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N O T I C E - - - - - -

This report summarizes as of the date of the study

the status of this phase of the design of the Experimental

Gas Cooled Reactor under construction in the Oak Ridge

Area. Since the data was developed prior to completion

of all design, fabrication and construction, the information

is subject to modification during the evolution of the

complete design of the entire facility and no attempt

has been made to revise, rewrite, edit or otherwise

modify the study to maintain the data current with related

research and develo,pent programs or subsequent design

revisions, Users are cautioned to avoid interpretations

and conclusions based on the incomplete data contained

herein.

Study No. 11-105-1 EGCR

THERPIAL AND TOTAL EPITHERMAL NEUTRON FLUX DISTRIBUTIONS

I N THE EXFERIMEMTAL G A S COOLED REACTOR

Prepared By: 6 W- Date: 2-23-60 Responsi'ble Phyl#cist

"

Approved By: Date: 2-23-60

Approved By: Date : 2-23-60

Approved f o r Ka i se r Engineers :

By: W. J . Dodson Date: 3-30-60 P r o j e c t Engineer

Approved f o r Union Carbide Nuclear Corpora t ion :

By : M, Bender Date: 3-15-60

Approved f o r Atomic Energy Comdss ion:

By: L. H. Jackson Date: 3-21-60

5 i Study No. 11-105-1 EGCR

Thermal and T o t a l Epi thermal Neutron F lux D i s t r i b u t i o n s

I. OBJECTIVE

t o t a l ep i the rma l neu t ron f l u x d i s t r i b u t i o n s i n t h e EGCR from t h e c e n t e r of t h e c o r e through t h e b i o l o g i c a l s h i e l d . v ide d a t a f o r K a i s e r Engineers1 c a l c u l a t i o n s of b i o l o g i c a l s h i e l d i n g a g a i n s t neut ron and gamma r a d i a t i o n . provide d a t a f o r neut ron and gamma h e a t i n g c a l c u l a t i o n s f o r r e a c t o r components and for s t r u c t u r e s e x t e r n a l t o t h e r e a c t o r .

The o b j e c t i v e of t h i s r e p o r t i s t o determine t h e thermal and

T h i s w i l l p ro-

It w i l l f u r t h e r

11. SUMMARY AND CONCLUSIONS

1. The maximwr: va iues sl the neut ron f l u x d i s t r i b u t i o n are p resen ted i n F igu res 1 throagh 8. The d i f f e r e n c e i n t h e s h i e l d i n g e f f e c t i v e n e s s of o rd ina ry conc re t e i n t h e radial b i o l o g i c a l s h i e l d and t h e heavy conc re t e i n t h e a x i a l b i o l o g i c a l s h i e l d may be seen by examining t h e s e f i g u r e s . t h e r m a l f l u x bui ldup , s i m i l a r t o t h a t found i n t h e g r a p h i t e re- f l e c t o r . f l u x i s a t t e r u a t e d through t h e complete s h i e l d .

f l u x and should be used w i t h c a u t i o n . damage t o s t e e l i s caused by fas t f l u x , b u t only by t h a t f l u x above e n e r g i e s of approximately 1 MeV, which i s n o t t h e f a s t f l u x r epor t ed h e r e ,

The o rd ina ry c o n c r e t e pe rmi t s a

I n l-eavy conc re t e t he re i s no such bui ldup a s t h e thermal

2 . It should be noted t h a t t h e fas t f l u x i s a t o t a l ep i the rma l F o r example, t h e r a d i a t i o n

The f a s t f l u x d i s t r i b u t i o n i s g iven i n Study No, 11-105-2.

111, GIVEN DATA

a x i a l d i r e c t i o n s are based on t h e d e s c r i p t i o n g iven below: The mock-ups of t h e r e a c t o r s t r u c t u r e i n t h e r a d i a l and

R a d i a l S t r u c t u r e Core r a d i u s . . . . e . . . . . R e f l e c t o r t h i c k n e s s . . e . . . . , . . . Void space . . . e . . . e e

Temperature bar r ie r i n s u l a t i o n . . . . . . . Temperature b a r r i e r ( t h i c k n e s s ) . ., . . . e . . Pressure v e s s e l ( t h i c k n e s s ) . . . . e . . . Pressu re v e s s e l e x t e r n a l i n s u l a t i o n . . , .

( t h i s i s assumed t o be only 1/16 i n . s t ee l )

S h i e l d coo lan t b a f f l e ( t h i c k n e s s j . . . . . . B i o l o g i c a l s h i e l d ( t h i c k n e s s } . .. . . . . . e

B i o l o g i c a l s h i e l d c o o l a n t gap . . . e 0 . .

66.3 in. 26.67 i n . 21.95 i n .

4 i n . 1 i n . 2.75 i n . 4 i n .

107.5 i n . 3/16 i n . 10 f t

Axial S t r u c t u r e Core h e i g h t . a e . . . . . . . 14 ft 6 in. R e f l e c t o r t h i c k n e s s , ., . . . . . . 2 f t 3.75 i n . Top p l a t e ( t h i c k n e s s ) . . . . . . . . . . 1 i n . Temperature b a r r i e r i n s u l a t i o n . . . . . 4 i n .

Temperature b a r r i e r ( t h i c k n e s s ) . . . , . . 1 i n . ( t h i s i s assumed t o be only 1/16 i n . s t e e l )

1

i .

- i L study NO, 1s-105.1

IBGCR P P ~ B S U F ~ vessel (thickness) .4 in. PPesoure vessel external Insulation . 4 in.

