PLUTONIUM HANDLING SAFETY ANALYSIS OF THE ROCKY …

PLUTONIUM HANDLING SAFETY ANALYSIS OF THE ROCKY FLATS

YUCLEAR . , SA~-E,TY, FACILI-TY '?'- "

THE DOW CHEMICAL COMPANY ROCKY FLATS DIVISION

P. 0. BOX 888 GOLDEN, COLORADO 80401

U.S. ATOMIC ENERGY COMMISSION CONTRACT AT(29-1)-1106

DISCLAIMER

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L E . G A L N O T I C E I This report was prepared a s an ah?ount of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission:

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November 8, 1967 RFP-977 UC-46 CRITICALITY

STUDIES TID-4500

PLUTONIUM HANDLING SAFETY ANALYSIS OF THE ROCKY FLATS

NUCLEAR SAFETY FACIL ITY

Douglas C. Hunt Grover Tuck

THE DOW CHEMICAL COMPANY ROCKY FLATS DIVISION

P. 0 . BOX 888

. . GOLDEN, COLORADO 80401

U. S. ATOMIC ENERGY COMMISSION CONTRACT AT(29-1)-1106

RFP-977

ii

C O N T . E N T S

I ~ ~ ~ r o d u c t i o n .................................................................................... 1 I . Object ives of the Nuclear Safety Fac i l i ty Experimental Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

I1 . The Nuclear Safety F a c i l i t y Experimental Program ............................................. 1 111 . Administrative Control Re la t ive to Nuclear Safety ............................................. 2 IV . Descript ion of the Nuclear Safety Fac i l i ty .................................................... 5 V . F i s s i l e Material Handling in the Nuclear Safety F a c i l i t y ........................................ 9

VI . General Categories for Maximum Credible Accident Ca lcu la t ions ................................. 10 VII . Method of Accident Analys i s ................................................................. 12

.................................................. VIII . Analys i s of the Maximum Credible Accident 18 IX . Operat ing Cri ter ia Appropriate to the Maximum Credible Accident Analys i s . . . . . . . . . . . . . . . . . . . . . . . . 20 X . General Experimental Design Cri ter ia .......................................................... 21

XI . ..Comparison of Plutonium and Uranium Maximum Credible Acc iden ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 .................................................................... XI1 . Summary and Conclus ions 23

. Appendix A . Derivat ions ......................................................................... 24 ............................................................. Appendix B . Nuclear Safety Committee 29

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

A C K N O N L E D G M E N T S

Appreciat ion i s e x p r e s s e d t o Vincen t C . V e s p e , Dave Wood, and' Dave P e r s o n s of the U. S. Atomic Energy Commission, Division of Operat ional Safety, Albuquerque Operat ions Office, Albuquerque, New Mexico, for their comments and advice during preparation of the report.

In addi t ion, thanks a re expressed, t o W . R . Stratton of L o s ~ l a m o s Sc ien t i f i c Laboratory, L o s Alamos, New Mexico, for t echnica l adv ice on nuclear excurs ions . .

T h e a s s i s t a n c e of the ent i re Rocky F l a t s Nuclear Safety F a c i l i t y i -. s ta f f in gathering material, ana lyz ing d a t a , a n d performing com- puLaLio~~s i s a l s o g r a ~ e f u l l ~ ackr~owledged .

P l u t o n i u m H a n d l i n g . S a f e t y A n a l y s i s of t h e R o c k y F l a t s N u c l e a r S a f e t y F a c i l i t y

Douglas C. Hunt and Grover Tuck

INTRODUCTION

As a s e q u e l t o RFP-334 (classif ied) , Safety Review of the Rocky Flats Proposed Nuclear Safety Facility, th i s report emphas izes operat ional sa fe ty with respec t to c r i t i ca l m a s s experiments involving plutonium. Sec t ions I and I1 d i s c u s s the Rocky F l a t s experimental program and i t s ob jec t ives . Additional information on the faci l i ty and re la ted equipment a re presented in Section IV. Primarily the information r e l a t c s to faci l i ty vent i la t ion, d ra ins , and containment; and a more complete descript ion of the t w o s p l i t t ab les and the solut ion s y s t e m . Closure and scram speeds , a description of control c i rcu i t s and sa fe ty d e v i c e s a r e included. Sect ion 111 and V cover administrative controls relat ive t o nuclear sa fe ty . A detai led company- organization chart pertinent t o sa fe ty i s given along with a d i scuss ion of the responsibi l i ty of the Internal Review Committee, t ra ining of laboratory personnel , and genera l ru les for operation and handling of f i s s i l e material. Sec t ions VI, VII, and VIII are devoted t o considering poss ib le credible acc iden ts for var ious types of experiments which a r e typical of the Rocky F l a t s program, and a n a n a l y s i s and d i scuss ion of the resu l t s of the assumed maximum credible accident . Operating and t e s t des ign cr i ter ia a re s ta ted in Sect ions IX and X . T h e s e include respons ib i l i t i es of operating personnel , loading philosophy, and l imits on the ra te of addition of react ivi ty .

Section X1 r.nnt,ains a reana lys i s nf the high explosive equivalent , control-room d o s e , and fission-product concentration, based on the acc iden t assumed in RFP-334.

The appendices contain d e t a i l s of some calculat ional resu l t s and a descript ion of the Nuclear Safety Committee.

I. OBJECTIVES O F T H E NUCLEAR SAFETY FACILITY EXPERIMENTAL PROGRAM

The c r i t i ca l m a s s program a t Rocky F l a t s h a s five bas ic object ives:

A. T o obtain experimental d a t a necessary to eva lua te the cr i t ical i ty sa fe ly ol lulure processes ~u Le used a t Rocky F l a t s .

B. T o obtain experimental d a t a to eva lua te the s a f e t y margins of var ious nuclear s a f e t y ru les , now in effect a t the Rocky F l a t s P l a n t . T h e s e ru les in many c a s e s were arrived a t by approximate ca lcu la t ions or empiri- cal ly from multiplication d a t a not direct ly appl icable .

C. T o obtain da ta which c a n be used to produce economic manufacturing p r o c e s s e s and methods for transportation of f i s s i l e mater ials .

D. T o develop more economical and more accura te methods of predict ing cr i t ical i ty limits:

E. T o supply da ta usefu l t o other nuclear p rocess ing p lan ts and c r i t i ca l m a s s fac i l i t i es , even though the experiments wil l be designed to be of maximum benefit t o the Rocky F l a t s P l a n t .

11. T H E NUCLEAR SAFETY FACILITY EXPERIMENTAL PROGRAM

T h e experimental program a t Rocky F l a t s wil l cover the following genera l c a s e s :

A. Various metal s h a p e s of plutonium and enriched uranium ei ther bare or ref lected and/or moderated by s e v e r a l mater ials of in te res t t o Dow Rocky F l a t s f iss i le-mater ial handl ing p r o c e s s e s .

B. Plutonium a n d enriched uranium-metal s h a p e s in v e s s e l s containing aqueous so lu t ions of various concentrat ions of the above f i s s i l e i so topes .

, .

C. A number of interaction measurements involving f i s s i l e metal, oxide, and/or solut ion uni ts in arrays. T h e s e array measurements wil l include experiments to s imulate s to rage vau l t s and shipping a r rays utilizing Dow Rocky F l a t s products.

D. Boron s t e e l p l a t e s and borosi l icate Rasch ig rings in aqueous so lu t ions of plutonium and enriched uranium. T h e s e experiments wil l be used to derive data for the s to rage of ~ l u t o n i u m and enriched uranium so lu t ions .

E. F i s s i l e solut ion measurements in complex geometries.

111. ADMINISTRATIVE CONTROL RELATIVE T O NUCLEAR S A F E T Y

T h e management l ine organizat ion a t the Rocky F l a t s P l a n t of the Dow Chemica l Company, a s i t per tains t o Nuclear Safe ty , i s shown in Figure 1. Other Managers , reporting t o the General Manager are: Manufacturing Manager, John Epp; Manager Divis ion Serv ices , E. J. Walko; Manager Qual i ty , H. E. Bowman; Industr ia l Re la t ions Manager, C. M. Love ; a n d Fac ' i l i t ies Manager, D. M . B a s s l e r .

The Nuclear Safe ty F a c i l i t y i s operated by the Nuclear Safety Group, which in turn reports t o the Director of R e s e a r c h and Development . 'l'he Group includes l ia ison personnel which make u s e of the theoret ical and experimental da ta obtained in the laboratory and e l sewhere in so lv ing plant-engineering and production problems.

T h e fac i l i ty s taff present ly c o n s i s t s of f i f teen persons . T h e presen t educa t iona l l e v e l of the s taff i s a s follows:

Two PhD degrees in phys ics ; two Master degrees in physics; one Master degree in mathematics; four Bachelor degrees in phys ics ; one Bachelor degree in mathematics; two Bachelor degrees in chemical engineering; one Bachelor in b u s i n e s s administration, and two nondegree personnel .

T h e various experimental programs a r e a s s i g n e d t o the s e n i o r experimenters . A sen ior experimenter i s chosen by the Nuclear Safety Director only af ter he h a s demonstrated a good knowledge of reactor phys ics and a working knowledge of the performance of c r i t i ca l experiments by direct participation in various work groups.

The Nuclear Safety Group works direct ly with the various groups tha t handle f i s s i l e mater ials a t Rocky b'lats. ' l 'hese groups include a l l of Manufacturing, the Analytical Laboratories , Research and Development, and the Security Department (which handles off-site f i s s i l e mater ial t ransportat ion) .

The respons ib i l i t i es of the various groups, including Nuclear Safety, a re outlined in the Nuclear Safety Po l icy Guide for the Rocky F l a t s Divis ion.

t

I.!II;UHK I . Management Line Urganization at the Hocky Flats Plant, 'l'he How Chemical Company, Colden, Colopdo.

General Manager L . M. Joshel

Director

Research and Development L. A . Matheson

/

Director 1 Nuclear Safety C. L. Schuske

Plant Liaison

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Critical Mass Physics

B. Internal Review Committee for Experimental P l a n s

The Nuclear Safety Po l icy Guide for the Rocky F l a t s Division (Par . 3.2.4) s t a t e s a s follows: 6 L Procedures for c r i t i ca l and in situ experiments s h a l l be reviewed and approved by a n internal committee appointed by the Nuclear Safety Committee. The c r i t i ca l experiments and in si tu procedures wi l l be prepared by members of the Nuclear Safe ty Group." (See Appendix B.) \

Membership of the Internal Review Committee follows:

1. W . C. Bright, PhD, phys ics ; 1943-1954, T,ASI, ( L o s Alamos Scient i f ic Laboratory, L o s Alamos, New Mexico) Group Leader; 1954-to da te , Rocky F l a t s Technica l Expert ; Research and Development Nuclear P h y s i c i s t .

2. C . L. Schuske, MA, phys ics ; 1948-1952, Y-12 Oak Ridge, T e n n e s s e e , Nuclear Safety Engineer; 1952- present , Nuclear Safety Director a t Rocky F l a t s .

3. A sen ior experimenter from the Nuclear Safety Fac i l i ty who i s not responsible for the ini t ia l preparation of the part icular experiments being conducted and reviewed. T h e current senior experimenters are: Grover Tuck , MS, physics; D. C . Hunt, PhD, ~ h y s i c s ; Robert Rothe, PhD, ~ h ~ s i c s ; a n d Bruce Ernst , .BS, phys ics .

T h e approval by the comrrliLLee uf e ~ ~ e r i i i l e u t a l p lans must be unanimous. Any deviat ion from the written experimental plan must be approved by the Internal Review Comrnittcc. Thc following deviat ions a re considered the most s ignif icant :

1. Any modifications to scramming mechanisms. .

2. Major changes to support ing s t ruc tures for f i s s i l e mater ials and/or ref lectors .

3. Reactivity-addition modes which a re l e s s conservat ive than those given in the previously approved experimental plan.

Experimental assembly support and s a f e t y s t ruc tures are reviewed .by thc above committee, with addi t ional consul tat ion donc with Dow onginoors, to nosure that the experimental s t ruc tures wil l take. t.he designed loads under condit ions s u c h a s ear thquakes and any nnarhy nxplnsinnfi of a credible nature?

The Internal Review Committee i s guided by the following general r u l e s for assembly design:

1. Supporting members are t o be fabricated from non- flamniable mater ials .

2. F o r a l l experiments to be taken to c r i t i ca l , two independent s c r a m s a re required.

3. Mechanical integrity of the experimental apparatus i s s u c h that ea r thquakes or nearby explos ions of a credible nature wil l not bring about a prompt c r i t i ca l assembly .

4. All sc rams and controls a r e des igned on a fai l - s a f e b a s i s .

5. All hydrogeneous liquid f u e l s wil l be checked to s e e that no potent ial exp los ive hazard i s presented by their presence in the assembly room.

C. Training of Nuclear Safety Laboratory Personnel

All technical personnel have received training in reactor a n d c r i t i ca l m a s s phys ics . New personnel will a l s o rece ive s u c h training. Refresher courses in s p e c i a l i z e d a r e a s of reactor phys ics a r e a l s o given to a l l t echnica l personnel .

All t echnica l personnel have part ic ipated in cr i t ical approach in si tu measurements a t Rocky F l a t s . Over 1000 in si tu measurements have been made a t Rocky F l a t s over the p a s t 1 0 years .

Operating t raining for laboratory personnel i s planned a s follows: Two-week t raining courses a t the following cr i t ical-mass laborator ies: Oak Ridge National Laboratory, Oak Ridge, T e n n e s s e e ; L o s Alamos Scient i f ic Lahnratnry, L o s Alamos, New Mexico; Brookhaven National Laboratory, Upton, Long I s land , New York; and Hanford Laboratory, Richland, Washington. In addi t ion, a refresher course in heal th physics on the s a f e handling of plutonium and enriched uranium h a s been given by the Rocky F l a t s Heal th P h y s i c s Group t o a l l Nuclear Safety members.

D. Operat ions

1. OPERATING PRINCIPLES

The experimental programs a t the laboratory a r e es tab l i shed by a n appropriate m n a g e m e n t v o u p .

The management group includes representatives from Manufacturing and Nuclear Safety. All programs are carefully screened to assure that no other data exis t which can be used to solve the particular problem in question.

After the feasibil i ty of the program has been established, the responsibility for i ts organization and performance i s assigned to one of the senior experimenters.

The senior experimenter, with the ass is tance and consultation of other concerned groups, develops equipment and the written experimental plan for the ser ies of experiments. These plans are reviewed and approved by the Director of the facility and the Internal Review Committee (see Section 111-B). Necessary minor changes arising during the experiment are developed in consultation with other senior experimenters and the laboratory's Director. Such changes must be approved by the Internal Review Committee (see Standard Operating Procedures under Item 2).

