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ANL-7092 R e a c t o r T e lcbnology (TID-4500, 46th E d . ) AEC R e s e a r c h and D eve lopmerit R e p o r t

ARGONNENATIONAL LABORATORY 9 7 0 0 South C a s s Avenue Argonne, Illinois 60440

CATALOG O F NUCLEAR REACTOR CONCEPTS P a r t I. Homogeneous and Quasi-homogeneous R e a c t o r s Section 111. R e a c t o r s F u e l e d withMoltensalt Solutions

C h a r l e s E . T e e t e r , J a m e s A. Lecky, and John H.M a r t e n s

T e c h n i c a l Pu'blications D e p a r t m e n t

S e p t e m b e r 1965

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O p e r a t e d b y The U n i v e r s i t y of Chicago under C o n t r a c t W - 3 1 - 109-eng -38 with the U. S. Atomic E n e r g y C o m m i s s i o n

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TABLE O F CONTENTS Page -Preface

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P l a n of Catalog of Nuclear R e a c t o r Concepts.

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SECTION 111. REACTORS F U E L E D WITH MOLTEN-SALT SOLUTIONS. . . . . . . . . . . . . . . . . . . . . . . . Chapter 1. Introduction.

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Chapter 2.

One-region R e a c t o r s

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Chapter 3.

Two-region R e a c t o r s

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. PREFACE This r e p o r t i s a n additional section in the Catalog of N u c l e a r R e a c t o r Concepts that was begun with ANL-6892 and continued i n ANL-6909. As i n the p r e v i o u s r e p o r t s , the m a t e r i a l i s divided into c h a p t e r s , e a c h with text and r e f e r e n c e s , plus data s h e e t s that cover the individual concepts. The planof the catalog, with the r e p o r t n u m b e r s f o r the sections a l r e a d y i s s u e d , is given on the following page.

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D r . C h a r l e s E. T e e t e r , f o r m e r l y employed by the Chicago O p e r ations Office at Argonne, Illinois, is now affiliated with the Southeastern M a s s a c h u s e t t s Technological Institute, New Bedford, M a s s . Through. a consultantship a r r a n g e m e n t with Argonne National L a b o r a t o r y , he is continuing to help guide the organization and cofnpilation of this catalog.

J.H.M. S e p t e m b e r , 1965

PLANOFCATALOGOFREACTORCONCEPTS ANL - 6 89 2

Gene r a1 Introduction Part I.

Homogeneous and Quasi-homogeneous R e a c t o r s Section I..

Particulate-fueled Reactors

ANL- 6892

Section 11.

R e a c t o r s F u e l e d with Homogeneous Aqueous Solutions and S l u r r i e s

ANL-6909

Section 111.

Part 11.

R e a c t o r s F u e l e d with Molten- salt Solutions

Section IV.

R e a c t o r s F u e l e d with Liquid Metals

Section V .

R e a c t o r s F u e l e d with U r a n i u m Hexafluoride, Gases, o r P l a s m a s

Section VI.

Solid Homogeneous R e a c t o r s

This report

Heterogeneous R e a c t o r s Section I.

R e a c t o r s Cooled by Liquid M e t a l s

Section 11.

G a s - cooled R e a c t o r s

Section 111.

Organic-cooled R e a c t o r s

Section IV.

Boiling R e a c t o r s

Section V .

R e a c t o r s Cooled by S u p e r c r i t i c a l F l u i d s

Section V I ,

W a t e r - cooled R e a c t o r s

Section VII.

R e a c t o r s Cooled by Other F l u i d s

Section VIII.

Boiling-water R e a c t o r s

Section IX.

Pressurized-water Reactors

Part 111. Miscellaneous R e a c t o r Concepts

PART I. HOMOGENEOUS,AND QUASI-HOMOGENEOUS REACTORS

SECTION 111. REACTORS F U E L E D WITH MOLTEN-SALT SOLUTIONS

Chapter 1. Introduction The r e a c t o r concepts d e s c r i b e d in t h i s section utilize a fluid f u e l consisting of a fissionable m a t e r i a l dissolved i n a c a r r i e r of molten salt. Some s u c h concepts a l s o c a l l f o r a molten s a l t a s a p r i m a r y coolant.

