e i r o n p l a t e s o f 4 c m t k i c k n e s s . Every 8 c m a r o d f o r c i a t e c t o r l o a d i n g e n t e r s t o p e r m i t measure- men t s a l o n g t h e c c n t r a l a x i s o f t h e b l o c k . The s o u r c e ( an e n r i c h e d Uranium d i s k o f 80 cm d i a n e t e r ) i s p l a c e d a t 10 c m i n f r o n t c f t h e mock-up. With t h r e s h o l d ( S 3 2 ) , r e s o n a n c e (AulP7) and t h e r - m a l (Dyl65) a c t i v a t i o n d e t e c t o r s , t h e f l u x p r o f i l e s i n t h e empty i r r a d i a t i o n chamber have h e e a de- t e r m i n e d t o s t u d y t h e g e o m e t r i c a l c h a r a c t e r i s t i c s o f t h a s o u r c e n e u t r o n e m i s s i o n i n b o t h l o n g i t u d i n a l and r a d i a l d i r e c t i o n s . Alonq t h e c e n t r a l a x i s o f t h e i r o n b l o c k t h e f a s t f l u x (above a b o u t 2 MeV)hac; been measure? up t o a d i s t a n c e o f 50-60 c m . I t . f o l l o w s v e r y c l o s e l y t h e e x p o n e n t i a l a t t e n u a t i o n law. The n e u t r o n f l u x a t t h e g o l d r e s o n a n c e e n e r g y d o e s n o t however conform t o s u c h a s i m p l e r e l a t i o n s h i p . The oxper in ien th l d a t a are now b e i n g t r e a t e d ac3 i n t e r p r e t e d .

I . 4 . XEACTOR SHIELDING - TECHNICAL SIJPPORT S h i c l d i n g Problems i n -. t h e FINTOR R e a c t o r

a ) Bulk S h i e l d C a l c u l a t i o n s :

Bulk s h i e l d c a l c u l a t i o n s were per formed w i t h A N I S N . The 100 g r o u p DLC-2D l i b r a r y was c h o s e n as t h e b a s i c n e u t r o n d a t a l i b r a r y . Few g roup (15 and 22 g?-oups) l i b r a r i e s have been c o l l a p s e d , u s i n g AXISN, from t h e prev . ious 100 q r o u p one . Gamma-production c r o s s - s e c - t i o n s were t aLen from EL-3 and pho ton i n t e r a c t i c n c r o s s sect ior . ; f rom EL-1 . The main p u r p o s e o f b a l k s h i e l d i n g c a l c u l a t i o n s was ts d e t c r r i n e a mjlimum t h i c k n e s s i n n e r s h i e l 6 . The c r i t i c a l q u a n t i t y i s t h e r a d i a t i o n d m a q s i l l t h e magnet , which must n o t excezd 2 .7 d p a / ~ .

An a n a l . y s i s was c a r r i e d o u t ( w i t h t h ? 1 5 g r o u p neu- t r o n l i b r a r y ) t o d e t e r m i n e t h e b e s t c o n f i g u r a t i o n of a s h i e l d compcsed o f SS w i t h Poror, c a r h i d e o u t s i d e . The minimum t h i c k n e s s s h i e l d . to r e d u c e t h e r a d i a t i o n damage below t h e c r i t i c a l v a l u e , i s composed o f 40 c m o f SS, p l u s 30 cm o f ooron c a r b i d e . The e f f e c t o f t h e s p e c e d i s t r i b u t i o n o f t h e two m a t e r i a l s i s ~ o t a e r y i m p o r t a n t : an homogeneous m i x t u r e ( w i t h i~ v o l u ~ ~ e corn_ p o s i t i o n o f 60% SS, 40-4 C ) , n e e d s o n l y a few more c m t o r e a c h t h e same a t t e n u a t i o n .

The u s e o f SS and waLsr as s h i e l d i n g m a t e r i a l s , h r i n q s a f u r t h e r r e d u c t i o n ( i n t h e minj.murn t h i c k n e s s ) o f a h o u t 1 0 CNI. I n t h i s case t h e o p t i m a l c o n f i g u r a t i o n would b e a quasi-homogeneous ( a l t e r n a t e l a y z r s ) m i x t u r e w i t h 809 (by volume) SS and 20% w a t e r .

I n t h e i n n e r s h i e l d , where l i t h i u m i s n o t p r e s e n t , t h e c o n f i g u r a t i o n w i t h SS and water may be app;ied. The n e u t r o n s h i e l d i s f o l l o w e d by 1 5 c m o f l e a u (gamma-ray s h i e l d ) . The o u t e r s h i e l d h a s a L i t h i n m b l a n k e t o f a h o u t 70 c m . The n e u t r o n s h j - e l d c o n s i s t s o f a SS l a v e r (which a c t s a l s o as a r e f l e c t o r t o enhance t r i t i u m b r e e d i n q i n t h e b l a n k e t ) f o l l o w e d by E y e , w i t h a t o t a l t h i c k n e s s lower t h a n t h i i t needed i n t h e i n n e r s h i e l d (where t h e L i t h i u ~ i b l a n k e t i s m i s s i n g ) . The gamma-ray s h i e l d i s t h e same i n b o t h c a s e s .

b) ~hree-Dimensional Monte Carlo C~lculations

Neutron streaming through the divertor annular qaps and the injector tubes has been investigated with the 3D Monte Carlo code MCRSE-C. A 22 grou:> neutron it- brary, collapsed from the 1.00 grocp DLC- 2D library, has been prepared for these calculations.

There were essentially two variance reducing techniaues implemented in the 14c;lte Carlo i~lculations : biasinq of the ancjular distribution of the sourcx:, an3 swlittina.

T?x three-dimensionnl calculaticns show, on the contraiy, that the streaming of neutrons pro3uces hiqher than ad- qissible radiation levels. Let D-2 .7 l ~ - ~ d y a / ~ be the mximum damage that can he sccepted hy the copper stabilizer; thc Monte Carlo calculatioqs indicate that the damaqe to the DFC from neutrons streaming through the divcrtor annular gap is greater than 1.00 D in the inner park of the coils, and decreases to about 40 D in the outer part. Furthermore the neutrons streaming out of the divertor gap inpinge on the upper (or lower) part of the TF coils, the shielding ef+ect of the collector material being small. The damagc to the TFC caused by these nau- trons can again ex-eed 100 D.