2. STANDARD OPERATING PROCEDURES

a. The safety and operational procedures of a l l experimental programs involving f iss i le materials will be established jointly by the Director of the facility and a t least one other senior experimenter.

b. A senior experimenter will be in charge of a l l operations concerning a particular experiment. A minimum of two persons, one of whom is an experimenter, sha l l be present during any experiment involving fissi le materials.

c. A primary concern of the person in charge of operations will be the evaluation of personnel safety.

d. Any deviation from an established experimental plan will be approved by the Internal Review Committee.

e. All.experimental ~ l a n ' s must be understood by each participant ~ r i o r to the ~erformance of an experiment. If anyone has doubt of the safety of a articular action or s t ep , the experiment will be suspended until everyone concerned has been sat isf ied that to continue involves no undue risk.

f . Safety will not be compromised due to a program schedule.

g. The satisfactory performance of equipment used for new critical assemblies, including verification of fail-safe features and the adequacy of safety devices in effecting the required shut-down function, will be established prior to achieving initial criticality.

h. The reliability and function of the safety system will be established by a ser ies of pre-experiment t e s t s conducted a t the beginning of each operating day. The audible building alarm will, however, be tested only a t nlonthly intervals. The t e s t s will include observing and recording on appropriate check l is ts the response of detectors and their associated circuits to thc flux of a neutru~l UI.

gaii~l~~a-iuy auul L C .

i . Duriag operacing p e ~ i o d s , red s ~ g n a l lights will . designate areas between the perimeter fence and the assembly room walls from which a l l unauthorized personnel will be cleared before the commencenlent of operations. Persons are warned against entry into these areas by the signal lights and by appropriate signs and alarms. In addition, gates leading to these areas will be locked to preclude accidental entrance to these areas . The key will be in control of the senior experimenter.

j . Each experiment will be monitored by several . appropriate independent radiation-sensing devices. Four of these devices , in'dividually, will automati- cally initiate a scram of the assembly when a preset radiation level is exceeded. One of the devices may a l so respond to a strnnger signal and activate the building alarm. Any one of these scram signals will actuate a t least two independent scram mechanisms, each of which is capable of removing reactivity f a s l t r l11a11 111e lr~axirnurn reactivity insertion rate.

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k. M e a ~ ~ s are provided for the manual activatior~ of a scram during an experiment.

1 . Visual and audible indication of neutron multiplication will be provided to personnel during manual assembly of potentially critical configurations.

m. All approaches to critical with uranium will be made with a neutron source present.

n. Neutron multiplication measurements will be made in a l l attempts to achieve criticality..

o. Increases in.reactivity will be made in a con- , . trolled and reversible manner. Controls will be

such that react ivi ty may be removed during any center within the building. At the motor control center operation a t greater than the maximum rate of . further voltage reduction i s obtained from a 4 5 kva, addition of react ivi ty . Further react ivi ty addi t ions 120- or 240-volt, three-phase transformer for lighting wi l l not be m d e unt i l the e f fec t s of previous and power. A single-phase 10-kva, 120- or 240-volt addi t ions have manifested themselves. transformer suppl ies power for instrument'ation.

p. T h e number of persons , including vis i tors present A lightning arrestor sys tem a t the roof of the assembly in the control room during a n experiment, wil l be room a n d exhaus t s t a c k provides protection for the

' a t the discret ion of and s u b j e c t t o the direction of entire fac i l i ty . T h e grounding sys tem c o n s i s t s of a the senior experimenter in charge. perimeter wire around the assembly room roof with

wires leading to the ground a t the four corners and q. All 'members of the t echnica l s taff wil l be acquainted terminating a t the g o u n d in t r ios of grounding rods.

with the operation and location of radiation-survey D i s t a n c e s between grounding a s s e m b l i e s never instruments. exceed 80 fee t .

r . All f i s s i l e mater ial in the fac i l i ty i s sub jec t t o An outdoor-area lighting s y s t e m e x i s t s around the administrative control . Senior experimenters will entire fac i l i ty . be responsible for the s a f e transfer and s torage of f i s s i l e mater ials . All s to rage arrangements wil l A fire alarm and detect ion sys tem covers the com- be based on experimental r e s u l t s or wil l be in plete faci l i ty with a n autocal l -coded transmitter. A accord with es tab l i shed plant pract ice. securi ty s y s t e m interconnected with the plant sys tem

covers exterior entry w a y s . An optional blackout S. A permanent record of experiments wi l l be made system covering exterior lighting i s a l s o ava i lab le .

and kept. T h e plant d i sas te r warning sys tem i s included in the faci l i ty with speakers located through the building.

t . Permanent records of a l l experimental plans will, Internal Review Committee approvals wil l be kept T h e plant s team and condensate sys tem i s brought on file for review by interested part ies . into the fac i l i ty for purposes of heat ing, water d i s -

t i l la t ion, a n d hot-water heat ing. T h e domest ic cold u. Where poss ib le nonfiss i le material runs will be water supply i s t aken from a n ex is t ing 10-inch main.

made t o initially check the experimental equipment.

v. There must be a t least .one man t o the checking function anytime an experiment involving f i s s i l e material i s performed.

w. Except when a t e s t i s ac tua l ly in progress , a s ign should be placed on the assembly machine which s t a t e s the condition pertinent to operational sa fe ty of that piece of equipment.

IV. DESCRIPTION OF T H E NUCLEAR SAFETY FACILITY

A. Systems

1. UTILITIES

T h e san i ta ry sewage sys tem c o n s i s t s of a sewage lift s t a t ion and of d ra ins from the noncontaminated a r e a s of the building. An individual pipeline from the lift s t a t ion to a holding tank-pit area a l lows the t r ~ n s f e r hy an interconnect ing hose of ' the con ten ts within a waste-holding tank. T h i s tank s e r v e s a s a drain for the potentially contaminated a r e a s of the faci l i ty . Health P h y s i c s approval i s obtained before using the interconnecting h o s e , thus assur ing that only solut ions of s a f e radioact ive leve l s a re t ransferred to the l i f t s t a t ion . If the l eve l of contaminants i s over s a f e l eve l s , the waste-holding tank conten ts are transferred to a portable waste-holding tank via the connection near the holding pit. Health P h y s i c s monitoring of the t ransfer insures complete containment during t h i s t ransfer operation. An individual pump s e r v e s to lift so lu t ions from the waste-holding tank in the pit .

The e lec t r ica l sys tem for the fac i l i ty hegins at an out- Dist i l led water is stored in a f loat tank in the mixing

door pad-mounted transformer capable of delivering 300 room. A.second f loat tank prevents any d i rec t connec- kilovolt amperes (kva) of power. From th i s trans.former, tion between the domest ic water line enter ing the

a 480-volt, three-phase line e n t e r s a motor control assembly room and the remainder of the faci l i ty .

1. Office 6. Assembly Room . . 11'. \Vomen9s Lounge . 2. CountRoom 7. Lunch Room . . . 12. Maintenance Storage 3 . Electron,ics Laboratory 8. ~ a i n t e h a n c e Area (Mechanical Room) . 1 3 . Change Room . 4. Control Room 9. Janitor 14. Mixing Room 5. ' Material Storage 10. Air Lock ' 15. ' Solution St,orage

16. Assembly Hood . . ,

FIGURE 2 . Nuclear Safety Facility (Building 86).

A bot t led g a s sys tem h a s ou t le t s in the mechanical The assembly room hood, which conta ins uranium, or room, laboratory, mixing room, and assembly room. plutonium experiments , can be c,ompletely isolated Compressed a i r from a compressor located in the during a n experiment. 'l'he assembly room itself can mechanica l room a l s o s e r v e s t h e s e a r e a s , in additinn nlso he clos,ed off from the ou ts ide , An exhallst.

t o the control room. A s k e t c h of the faci l i ty floor system' pul ls a i r from the ent i re hot a rea . Balancing

plan i s shown in Figure 2. this sys tem with the two.air s o u r c e s pro,duces a negative pressure within the hot a r e a with respec t t o

2. VENTILATION atmosphere pressure. ~ i l t e r s a r e Incat.erl,at eech .

point of a i r pickup thraughtiut the exhaus1 s y s l e ~ n

T w o vent i la t ion sys tems supply a i r conditioning a t and a double bank of f i l t e r s i s located within an approximately 72OF to the fac i l i ty . One s e r v e s the external filter plenum near the base of the e x h a u s t assembly room and the other s e r v e s the remainder of s t a c k . T h e filter tank in the exhaus t plenum ex te rna l . the faci l i ty . T h e potent ial ly contaminated a r e a of the to the faci l i ty i s constructed with an .a i r lock al low- faci l i ty inc ludes the assembly room, mixing room, ing walk-in capabi l i t i es t o fac i l i t a te filter changing. f i s s i l e s to rage room, and the hal lway to the a i r lock. T h i s a r e a i s ca l led the "hot" a r e a ; the remainder i s 3. DRAINS

ca l led the "cold" a rea . A 16-inch radiat ion sh ie ld ing wal l approximately d iv ides the hot and cold a r e a s . . The san i ta ry drain s e r v e s the ent i re cold a r e a of the

faci l i ty . T h i s drain sys tcm tcrminotcs a t the sewage

In the e v e n t of a n excursion, the option e x i s t s t o s h u t lift s t a t ion , where two independent pumps del iver down the vent i la t ion se rv ing the cold a r e a . T h i s may sewage to a n ex is t ing line on the plant s i t e . Due to be done from the control room conso le by e lec t r ica l ly the elevat ion of th i s line, the s e w a g e pump s ta t ion operated va lves . T h e assembly room air conditioner w a s necessary .

i s mounted on the assembly-room wal l near the south- w e s t corner. It r ece ives ou ts ide a i r through an A second drain sys tem s e r v e s the ent i re hot area.

e lec t r ica l ly operated butterfly valve. Operation of Items s u c h a s the mixing room hood s i n k , decontami- th i s va lve i s poss ib le from the control room console. nation shower ( located in the mixing room), and tamper

tank drain in the a s s e m b l y room make up the hot drain system. T h i s drain g o e s to a waste-holding tank located in the holding p i t external to the faci l i ty . T h e pit con ta ins three v e s s e l s : a plutonium-holding tank, a uranium-holding tank , and the waste-holding tank. The plutonium- and uranium-holding tanks serve a s reservoirs for f i s s i l e so lu t ions tha t have undergone an excursion, t h u s permitting ear l ier a c c e s s to the assembly room after such a n excursion. T h e pit s e t s flush t o the ground with a removable 6-inch thick concrete cover . A manhole a l lows entry to the pi t area. Individual pumps t o the t anks permit t ransfers of solut ions. T h e conten ts of the plutonium- and uranium-holding tanks may be pumped back t o the .

mixing room and the waste-holding tank pumps t o a s tandpipe above grade. All t anks a r e made cr i t ical ly s a f e by use. of R a s c h i g r ings. T h e controls for the transfer of solut ions from the plutonium- and uranium- holding tanks a re in the mixing room, while the controls for the transfer of so lu t ions t o the plutonium- and uranium-holding t a n k s a r e a t the control console in the control room.

Moisture de tec tors ind ica te a n y build up of solut ion due t o tank leaks in the pi t a r e a and sound a n alarm in the control room. T h e plutonium tank in the pi t i s vented through a filter back t o the hot exhaus t system.

4. CONTAINMENT

Thc asscmbly room h a s 4-feet thick, concrete w a l l s on a l l s i d e s excep t the building s i d e which i s 5 fee t thick. T h e ce i l ing c o n s i s t s of a 2-foot thick concrete s l a b . A s t e e l lined concrete door i s suspended on a s t e e l I-beam track on the south exterior wall. T h e entrance from the building g o e s through a labyrinth cons i s t ing of two 90-degree corners in the 5-foot thick concrete wall. The s tructure s h i e l d s personnel exterior to the room from unsafc gamma- and ncutron-radiation lcvc l s during an experiment, or in the e v e n t of an excursion.

Inside the assembly room a t the south e x i t and a t the. labyrinth a re pressure-seal ing doors. T h e s e doors s e a l by means of a f l a t g a s k e t upon s t e e l door frames. They a l s o se rve a s blast-proof doors , s i n c e they a re constructed of heavy s t e e l p la te . All conduits enter- ing th'e assembly room a r e pressure-sealed a t their entrance to the room. All a i r d u c t s have electr ical ly operated butterfly-type v a l v e s for s e a l i n g a g a i n s t a i r flow. T h e interior wal l s u r f a c e s of the assembly room have received s e v e r a l c o a t s of s e a l a n t to ensure a smooth sur face and to fac i l i t a te decontamination.

Inside the assembly room i s a hood (Figure 2) which c o n s i s t s of a 10 by 1 6 by 19-feet high main compartment and a n a i r lock entry way. Air p a s s e s through f i l ters from the assembly room into the assembly hood, and then p a s s e s out through a plenum to the hot exhaus t line. T h i s air flow pattern can be s h u t down permit- t ing abso lu te containment within the hood during an experiment. T h e 6 by 5 by 8-feet high a i r lock entry way i s large enough for men and equipment to enter into the main compartment. Heavy c lear p las t i c windows a r e located on a l l w a l l s of the assembly hood for e a s y viewing of the experiments within. Liquid level gauges a re loca ted in one corner of the hood. T h e gauges may b e viewed by a closed-circui t parallax-eliminating televis ion sys tem. T w o gauges a re used , one for f i s s i l e solut ion a n d the second for ref lector liquid. T h e a s s e m b l y hood top i s removable to fac i l i t a te large equipment instal la- tion and removal. T h e top h a s a g a s k e t s e a l t o insure a pressure- t ight enclosure. Vane-type doors s e a l off the intake f i l t e r s during a n experiment.

T h e plutonium solut ion s y s t e m s valving i s mounted on the assembly room wal l in a separa te glove box external to the assembly room hood. Air e n t e r s into th i s glove box through a filter and then t o the hot exhaus t sys tem. T h e windows a r e loca ted about the glove box for operation and inspect ion. Moisture de tec tors a re located in the glove box for detect ion of l e a k s within the glove box. Instrumentation readout for these de tec tors i s located in the control room.

All the s m a l l e lec t r ica l condui t s enter ing the assembly room a r e s e a l e d . T h e larger conduits '

for controls and instrumentation from the control room terminate in pressure-sealed boxes with the ent i re instrument conduit sys tem under p ressure , insuring a positive. block a g a i n s t a i r leakage from the assembly room to the control room.

Storage tanks for plutonium- and uranium-fissile so lu t ions a r e located in the mixing room. T h e plutonium t a n k s a r e contained in a hooded a r e a with a separa te glove box for valving. An a i r lock cornpart- ment a l lows entry into the tank a r e a for maintenance. Moisture de tec tors report l eaks there to the control room. A second glove box conta ins the quick con- nect ions for transferring so lu t ions into the s to rage tanks . T h e uranium tanks a re s e t in the open a r e a of the room, s i n c e containment is not a problem. Both the uranium and plutonium s torage tanks a r e located in a pit a r e a within the mixing room insuring gravity drain from the assembly room experimental v e s s e l

back to the s to rage tanks within t h e mixing room. T h e w a l l s a r e painted with two c o a t s of a n acry l ic cover , while the floor i s painted with a s t r ippable s e a l a n t .