( t h i g is aseumd t o be on ly 1/16 In. steel) Biological shield 10 ft 6 in,

Ordinary concrete fs used in raOIal biological s h i e l d . Hcawy ('ferrophosghorous) concrete wss used in tho axial biologf- caP shield. Reactor t h e m 1 power 84.3 Mw. Additional data used h e r e wepe derived in A-C Title I StuUy No. 116 and am referenced In t h e section a i t h i s report coverlng calculations,

8 .

2. The a a s q t i o n a made I n A-C Title I Study No. 116, which

3. In calculating the radial neutron flux distpibution, t h e

4JB aesumptbons inherent %n the Val Prod code ape made hem

dePive the data used In' that report , are also made here,

axial maxlmm-to-average ratio of the the& flux was assumed to be 1068a0

In detemlnlngg both' the exfall and mdI.1 flux d%strf- bution, the coro um abd~umed t b be errdo o f 8 hossegeneme laafxture of nater%allr, i o e o r n o 3 u e l rotatfen 6eheme ma m w k e d ~ , Fuel n s ae~umed t o be made up of the corn a v o w e of 18otopsr present in M eqtaflibpfum core,

40

.5 . Xeatpg omurete oontalns water f n the mount of 303$ by wol$h* P

v. .QF A # U 8x9 . -

. . . . A - . . .. . . ..

. .. . . .. . . . . .

t

The flux.'v&l&a calouleited are the maxlmua values since they am given along the axle of the reactor rehepa the kadlal &atpi- bution is a ~~~axblgullb, and 1x1 a radial plane whom the dfetflbutlora $8 8 ~perxUms. Values of' the f lue8 in the m a l

rrial @

2

Study No. 11-105-1 EGCR

d i r e c t i o n out i n t h e p r e s s u r e v e s s e l and b i o l o g i c a l s h i e l d hzve no t been a t t e n u a t e d f o r t h e spatrial d i s p e r s i o n of t h e f l u x emanating from the r e a c t o r .

co re i s homogeneous. The f i n a l f l u x d i s t r i b u t i o n w i l l depend on t h e f u e l r o t a t i o n program, t h e method of o p e r a t i n g c o n t r o l rods , and t h e c o n t e n t s of t h e exper imenta l l oops . S ince none of t h e s e were determined, i t was necessa ry t o make t h e above assumption about t h e c o r e c o n t e n t s . It i s obvious, i f one examines F igu res 1 and 59 that t h e a b s o l u t e f l u x va lues a t t h e c o r e c e n t e r a r e n o t t h e same f o r t h e a x i a l and radial d i s t r i b u t i o n s . These va lues were based on assumptions which would give c o n s e r v a t i v e ( h i g h ) va lues of neut ron flux, I n c a l c u l a t i n g t h e r a d i a l d i s t r i b u t i o n , a maximum-to-average r a t i o of t h e core a x i a l t h e r m a l f l u x d i s t r i - b u t i o n was assumed t o be l.620 T h i s va lue was determined i n A-C T i t l e I Study No. 116, and is assumed t o g i v e a r e l a t i v e l y high r a d i a l f l u x va lue , I n c a l c u l a t i n g t h e a x i a l f l u x d i s t r i b u t i o n , t h e maximum-to-average r a t i o of l0335 for t h e c o r e r a d i a l thermal f l u x d i s t r i b u t i o n was used. T h i s va lue was c a l c u l a t e d f o r t h e r a d i a l d i s t r i b u t i o n and i s h i g h e r than t h e va lue obta ined from a c a l c u l a t i o n of a d e t a i l e d core mock-up done by ORNL which inc luded t h e e f f e c t s of t h e exper imenta l t ubes , and i s t h e r e f o r e assumed t o be conse rva t ive . The c a l c u l a t e d va lue of t h e r a t i o o f t h e maximum- to-average co re a x i a l f l u x d i s t r i b u t i o n i s 1.23. t i v e l y sma l l value, but because of t h - i s t h e c o r e f l u x a t t h e r e f l e c t o r c o r e i n t e r f a c e w i l l have a r e l a t i v e l y h i g h va lue , and t h e f l u x va lues i n t h e r e f l e c t o r and o u t t o t h e b i o l o g i c a l s h i e l d w i l l tend t o be h i g h . Ther fore , even i f t h e a c t u a l c o r e o p e r a t i n g f l u x d i s t r i b u t i o n cannot be determined a t t h i s time, t h e va lues r e p o r t e d here shoi-lld be conse rva t ive .

The mock-up used i n Val Prod t o c a l c u l a t e t h e a x i a l f l u x d i s t r i b u t i o n inc luded a 2.75-in. t h i c k p r e s s u r e v e s s e l . The curves of t h e a x i a l f l u x d i s t r i b u t i o n through t h e pressure vessel have been e x t r a p o l a t e d t o give t h e d i s t r i b u t i o n through a 4 .0- in . v e s s e l

The c a l c u l a t i o n s were made on t h e assumption t h a t t h e r e a c t o r

T h i s i s a r e l a -

Neutron c r o s s - s e c t i o n a l va lues f o r c o n c r e t e are no t p r e c i s e b u t are t h e best va lues o b t a i n a b l e , Some of these va lues are taken from ANL-5800 where r e p r e s e n t a t i v e va lues are l i s t e d f o r s e v e r a l types of conc re t e . The slowing-down c r o s s s e c t i o n of heavy conc re t e f o r t h e fast group was c a l c u l a t e d on t h e basis t h a t t h e water c o n s t i t u e n t causes a lmost all t h e s lowing down of neu t rons . Water con ten t of t h e c o n c r e t e was obta ined from Kaiser Engineers as 3 . 3 s of t h e t o t a l weight,

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