The presence of the injector tubes considerably w-akczs the perfsrmancc of tke outer shield and enhances the fluxes in the neighbourhood of the TP coils. J,Sthi.um is absent in this region, and the neutron shield is crossed by 60 cm diameter injectors.

Radiation damage to the TFC may be locally enhanced by a factor 3.0. Heat deposition and radiation damaae to the electronic equipment of the Fnjectcrs can also raisa problems.

REF. : R. F?ick, C. Ponti, G. Realini, R. Van Ileusden; Proc. of the PIFTIl INTERNATIONAL CONl.TRJ??CE ON REACTOR Sl1IELIlING, Knoxville, ~ennessee (1977) .

1.5. SiIIELDING DATA RANK AND 1NFORMATION

A Shor t Review - The SnB (Sh ie ld ing Data Dank) has been r e q u l a r l y updated wi th bibliographic r e f e r e n c e s from t h e ESIS Xewsle t te r and o t h e r s s e l e c t e d from i n t e r - nc t io r la l j o u r n a l s and r e p o r t s . Up t o now t h e t s t a l r e f e r e n c e s a r e about two thousand.

The ESIS Newsle t te r has been i s s u e d two times accord ing t o schedule i n a new and improved format .

ADD. REP. : 6. Strohmaier , P?. Uhl and W. Matches : Appli c a t i o n o f Nuclear Reactor Models f o r ~ e u t r o n Nuclear Data Eva lua t ion : S t a t i s t i c a l and Op- t i c a l Mcdel C a l c u l a t i o n s f o r Ba 134-130" t o be publ i shed i n NSE.

A . Dubi, Y.S. Horowitz and 1%. Rip•’ : "Calcula t i o n o f t h e Yotal Flllx a t a P o i n t by t h e 310nEe Car lo Track Rota t ion Es t ima to r " t o be puhl i sh~x7 i n NSE.

11. ASSESSMXNT STUDIES O'N NUCLT'AR TRAP;SMUTATIOPI O F ACTINIDES

The s c o p e o f t h i s a c t i v i t y i s t o d e m o s t r a t e t h e n e u t r o n - p h y s i c a l and t e c h n i c a l f e a s i b i l i t y and 'he c o s t / r i s ; - i m - p l i c a t i o n o f a c t i n i d e t r a ~ i s n u t a t i e n i n f i s s i - o n reactors. The work wi l l . b e b a s e d on t h e r e s u l t s o f t h e f o l l o w i n g s t l i d i e s o b t a i n e d d u r i n g t h e p r e c e d i n g r e s e a r c h program :

a ) E s t i m a t e o f t h e magni tude o f t h e h i q h e r a c t i n i d e p ro - blem.

I n t h i s c o n t e x t t h e c o n c e r t r s t i o n o f i n d i v i d u a l . a c t i - n i d e s i n d i s c h a r g e d f u e l s o f a l l r e a c t o r t y p c s i n t e r e s - t i n g f o r t h e n u c l e a r power g e n e r a t i n g sys t em qf t h e EC h a s been c a l c u l a t e d a x 3 a f o r e c a s t f o r t h e accumula- t i o n o f h i g h e r a c t i n i d e s i n t h i s s y s t e m h a s heen p e r - formed. These r e s u l - t s w i l l p e r m i t t h e a s ses s rne1~2 o r t e c h n i c a l i m p l i c a t i o n s i n t h e d i f f e r e n t s t e p s o f t h e f u e l c y c l e caused by m a i n t a i n i n g h i g h e r a c t i n i d e s i n t h e f n e l c y c l e .

b ) N u c l e a r d a t a f o r h i g h e r a c t i n i d e s and s e n s i t i v i t y s t u d i e s .

Highar a c t i n i d e n u c l e a r d a t a , most i m p o r t a n t f o r t h e c a l c u l a t i o n o f t h e b u i l d - u p and d e s t r u c t i o n o f a c t i n i d e s i n d j f f e r e n t r e a c t o r s a s w e l l a s f o r t h e h a z a r ? i n 2 e x o f h i g h - l e v e l w a s t e have been i d e n t i f i e d and s h a l l in-- d i c a t e p r i o r i t i e s f o r f u r t h e r work t.o impro-n t h e d a t a . C r o s s s e c t i a n s f o r f a s t n c u t r o n e n e r g i e s a r e b e i n g mea- s u r e d by i n t e g r a l as w e l l a s d i f f e r e i r t i a l t c c h n i a u e s and w i l l p a r t l y b e c a l c u l a t e d by t h e o r e t i c a l methods .

C ) Demons t ra t ion 3f t h e n e u t r o n - p h y s i c a l f e a s i b i l i t y of a c t i n i d e t r a n s m u t a t i o n i n l i g h t w a t e r r e a c t o r s rind 2 a s t b r e e d e r s .

It hds been proved t h a t i n t h e c a s e o f homoqeneous r e - c y c l e ( h i g h e r a c t i n i d e s , homoqeneously mixed wi.th f u e l ) o f s e l f - g e n e r a t e d h i g h e r a c t i n i d e s t h e i r i n v e n t o r y w i t h - i n t h e r e a c t o r core and t h e i r e f f e c t on t h e o v e r a l l - r e a c t i v i t y a r e s m a l l ; t h e t r a n s m u t a t i o n r a t * a m o i ~ n t s t o r e a s o n a b l y h i g h v a l u c s ( i n t h e o r d e r o f t e n per c e n t ) ; and t h e reactivity r e d u c t i o n i,y t h e c o n t a m i n a t i o n o f h i g h e r a c t i n i d e s w i t k r a r e e a r t h s i s a c c e p t a b l e i n t h e case o f t h e f a s t b r e e d e r .

d ) Analys i s of t h e f u e l c y c l e ( c o s t - r i s k ) when r e c y c l i n g a c t i n i d e s o t h e r than f u e l .