1. HORIZONTAL T A B L E

The-hor izon ta l table i s loca ted in the assembly room and wil l be used t o s tudy both s o l i d and liquid arrays, a s w e l l a s larger-scale s o l i d a s s e m b l i e s . T h e hori- '

zonta l t ab le i s s p l i t and c o n s i s t s of a f ixed and a movable t a b l e , e a c h 8 5 inches wide by 7 4 inches long. - The movable t ab le i s operated by a hydraul ic cyl inder , It is retracted ( thus separa t ing the array or assembly) on the s i g n a l t o scram. T h e t a b l e s a reapproximate ly 60 i n c h e s apar t , when fully open. Upon a closing command, the movable t a b l e s h u t s ini t ia l ly a t a maximum r a t e of 6 0 inches per minute (in/min). In the f inal 6 inches of c losure , the r a t e i s reduced t o a maximum va lue of approximately 0 .15 in/min. T h i s is accomplished by a control va lve in the o i l l ine to the main cyl inder . T w o v a l v e s in para l le l supply oi l t o t h e cy l inderand in the l a s t 6 i n c h e s of c losure , one v a l v e i s turned off. T h e c los ing r a t e s a r e ad- jus tab le from nearly ze ro in/min t o the maximum ra te . T h e normal opening rate i s 6 0 in/min. T h e scram i s powered by accumulator t anks and opera tes a t a rate of 4 i n / s e c in the f i r s t 6 inches of t ravel .

Limit s t o p s a r e located on both s i d e s of the table and a r e manually ad jus tab le , a l lowing a p rese t c losure limit in the f ina l 1 2 inches of c losure. T h i s limit i s control ledlby s c r e w jacks mounted t o the f ixed table and ex tending t o s t o p blocks a t t ached to the movable table . T h i s insures a n a b s o l u t e limit to the closure d i s t a n c e of the two tab les . A manually ad jus tab le accelerometer a l s o l imits the c losure ra te within the f inal 6 inches . If th i s rate i s exceeded , a scram i s ini t ia ted. An interlock with the accumulator t anks insures a s c r a m , if t h e accumulator t ank pressure is reduced below a prcsc t va luc .

Addit ional s c r a m s used with the horizontal table wil l be pecul iar t o the part icular experiment involved and wil l operate in s e r i e s with the other sc rams . Also a l l va lv ing controis a re connected in a fai l -safe manner a s s u r i n g a scram upon power fai lure .

Differential t ransformers a r e used t o read out the f inal 6 inches of c losing. T h e ent i re 6 0 inches of t ab le closure a r e monitored by a synchronous motor-generator s e t .

2. VERTICAL T A B L E

T h e ver t i ca l t ab le i s a s imple assembly device located in the assembly hood. I t wi l l be adap ted to a variety of so l id uranium and plutonium.assembly t e s t s . , .,

T h e lower table i s ra i sed a n d lowered by a hydraulic cylinder and c o n s i s t s of a n 18-inch diameter round . '

plate mounted to the cyl inder shaf t . Small or i f ices in the oi l l ines regulate the travel s p e e d with an auto.- matic s p e e d reduction occurring a t a p rese t height. The ini t ia l r i s e s p e e d i s 20 in/min maximum without ,

load. At the point of s p e e d reduct ion, t h i s ra te i s reduced t o approximately 0 .15 in/min. Slower r a t e s or closure a r e ava i lab le using a s m a l l sc rew cylinder' connected in paral le l with the main hydraulic cylinder. The normal minimum rate of lowering the table i s 40 in/min. Speeds greater than t h i s a r e rea l ized depending on the table load. T h e maximum tab le t ravel i s 24 inches from fully lowered to fully ra i sed .

Scram of t h i s t ab le i s accomplished by a magnetic la tch between the tab le a n d hydraulic cylinder s h a f t and by a n increased lowering rate of 'the cylinder shaf t . T h i s c a u s e s the table t o undergo f ree fa l l for approximately 9 inches af ter the sc ram command h a s been ini t ia ted. The r e m i n d e r of the table travel i s a t a rate of approximately 2 f e e t per second (f t /sec) .

m ~ c \ippw t&le uurluitiLti or u t i tuinlcss s t c c l membrane 24 inches in diameter. Manual adjust- ment a l lows posi t ioning the upper table between 6 and 8 feet above the floor. A nitrogen-operated cylinder provides a second means of scram for the vert ical table . Inter locks forbid a n experiment to be performed when the magnet i s open, when there is no scram pressure ava i lab le , when the oi l l eve l s a re improper, or when the upper cylinder i s not s e t . All valving and controls a re connected in a fail-safe manner a s s u r i n g scram upon power failure.

Differential bansformers r e a d out t h e f ina l 2 inches of c losure of the lower table . Also , a servo-loop sys tem . reads the position of the lower t a b l e over i t s ent i re 2 f e e t of t ravel .

T h e original lower t ab le h a s been rep laced by a s imilar low m a s s table designed t o reduce environ- mental e f fec t s on the criticality of unref lected t e s t assembl ies . A future modification of the upper table i s planned which would increase i t s load capaci ty from 500 t o 1500 pounds.

3. SOLUTION SYSTEMS

The solution systems consist of tanks used for solution mixing, rinsing of experimental parts and apparatus, and storage of prepared solutions. Tanks for temporary holding of excessively radioactive solution or of solution waiting to be concentrated and a tank for collection of waste solution are a l so part of the solution system [see Section IV , (A) (311.

Canned-rotor leakproof pumps are used for transferring solution between the tanks through suction and d is - charge manifolds.

Four metering pumps and 2 transfer pumps, located in the mixing room, are used to transfer concentrated f issi le solutions t o the experimental vesse l in the assembly room. Three of these pumps are for enriched uranium and three for plutonium solutions. The transfer pumps serve a s a f a s t feed a t a maximum rate of 15 gallons per minute. The metering pumps have variable rates of 6.6 to 0.33 gallons per hour and 70 to 3.75 gallons per hour. For dilute solutions, a system of 2 storage tanks, 1 rinse tank, 2 transfer pumps, and a

. slow metering pump is situated in the assembly room and functions similarly to the concentrated solution S ~ Y L ~ I I I . i \ ll 01 111e ~ U I I I ~ S s u p p l y i ~ ~ ~ fissi le s u l u l i u ~ ~ to experimental vesse ls are controlled by the safety interlock system. All valves directly controlling solution flow to the experimen.tal vesse l are air- operated and/or air-controlled and electrically actu- ated. These valves and the metering and transfer

pumps are remotely operable from the control room. The valves are fail-safe s o that in the event of a power or air-pressure failure, fill lines are closed and drain lines open. Local control of the fast pumps for snl~it inn mixing is also fnr concentrated and dilute solutions in the mixing room and assembly room, respectively. Uranium experiments are conducted on a solution base located in the assembly- room hood. The solution base has two fill-drain lines, one for uranium solutions (both dilute and concentrated), and one for reflector liquid. There are 2 independent d u m p val\;es for each fill-drain line and 2 safe-geometry dump tanks for the f issi le solution tank. In case of a scram, the f issi le solution is immediately dumped into the dump tanks, causing the system to become subcritical. The dump tanks are interlocked to ensure that the); are empty beforean experiment can be started. For plutonium-solution measurements a separate solution base in a separate hood i n the assembly room is planned.

Dilute-uranium solutions are to be concentrated by an evaporator system which is to be located i n the

holding pit and fed by the holding tank contents. The lot\' level distillate will be piped to the waste- holding tank where it will be treated a s contaminated waste. The system i s t o be completed in Fisca l Year 1968.

4. REFLECTED AlIETAL PARTS SYSTEAIS

a . Enriched Uranium Assemblies - A tank reservoir combination located in the assembly room, i s used to measure the fully reflected critical mass of metallic uraniuni assemblies. The tank i s 52 inches high and 27 inches in diameter. It h a s a single fill-line and 2 separate independent drain lines which serve a s scram mechanisms. For fully reflected assenlblies, a conlpressed air bubbler a c t s a s an additional scram device. A submersible pump, located in the reservoir, sup- plies liquid to the tank via an orificed piping manifold which allows several pumping rates. The neutron source, which is always present in uranium experiments, is capable of being remotely introduced to or removed from the system. Several hundred cri t ical and subcritical experiments on enriched uranium assemblies have been with this system.

b. Plutonium Assemblies - Alletallic plutoniunl asseni- blies are contained in an independently plumbed and . . sealed tank which fi ts inside the enriched uranium metal parts tank. The tank plumbing is similar to the uranium tank and is vented to the building hot- exhaust. Plutonium assemblies are put together i n the plutonium handling co~nplex which is located in the mixing room.

V . . F'ISSILE M A T E R I A L I.IAiiDLIN(; I N TLIE NUCLEAR SAFETY FACILI'I'Y

!\. Fiss i lc Material 'rransl'cr Procctlurcs

The production buildings package r a t e r i a l for transfer. Radiation labels are placed on the outside of the containers. The method of packaging is a s follows:

I . SOLUTIONS

Plutonium solutions are to be contained in an annular vessel 24 inches high and 20 inches i n o'uter diameter with a 1.5-inch thick wall. 'I'he vesse l i s equipped with a dry-box top for contamination containment and wheels for transporting.

Uranium s o l u t i o n s a r e contained in a 55-gallon drum .

f i l led with tempered borosi l icate R a s c h i g r ings. T h e drum h a s w h e e l s for e a s e in transporting. L i d s on drums a r e f a s t e n e d t o preclude s p l a s h i n g of solut ion or l o s s of r ings by tipping.

2 . DRY COMPOUNDS OR METAL

P r e s e n t l y u s e d assembly-carrying c a s e s a n d shipping conta iners approved for Rocky F l a t s intraplant t ransfers a r e u t i l i zed for t ransport ing uranium and plutonium metal a n d dry compounds.

T h e Hea l th P h y s i c s Group in the production building conduc ts the f i n a l inspect ion of the sh ipp ing containers for p o s s i b l e contamination. Car r ie r s a r e labeled by Hea l th P h y s i c s for t ransfer .

Nuclear f u e l sh ipments a r e de l ivered t o the Building 86 Eas t - rece iv ing dock by P l a n t Pro tec t ion , who obtains the s igna ture of the senio; experimenter or laboratory director on t h e courier rece ip t . Other sh ipments a r e moved to the Building 8 6 Eas t - rece iv ing dock by P l a n t Serv ices . Al l f i s s i l e mater ial t rans fe rs a re accompanied by Internal T r a n s f e r R e c e i p t s . Loading c rews furnished by Plarit S e r v i c e s a r e physical ly respons ib le for loading the v e h i c l e a t the production building and unloading the v e h i c l e a t Building 8 6 under the superv is ion of the s e n i o r experimenter or the laboratory director .

Solution conta iners a r e t ransferred from the E a s t - rece iv ing dock to the mixing room v ia the Vault Hoom. T h e s o l u t i o n s a r e t ransferred from t h e shipping conta iner t o the appropriate s to rage t a n k s in t h e mixing room. Solut ion s to rage t a n k s a r e a s fol lows:

1. Uranium so lu t ion , five 320-gallon t a n k s and two 100-gallon tanks.

2. Plutonium so lu t ion , f i v e 55-galloll t anks .

All s to rage t a n k s a r e s t a i n l e s s s t e e l and a r e about 30-volume percent (vol %) f i l led with borosi l icate g l a s s annuli (Rasch ig rings). T h e r ings a r e 1 . 0 inches in outer diameter , 1 .75 i n c h e s long, have a 0.25-inch wal l t h i c k n e s s , and contain 12-weight percent (wt %) boron oxide (B,O,).

Dry s o l i d s and metal are s t o r e d in the s to rage vaul t and in the plutonium handling a r e a of the mixing room. T h e sh ipp ing containers u s e d for the t ransfer a re a l s o used for s t o r a g e according t o the l imits spec i f ied in the Building-86 Cri t ical i ty Manual. Enriched uranium experimental components a r e present ly s to red a t a tmospheric p ressure in commercial 16-quart pressure

cookers. Plutonium components a r e p e a s e d and s tored in 8-quart pressure cookers a t a tmospheric pressure and low relat ive humidity.

Material i s repackaged in Building 8 6 us ing the same procedure and shipping containers used in the production buildings. T h e shipping containcrs a re returned t o the production building in the s a m e manner, a s when originally transferred t o the Nuclear Safety Fac i l i ty .

B. Contamination Control in the Nuclear Safety F a c i l i t y

The Rocky F l a t s Hea l th P h y s i c s Group pravides the operat ional and s taff support needed for contamination de tec t ion .

The accep ted procedures for handling plutonium in other par t s of Rocky F l a t s a r e u s e d in the cr i t ical mass faci l i ty . F o r experiments involving plutonium, some form of primary containment i s to be provided, such a s p las t i c bags , c ladding, or canning.

Experiments involving the use of the ver t i ca l t ab le or those to be performed in the solut ion v e s s e l require secondary containment. At p resen t , t h e s e sys tems are in the assembly-room hood enc losure which res t r i c t s any contamination spread from experiments involving t h e s e s y s t e m s . If necessary to restr ic t further the spread of contamination, the solution v e s s e l or e i ther s p l i t table may be completely enc losed within a temporary polyethylene bag., In some c a s e s , contamination wil l be controlled within the hood by plating metallic components or e n c a s i n g metal components in p las t i c b a g s or metal c a n s . In other c a s e s , the experiments wil l be performed in a s m a l l portable low m a s s tank. E a c h of the methods used for addi t ional containment within the hood must be carefully s e l e c t e d s o there wil l be no interference with the experiment or s ignif icant ly influence the r e s u l t .

Other p l ~ ~ t n n i ~ l m erper imants performed outside the hood wil l involve only canned metal a s s e m b l i e s or arrays of canned metal components, thus reducing the possibi l i ty of assembly-room contamination.

VI. GENERAL CATEGORIES F O R MAXIMUM ' CREDIBLE ACCIDENT CALCULATIONS

A. General

Four types of t e s t s c a n be used to represent the scope of the ant icipated Rocky F l a t s plutonium experimental

program. T h e s e four t e s t s , with the r e s u l t s of maximum credible acc iden t (MCA) for e a c h type , a re d i s c u s s e d .

separa te ly below.

B. Unreflected, F a s t , Metallic Sys tems

1. T Y P E S O F T E S T S R E P R E S E N T E D

T h i s t e s t represen ts any unref lected, metallic assembly having a mean neutron energy of the order of 1 0 0 kev or greater. Any addition of moderator or reflector would tend to l e s s e n the severi ty of excurs ions in th i s type of sys tem.

2. DESCRIPTION O F . TEST

T h e t e s t i s t o determine the c r i t i ca l th ickness of a plutonium metal cyl inder 16 cent imeters (cm) in radius. Th: t e s t i s being conducted on the ver t i ca l s p l i t table . The s i tua t ion for the assumed excursion i s that one half the c r i t i ca l m a s s ~ l u s 5 percent h a s been loaded t o each s i d e of the opened s p l i t t ab le . T h e total m a s s of plutoniuT i s 57 kilograms (kg).

3. ASSUMED FAILURES, RESULTS AND CONSEQUENCES

T h e table i s c losed . I t i s assumed tha t a l l sc rams and table controls fa i l , r esu l t ing in a prompt c r i t i ca l excursion which i s quenched by thermal expansion. The excursion i s assumed to continue in the de layed cr i t ical region unt i l suff icient h e a t i s developed t o produce a part ia l phase change which completely quenches t h e sys tem. T h e assumed react ivi ty inser t ion rate i s 360 dol lars per s e c o n d ($/set), which requi res a t ab le speed of approximately four t imes the maximum

- . c srasd ava i lab le fu r he Rocky F l a t s table .

The resu l t s of the assumed excursion a r e 2 x loi6 , f i s s i o n s in the prompt sp ike and 5.95 x loi6 total

f i s s i o n s . T h e high explos ive equ iva len t i s 3 x lo4 pounds (lb). T h e maximum gamma d o s e to personnel i s 2.71 x rads (radiation absorbed dose) . T h e neutron dose i s negligible. Some decontamination of the assembly room wil l be required, if the coat ing on the plutonium components i s ruptured by the phase change.

C. Reflected, .Fast, Metallic Systems

1. TYPES O F TESTS R E P R E S E N T E D

T h i s t e s t i s typical of ref lected f a s t , metal a s s e m b l i e s of most geometr ies and reflector mater ials . Again, the

addition of moderator or reflector only l e s s e n s the e f fec t s of any excursion for s y s t e m s of th i s type.

2. DESCRIPTION O F T E S T

T h e t e s t i s to determine the c r i t i ca l mass of a metal sphere with a n infinite water reflector. A plutonium sphere i s mounted in a cyl indrical tank, which i s slowly being f i l led with water . T h e addi t ion of react ivi ty i s controlled by the addition of reflector material. T h e to ta l mass of plutonium (which i s . supercr i t ical when fully ref lected) i s 5 . 8 kg.


The fill-drain controls a re assumed to f a i l s o that the tank inadvertently f i l l s . T h e assumption, that the assembly i s in the de layed c r i t i ca l range when the tank i s completely ful l , r e s u l t s in the most f i s s i o n s and i s u s e d in t h e s e ca lcu la t ions . T h e excursion i s quenched by the evaporat ion of. one half the reflector material. . .

T h e r e s u l t s of the assumed excurs ion a re 8 x 10'' total f i s s i o n s , no high explos ive equ iva len t , a negligible neutron d o s e , and a n integrated gamma dose t o personnel of 3 .65 x lo-' r a d s . Some a s s e m b l y room decontamination may be necessary .

D. Solution Systems


T h i s t e s t typif ies any solut ion sys tem experiment. All solut ion t e s t s have in common the quenching mechanisms of e jec t ing core mater ial by sudden vaporization of some of t h e solut ion during a prompt excursion and s low vaporization of core mater ial during a de layed c r i t i ca l excurs ion . T h e s e s y s t e m s are a l s o self-regulating due to formation of micio- bubbles and to a large negat ive Doppler react ivi ty temperature coeff icient ( s e e Sect ion VII). T h e

'

assumed s i tua t ion represen ts a n extreme c a s e for most solut ion t e s t s .

2. DESCRIPTION O F T E S T

A large spher ica l 47.8-cm rad ius t ank i s be ing filled with a n over-moderated plutonium water solut ion hav ing a h y d r o g e n - t ~ - ~ l u t o n i u m ra t io of 2656. T h e tank top conta ins a 30-cm diameter opening which i s baffled s o that any e jec ted core mater ial cannot return t o the tank.


1t ' is a s s u m e d a l l controls a n d s c r a m s f a i l a l lowing the tank t o be completely f i l led with core mater ial . At t h i s time the a s s e m b l y i s prompt-critical, and the h e a t g e n - e r a t e d vaporized t h e c e n t e r ' l o percen t of core volume, e j e c t i n g core mater ial , and quenching the react ion.

T h e a s s u m e d excursion produces 6 x 102.8 t o t a l f i s s ions . T h e high explos ive equ iva len t is l e s s than the other c a s e s b e c a u s e of the large amount of energy required t o h e a t and vaporize the core mater ial and the relat ively long neutron l i fet ime.

T h e c o n s e q u e n c e s t o personnel ou ts ide the assembly room are minimal; the maximum gamma d o s e i s 27.4 mill i rads and the neutron d o s e i s negl igible . Decon- taminat ion of the assembly room c a n b e handled by the u s u a l methods.

E. Arrays h


T h e t e s t i s represen ta t ive of any experiment in which a large number of relat ively s m a l l p i e c e s a r e assembled in a n array t o determine a c r i t i ca l m a s s . T h e s e ' t e s t s would b e made t o determine the capac i ty of s torage a r e a s a n d t ransportat ion l imitat ions.

2. DESCRIPTION OF TEST

T h e s y s t e m c o n s i s t s of a 20 by 20-array of 100-CIII luug plutonium rods . E a c h rod i s 1 .56 cm i n rad ius and i s contained in a c a n suff icient ly large t o permit thermal expansion. T h e assembly u t i l i zes the horizontal s p l i t table with one half of to ta l m a s s on e a c h end of the table . T h e to ta l mass i s about 6000 kg of plutonium. T h e worth of one addi t ional rod i s a maximum of 506.

3. MAXIMUM CREDIBLE .ACCIDENT

Tkis t e s t is considered to. be the maximum credible a c c i d e n t for the faci l i ty . T h e r e a s o n s for t h i s choice a re the large m a s s of plutonium involved and the l e s s favorable temperature coef f ic ien t of react ivi ty . T h i s t e s t i s d i s c u s s e d in d e t a i l in the nex t t w o s e c t i o n s .

VII. METHOD O F ACCIDENT ANALYSIS

A. General

T h e 'most app l icab le exdurs ion 'ca lcu la t io i s on s o l i d '

or i e a r i s o l i d nieial systkhs 'have been done by

Stratton (14).: T h e s e ca lcu la t ions were done in con- *

nect ion with the Godiva experiments . T h e relat ively unknown excursion charac te r i s t i cs for plutonium a r e determined by comparison of the excursion parameters of plutonium and uranium.

B. Godiva Excursion Charac te r i s t i cs

1. DESCRIPTION O F GODIVA

The original Godiva assembly w a s a n unreflected metal sys tem fabricated in three s e c t i o n s t o form a sphere. T h e c r i t i ca l m a s s w a s about 54 kg of uranium enriched to 93-percent uranium 235 ("=U). In Godiva, a burst w a s iairiared by (a) e s ~ a l l i s h i l ~ ~ J e l a y c d c r i t i ca l by ad jus t ing control rods, (b) lifting t h e top sec t ion t o reduce react ivi ty t o al low d e c a y of the neutron popula- tion, a n d (c) luweriug t.Le top s e c t i o n into place and rapidly inser t ing a burst rod.w.orth s l igh t ly more than $1. 'l'he Godiva expe.riments thus g a v e data on rhe i o ~ a l number of f i s s i o n s produced in the prompt burst-spike versus s t e p addi t ions of reac t iv i ty above prompt critical.

2. SMALL STEP ADDITIONS O F REACTIVITY

The prompt burst y ie ld depends l inearly on the magnitude of Godiva s t e p addi t ions of react ivi ty of l e s s than 5 c e n t s (4). T h e yield i s a l s o independent of the prompt neutron generat ion time, s i n c e the temperature e f fec t s (thermal expansion and the Doppler effect) which change the react ivi ty appear a lmos t ,s imultaneous with the buildup of the neutron flux.

3. LAHCE STEP ADDITIONS O F REACTIVITY

Godiva i s n o longer in mechanical equilibrium for reactivity s t e p addi t ions of greater than 54. T h u s , energy in the burst-spike i s being generated fas te r , than the sys tem can expand t o maintain equilibrium. In t h i s c a s e . a dependence of the prompt burst-yield '

on the prompt neutron-generation time begins t o develop a s s t e p inser t ions become progressively greater than 54.

When the s t e p inser t ion e x c e e d s 17$ , Godiva d a t a indicate tha t a metal l ic sys tem i s blown apart .

4. RAMP ADDITIONS O F RF=ACfTIVITY

The Godiva experiments give d a t a on s t e p addi t ions of react ivi ty s i n c e the react ivi ty insertion time i s generally l e s s than the de lay time for excursion

, . . . .

' s e e numbered references . " '

initiation in a prompt cri t ical system which i s assem- bleg with np ne'"trqn source present. If a neutron source i s s t e p additions are not possible and the excursion i s speci f ied by a continuous (or ramp) reactivity insertion rate. Calculations of the prompt burst-yield of Godiva versus ramp-reactivity insertion rates (for several delayed cri t ical power 1evels)'are presented by Stratton (14). It may be shown that the spike ,l,ield (for relatively fas t ramps) i s close to the. . . same value that would be obtained in an excursion in which the s tep increase i n reactivity i s equal to the maximum value of excess reactivity physically reached during the ramp insertion.

5. KINETIC ENERGY DEVELOPED IN . .

ESCURSIOYS . .

In an excursiori, a certain fraction of the total energy .

developed 'will' appear a s kinetic energy (KE) (i.e'., energy available to do physical damage in an accident). l ' h i s fraction i s ca'lculated by Stratton (14) a s a' func-' tion o f t h e Godiva pronipt-burst fissi0.n density for s tep reactivity insertions. '

, I

l h e kinetic'energy fraction is inversely'proportional to thc burst-spike r ise tirrle L ~ , \rhich i s ' t he time from burst initiation, by either a ramp or a s tep reactivity insertion to the peak of the burst spike. The to i s observed for Godiva for various s t e p reactivity insertions and to may be calculated for corresponding" ramp-reactivity insertion rates ("corresponding" ramp-, insertion rates are those which aie calculated to

'

give the same burst yield a s a. certain s t ep insertion). In a l l c a s e s , to for a step,insert ion is l e s s than to for a corresponding ramp-insertion rate, s o that the kinetic energy fraction for s t eps shoald al\\rays he greater than the corresponding ramp kinetic energy fraction. This fact is used later to make a conser- vative estimate of the high explosive (HE) yield from an excursion.

C . Cornparison ol' Uranium and IJlutoniurn Excursion I'aramelers

1.. GENERAL

Excursion characteristics are a function of temperature coefficients of reactivity, expansion times, and neutron lifetimes. 'l'hese quantities determine the period of a Yystenr a ~ i d its Lil~re val.iati.o~l s o that a h~owledge of them for any two systems permits a .

comparison of excursions in the two syste,ms. .

2. TER/IPERArLURE COEFFICIENTS OF REACTIVITY

a. Introduction

In the Godiva esperiments, a s \\fell a s in most escur- sions which could o'ccur in critical mass facil i t ies, the quenching mechanism i s associated \vith the temperature rise of the system that occurs a s the excursion proceeds. The effect of temperature i's usually expressed in terms of temperature coefficients of reactivity, that i s , the change in reactivity, p (rho), per degree tenlperature change of the system. If the net reactivity temperature coefficient is negative, the systeni will become less reactive a s the temperature r i ses and will quench itself provided the initial rate of reactivity addition is not too great. If the net coefficient is positive, the systern will become more reactive and quenching t\lill finally occur by core vaporization. The two teniperature effects which normally influence reactivity in Godiva-type systems are thermal expansion and the nuclear Doppler effect. These effects will be treated separately. .

b. Thermal Exuansion

Generally, the reactivity of a systeni \\.ill change upon thermal .expansion due LO changes i n system r density and dimensions. For one-dimensional niulti- region systenis, the coefficicnts of reactivity are found using computer codes which solve the Holtzlnann equationcin either the S,, or diffusion approsiniation. 'I'l~t: procedure is to obtain a critical dimension of a system and a .multiplication factor (keffectixTe) using a 6' room temperature" s e t of densit ies for the constitu- ents. Next, the critical dimension is changed such that it is appropriate to an elevated temperature. Likewise the constituent densit ies are changed such that they are appropriate to this new temperature. A nettJ multiplication factor is then calculated and dp/dT, due to thermal expansion, deterlnincd from the relation:

'l'his is valid for small A k e f f . Such expansion coefficients give good agreement with coefficients calculated from diffusion-theory.cxpressions for the multiplication constants of single region systenis [Glasstone and l3dlund (/I.)].

For arrays, an expression for dp/dl'(expansion) is derived i l l Appendix A , Item 2 , Page 25. 'I'he espres- sion is obtained using the standard fo~:niula for thc

multiplication fac tor of a s y s t e m conta in ing f i s s i l e mater ial , which i s :

where kmis t h e infinite array multiplication, factor , and L i s t h e nonleakage probability fur the a r ray . Equa t ion 2 i s different iated with r e s p e c t t o temperature (with L given by Equat ion A S of Appendix A, Item 2 , P a g e 251, to give:

In Equa t ion 3 , the following apply:

a - the l inear thermal expansion coeff icient (alpha) C - the array interaction correct ion f = lo/ho 1, - 4S/V

S - sur face a r e a of a n array e lement V - volume of a n array e lement Xo - absorpt ion mean free path in a n array

member (lambda) k - a cons tan t dependent 011 the array element

geometry x i - the array e lement Jimerlsicjns

Z - sum of terms of index i

T h e method of determining dp/dT(expansion) from Equat ion 3 i s out l ined in Appendix A, Item 2 .

T h e v a l u e s of dp/dT(expansion) a s computed for the s y s t e m s cons idered in the MCA ca lcu la t ions a re shown in Table I ,

T A B L E I. Expansion React iv i ty Temperature Coeff ic ients .

System

Bare Plutonium-239 Sphere Bare I.3nriched Uranium Sphere Reflccte(l Plutonium-239 Sphere 13are I-'lutonium-239 Solution Sphere Plutonium-239 Cylinder Array

* Reciprocal Kelvin d e g r e e s .

T h e coeff icient for the bare enriched uranium sphere i s computed in order t o allow comparison of quenching mechanisms in Godiva and the s y s t e m s considered in th i s report.

c. Nuclear Doppler Ef fec t Coeff icients

T h e react ivi ty of a sys tem i s a f fec ted by temperature changes through a change in the microscopic neutron- absorption c r o s s s e c t i o n s . T h i s change in c ross s e c t i o n s is ca l led the Nuclear Doppler Ef fec t and c a u s e s the resonant peaks in the absorpt ion c ross s e c t i o n s v e r s u s energy profiles to be broadened and f la t tened in s u c h a way that the a r e a under the peaks remains constant . T h i s e f fec t increases ~ l l e Lu~al neutron absorpt ion in a manner w h ~ c h i s proporrfonal to the concentrat ion, i . e . , the fuel to moderator rat io . T h e Doppler react ivi ty coeff icient i s found using a method s imilar t o that used t o determine the thermal expansion react ivi ty coeff icients . T h e procedure i s to obtain. s e t s of temperature-dependent absorpt ion c ross sec t ions .and then to find the multiplication cons tan t of a sys tem a t s e v e r a l temperatures , us ing computer-coded transport equat ion so lu t ions . The s e t of absorption c r o s s s e c t i o n s u s e d t o determine Doppler coeff icients in th i s report i s due t o Greebler and Goldman (3), who have made a theore t ica l deter- mination of Doppler modified absorpt ion c r o s s s e c t i o n s of uranium 238 (238U), ~ l u t o n i u m 239 (239Pu), and plutonium 240 ( 2 4 0 P ~ ) .

'I'he vallles 01 dp/dT(fioppl tr) for the S Y S L ~ I I I S U U I I -

s idered in the 'VICA ca lcu la t ions are shown in T a b l e 11.

T A B L E 11. Doppler React iv i ty Temperature Coeff ic ients

Jp/JT at 3 0 0 ~ ~ Temperature

(OK-') Dependcncc

Barc Plutonium-239 Sphere +0.2D x 1 o e 6 T-2 .4

Bare Enriched Uranium Sphere* +0.25 X

Reflected Plutonium-239 Sphere -3.3 X T-2.2

Plutonium-239 Solution Sphere -2.94 X lo-' P o s i t i v e >510°K

Plutonium-239 Cylinder Array f 0 . 2 3 X l o m 6 ,r= a .q

* Computed from measured-Godiva total reactivity- lemperature c o e f f i c i e n t .