A survey s tudy on t h e problems involved i n d i f f e r e n t s t e p s of t h e f u e l c y c l e o f p r e s e n t and zdvanced reac- t o r s w i l l pe rmi t t o q u a n t i f y t h s a d d i t i c n a l i m p l i c a t i o n s caused by h ighc r a c t i n i d e r e c y c l e and t o propose pos- s i b l e t e c h n i c a l s o l u t i o n s f o r s p e c i a l a r i s i n g problems d u ~ i n g f a b r i c a t i o n , r ep roces s ing and t r a n s p o r t . The aim is t o e l a b o r a t e a f low-sheet f o r t h e f u e l c y c l e w i th a c t i n i d e s d e c i d i n g on p o t e n t i a l c n t i o n s a s heteregeneous or homoqeneous r e c y c l e schencs , blendii lu o f a c t i n i d e f u e l e lements w i th nczmal f u e l b e f o r e re i , rocess ing, p lutcnium e x t r a c t i o n from 2 c t i n i d e f u e l elemeli ts , s e p a r a t i o n i:eqrees o f f i s s i o n produc t l an than ides from h i g h c r a c t i n i d e s , d i l . u t i o n m a t e r i a l f o r s p x i a l a c t i n i d e f u e l e lements e t c .

I n t h i s c o n t e x t t h e fo l lowing work has been accomplished d u r i n g t h e j ~ c r i o d o f c o n s i d e r a t i o n :

X I . 1. PREDICTIONS FOR TIIE HIGH-LEVFL -- ALP!IP.-ACTIVE WAS'I'T: TO BE GENERATED BY N ~ L E A R POWEE STATIONS I N TI!E FIEMRER STATES -OT~~F~OPEAN COMMUE:ITY ----.--

S t a r t i n g wi th a f o r e c a s t f o r t h e n u c l e a r power capa- c i t y t o be i n s t a l l e d i n t h e member s t a t e s of t h e 1:uro- pean Communities be fo re t h o end o f t h i s cen tu ry : a p r e d i c t i o n i s made of t h e annual p ~ o d u c t i o n o f k.i.gh- l e v e l b lpha-ac t ive wasts fzom rep roces s ing p l a n t s and t h e corresponding accun~u la t ion up t o t h e y e a r 2000. The i s o t o p i c composikion of t h e a lpha -ac t ive waste from i n d i v i d u a l reacLor t y p e s was c a l c u l a t e d and an e s t i m t i o n o f t h e i n i l u e n c e of r e c y c l i n g plutonium t h r o ~ q h l i g h t wate r r e a c t o r s on t h e produced q u a n t i t y o f h ighe r a c t i n i d e s i s made.

REF. : E. SCHMICT, EUR-5630.?(1976).

11.2. MEASUREMENT OF THE FISSION CROSS Sl?CTION -- 07 A m 2 4 1 .

I n a c o l l a b o r a t i o n between GFK Karisruhe and t h e CCR I s p r a t h e measurements of t h e f i s s i o n cross s e c t i o n Of Am241 have s t a r t e d i n summer 1976.

A s neutron source t h e 3 MeV Van de Graaff a c c e l e r a t o r o f t h e GfR i s used . The neu t r cxs a r e genera ted by a

proton beam using the Li7 ( p , ~ ) Be7 reaction. The encrgy range investigated reaches from about 1.00 keV to 1.3 MeV. The fission cross section of Am241 is measured relative to the U235 cross section. Two different methods are schedu1ed:one method consists in the detection of the prompt fission neutrons, the other in the detection of t h ~ tission fragments. Only the first method has be^^ applied up to now. Three thick samples of 3 . 5 g R1241, 7.1 7 U235 and a dummy sample of 3.5 g Unat are exposed o;le after another to the pulsed neutron beam (pul.se wi.dth 1 ns, repetition rate 5 MHz), and -the flssion neutrons recorllerl by a scintillation detector. Neutron enerqy determination 2nd backgroxnd discrimination were acsomplished hy titx?-of-flight techniques. The results ohtaincd with this method shox a statistical error between 1 and 6% but they can be affected by a syst?matic error due tn the not. exactly known energy dependence of the . -vaiues for U235 and Aln241. This error vil.1 he corrected by a normalization of the cross sections with thr second method.

In this experiment a gas scintillation chamber is located in the neutran beam of the VDG with two thin sarqles of Am24!. and ~ ' 2 3 5 (1 mg) . The chamber i.s divided by the two samples into optically decou~led thirds, each inspected by a photornul.tiplii?r,. Thc main problem in this measnrement is the elimination of the high &-background durillg the detection of the fission fragxents. This is achieved by choice of the scintillation gas, discrimination, coinciuence and time-of- flight techniques. Another problem is the stab1.e opera- tion of the photomultipliers in the presence of a high o( -background. For this reason a spectrum stabilizer which used the o( -radiati.on for stahi!.i.zati.on was designed. The in~tallation has been tested and will he installed at the GFK in the next future. .

REF. : W. Iiayc, 11. Ilettinqor, F. I(ae~;)eler, S . Kumy~f and K. Wisshak - Proc. of the 1st Technical Meeti.ng on the Nuclear Transmu. of Actinides - Ispra (1977)

11.3. 1DEI.ITIFICATIOM OF THE MOST IMPORTANT NVCTXAR DATA . - - P ~ R THE ~ u I ~ D ~ u F T - A C T ~ N I D C S ~ ~ -

The anaiyt.j.ca1. e v a l u a t i o n c o n s i s t s i n - a ) e s t a - b l i s h i n g t h e t r ansmuta t ion schemes ,:or t h e i s o t o p e s under c o n s i d e r a t i o n and, i f p o s s i b l e , s i m p l i f y i n g t h e s e Schemes - b) wr i t i i ig up t h e d i f f e r e n t i a l . e- q u a t i o n s d e s c r i b i n g t h e p h y s i c a l phenomena repre- s en t ed by t h e prev ious schemes - c) sol-ving t h e s e equa t ions - d ) e v a l u a t i n g t h a s c n s i t j v i t i e s - e ) i d e n t i f y i n g t h e most impor tan t nuc l eh r d a t a ,

This approach has been a p p l i e d t o some a c t i n i d e s : U-235, 236, 237, 238, 239 Np-237, 23G, 239 Pu-238, 239, 240, 241, 242 A m - 2 4 1 , 2421n, 242 York i s i n p r o g r e s s f o r ?u-243, Am-243, Cm-242, 243,244,245,246. The r e s u l t s ob ta ined a r e a p p l i c a b l e t o LNRs, H W R s , G C R s , A G R s and FBRs.

Some fundamental r e s u l t s which have appeared d u r i n q t h i s s tudy +ye :

- when p r e s e n t i n g a numerical va lue f o r a s e n s i t i v i t y a l l t h e in format ion which has been used f o r i t s \?va - l u s t i o n shocld be g iven : a numerical va lue o f a s e n s i t i v i t y g i v m wi thout t h i s in format ion is u- s u a l l y of no u t i l i t y . - It i s u s u a l l y n o t p o s s i b l e t o d e f i n e a s e n s i t i v i t y c o e f f i c i e n t which i s c o n s t a n t even f o r a r e l a t i v e l y smal l domain o f v a r i a t i o n of a parameter .

- The s e n s i t i v i t i e s s t r o n g l y d i f f e r from one t y p e of r e a c t o r t o ano the r .

- They s t r o n g l y depend on t h e f l u x l e v e l i n t h e reaG- t o r .

- They s t r o n g l y dcpend on t h e r e a c t o r o p e r a t i o n t ime . - Nheri a r e a c t o r i s run a t conc tan t power t h c s ensL t i - v i t y t o a parameter is i n . f a c t a compound s e n s i t i - v i t y s i n c e i t s va lue depends no t on ly on t h e v a r i a t i o n of t h e parameter b u t a l s o on t h e v a r i a t i o n o f t h e f l u x i n t h e r e a c t o r .

From t h e s s remarks it fo l lows Lhat it i s n o t p o s s i b l e t o s ta te , i n a l l g e n e r a l i t y , t h e most impor tan t n u c l e a r d a t a . A d e t a i l n d s tudy should be made f o r each p a r t i - c u l a r c a s e .

I t may however be mentioned he re t h a t , a s f a r a s t h e build-up of a c t i n i d e s i s concernecl, t h e most impor- t a n t d a t a on t h e a c t i n i d e s eva lua t ed a r e t h o s e con.. c e rn ing t h e Np-237 c a p t u r e c r o s s s e c t i o n , t h e Pu-238 thermal d a t a on c a p t u r r . t h e Pa-238 f a s t f i s s i o n c r o s s s e c t i o n , t h e A m - 2 4 1 a c t i v a t i o n c r o s s s e c t i o n s , t h e Am-242m thermal d a t a and t h e Am-242n f a s t f i s s i o n c r o s s s e c t i o n . A s a t i s f y i n g s t a t u s appears t o hcve been achieved i n t h e e v a l u a t i o n nf t h e decay c o n s t a n t s .

1 1 . 4 . A C T I N I D E INCINCRATIOFI AND T ~ N C ~ I U T A T T O ~ I IN A TIIERb'AT, - ZKD-ITAFA s 1, ~r:?i+io I<

C a l c u l a t i o n s concerning t h e inti-neration and t h e t r a n s - mutat ion of monoisotopic f u e l s c o n s i s t i n y o r i a i n a l l y of Xp-237, Pu-238, Am-241, Am-243, C m - 2 4 2 , Cm-243, C R - 2 4 1 , Cm-245 and Cm 24G have been pcrforniecl f o r a Lt7R an;l FBR o p e r a t i n g a t two d i f f e r e n t f l u x l e v e l s :

a ) 6 = 3 . 1 0 ' ~ and 5-10" nn/m s . o p e r a t i n g t ime : 1000 d.

b) FBR - gi - 6.10" and 1.10'~ n/cm s o p e r a t i n g t ime 549 and 1000d.

The fo l lowing r e s u l t s have been o b t a i n & :

- The PBR seems t o be g e n e r a l l y more e f f i c i e n t f o r i n c i n c - r a t i o n than t h e LWR i f t h e a c t i n i d e i s p lace? i n a re- g ion of high f l u x of t h e r e a c t o r ( ca scs of Elp-237, Pu-238, C m - 2 4 G ) .

- The d i f f e r e n c e s between t l ~ e r e s u l t s ob ta ined wi th t h e two r e a c t o r s a r e n o t s u f f i c i e n t l y impor tan t t o a l low an immediate d e c i s i o c i n favour of one r e a c t o r o r t h e o t h e r ( ca ses of Am-241, Cm-24!;).

I n some c a s e s such a s t h o s e o f Am-243, Cm-244 and espe- c i a l l v Cm-243 a b e t t e r percentage of i n c i n e r a t i o n i s oh - t a ine i i i n t h e LWR.

- Incinr2ration o f Cm-246 , wh i l e made more c f f i c i e n t l y j n t h e F13R, and i n c i n e r a t i o n of Am-243, seen t o h e d i f f i c u l t t o ach ieve .

- S e v e r a l c y c l e s of r e a c t b r operati.on a r e necessary t o ach ieve a s u f f i c i e n t d e s t r u c t i o n of an , ac t in ide . The n u ~ b e r of r e q u i r e d r e c y c l e c i s probably noL cx- c e s s i v e .

1:lFCUI;:ICL OF NUCLEAR - DATA -- UNCERTAINTIES ON RFSULTS hZCVCLIIJC; ACTI?!IDCS OT!lI:R TlIA!I F ~ E L - The u n c e r t a i n t i e s i n n u c l e a r d a t a a r e due t o k w o in - dependent sou rces . F i r s t l y , b a s i c n u c l e a r d a t a as f u n c t i o n o f energy may be f a u l t y . Secondly, by e l a - b o r a t i n g b a s i c n u c l e a r d a t a , e r r o r s mey b e intro?.accd i n t h e e f f e c t i v e nuc lear c r o s s ~ e c t i o a s u s inq approaches f o r t h e neutron spectrum, i t s v a r i a t i o n d u r i n g i r r a d i a - t i o n , t h e s e l f - c h i e l d i n g e f f e c t s , e t c . The e f f e c t of t n e s e u n c e r t a i n t i e s on t h e amount o f a c t i - n i d e s o t h e r than f u e l genera ted by o p e r a t i n q d i f f c s e n t power r e a c t o r t y p e s , on t h e r e l a t i v e r a d i o t o x i c long- term hazard , and on t h e tral lsmiltat ion r a t e h a been nu- m e r i c a l l y e v a l u a t e d , p rov id ing t a b l e s s f s e n s i t i v i t y c o e f f i c i e c t s .