The theol.etical va lues of t h e l)oppler react ivi ty coeffi- c ien t a r e uncertain for any sys tems whose mean neutron energy i s greater than or about e q u a l to 100 electron vol ts (ev) because of the uncertainty in the nature of the resonance peaks above t h i s energy. T h u s the va lues of dp/dT(Doppler) quoted a b o v e , for the three pure metal s y s t e m s can be considered only order-of- magnitude es t imales . Iluwever, a n expcrimentol

measurement on plutonium in a neutron spectrum In the equat ion, v i s the neutron veloci ty, Ea (sigma)

with a mean energy of about 1 0 0 kev [Kato and the macroscopic absorpt ion c r o s s s e c t i o n , and k, the

Butler (9)] gives a n upper limit for dp/dT(Doppler) infinite medium multiplication factor .

of 0 .356 x (OK-') a t 370°K. T h u s the above value calculated for a bare P u sphere i s considered Using 1 million electron vol ts (mev) a s the neutron

to be reasonably accura te . energy:

d . Conclusions:

The v a l u e s of the react ivi ty temperature coeff icients which appear in T a b l e s I and I1 a re computed .in the diffusion approximation. In t h i s approximation, the total coeff icients for all the s y s t e m s considered a re s e e n t o be more negat ive in va lue than the Godiva cocfficicnt.

. , .

3. EXPANSION TIMES O F PLUrrONIUM AND URANIUM

The time required for expansion can be es t imated from the following formila ( s e e Appendix A , Item 1, P a g e 24 , for derivation):

In Equat ion 4:

p - ind ica tes pluton'ium u - ind ica tes uranium a - the l inear temperature coeff icient of expansion po - the m a s s d e n s i t y Y - Young's Modulus t - time required for expansion

T y p i c a l va lues of a , po , and Y a r e shown in T a b l e 111.

TABLE 111. Expansion Parameters.

Parameter Plutonium Uran ium

~ ( O K - ' ) 5 6 . 7 x 13 x Po 19.6 1 8 . 6 (grams per cubic centimeter) Y 12.7 X l o6 28 x 1 0 6 (pounds per square inch)

Using the Table 111 va lues , Kquation 4 g i v e s t / tu = 1 . 4 P

s o tha t plutonium (p) expands about 1 .4 t imes a s f a s t a s uranium (u) for a given s t e p increase in temperature.

4. NEUTRON LIFETIME

The neutron l i l e ~ i n ~ e (I*), lur a llletal sys tem c a n be est imated from:

l* for plutonium = 2.5 x s e c o n d s I* for uranium = 5.24 x lo-' s e c o n d s

The neutron lifetime va lue for uranium reported in the !iterature on the Godiva t e s t s i s 6 .6 x lo-' s e c which agrees reasonably w e l l with the theore t ica l value calculated above .

D. Calculat ion of Excursion Charac te r i s t i cs

1. TOTAL FISSIONS PER GRAM IN THE PROMPT BURST S P I K E

T h e experimental da ta on Godiva-burst y ie lds for various s t e p react ivi ty inser t ions a r e well explained by hydrodynamic and reactor kinet ic theories . T h e u s e of the same theor ies in the prediction of burst y ie lds for ramp inser t ions in Godiva should thus be qu i te accurate . T h e burst y ie lds for ramp inser t ions of react ivi ty a re given approximately by the following theoret ical express ion [Hansen (511:

a - the ramp. inser t ion rate L* tho noutron gonoration time -

Eo - the in i t i a l power leve l

- aap /dT b . = C p ~ m

dp/dT - the react ivi ty temperature coeff icient

CD - the h e a t capac i ty per uni t m a s s a t cons tan t pressure

Pm - i s t h e m a s s dens i ty

Equation d may be u s e d t o es t imate the relat ive prompt burst y ie lds for e q u a l assembly r a t e s in metal s y s t e m s of different mater ials . From Equat ion 6 and Par t C of t h i s s e c t i o n , i t may be shown t h a t for e q u a l ramp inser t ion r a t e s , a plutonium sys tem wi l l have a smaller burst-yield than a corresponding oralloy s y s t e m .

T h u s , us ing Godiva ca lcu la t ions , a conservat ive e s t i - mate of the to ta l f i s s i o n s per gram in the prompt burst sp ike for an alpha-plutonium, Godiva-type excursion

may be made. T h e method i s t o compute the maximum poss ib le reac t iv i ty inser t ion ra te for a plutonium Godiva-type s y s t e m and f ind from c a l c u l a t i o n s made on Godiva [Stratton (1411 the corresponding number of f i s s i o n s per gram in the prompt burs t s p i k e . The to ta l prompt burst f i s s i o n s are then found by multiplying by ~11e m a s s of he sys tem.

2. T O T A L FISSIONS PER GRAM IN T H E EXCURSION

After the s y s t e m h a s been brought to de layed c r i t i ca l by t h e prompt burst , i t wil l general ly remain in de layed c r i t i ca l unt i l dp/dV x AV = @. In the noted express ion , +/dV = dp/dT x (dV/dT);' and V i s the volume of the

sys tem. T h e to ta l excurs ion f i s s i o n s a r e then obtained by f inding a AV suf f ic ien t to quench the sys tem and computing the number of f i s s i o n s needed t o increase the volume of the sys tem by th i s amount.

3. P R E S S U R E E F F E C T S

The s h o c k overpressure, due to the s y s t e m kinetic energy developed in the prompt burst s p i k e , i s e s t i - mated as fol lows. F i r s t , a s t e p addi t ion of react ivi ty corresponding to the maximum ramp-reactivity addi t ion rate i s a s s u m e d . F o r th i s s t e p addi t ion, and i t s a s s o c i a t e d prompt burst-fission d e n s i t y , a kinet ic energy fract ion i s determined [Stratton (14)l. T h e kinet ic energy fract ion i s multiplied by the to ta l 11u111,Ler uf l i s s i o n s i n the prompt burst s p i k e ( a s deter-

mined in the previous sec t ion) and converted to a ,

high explos ive (HE) equiva len t by the ,conversion factor, 1 pound H E = 7.1 x 1016 f i s s i o n s ; F i n a l l y , s i n c e t h i s ca lcu la t ion h a s been done for oral loy, the resu l t i s multiplied by (1*,/1* )-I. (As noted ear l i e r ,

P . u - i n d i c a t e s uranium and p - ~ n d i c a t e s plutonium.) The l a s t s t e p i s necessary s i n c e for s t e p addi t ions of reac t iv i ty , the half width of the burst s p i k e is proportional to l* [Stratton (14)].

' I h i s should give a conservat ive es t imate for the HE equiva len t , s i n c e (Section VII-B) the u s e c;f the Godiva kinet ic energy fract ion i s conservat ive.

T o r e l a t e t h e HE equiva len t of a n excurs ion t o the abi l i ty of t h e faci l i ty to contain s u c h a n explosion, the fol lowing relat ion ( s e e Appendix A, Item 3 , P a g e 28) i s used t o es t imate the overpressure a s s o c i a t e d with the explosion:

In Equation 7 , AF! i s the overpre,ssure, R i s tthe.radius

of the sphere , r i s the d i s tance from the sphere , (rho) i s the sphere d e n s i t y , p f and I3 are respect ively the .

densi ty and bulk modulus of air,, and AKE i s the ainount of energy r e l e a s e in the excursion tvhich appears a s kinetic energy of the s p h e r e . Equat ion 7 is used.,to , find the overpressure a s s o c i a t e d with any Godiva-type excursion by finding the f iss ion dens i ty a s s o c i a t e d with the excursion and hence the resul tant AKE, a s in the preceeding paragraph.

A s t a t i c overpressure wi l l occur (in addition t o the . :, shock overpressure) due to the hea t ing of the a i r in thc a s s e n ~ b l y roonl. T h e overpressure i s computed by maklng a calorimetric ca lcu la t ion of the equilibrium assembly-room temperature, taking into account the la tent hea t of phasc transformation of p lu ton iu~r~ and the hea t capac i ty of the assembly-room w a l l s and equipment. No alloivance i s made for any leakage of heat from the assembly room. T h e pressure corre- - :

sponding to the equi1ibrium:ternperature. is, then com: : puted from the perfect g a s law. .. . .

E. Evaluat ion of Personne l Health Hazards

1. SHIELDING

For a source in the assembly room, the minimum personnel protection i s 5 f e e t of concrete . T h e s h i e l d i ~ i ~ ca lcu la l ions a r e based on a source s t rength I J ~ 1 .y. 1Uln IISSIOIIS.

a . Gamma R a d i a t i u l ~

The maximum gamma dose a t 9.14 meters (the .minimum' source-obscrver separa t iun) was ca lcu la ted us ing

. . TIi - dnse in rads fro111 d~cr i-energy group

Ky - 1.60 x lo-' rad-cm2/fission Ni - number of photons/f iss ion in the i- .

energy group ,

Q - numbcr of f i s s i o ~ l s pt,i/p - energy m a s s absorption c o e f f i ~ i e n t in t i s s u e

'for th'e i-energy group ( ~ m ' / ~ m )

hvi - energy of the i-energy group (mev)

Bi - buildup factor for T cm of concrete in the , i-energy group

Z - at tenuat ion coeff icient of concrete in the i-energy group (cm- '1

r - the source-observer separa t ion (cm)

A total gamma dose of 4.56 x rads i s found from Equation 8 by summing the contributions from the individual energy groups.

b. Neutron Radiat ion

The neutron dose from 1 x 10'' f i s s i o n s i s ca lcu la ted using:

D - dose in rads Q - number of f i s s i o n s F - fract ions of neutrons e s c a p i n g v e s s e l per f i s s ion Kn - 1.76 x lo- ' rad-square cent imeters per f i s s ion T - th ickness nf s h i e l d in cent imeters or - removal c r o s s s e c t i o n r - source-observer separat ion in cent imeters

T h e maximum dose i s found from Equation 9 to be 8 . 5 9 x lo-' rads .

c . Discuss ion

The ca lcu la t ions reported here a re described in d e t a i l and compared with experimental d a t a by Lagerquis t (10).

Doses a r e obtained for other source s t rengths by a l i n e a r ' s ~ a l i n ~ from the above r e s u l t s .

2. ACCIDENTAL RELEASE O F PLUTONIUM T O T H E ENVIRONMENT

The possibi l i ty of the r e l e a s e of aerosol ized plutonium from within a n enclosure i s considered in de ta i l by Hunt (7). Hunt's methods and calculat ional resu l t s are used t o es t imate the likelihood of a hazardous r e l e a s e of plutoniulll L U ~ l ~ t : a ~ r ~ ~ u s p h e r e a s s o c i a t e d with the assumed excurs ions .

In h i s t reatment , Hunt a s s u r e s rapid oxidation or burning of the plutonium involved in the r e l e a s e s he con- s i d e r s . T h e probability of s u c h pyrophoric-plutonium behavior d i p e n d s primarily on the ambient temperature, the 3urfacc to volu~ii t (S/V) raLio of the metal, and the heat capac i ty (C) of the metal. Experiments performed at Rocky F h t ~ Divis ion [Thompson (1511 L U J e ~ e r m i n e the pyrophoric properties of metallic plutonium indicate that spontaneous ignition of foi ls (S/V = 0 .54 cm-'; C = 0.19 calorie/OK) d o e s UOL occur in a i r below 400°C. 0ther .Rocky F l a t s experiments demonstrate that plutonium foi ls heated to 950°C in an inert atmosphere tend to form a protective oxide r.nat.ine when oxygen and argon are added. It i s , l ike ly that a n encapsu la ted plutonium component would not burn; but would form

such a protective coat ing if the encapsu la t ion were : ruptured when the component i s a t a n e leva ted temperature. T h e observat ions of Hilliard (6), based mostly on Hanford Laboratory experience, subs tan t ia te the Rocky F l a t s experimentation. It i s concluded that spontaneous ignition of plutonium a s s o c i a t e d with the excursions assumed in th i s report i s not l ikely, but': that rapid sur face oxidation not 'accompanied by burning may occur. . *

3. FISSION FRAGMENT RELEASE

A study of the hazards connected with "restricted" fission-product r e l e a s e from the assumed excurs ions h a s been made by Hunt (8). In the report , Hunt's conclusions and me t.hods a r e assumed val id.

F'. Conserva t iveness of Analysis

1. CALCULATION O F T O T A L EXCURSION FISSIONS

T h e es t imate of total sp ike f i s s ions i s conservat ive s ince the to ta l reactivity-temperature coeff icient for plutonium s y s t e m s h a s been assumed to be equa l to the Godiva-temperature coeff icient , whereas it i s .

a lways greater (in negat ive magnitude) than t h e Godiva coefficient ( s e e Equat ion 6 , P a g e 15). . T h e es t imate of the number of f i s s i o n s in the "tail" of the prompt sp ike i s a l s o conservat ive s i n c e a to ta l alpha-to-beta phase change i s assumed to occur. 1 t . i ~ supposed that this phase change d o e s not quench the s y s t e m until the temperature of the metal h a s reached 250°C. In reality only a part ia l phase change i s needed to quench Godiva-type excurs ions and the phase change begins a t 12Z°C, going t o completion in about 30 s e c o n d s a t 250°C [Wilkinson (16)l.

2. CALCULATION O F HIGH EXPLOSIVE EQUIVALENT

T h i s ca lcu la t ion takes account of the difference in neutron generation t imes by multiplying the Godiva high explosive equivalent by the rat io of the'uranium and plutonium generat ion t imes. The calculat ion i s conservat ive s i n c e it a s s u m e s the high explosive - yields for corresponding step-and-ramp react ivi ty addi t ions are the s a m e ( s e e Section VII-B).

3. E S T T A r i I O N O F T H E CHEMICAI, HAZARD

The possibi l i ty of.plutonium ignition in a n excursion is discountcd on tile Las i s of experimental d a t a on . plutonium heated in a i r [Hilliard (6); Thompson (1511. 171e a n a l y s i s i s conservat ive in the c a s e of the

maximum cred ib le acc iden t chosen ( i .e . , the large array) s i n c e in th i s experiment the plutoniunl compo- nen ts wi l l be canned in individual con ta iners .

4 . D I R E C T RADIATION DOSE FROM AN EXCURSION

T h e e s t i m a t e of a gamma-radiation d o s e a n d a neutron d o s e p o s s i b l e ou ts ide the assembly room i s obtained in Sec t ion VII for a source of 10" f i s s i o n s and i s l inearly s c a l e d from this t o give the dose for any excursion. T h i s a n a l y s i s i s bel ieved to be accura te and compares w e l l with experimental da ta .