By means of t h e s e t a b l e s , a sequence o f t h e most impor- t a n t nuc l ea r d a t a f o r neu t ron-phys ica l c a l c u l a t i o n s con - c e r n i n g t h e a c t i n i d e r e c y c l e concept can be prov ided . I n connec t ion wi th i n v e s t i g a t i o n s on t h e s t a t u s o f t h e accuracy o f n u c l e a r d a t a , a p r i o r i t y l i s t f o r improving b a s i c r u c l e a r d a t a by exper iments o r t h e o r e t i c a l models m y be e s t a b l i s h e d .

REF. : E. Schmidi, Proc. o f t h e 1st Technica l Meeting cn t h e Nuclear l ' r , - ,ns~mta t ion of Ac t in ides , I s p r a (1977) .

11.6. REACTOR PHYSICS ASPECTS OF BURNING ACTINIDES I?? A NUCLEAR REZCTDR --7

A s h o r t s tudy o f t h e d i f f e r e n t r e c y c l i n g s t r a+ . eg i e s o f ac- t i n i d e s o t h e ~ . t han f u e l was c a r r i e d o u t and nrrclear d a t a requi rements f o r a c t i n i d e build-up anG t r ansmuta t ion s t u d i e s were e s t a b l i s h e d .

The e f f e c t s r e c y c l i n g a c t i n i d e s i n a n u c l e a r r e a c t o r on t h e f l u x d i s t r i b u t i o n , t h e i n f i n i t e neu t ron multip1ic:ation fac- t o r , t h e i e a c t i v i t y c o n t r o l system, t h e r e a c t i v i t y c o e f f i - c i e n t s and t h e de layed neu t ron f r a c t i o n were e l a b o r a t e d con- s i d e r i n g a n o t i o n a l LWR o r a LMFBR a s an A c t i n i d e Transmuta -- t i o n Reac tor . Some o p e r a t i o n problems o f ~ c t i n i d e Transmutation r e a c t o r s were shown which a r e caused by t h e o( -decay h e a t and t h e build-up o f neu t ron sou rces i n A c t i n i d e T a r g s t Elements.

REF. : W. Wage. F. Schmidt - Proc. of t h e 1st Technica l Meeting 01: t h e Nuclear Transmutation o f A c t i n i d e s , I s p r a (1977).

From a p o i n t o f view o f t h e n e u t r o n p h v s i c s , it i s rea- s o n a b l e t o c o n s i d e r t r a n s n i u t a t i o n o f a c t i n i d e s o t h e r t h a n f u e l i n n u c l c a r r e a c t o r s a s f e a s i b l e , i f t h e f o l l o w - i n g c r i t e r i a c a n b e f u l f i l l e d :

- Th? i n v e n t o r y o f a c t i n i d e s o t h e r t h a n f u c l i n ?-he r e a c - tcr a t c o n t i n u a l r e c y c l e c o n d i t i o n s r e m a i n s s m c t l l s u c h t h a t a c t i n i d e r e c y c l e may h e c o n s i d e r e d a s a p e r t u r b a - t i o n o f t h e normal. r e a c t o r o p e r a t i o i l i n c a c e o f homoqeneous a s w e l l a s h e t e r o y e n e o u s r e c y c l e schemes .

- The t r a n s m u t a t i o n r aLe r e p r e s e n t i n g t h e pe rccn taq t? o f a c t i n i d e s o t h e r t h a n f u e l d e s t r o y e d d n r i n q o y ~ e i n - c o r e t i m e p e r i c d i s g r e a t enough t o j u s t i f y t h e r e c y c l e con c e p t .

- The r e a c t i v i t y l o s s cal lscd hy t h e p r e s e n c e o f ac t in i .c les o t h e r t h a n f u e l , c c n t a n i n a t e d w i t h r a r e e w t h s , i n t h e c o r e must n o t b e p r o h i b i t i v e .

- I t must b e p o s s i b l e t o s u i t a b l y t a i l o r t h e s p e c i f i c power ene era ti on i n t a r q e t e l e m e n t s c o n t a i n i n g a c t i n i d e s o t h e r t h a n f u c l i~ o r d e r t o r ema in i n t h e i i m i t s p r e s - c r i b e d f o r t h e c o ~ s i d e r e d power r c a c t o r .

The c a l . c u l a t i o n a 1 r e s u l t s o f t h e s e u u a n t i t i e s f o r a no- t i o n a l 1000 M W e l i g h t w a t e r r c a c t o r and t h e K a r l s r u h e MA1 f a s t b r e e d e r a r e p r e s e n t e d . I t i s d e m o n s t r a t e d t h a t , i n p r i n c i p l e , b o t h r e a c t o r t y p e s c a n b e c o n s i d e r e d a s d e v i c e s f 3 r t r a n s m u t i n g h i c h c r a c t i n i d e s .

REF. : J. C a n l e t t i , E . Schmid t - P r o c . o f C!le 1st T e c h n i c a l Mee t ing on t h e N u c l e a r T r a c s m u t a t i a n of A c t i n i d e s , I s p r a ( 1 9 7 7 ) .

11.8. O R G A Y I ZATTOEJ OF TIIE "FIRST TITIINICAI, PllTTINC, OU Till? NC'IJ-FAR TRA?!SHUTATIO?I OF IICTI:IIDCS". ---- --

During March 1977 t h e Commission organized a t i t s J o i n t Research Cent re I s p r a , I t a l y , a meeting on t h e Nuclear Transmutat icn o f Ac t in ides i n F i s s i o n Reac- t o r s sponsored by t h e OECD/MEA i n o r d e r t o d n t a b l i s h c o n t a c t s between workers i n t h i s f i e l d and t o pro- v i d e a b a s i s f o r exchanoe of in format ion .