5. ESTIMATION O F FISSION FRAGMENT RELEASE

T h e method of ca lcu la t ion of the ac t iv i ty concentrat ion due t o f iss ion-fragment r e l e a s e and the conservat i i ie nature of th i s calculat ion i s outlined in RFP-334 (c lass i f i ed) , P a g e s 8385 (13). T h e assumptions made ( s e e Sec t ion VII-E-4.) in the ca lcu la t ion of the r e l e a s e from the plutonium MCA which differ from those made in the a c c i d e n t a n a l y s i s p resen ted in RFP-334 are: (a) only ground r e l e a s e occurs ; (b) f i s s ion fragments generated within two mean free pa ths of a n y metal surface a r e r e l e a s e d , and (c) moderately s t a b l e (inversion) wea ther condit ions a re present . Assumpt ions (a) and (r.) maximize the ac t iv i ty concentrat ion a t 100 meters from the assembly room, and a re t h u s more conservat ive than the assumpt ions of s t a c k r e l e a s e a n d extremely uns tab le weather condit ions made in RFP-334 . Assnmption (bj i s a l w a y s conserva i ive , IJUL i t i s e s p e c i a l l y s o in t h e c a s e of the plutonium MCA where canned compor~emts are used .

6. BTSJJ-allTNC, CONTAINMENT OF EXCURSION P R E S S U R E E F F E C T S

T h e e s t i m a t e of the overpressure a s s o c i a t e d with a prompt burst s p i k e ( s e e Lquat ion 7) i s made by assuming t h a t a l l plutonium-metal sys tem bursts a r e equivalent t o a Godiva-type burst of t h e s a m e f i s s ion dens i ty and multiplying the resu l tan t overpressure by the ratio of the Godiva-to-plutonium neutron generat ion t imes.

For compound s y s t e m s s u c h a s t h ~ bare array a sum- m t i o n over the product ( A K E ; R ; ) ~ , ;here i refers t o

the i -system e lement , i s n e c e s s a r y . T h e total AKE e q u a l s the sum over i of the e lementa l AKE;, but the smal le r v a l u e s of R i compared t o the R of a s i n g l e

unit s y s t e m and the interference of the p ressure w a v e s from the individual uni ts c a u s e s 7 ( A K E ~ R ~ ) ~ 2 R S ' ( A K E ~ ) . T h e appl icat ion of Equat ion 7 t o

1 multlple uni t s y s t e m s should thus be conservat ive.

It i s a l s o assumed that the Godiva sphere expands uniformly. T h e lat ter assumption i s conservat ive s i n c e the bulk of the hea t ing oc,curs near the center of the sphere . T h e overpressure obtained from Equat ion 7 may be re la ted to a part icular amount of high explos ives s e t off in the room and a l s o related t o the d e s i g n s t r e s s of the assembly room. Such comparisons reveal that the assembly-room wal l s should be a b l e t o s u s t a i n an explosion of approximately 5 pounds of high explos ive . E s t i m a t e s made by Stratton (private communication) indicate the assembly room could s u s t a i n a s h o c k equivalent t o a t l e a s t 2 5 pounds of high explosive. It i s thus f e l t tha t the es t imates of overpressure made with Equation 7 are conservat ive.

T h e est i rnatas made of the s t a t i c overpressure produced a r e conserval ive s i n c e i t i s assumcd that there i s no h e a t l o s s from the assembly room. Also , in the c a s e of the MCA, the h e a t content of the system required for q u e n c h i r ~ ~ Ilas a1111usl ~ t i ' t a i 1 1 1 ~ bccn overestimated.

7. RELEASE OF PLUTONIUM

T h e amount of plutonium r e l e a s e h a s been est imated for the MCA on the b a s i s of bare plutonium metal exposed to the air . Such a n es t imate i s ultra- conservat ive s i n c e canned plutonium components a re used in ehe cast! o l i l ~ e large a l l ay . Tliiis no rcloaoo can occur u n l e s s the c a n s a r e ruptured by expansion, which i s not likely for a 250°G temperature change.

VIII. ANALYSIS OF THE MAXIMU'M CREDIBLE, ACCIDENT

A. Specif icat ion of the Accident

?'he sys tem picked as the potent ial MCA i s the large array descr ibed in Sect ion VI-E. No rcflector or moderator materia.1 i s p resen t and he e l l e c t s of t h e table , f lours , vvalls, and cladding aro neglected. The array i s assembled s o that half of the array i s on each half of the opened-horizontal s p l i t t ab le . T h e dimen- s i o n s of each half a r e 213.9 by 2 1 3 . 9 by 50 cm. When the t a b l e i s c l o s e d , the array i s in the geometry described in Secliorl VI-E.

T h e 50-cm long cyl inders a r e mounted in a low dens i ty pipe-type support rack, E a c h cylinder is clamped on the inner end only s o that i t i s f ree t o expand longitu- dinally outward. Transverse motion i s res t r i c ted to a few mils by guides on the rack.

The t e s t i s t o determine the c r i t i ca l mass and the element s p a c i n g for th i s type of array. T h e m a s s increments a r e added with the tab le open and the table i s then s lowly c losed . Severa l reciprocal multiplication counts a r e taken while the table i s c los ing and a t l e a s t one with the tab le closed. F o r each subsequent run the table i s opened and the next m a s s increment added.

2. ASSUMED FAILURES

The following postulated sequence of e v e n t s r e s u l t s in the excursion:

a . T h e opened table i s loaded s o iha t the array i s supercr i t i ca l with the tab le c losed . T h i s requires that :

(1) Both the loader and the load checker make a n error, or

(2) Both the men independently calculat ing the , reciprocal multiplication curve make the same mistake.

b. T h e tab le completely c l o s e s on high s p e e d . , I I h i s requires:

b. Delayed Cr i t i ca l Excursion Charac te r i s t i cs

T h e temperature of the sys tem increases s lowly unt i l the alpha-to-beta phase change i s completed. The phase change c a u s e s a n 8.6-percent, increase in volume which i s considerably more than enough to c a u s e the react ivi ty to decrease by a factor of beta . The relat ively long reac tor periods in de layed cr i t ical -

would probably allow the complete phase change before 250°C i s reached.

c. Prompt Cr i t i ca l E,xcursion Charac te r i s t i cs

At about 2-cm separa t ion , the sys tem becomes prompt cr i t ical with the tab le continuing to c l o s e on high s p e e d . When prompt cr i t ical i s reached, a sharp sp ike of f i s s i o n s i s produced and the react ivi ty of the sys tem i s reduced by thermal expansion to the de layed cr i t ical region in l e s s than a mil l isecond. Severa l much smaller secondary s p i k e s may be produced a s the t ab le i s c losed . When in the c losed posi t ion, the sys tem i s in the de layed c r i t i ca l region and "cooks" until thermal expansion or a phase change c a u s e s the sys tem t o become subcr i t i ca l .

B. Consequences of the Accident

1. RESULTS (1) All s c r a m s f a i l t o operate.

(2) T h e operators f a i l to notice the s h a r p increases in counting r a t e s or the table controls f a i l s o that the operators cannot s t o p the tab le movement.

3. EXCURSION CHARACTERISTICS

a . P o s s i b l e Excursion T v ~ e s

The r e s u l t s of th i s sequence of even ts depend on how much e x c e s s m a s s w a s added. T w o poss ib i l i t i es exis t :

(1) T h e e x c e s s m a s s i s such that the system remains in delayed c r i t i ca l when the table i s c losed . In the calculat ions i t i s assumed one rod (about 50Q worth of react ivi ty) i s added to the just de la ied-c r i t i ca l array.

(2) 'I'he e x c e s s m a s s ig s u c h that the sys tem becomes prompt c r i t i ca l before or a t the completion of table closure. For calculat ional

-purposes, i t i s assumed that s i x rods (about $3 worth of react ivi ty) are added t o the jus t c r i t i ca l array.

T h e maximum credible react ivi ty addition rate for the postulated a c c i d e n t i s computed to be no larger than lO$/sec which corresponds to the maximum closure speed for the horizontal table . For th i s react ivi ty addition ra te , the number of f i s s i o n s in the prompt burst sp ike i s 2 x 10''. T h e number of f i s s i o n s required t o r a i s e the temperature of the s y s t e m s u f f i - ciently for a phase change to go t o a completion i s 9.27 x 10". T h e temperature of the array would then increase t o about 250°C. T h e HE equivalent i s calculated t o .be 1 . 8 x pounds.

2. POSSIBLE HAZARDS

a . nadia~iu l l

(1) Direct Dose

T h e gamma radiation d o s e in the control room due to the excursion i s ca lcu la ted to be 0.0423 rads and the neutron d o s e i s ca lcu la ted to be 8.03 x lo-' rads . T h e s e d o s e s a r e much l e s s than the maximum al lowable "one-shot" dose of approximately 25 rads . T h i s d o s e occurs over a period of about 15 minutes al lowing adequa te evacuat ion time before the entire dose i s effect ive.

(2) F i s s i o n Produc t R e l e a s e

T h e maximum concentrat ion of f i s s ion products p o s s i b l e a t var ious d i s t a n c e s from the assembly room, e x p r e s s e d in t e rms of the to ta l maximum per- m i s s i b l e limit (MPL), is shown in T a b l e IV.

I t is s e e n tha t the f i s s i o n product r e l e a s e should g ive r i s e t o n o appreciable hazard.

TABLE IV. Maximum Fiss ion Product Concen- tration at Several Distances from Assembly Room.

Distance (meters) Health Hazard to: Fraction of MPL

100 Facility Personnel 1.13 X l o e 3 1.000 Plant Persmnel 2.01 x lo-'

10,000 OffSite Persons 1 .29 X lo-'

b. C h e m i c a l

T h e temperature r i s e to 250°C which occurs in the array wi l l probably not l ead t o ignition of the array but, a s mentioned in the preceeding s e c t i o n , only t o a n increase in the surface-oxidat ion ra te . T h i s conclusion i s der ived from d a t a on the pyrophoricity of plutonium presen ted in Sec t ion VII-E. Also , a n y chemical hazard wil l be cons iderab ly minimized by the f a c t that the array e lements a r e to be canned in individual con- t a iners . T h u s the poss ib i l i ty of a chemical explosion, the des t ruc t ion of the array by burning of the plutonium, or plutonium r e l e a s e by f laking off the oxide coa t is considered negl igible .

c. P r e s s u r e E f f e c t s

(1) Impulse P r e s s u r e

T h e H E equiva len t of t h e MCA h a s been s t a t e d t o be 1.8 x lo-' pounds. Such a n explosion should lead t o a n overpressure a t w a l l s 15 f e e t away of about 1.6 x lo-' a tmospheres ( s e e Equat ion 7) , which i s w e l l below t h e impulse overpressure of 0.3 atmo- s p h e r e s tha t t h e assembly-room w a l l s a r e designed t o wi ths tand .

(2) S teady P r e s s u r e

After the array h a s reached 250°C and h a s quenched i t se l f , i t wil l s t a r t t o come t o thermal equilibrium with t h e a s s e m b l y room.and i t s con ten ts . Us ing t h e method outlined in Sect ion VII-D, i t i s es t imated t h a t the f ina l temperature of the a i r i n the assembly room i s 37OC, leading t o a s t a t i c overpressure of

4 x lo-' atmospheres . Such a p ressure is s t i l l we l l within the des ign s t r e s s e s of the assembly-room w a l l s and ce i l ing s o that no s ignif icant damage t o the s t ructural . integri ty of the assembly room should occur.

IX. OPERATING CRITERIA A P P R O P R I A T E T O T H E MAXIMUM CREDIBLE ACCIDENT ANALYSIS

A. General

A loading philosophy and reasonable operating limits c a n d o much tb reduce the possibi l i ty of a n nccidcnt and y c t bc of slich n nntlirc as t o not iindiily hamper the operat ions. 'I'he difficulty in spec i fy ing these l imits for the faci l i ty in genera l l i e s in trying t o choose reasonable v a l u e s for a wide variety of t e s t types. F o r example, the m a s s loading increments for a solut ion t e s t c a n be made e a s i l y a s smal l a s des i red , and the ra te of addition of react ivi ty ad jus ted t o give adequate time for control a n d operation of the scram mechanism, while completing the t e s t in a reasonable time. On the other hand, a t e s t ut i l iz ing metal components may become prohibitively expens ive , if the m a s s increments a r e limited t o a smal l value.

T h e prac t ica l approach t o spec i fy ing s u c h l imits i s t o s p c c i f y t.hcm nccording t o a n opcrntionnl criteria. F o r t e s t s where i t becomes n e c e s s a r y to exceed the limits, a s e p a r a t e s e c t i o n wil l be added t o the experimental plan just i fying t h i s ac t ion and de ta i l ing the added precaut ions taken t o insure a s a f e operation.

T h e s e operat ional l imits apply only t o f i s s i l e sys tems which have not been previously assembled . For known ( i . e . , previously assembled) s y s t e m s the limits may be exceeded . Such known s y s t e m s a r e usual ly assembled without reciprocal multiplication measurements Bur with careful monitoring of the s t r ip-cl~art readouts of the radiat ion-sensing dev ices .

B. Limits on Addition of React ivi ty

During the course of any c r i t i c a l m a s s experiment a t l e a s t two instruments indicating the relat ive power leve l of the ' sys tem are recorded. T h e operat ional react ivi ty addition-rate cr i ter ia i s then assumed to be that the indicated power leve l of the sys tem wi l l not increase by more than a factor of e (2.718) in one minute.

C. Assembl ies with Pos i t ive Temperature Coeff icient c . One man wil l s e l e c t and load the m a s s increment A!

and the other wi l l check the operation. Assembl ies which may have a posi t ive temperature 4

coefficient a re never taken t o cr i t ical and require addi t ional s a f e t y provisions. The type of added sa fe ty f e a t u r e s wi l l depend on thc cxperinler~lal s e t u p X. GENERAL EXPERIMENTAL DESIGN CRITERIA and may include smal le r loading increments and reduced table s p e e d s . T h e s e fea tures a n d limits wil l A. Mechanical Design be de ta i led in e a c h experimental plan.

D. Cri t ical Experiments ' 1. GENERAL RULES

Systems a r e not taken to c r i t i ca l unt i l a s e r i e s of subcr i t ical measurements have shown the s y s t e m t o be performing properly. Sys tems a r e never alloweci t o become prompt c r i t i ca l and while in de layed c r i t i ca l a posi t ive period limit is spec i f ied in the experimental plan. T h e pried limit depends on the sys tem type and i s currently t aken a s n o l e s s than one minute for any sys tem. T h e limit on sys tem power leve l i s determined by the purpose of the experiment and i s usua l ly taken a s the minimum flux needed to ac t iva te a flux- mapping s e n s o r . A further limit on c r i t i ca l experiments i s that i t must be poss ib le while in de layed c r i t i ca l t o allow a reactivity-addition ra te of a s s m a l l a s 5$/sec under the most extreme reactivity-addition circumstances.

E. Operating Procedures

T h e following procedures have been evolved a s a resu l t of the MCA a n a l y s i s d i s c u s s e d in t h e preceding three s e c t i o n s . T h e s e ~ r o c e d u r e s , together with the Standard Operating Procedures s e t forth in Section I11 and the prior consilderations of th i s s e c t i o n , comprisc the entire s e t of Operat ing Limi t s for the Nuclear Safety Fac i l i ty .

Accepted design pract ice i s , fo l lowed for a l l equipment t o be used . F o r the u s u a l t e s t , a l l 'materials (moderator, f i s s i l e mater ial , and reflector) wil l be so l id ly mounted with adequate f i re-resis tant fixtures. F o r the excep- tional t e s t , where a s o l i d mounting interferes with the t e s t operation or appreciably l e s s e n s the qual i ty of the data obtained, precaut ions a r e t aken t o ensure tha t t e s t mater ials cannot f a l l together into a c r i t i ca l mass .

2. STRESS ANALYSIS

A s t r e s s a n s l y s i s i s performed on any design where failure of the s t ructure cou ld . resu l t i n a n excursion. Prior to any t e s t , a check run of a l l equipment i s made using dummy weights in place of fuel .

3. SOLUTIONS

All so lu t ions a r e to b e checked to ensure that under credible excursion condit ions their chemical behavior wil l not lead to hazardous s i tua t ions , s u c h a s f i res or explosions. ,

4. EQUIPMENT CONTROL MECHANISMS

I . HESPONSIBfiITIES O F OPERATING Control mechanisms for table movement or solut ion PERSONNEL tank f i l l ing a re t o be des igned s o a s t o give the

experimenter adequate control of the t e s t . Some The primary responsibi l i ty for s a f e t y r e s t s with the general guide l ines a r e a s follows: operating crcw. T h i s i s accomplished by e a c h man ac t ing a s a n independent check on the other for the a . T h e experimental apparatns wil l be designed s o lcwOing and instrument-monitoring operat ions. E a c h that react ivi ty i r lcreases a s smal l a s IOQ are s t e p wil l be cross-checked t o ensure agreement. poss ib le .

Specif ic requircnlcnts are: b. The d e l a y time from scram s e n s i n g t o scram

operation must b e no more than 0.5 s e c . a . T w o men wil l independently read , c a l c u l a t e , and

plot thc reciprocal mul t~p l ica t ion curve, determine 5 . PLUTONmM c O N T A m M ~ W the extrapolated c r i t i ca l parameter, and determine the next load increment.

All plutonium solut ion experiments are t o be performed b. T w o mcn wil l ~rronitor the rad ia t ionde tec t ion instru- inside a su i tab le hood while a l l plutnnium metal experi-

ments t o determinc if a count is needed between the ments a r e done ei ther in a s e a l e d compartment or with predetermined counting posi t ions. encapsu la ted or contained components.

6. REDUNDANT SCRAM MECHANISMS

F o r a n y t e s t in which the a s s e m b l y i s t o be taken c r i t i ca l , a t l e a s t two independent sc ram mechanisms wi l l be incorporated. One s c r a m mechanism i s suff i - c ien t for t e s t s t h a t a r e no t t o be t a k e n t o cr i t ical .

B. Nuclear Des ign

1. LOADING INCREMENTS

T h e a v a i l a b l e loading increments a r e t o conform with the opera t ing c r i t e r ia and loading philosophy.

2. MAXIMUM nATE OF ADDITION O F REACTIVITY

T a b l e s p e e d s and tank-filling r a t e s a r e t o b e s low enough t o conform with t h e operat ing cr i ter ia .

3 . T E M P E R A T U R E C O E F F I C I E N T O F REACTIVITY

Experimental a s s e m b l i e s a r e t o be des igned to c rea te the maximum p o s s i b l e negat ive temperature coeff icient of reac t iv i ty cons i s ten t with the purposes of the t e s t .

C. Instrumentat ion

T h e minimum s a f e t y instrumentation for a n y t e s t i s :

1. T w o independent neutron-sensi t ive ion chambers which a re monitored in the control room by l inear picoammeters . T h e s e meters a r e to have both a low l e v e l t r ip which s c r a m s t h e t e s t and a high l e v e l t r ip which p o d u c e s a n alarm s i g n a l in 'the control room.

2. An addi t ional neutron-sensi t ive chamber which i s monitored in the control room by a power leve l period-meter combination. E i ther of t h e s e mete rs mus t be capable of scramming the experiment if p r e s e t meter read ings a r e exceeded .

3. A gamma-sensitive chamber which i s monitored in t h e control room by a log-scale current meter whose low leve l t r ip produces a sc ram and whose high leve,l.trip produces a n alarm s i g n a l in the control room.

. >

4. T w o gamma-sensi t ive d e t e c t o r s loca ted outside t h e asskmhly room labyrinth which ac t iva te a building-alarm sys tem.

XI. COMPARISON O F PLUTONIUM AND URANIUM MAXIMUM CREDIBLE ACCIDENTS

A. General

Schuske (13) e v a l u a t e s the acc iden t potent ial for a n assembly c o n s i s t i n g of a l t e rna te uranium foi ls and graphite p la tes . T h e a n a l y s i s of the uranium acc iden t and plutonium a c c i d e n t differ in t h a t the uranium acc iden t involves a thermal assembly , while the plutonium acc iden t , involves a f a s t array. T h e s e acc iden t types have different quenching mechanisms. In the uranium-assembly part ia l core, vaporization is assumed t o occur and t o quench' the excursion whereas thermal expansion and a part ia l phase changc IS a s s u m e d ' t o quench the excuFsi6fl in he plu lu l l iu~ l~ aria); before vaporization occlirs. T h e assumpt ions made in evalua- t ing the potent ial hazarrl a s s o c i a t e d with the two acc iden ts ' a re a l s o different and a r e d i s c u s s e d later . F o r e a c h acc iden t the ca lcu la t ion of the t o t a l number of f i s s i o n s produced, the control room radiat ion d o s e , the equivalent high explosive yield, and the con'cen- tration of f i s s ion ~ r o d u c t s r e l e a s e d outside the assembly room a r e performed differently and a re d i s c u s s e d separa te ly be low.

B. T o t a l Number of F i s s i o n s Produced

F o r the uranium maximum-credible acc iden t a to ta l re lease of 1,7 x 10" f i s s i o n s occurs [Schuske (131, P a g e 791. T h i s number of f i s s i o n s i s required t o caiisa a 10-percent Core vaporization of the uranium assembly. No react ivi ty reduction mechanism other than core vaporizat ion i s assumed t o occur.

In thc plutonium maximum-credible acc iden t , thermal expansion and a part ia l phase change c a u s e s the sys tem react ivi ty t o d e c r e a s e with increas ing temperature, s u c h that a temperature r i s e t o about 250°C will c a u s e the s y s t e m to become subcri t ical . T h i s temperature r i s e a n d part ia l phase change in the plutonium s y s l e l ~ i wi l l yield 3.27 x 10" to ta l f isuiono and wil l not c a u s e any vaporization of the plutonium (Section VII-B).

C. 'I'he Control Room Radiat ion Dose

T h e control-room radiat ion d o s e from the uranium acc iden t [Schuske (13), P a g e 821 w a s obtained from a graph of t ransmit ted neutron and gamma radiat ion versus concrete sh ie ld t h i c k n e s s e s [Brodsky and Beard (111. S ince the publication of RFP-334

[Schuske (13)], i t w a s found tha t the concrete sh ie ld upon which the graph in TID-8206 [Brodsky and Beard (I)] w a s based , contained water windows. T h e data from the graph were therefore inapplicable to the nearly so l id conc?ete w a l l s of the Hocky F l a t s Fac i l i ty . A recalculat ion of the dose from the uranium acc iden t ( i .e . , from a source of 1 .7 x 10" f i s s ions in the assembly room), us ing , the method outlined in Sect ion VII-E, gives a control-room gamma d o s e of 1 . 5 2 x rads

' and a control-room neutron d o s e of 3 .04 x rads . T h e s e d o s e s are wel l below the al lowable health

' p h y s i c s limits.

'. The corresponding control~room d o s e s from the plutonium maximum-credible acc iden t t reated in th i s addendum' have been determined in Sect ion VIII-B to be 0.1'19 rads for gamma radiat ion and 8.03 x rads for neutrons. . Only 2.15 percent of the d o s e from .the plutonium acc iden t appears instantaneously, wh'ile the entire dose from the uranium acc iden t appears instantaneously. T h e remainder of the dose from the plutonium acc iden t appears over a n interval of approximately

. 15 minutes al lowing adequa te evacuat ion time and rendering the plutonium acc iden t ~ o t e n t i a l l ~ no more dangerous than the uranium. acc iden t .

D. T h e Equivalent High Explosive Yield

In the uranium maximum-credible acc iden t , i t w a s assumed that the to ta l f i s s ion re lease wen.t into a Codiva-type burst charac te r i s t i c of a f a s t uranium sys tem. In this c a s e , it w a s estimatecl by,schu;ke (13) that the to ta l yield of 1 . 7 , ~ 10'' f i s s ions ( a f i s s ion densi ty of 3.4. x 1013 f i s s i o n s per gram) g ives r i s e t o a high explosive yield of 3 . 6 pounds. T h e explosive yield from a sys tem being compared with Godiva must however be multiplied by the rat io of the prompt neutron generation t imes of Godiva and the uranium sys tem - - s ince the HE equivalent i s inversely proportional LO

the half width of the prompt burst sp ike , which in turn i s inversely proportional to the neutron lifetime. F o r the uranium assembly , th i s rat io i s about lo- ' SO that the high explosive yield diminishes from 3.6 to 3.6 x lo-' pounds.

For the plutonium maximum-credible acc iden t the method of calculat ion of high explosive y ie lds i s outlined in Section VII. T h e r e s u l t s of th i s a n s l y s i s a r e given in S e c t i o n VIII-R and show that a prompt h ~ ~ r s t ,

sp ike of 2 x 10" f i s s i o n s ( a f iss ion dens i ty of 3.24 x 10" f i s s ions per g a m ) . h a s a high explosive equivalent yield of 1 . 8 x lo- ' pounds. 'The uranium

acc iden t i s thus considerably l e s s dangerous than the plutonium one with r e s p e c t t o . H E equivalent .

E. F i s s i o n Fragment R e l e a s e

Schuske (13) computes the fission-fragment r e l e a s e from the enriched uranium maximum-credible acc iden t a s being 1 /45 of the MPL a t 1 0 0 meters from the assembly room. Using the more prec i se ca lcu la t iona l method of Hunt (7), the MPL fraction a t 100 meters from the assembly room for the plutonium MCA i s 2.01 x lo-'. A comparison of assumpt ions made in the two ca lcu la t ions i s shown in T a b l e V .

T A B L E V . Comparat ive F i s s i o n F r a g m e n t R e l e a s e A s s u m p t i o n s .

A s s u m p t i o n Uranium P l u t o n i u m

(RICA) (kICA)

Source H e i g h t 1 7 . 7 ( m e t e r s )

Weather T y p e E x t r e m e l y U n s t a b l e ( T y p e A )

P e r c e n t F i s s i o n F r a g m e n t s Entrained in Air L c o k i n g from Asse 'mbly R o o m

P e r c e n t F i s s i o n F r a g m e n t s D e p o s i t e d in L e a k P a t h s

F a c t o r Iod ine 1 3 1 MPC i s S c a l e d D o w n D u e t o Short -L ived F i s s i o n F r a g m e n t s

Vo lume-Source U i l u t i o n F a c t o r P e r c e n t of T o t a l F i s s i o n

F r a g m e n t s l l ~ l a a s ~ r l T o t a l F i s s i o n s in h4CA F a c t o r by w h i c h Iod ine 131 h l P L

i s S c a l e d Up D u e t o Cont in - u o u s E x p o s u r e A s s u m p t i o n s

OLacrvatiurn l'vir~t L) i~ tog~cr : from P l u m e A x i s ( m e t e r s )

A s s u m e d Wind V e l o c i t y ( m e t e r s per s e c o n d )

h loderate ly S t a b l e ( T y p e F')

100.

If Hunt's a n a l y s i s method i s appl ied to the uranium MCA, the MPL fraction is 1 .81 x lo-'. T h e MPL fract ions for the uranium and pldtonium MCA's a re thus a lmos t equa l a t 100 meters from the faci l i ty . At other d i s t a n c e s from the f a c i l i t y , the e leva ted source height assumed for the

.uranium MCA wil l lead to MPL fract ions l e s s than those for the plutonium MCA.

It is concluded from the a n a l y s i s presented in th i s sect ion that the plutonium 'MCA considered here

d e s c r i b e s t h e mos t s e v e r e a c c i d e n t that can occur and APPENDIX A. Derivat ions thus d e f i n e s the envelope within which the N u c l e a r , Safe ty F a c i l i t y mus t operate .

1. Expansion T i m e s of Plutonium and Uranium

XII. SUMMARY AND CONCLUSIONS

T h i s report, together with RFP-334 [Schuske (13)], con- se rva t ive ly e s t i m a t e s the a c c i d e n t potent ial a s s o c i a t e d with the mos t hazardous t y p e s of f iss i le-mater ial opera- t ions an t ic ipa ted in the Rocky F l a t s Nuclear Safety F a c i l i t y . T h e e m p h a s i s in t h i s report i s on adminis- t ra t ive controls a n d experimental operat ing cr i ter ia which maximize s a f e t y without unduly hampering opera- t ions . RFP-334 d o e s not fully cover t h e s e top ics and a l s o d e a l s s o l e l y with experiments involving uranium s y s t e m s . T h i s report cons iders the a c c i d e n t potent ial of s e v e r a l types of prospect ive plutonium experiments and s e l e c t s one of these experiments (a large array of plutonium cy l inders ) a s the maximum-credible plutonium acc iden t . T h e acc iden t potent ial of th i s MCA i s ana lyzed in d e t a i l , and i t i s concluded that th i s acc iden t i s wel l within the containment ab i l i ty of the Nuclear Safety F a c i l i t y . T h e s p e c i f i c conc lus ions are t h a t a nuclear excurs ion in the large array (which c o n s i s t s of 400 one-meter long by 3.1-cm diameter plutonium cylin- d e r s , uniformily spaced within a 213.9-cm square array)

The time required for thermal expansion c a n be e s t i - mated from the following considerat ions. If free to expand, a rod would expand according to:

-- AL - a A T , where L o

A L = change in length Lo = ini t ia l length of rod a = l inear thermal expansion coeff icient (alpha) AT = temperature change

If the rod were not f ree to expand, the compression would be increased by a suf f ic ien t amount to produce the s a m e fract ional change in length. T h i s compression force, F , i s given by:

F=- , where (A-2) L o

Y = Young's Modulus A = cross -sec t iona l a r e a of rod

wil l c a u s e : Now assume the expansion force i s appl ied a t the center of the rod s o t h a ~ half of the mass, M , is accelerated in

A. A maximum gamma d o s e of 4 .23 x lo- ' rads. each direction. T h e n from Newton's second law, assuming cons tan t acce le ra t ion , t h e time, t , for expanding a

B. A maximum f i ss ion fragment fraction with r e s p e c t distance, x, is: t o the total MPL of 2 .01 x a t 10'0 meters from t h e faci l i ty .

C . A high explos ive equ iva len t of 1.8 x pounds.