The Meeting wzs d e a l i n g w i t h t h r e e main t o p i c s : a ) r e a c t o r phys i c s problems, h ) f ~ e l c y c l e i q l i c a t i o n s , C ) chemical e x t r a c t i o n techniques . Seve ra l ~ o r k s h o p s e l a b o r a t e d reco~naenda t ions g i v i n g q u i d l i n e s f o r t h e f u t u r e work i n t h e s e a r e a s . The proc~ecl . ings of t h e meeting w i l l be publ i shed soon.

COMMISSARIAT A L'ENERGIC ATOMIQUE

DIVISION D'ETUDES ET D E D E V E L O P P E M E N l ' DES REACTEURS

REACTOR PHYSICS ACTIVITIES IN TRANCE

JUNE 1976 - M A Y 1977 2oTH NEACRP meeting

JUNE 2nd - 6 t h K C N PETTCN NETHERLANDS

J.Y. B A R R E - J . BOUCHARD

I - GENERAL

N E A C R P - L -180 f

JUNE 1977

The 01-ientai:ions of t h e French nuclear energy proaram was confir!ned

a t ShLZBURG (1) i n May 1977 : wi th in t h e ten coming y e a r s , t h i r t y 900 ;4Ue Pi4R

p l a n t s and .twelve 1.300 Rl!e PI?;! p l s n t s would have t o be added t o t h e p re sen t a v a i l a b l e s t a t i o n s . Further:~ore, t h e f i r s t conlnlercial breeder a t t h e indus-

t r i a l l eve l would be opera t ionnal i n 1986.

The f i r s t 900 Mble PIdR p l a n t , FESSENHEIH 1, went c r i t i c a l M A R C H 7 ,

t h i s year,was connected t o t he g r i d on April 6 and i s going now t o nominal

power.. The l o a d i n g o f t h e s e c o n d p l a n t a t t h e same l e v e l ,

FESSENHEIM 2 , s t a r t e d i n March 1 9 7 7 . . T h e p l a n t s h o u l d be c r i t i c a l

i n J u n e 1 9 7 7 . I t w i l l be f o l l o w e d t h i s y e a r by B U G E Y 2 ( 9 0 0 MWe).

The d e c i s i o n t o c o r i s t r u c t SUPER-PHENIX 1 ( 1 2 0 0 .MWe) , t o be b u i l t a t CKEYS-MAI-VILLE on t h e Rti6ne r i v e r was t a k e n by NCRSAin April

1977 and main a q r c m c n t s a t t h e government l eve l were obta ined("d6cre t

d l u t i . l i t i . publiqub D U ~ " s i ~ r l c M?.Y 1977). Manufacturing enrichments hzlve t o

be f ixed a t t h e end of t h i s y e a r . Design works concerning t h e second p l a n t

a f t e r SUPER-PIIEN IX 1 , cal l c d SPC~NE, t ; i - n t .in t h e power range 1200-1800 iNik . . .

each, a r e going on. 50th c l ? 5 s i c a l and h e t e r o g e n e o u ~ ~ c o ~ C e i , t s at-e looked to. 3 : .-\ , : .;: ..' 1. LJ I $ ' I : >

The reactor CABRI a t CADARACHE orientated on f a s t reactor safety experiments, especial ly fuel analysis in power t ransients due t o r eac t iv i ty

increase, went c r i t i c a l on March 25 and i s going on to power. The f i r s t

experiments a r e planned f o r the end ' of t h i s year.

A large amount of physics s tudies re la ted t o the various aspectsof the

fuel cycle (wastes$ ~eprocessing plants ' f o r exampie) here .launched dur ing . th i s

year and will have t o be increase i n the future , f o r example t o t e s t the i:nterest.. o f the :new fuel: xyc1 e s . recently suggested ..

The agreements between Westinghouse, EDF, FRAMATOME and CEA on

l i g h t water reactors are operationnal and the program commonly decided i s now going on.normally. The planned cooperation between FRANCE and Federal Repu-

. . .

b l i c of Germany on f a s t breeder reactors should be def ini t ively agreed v e r y

soon ' . These large agreements i n the industr ia l and R and D f i e l d s between GFK and INTERATOM on the FRG s ide , CEA and NOVATOME on the FRENCH

s ide , together with their: respective point partners B E N E L U X countries and . ~

ITALY, will lead t o a coordonated and more e f fec t ive common research program . .

f o r LMFBR development. Finally a more general agreement on safety and . .

physics aspectsof f a s t reactors was signed between ERDA and CEA a t the

'beginning of t h i s year.

11 - LIGHT WATER REACTOR PHYSICS

Many s t u d i e s a r e b e i n g c a r r i e d on , i n t h i s f i e l d , due t o t h e l a r g e program o f p r e s s u r i z e d w a t e r r e a c t o r s b e i n g p r e s e n t l y o r d e r e d o r f o r e s e e n

i n FRANCE.

The r e l a t e d a c t i v i t i e s i n c l u d e :

- t h e o r e t i c a l s t u d i e s m a i n l y connected w i t h t h e improvement o f t h e NEPTUNE s y s t e e ~ o f codes wh ich has been developped by C.E.A. f o r g l o b a l

c a 1 c ~ ~ ' l a t i o n s o f the rma l r e a c t o r s , u s u a l l y PWR t y p e ( 2 ) ;

- e x p e r i m e n t a l works, pe r fo rmed on C.E.A. f a c i l i t i e s and comple ted by a n a l y s i s o f t h e r e s u l t s o f p r e v i o u s l y ach ieved exper imen ts and by t h e

f o l l o w i n g o f s t a r t - u p and o p e r a t i o n o f power r e a c t o r s , a r e used f o r t h e

q u a l i f i c a t i o n o f t h e NEPTUNE system.