T h u s , from (A-2) and (A-3), U. A negligible re lease of plutonium outs ide the

fac i l i ty . 2MLox t2 = -

Y AAL

T h e radiat ion d o s e in Item A i s w e l l below al lowable Heal th P h y s i c s l imits and the high explos ive equ iva len t Now,

i s too s m a l l to c a u s e any s ign i f ican t damage to e i ther the fac i l i ty or the t e s t s y s t e m . M = L,Apo, or

T h e report a l s o makes a c r i t i ca l comparison of the 2Lop ox t2 = - a Y A?'

uranium MCA considered in the initi;l report , RFP-334 , and the plutonium MCA. I t i s concluded that the plutonium a c c i d e n t i s the more hazardous of the two, and F ina l ly assume x, Lo , and A T are the s a m e for both thus i s the limiting MCA for the Rocky F l a t s Nuclear mater ials and compare plutonium and uranium expansion Safety .Fac i l i ty . t imes a s follows from the above:

Then &om Equat ion A-7 and A-8, the,expansion reactivity-temperature coeff icient (dkeff/dT,)x is :

where the subscr ip t s p and u refer to plutonium and a c X ( k f + i ) uranium. Equat ion A-6 a l lows a qual i ta t ive comparison

of expansion t imes of plutonium and uranium. (dke~f /dT)x - ($JX = k w - d T [ k f 2 + f + C f ] (A-101

2. Derivation of the Expansion React ivi ty Temperature '

) [ ( + ,

I

. - . .. Coeff icient for a n Array 2 =-k, .

.airx k f 2 + f + C ' , .

The expression for the effect ive multiplication cons tan t .. . . of a n array i s t aken to be:

. . - I ' -

keff = k, L, (A-7)

where k, i s the infinite array multiplication constant since L - - !GO - 1 when keff = 1 , and L i s t h e effect ive array nonleakage probability. k f 2 + f + C ' C ' ( k f + l ) The form for L i s assumed to be [Rothenstein (1111:

Equat ion A-10 may be written:

k = a geometry dependent c o n s t a n t , ,

f I l0 /A, 1, = 4 V / S . ,

V = array element volume S = array element sur face a rea A, = mean f ree path in a n array element here interpreted

a s the average d i s tance of t r a v e l i n an array element fro111 birth t o capture.

C ' = 1 - C C = array interact ion correction (Dancoff Shadowing-

Fac:tnr) -:

The value of k, i s es t imated from the four-factor -

formula and the computed energy spectrum. For the array, it is assumed kd,cis equa l tn 7 f o r a s ing lc .. array element; and h o b i s computed for the array from Equat ion A-8 by s e t t i n g kefl = 1 and C ' = 1 ( i . e . , applying Equatioii A-7 t o a s ingle critical-array .

element). . .

Thus:

For the individual terms in Equat ion A-11:

J , d f ac' = k c - + - (kf + l ) , and .(A-12)

d l - dT

If the only reac t iv i ty change is due t o thermal expansion then in E q u a t i o n s A-12 and A-13:

ac ' a c - = -1 Xi - , and d T i dXi

In t h e a b o v e express ions , a is t h e l inear thermal expans ion c o e f f i c i e n t and Xi a r e cr i t ical-array element dimens-ions. T h e la t t i ce s p a c i n g i s assumed temperature independent .

Therefore ~I.VIII Equa t ions A-14 and A-15, Equat ion A-12 hecomes:

And Equa t ion A-15 becomes:

Subst i tut ing in Equat ion A-11 and co l lec t ing terms g i v e s

T h e p h y s i c a l interpretat ion of the terms in Equa t ion A-12 i s :

a . T h e term proportional t o + f x i aC/dXi represen ts a n added react ivi ty due t o the increased number of neut.rons coming from neighboring-array members when the temperature i s increased . T h i s i s caused by the' inc reased leakage of neighboring-array members.

b. T h e term proportional t o +2fk represen ts an increase in react ivi ty due t o the increased c ross -sec t iona l a r e a of the individual array element . T h i s means more of the neutrons from other e lemcnts may in te rac t with a given a r ray element .

c. T h e term proportional t o -:xi dC/dXi represen ts a reduction in react ivi ty c a u s e d by the increase in s i z e of other array e lements than the one considered giving r i se t o a reduced interact ion. T h i s i s c a u s e d both by a n increased amount of the equilibrium

neutron flux be ing absorbed by neighboring-array e lements a n d a n increase in the sh ie ld ing of the given array e lements from neutrons emit ted by sh ie lded neighbors.

d. F ina l ly the term -(k, - l / k ) {2f(2kf + 1)I l e a d s to a reduced react ivi ty due t o the increased leakage of the s ing le e lement considered.

T h e term C in Equat ion A-16 represen ts the fract ional reduction in t h e neutron-flux incident on a n array element due t o the p resence of other array e lements . For arrays, which by definition have no intervening moderator between e lements , th i s i s the fraction of the neutrons emit ted by a n array element which inter- cepts unshielded neighboring-array e lements [ D P O O ~ Q F (?)I. The C i s assumed t o be given by the following formula:

where ii, and ii2 a re the average number of n e a r e s t and next neares t neighbor-array elements and C, and C2 a r e the i n t ~ r a c t i o n terms evaluated a t the average s p a c i n g - dl and d, of neares t and next neares t neighbor-array elements . Equat ion A-17 neg lec t s any interact ions beyond the next n e a r e s t neighbors but inc ludes contributions from sh ie lded next neares t neighbor-array elements . F o r relat ively large a r rays , t h e s e two I I errors" a r e approximately cnmpensatory. F o r cylinders , the terms C, and C, a re taken to be of the form:

The f i rs t terr~r g ivcs the probability that neutrons which are emitted into a plane perpendicular to the a x i s of a cylinder, by a line source on the cyl inder 's a x i s , wil l be intercepted by a s e c o n d ident ical cyl inder whose a x i s i s paral le l t o the a x i s of the first cylinder. Thc second term g ives the probability that neutrons elllitted into a plane which conta ins the a x e s of two idcnt ical paral le l cyl inders , by a point source a t the ccntcr of, one of the cy l inders , wi l l intercept the s e c o n d cylindcr.

Here r and h a r e t h e cylinder radi i and height respectively and di i s the center-to-center spac ing . F o r paral le l cyl inders arranged in a n nxn array, ii, and ii, are given a s :

RFP-977

And jl and j2 are given as : f = 0.358 C = 0.4245

- d d, = -7 [2.326(n - 4)' + 18.292(n - 2) + 36.131, (A-22) (2) Critical Spacing Calculation

n

From Equations A-17 through A-22: where d i s the minimum center-to-center spacing.

The array-reactivity temperature coefficient i s computed C = T i l 0.318 sin- ' a s follows:

a. The geometry of an array element and the number and arrangement of array elements are selected. Each array element must be subcritical and the

(l?) 0.6637 tan-' + 0.318 ii, s in- ' - [ , loo ] 2(d, - I .S6)

critical array spacing i s s t i l l undetermined. - n, = 7.39 -

b. The value of k, for the array is estimated from the n, = 13.68 - four factor expression and values of k are obtained d l = 1 . 2 0 0 d - from Rothenstein (11). d2 = 2.311 d

C. The value of ho for an array member i s estimated by finding the dimensions of an isolated critical array element and solving for Xo using Equation A-9. The value of f for an array element i s then calculated.

d. The value of C for the critical array is determined from Equation A-7 by sett ing keff = 1 and using the array value o f f computed in (c) above.

e. The critical array spacing i s computed from Equation A-17 aud, in the case of cylinders, Equations A-18 through A-22.

f . Equation A-17 is then differentiated with respcrt

, to thc wiay element dimensions to obtain dC/dXi

g. Equation A-16 is solved for (dp/dTIx for the array. The calculation of (dp/dT), for the Hazards Report critical array is a s follows:

(1) Array Specifications

An array of 400 metallic 2 3 9 P ~ cylinders with nn reflector "1. moderator present arranged in a 20 by 20 square array, having:

And,

C = 7.39 x 0.318 s in- ' 2(1.2d - 1.56) 1 loo I

+ 13.68 x 0.318 s in- ' - (2 :i?d)

0.637 tan'.' [ 2 ( 2 . 3 1 ~ - 1 . 5 6 j

By iteration d i s found to be 11.1 cm. . . . .

(3) Calculation of C X ~ S C ~ / ~ X ; 1

For cylinders, from Equations A-17 and A-18:

dC 2rii, -3 h r- dr = - n [a: - ..) tan-l 17} 2(J1 -

h = 100. cm-cylinder height - 4hT1 16 - r) s i n n 1 ( r / & j r = 1.56 cm-cylinder radius dh n2 -42, - r)' + h2 k = 1 /3 ho = 5.58 cm 4 16 --I-) sin-' (r/&')] + --? 1, = 3.12cm n2 4(d2 - r)' + h2

Equat ions A-23 and .4-24 then g ive , with the v a l u e s of r , i i l , L, a,, ii,, and 2, given i n par t s (a) and (b):

rxiac/axi = 0.5301 i

(4) Ca lcu la t ion of (dp/a'T),

Equa t ions A-28 and A-26 then give:

2 2nip2~Rr '4 dr ' = -nFU2 R3 AKE = - 0

5 (A-29)

Equat ion A-29 may then be solved for U and combined with A-25 to give:

F ina l ly assuming a i r t o be an idcal g a s :

Wl~ere p f is the d e n s i t y of a i r , p i s the abso lu te pres- s u r e , and y (gamma) i s the spec i f ic h e a t ratio. 3. 'Calculation of Overpressure from Expansion of

' a Sphere

S o that Equa t ions A-30 and A-31 give: T h e overpressure, Ap, due to expans ion of a sphere may be written [Sears and Zemansky (12)l:

For a Godiva-like excursion in the Nuclear Safety Fac i l i ty Assembly Room involving a n alpha-plutonium metallic sphere , t h e parameter va lues in Equntion A-32 are:

u = veloci ty of sound in fluid H = s p h e ~ e tddlul; B = bulk modulus of fluid r = d i s t a n c e from sphere U = veloci ty of sur face of spl~ari: y = 1 . 4

p = 1UVdy~~cs pur Pqrjnra sent imeter pf = 1.18 x grams per cubic cent imeter

H = 5 c m 7 = 19.G grams per cubic centimeter r - 4.57 x 10' cm (average assembly to wal l d i s tance)

F'or a sphere eht: diffcrent ial kinet ic energy i s given by 2npvZ(r ') r ' dr ' where r ' i s the rad ius of a volume e lement , v(r ') i s the expansion veloci ty of a volume element , and i s the average m a s s dens i ty of the sphere . T h e to ta l kinet ic energy change a s s o c i a t e d with the expans ion , AKE i s thon: ?'he v a l u e s ilr Equat ion .4-32 then give:

Values of AKE corresponding to excursions of different magnitudes may be computed us ing the methods of Section VII-D. The associated overpressures computed from Equat ion A-33 appcar in T s h l e A-I.

Assume for the ca lcu la t ion of U tha t the fract ional change in rad ius of e a c h part of the ophere i s the same or:

d r ' dR - - - r ' - R TABLE A - I . Overpressures for Several Excursions

T h i s assumption means that the internal s t r e s s and bulk modulus must remain c o n s t a n t during the expansion.

Overpressure ( a t ~ ~ l o s p h c r c o ) Total Prompt F i s s i o n s '

T h u s , v(r ') i s now wri t ten us ing Equat ion A-27 a s :

d r ' r ' d H r 'U v(r') - = - - = - dt H d t R

APPENDIX B. Nuclear Safety Committee

The Nuclear Safety Committee i s a manager's committee - cons i s t ing of the plant manager, other managers , and the superv isors of the groups that work with f i s s i l e material. T h e committee c o n s i s t s of approximately 24

-.

members including department h e a d s of: Manufacturing, Technica l Serv ices , Administrative Serv ices , General Serv ices , F a c i l i t i e s , Securi ty , Research and Development, and Heal th P h y s i c s .

T h e committee mee ts once a month with s p e c i a l meetings a s required.

The funct ions of the' Nuclear Safety Committee a r e to:

1. Formulate nuclcar s a l e t y policy for recommendation t o the P l a n t Operat ing Board,

2. Review infractions of nuclear sa fe ty rules .

3. Review nuclear s a f e t y near m i s s e s .

4. Review nuclear s a f e t y incidents and acc iden ts a t Rocky F l a t s and e l sewhere .

' 5. Review simulated incidents and s t u d i e s .

6 . Review a u d i t s and inspec t ions performed by Nuclear Safety, operat ing groups, ex te rna l con- s u l t a n t s , and the Atomic Energy Commission.

BIBLIOGRAPHY

1. Allen Brodsky and G. V. Beard. A %ompendium of In,formation for Use in Controlling Radicition Emer- gencies. TID-8206. Oak Ridge National Labora- tory, Oak Ridge, T e n n e s s e e . 1950. P a g e 83 .

2. L. Dresner. Resonance A bsorption in Nuclear Reactors. Pergamon P r e s s , Inc., New York. 1960. Chapter 7 , P a g e 90 .

3 . P. Greebler and E . Goldman: Doppler Calcula- tions for Large Fast Ceramic Reactors. GF:AP-IIOP2. Cene~.r i l E lec t r ic Atomic Power Company, San J o s e , California. 1962.

4 . S. Glass tone and M . C . Edlund. The Elements of Nuclear Reactor Theory. D. Van Nostrand Company, New York. 1952. Chapter 1 1 , P a g e 339.

5. G. E . Hansen. Burst Characteristics Associated with the Slow Assem.hly of Fiss io~aLle: h.futerials. LA-1441. L o s Alamos Scient i f ic Laboratory, L o s Alamos, New Mexico. 1952.

6 . R . K. Hil l iard. Characteristics of Burning Pluto- nium. HW-77531. Hanford F a c i l i t i e s , Richland, Washington. 1963.

7 . D. C. Hunt. The Restricted Release of Plutonium. RFP-799. Rocky F l a t s Divis ion, T h e Dow Chemical Company, Golden, Colorado. October 17 , 1966.

J

8. D. C. Hunt. An Evaluation of the Leakage Rate Specifications for the Rocky Flats Plant Nuclear Safety Facility. Internal Report for Atomic Energy Commission, Washington, D. C. 1966.

9. W . Y. Kato and D. K . B l ~ t l e r . '6Measure~rlent of t h e Dopplcr T e ~ i l ~ e r a t u r e Coeff icient in a n EBR-I Type Assembly." Nuclear Science and Engineering, 5:320. 1959.

10. C . R . Lagerquis t . "Theoret ical Dosimetry Considerat ions for the Rocky F l a t s Nuclear Safety Faci l i ty ." Internal Report. 1965.

11. W . Rothenstein. "Collision Probabi l i t i es and Resonance Integrals for Lat t ices ." Nuclear Science and Engineering, 7:162. 1960

12. F. W . Sears a n d M . W . Zemansky. University Physics. Addison-Wesley Publ i sh ing Company, Reading, Massachuse t t s . 1955. Chapter 21, P a g e 357.

13. C . L. Schuske . Safety Review of the Rocky Flats Proposed Nuclear Safety Facility. RFP-334. Rocky F l a t s Divis ion, T h e Dnw Chemiool Company, Golden, Colorado. October 1 4 , 1963. (Classif ied)

14 . W . R. Strat ton. "A Review of Cri t ical i ty A c c i d e l ~ ~ s , " Chapter 5, P a g e 163. Progress in Nuclear Energy: Technology Engineering and Safety. Volume 3 . Editor , C . M . Nichols . Series IV. Pergamon P r e s s , Inc., New York. 1960 ,

15. M. A. Thompson. The Oxidation and Ignition of Plutonium. RFP-491. Rocky F l a t s Divis ion, The Dow Chemical Company, Golden, Colorado. March 21 , 1966.

16. W . E. Wilkinson, Editor. Extracrirle and Physicul Metallurgy of Plutonium and i t s Alloys. Inter- s c i e n c e Publ i shers , Inc., New York. 1960.

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