The main programs a r e devo ted t o uran ium f u e l l e d PWR, e i t h e r l a r g e

s i z e p l a n t s o r average power r e a c t o r s . N e v e r t h e l e s s some s t u d i e s a r e a l s o

made f o r t h e e v e n t u a l i t y o f p l u t o n i u m r e c y c l e i n l i g h t w a t e r r e a c t o r s ,

most o f them i n t h e framework o f a coninion proqram o f t h e European Communi-

t i e s ( 3 ) .

11.1.1 - Severa l improvements have been lnade o r a r e i n p r o g r e s s f o r t h e NEPTUNE systeni o f codes. The f o l l o w i n g i t e m s may be p o i n t e d o u t :

a ) C e l l and subassembly c a l c u l a t i o n s : a new code u s i n g two ,dimen-

s i o n s ( x , y ) c o l l i s i o n p r o b a b i l i t i e s has been w r i t t e n and i s p r e s e n t l y on

t e s t . D u r i n g t h e same t i n e t h e m u l t i c e l l p rocedure i s improved b y i n t r o d u -

c i n g t h e a n i s o t r o p y and a z i n w t h a l d i s t r i b u t i o n o f t h e c u r r e n t a t t h e i n t e r -

f a c e o f e l e m e n t a r y c e l l s .

b) S p a t i a l c a l c u l a t i o n s : i n o r d e r t o comple te t h e 3 D c a l c u l a t i o n

p o s s i b i l i t i e s f o r wt i ic ! i we a l r e a d y used t !?e f i n i t e e lement method (code g 7 ,-.. ..! ; !* ; ;:* ?.; ti l i. 4 ,.,

TRIDENT) new codes a r e being written which are based upon the f i n i t e d i f -

ference method and the axial ,syhthesis. /6/

c ) The coupling of neutronics and thermohydraulics i n 3 D calcu-

la t ions which has been achieved with the TRIDENT and FLICA codes has been

applied for TIHANGE and FESSENHEIM reactor calculat ions .

d) A l o t of works has been devoted t h i s year t o the application of the NEPTUNE system for calculations of l i g h t water reactors with a p la te

type fue l . Due t o the complexity of t h i s design, two reference codes have

been used : TRIPOLI, a 3 D Monte Carlo calculation and DOT a 2 D t ransport a

calculation (SN),. For the cruciform control rods, a transport-diffusion

equivalence i s systematically applied ./4/

e ) The code used t o tabulate cross sections of resonant kernels

has been automatized (AUTOSECOL). I t will permit a quick treatment and t e s t of every new data f i l e . Furthermore a "mixture isotope" can be created by

t h i s code. as f o r instance a natural hafnium.

11.1.2 - In the presertprocedure we have t o adjust the resonant cap- tu re of 2 3 8 ~ and t h i s i s not very sa t i s fac tory from the physical point of

view, b u t needed i n order t o get correct r eac t iv i ty values. A strong e f f o r t

i s presently being made t o t r y t o obtain a bet ter understanding of t h i s pro- @ blem and thus t o avoid t h i s adjustment. This work i s perforined by three

ways :

a ) A c r i t i c a l study of nuclear data (resonance parameters) ;

b) A t e s t of the formalis~n used in the ce l l code APOLLO which i s

based upon an equivalence between an homogeneous medium and the actual geo-

metry. Monte Carlo calculationsare used as references for t h i s t e s t .

c ) The use of the REICH and MOORE formalism t o bu i l t detai led cross

section curves taking in account resonance interferences.

All these studies are s t i l l in progress b u t preliminary r e su l t s seen1 to be promising.

11.1.3 - The use of gadol in iunas a burnable poison i s s tudied f o r

PWR. Several p o s s i b i l i t i e s a r e inves t iga t ed and f o r some of them i t i s ne-

ces sa ry t o p u t t h e gadolin-iunin srnall p a r t i c l e s of oxide (Gd203) i n t h e

f u e l . Then we have a double l te terogenei ty and a spec ia l t rcatnient must be

developyed in order t o c a l c u l a t e with accuracy t h e e f f i c i e n c y of t h e poison and i t s burn up. S a t i s f a c t o r y r e s u l t s have been obtained f o r t h e i n i t i a l

s t a t e using an equiva lent homogeneous medium b u t i t i s s t i l l needed t o t e s t

t h i s procedure f o r burn u p c a l c u l a t i o n s .

11.2.1 - C r i t i c a l f a c i l i t i e s -- -. --

The use of c r i t i c a l f a c i l i t i e s f o r l i g h t water r e a c t o r physics

has been reduced during t h e l a s t year due t o t h e fol lowing reasons :

- The MINERVE r e a c t o r has been shut dokn a t t h e FONTENAY A U X ROSES research c e n t r e on niay 1976 and then disniantled an3 t r a n s f e r r e d t o t h e

CADARACHE c e n t r e . I t i s now loca ted i n t h e same b u i l d i n g t h a t tkie EOLE f a c i -

l i t y and wi l l be r e s t a r t e d u p on ju ly 1977 and operated f o r a new cainpaign

of M E L O D I E experiments inc l uding osc i 1 l a t i o n measurements of gad01 -ii?iuni

'. poisoned f u e l s ;

- The E O L E r e a c t o r has been p a r t i a l l y stopped during the second ha l f o-f 1976, d u e t o t h e works r e l a t e d t o t h e MINEKVE t r a n f e r . Af t e r

that:, i t s a c t i v i t y f o r t h e f i r s t months of 1977 has been devoted t o an expe-

rimental program concerning t h e SCARABIE cxpcrirnents (See 5 IV). O n and a f t e r september i t k i l l be used f o r a program aiming a t a q u a l i f i c a t i o n of c r i t i c a l i t y c a l c u l a t i o n s f o r t h e s to rage of l i g h t water r e a c t o r f u e l s ;

- A Z U R , t h e t h i r d l i g h t water moderated c! - i t ica l f a c i l i t y loca ted a t C A D A R A C H E , has been used f o r measureixnts r e l a t e d t o t h e physical s tudy

of t h e CAP r e a c t o r .

11.2.2 - I r r a d i a t e d f u e l measurements - -

I n t h i s f ie ld,the works i n proyress are dea l i ng w i t h t h r e e main

t o p i c s :

- Measurements o f power and burn up d i s t r i b u t i o n s by means o f gammg spectrometry on f u e l subassemblies i n the storage pool o f t h e CHOOZ

r e a c t o r (Cent ra le i\!ucli.aire des Ardcnnes) , . A new campaign has been car- r i e d on du r ing t h e shutdown f o r r e f u e l l i n g and maintenance a t t h e e?:d o f

t h e bth cyc le (october-november 1976). Abdut twenty subassemblies have been

measured i i ? c l uding prototypes .o-f p l utoriium -fuel elements ;:

- Study o f ac t i n ides , o thers than t h e main isotopes o f uranium and plutonium, o f which t h e knowledge i s impor tan t f o r t h e o u t o f p i l e f u e l cy-

c l e . Measurements o f the f u e l contents i n nept.unium, americium, curium,

2 3 8 ~ u , 2 3 2 ~ areperformed on i r r a d i a t e d f u e l s froin several reac to rs and w i t h

var ious burn ups,;

- The burn up o fgado l i n ium used as a burnable poison. A spec ia l i r r a d i a t i o n (LOCUSTE experiments) has been completed i n a research reac to r

w i t h var ious composit ions o f Gd-U ox ide mix tures .

11.2.3 - -- Analys is o f experimental - - r e s u l t s

a) MINERVE 17 x 17 experiments

The r e s u l t s obta ined on several con f i gu ra t i ons r e a l i z e d w i t h a

PWR 17 x 17 t ype f u e l have been analysed, a l l o w i n g us a t e s t o f t h e neutro-

n i c parameters f o r t h i s type o f l a t t i c e s ( B ~ , convers ion f a c t o r , f i s s i o n

r a t e r a t i o s ) . I n a d d i t i o n these r e s u l t s gave t h e p o s s i b i l i t y t o check :

- power d i s t r i b u t i o n c a l c u l a t i o n s i n per turbed l a t t i c e s ( s i m u l a t i o n o f water holes and rod c l u s t e r s ) ,

- methodsand codes used f o r t h e ana lys i s o f i n core f l u x measurements i n powo- reac to rs . For t h i s aim, f i s s i o n chambers s i m i l a r t o those

wh.ich are pu t i n FESSENIfEIM have been compared i n MINERVE t o gam-

ma 1neasureii:ents on t h e nelghborir ing f u e l rods. ~7~ //

b ) AZUR exper in ien ts and CAP s t a r t u p

The c r i t i c a l exper in ien ts pe r fo rmed i n t h e AZUR f a c i l i t y d u r i n g 1976

f o r t h e CAP program i n c l u d e d t h e s t u d y o f t h r e e c o n f i g u r a t i o n s (4 , 9 and

16 subassen ib l i es ) . The r e s u l t s have been comple ted w i t h t h e p h y s i c a l t e s t s

d u r i n g and a f t e r t h e s t a r t up o f t h e CAP r e a c t o r .

Thc a n a l y s i s o f t h i s s e t o f d a t a b r o u g h t many i n f o r m a t i o n s , m a i n l y

f o r t h e f o l l o w i n g i t e m s :

- neu'o-onic c h a r a c t e r i s t i c s o f a PWR 17 x 17 t y p e l a t t i c e w i t h an avercige enr ichmc'n t o f about 6 %,

- p o w r d i s t r i b u t i o n s i n c o n f i g u r a t i o n s w i t h s e v e r a l t y p e s o f i n t e r a c t i n g po isons ,

- r e a c t i v i t y c o e f f i c i e n t s .

R e s u l t s o f t h e p h y s i c a l t e s t s o b t a i n e d d u r i n g t h e s t a r t up and t h e

normal o p e r a t i o n o f t h e T l i l A N G E r e a c t o r (PWR 900 MWe) have been ana lyscd

w i t h th!? NIIPTIJ?!E system.

The same codes were a l s o used t o make conipar ison o f c a l c u l a t e d va-

l u e s w i t h t h e e x p e r i m e n t a l ~ k : u l t s o f garnilla spec t ron ie t r y on t h e f u e l subas-

semb l ies o f t h e Ct iOOZ r e a c t o r .

d ) Ma in c o n c l u s i o n s

As a g e n e r a l c o n c l u s i o r l we have a good agreement between exper imen ts

and c a l c ~ i l a t i o n s f o r a l l t h e s e cor ipar isons and o t h e r s based upon r e s u l t s o f

f o r e i g n o r p r e v i o u s exper i i : ien ts . R e v e r t h e l e s s i f wc d o n ' t p e r f o r m any ne\v

adjusteinc: l t o r t h e da-ia we gel: SOW s y s t e m t i c d i s c r e p a n c i e s , m a i n l y on

two para!i ;cters :

- t h e tempera tu re c o e f f i c i c i ~ t and t h i s i s p r o b a b l y due t o an i n s u f - f i c i e n t kno i : lcd le o f t h e 2 3 5 ~ c r o s s s e c t i o n s shape i n t h e t h e n n a l

f i e l d ,

- the build u p of plutonium in i r radiated fue ls which i s overest i - mated by about 5 % with a s e t of data adjusted on the i n i t i a l

s t a t e .

11.3 - Plutonium recycle ----------- s tudies

Although the normal use of plutonium i s t o fuel f a s t reactors ,

some physical s tudies are devoted t o an eventuali ty of plutonium recycle

in l i gh t water reactors . Mixed fuel loadings have been already studied in

the pas t and also osc i l l a t ions measurements on plutonium samples.

I n the framework of a common research program, s ta r ted by the

European Communities two years ago, the following studies are already

coilipl eted :

- part ic ipat ion in the benchmark calculations and synthesis of the r e su l t s of comparisons between several codes,

- real izat ion of a s ens i t i v i t y study in order t o point out the main needs on higher isotope cross sections.

Furthermore new programs have been defined during the l a s t months

and are now going on :

- an irradiati.on of some pure isotopes of plutonium, americium. and curium i n a special device (mini- la t t

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NEA COMMITTEE ON REACTOR PHYSICS...REACTOR PHYSICS ACTIVITIES IN OECD COUNTRIES This document is a compil.ation of national progress reports pre- sented to the Twentieth Meeting of