H. G. M a c e h e r s o n h a s reviewed the technology of m o l t e n - s a l t reactors.',' The fissionable compound usually chosen is u r a n i u m t e t r a f l u o r i d e . 2 Uranium fluorides other than the t e t r a f l u o r i d e have the disadvantages of higher volatility, instability, o r c o r rosivity. Chlorides o r f l u o r i d e s as solvents have b e e n given the m o s t c o n s i d e r a t i o n b e c a u s e of the need f o r radiation stability and high solubility. The c h l o r i d e s a r e u s e d f o r fast r e a c t o r s , and t h e f l u o r i d e s , b e c a u s e of t h e i r low c r o s s s e c t i o n s f o r t h e r mal n e u t r o n s , a r e b e s t f o r t h e r m a l and e p i t h e r m a l r e a c t o r s . Compounds o t h e r than f l u o r i d e s and c h l o r i d e s have b e e n suggested, including phosphates, s u l f a t e s , 4 sulfide^,^ hydrosulfides , 4 and hydroxides . 5 , 6 Molten fluoride m i x t u r e s , e.g. L i F - N a F , have the m o s t d e s i r a b l e p r o p e r t i e s : they d i s s o l v e adequate amounts of fuel; they have s a t i s f a c t o r y h e a t t r a n s f e r p r o p e r t i e s ; they r e s i s t radiation; they c a n t o l e r a t e a n a c c u m u lation of f i s s i o n products; the melting points a r e low enough t h a t c o r r o s i o n p r o b l e m s of e x c e s s i v e l y high t e m p e r a t u r e s a r e avoided; and the vapor p r e s s u r e s a r e low enough t o p e r m i t l o w - p r e s b u r e operation,49798Although fluorine itself h a s some m o d e r a t i n g p r o p e r t i e s , a b e t t e r m o d e r a t o r m u s t b e p r e s e n t , e i t h e r i n the m o l t e n - s a l t m i x t u r e o r as a s e p a r a t e s t r u c t u r e , to obtain a t h e r m a l r e a c t o r of r e a s o n a b l e s i z e . The a l k a l i m e t a l fluor i d e s have been e s p e c i a l l y c o n s i d e r e d a s solvents b e c a u s e they have low melting points. B e r y l l i u m fluoride m a y b e added t o the m i x t u r e as a m o d e r a t o r , and t h o r i u m t e t r a f l u o r i d e c a n be added f o r conversion. Graphite and b e r y l l i u m a r e c o m m o n l y used as s t r u c t u r e d mode:ra t o r s . D i s c u s s i o n of s t r u c t u r e d - m o d e r a t e d r e a c t o r s i n t h i s s e c t i o n m a y a p p e a r anomalous, i n t h a t m o s t r e a c t o r s i n t h i s first p a r t of the catalog have completely homogeneous c o r e s . The fuel i t s e l f , however, is a hornogeneous solution, and s u c h s t r u c t u r e - m o d e r a t e d r e a c t o r s a r e o t h e r w i s e c l o s e l y r e l a t e d to the m o r e homogeneous ones. Molten-salt r e a c t o r s c a n b e c l a s s i f i e d i n s e v e r a l w a y s - - b y the p u r p o s e of the r e a c t o r , by the u s e o r nonuse of a s e p a r a t e m o d e r a t o r , by the cooling method ( i n t e r n a l o r e x t e r n a l ) , o r by the c o r e a r r a n g e m e n t

(one- o r two-region). F o r t h i s catalog, the classification will be by oneand two-region r e a c t o r s . Chapter 2 will c o v e r the first and Chapter 3 the second. According to M a c P h e r s ~ n the , ~ m o s t a t t r a c t i v e types a r e the one-region, g r a p h i t e - m o d e r a t e d r e a c t o r : and the two-region r e a c t o r . The one-region r e a c t o r is s i m p l e r , and it i s c h e a p e r to c o n s t r u c t and o p e r a t e f o r small power s t a t i o n s . Most of the one-region r e a c t o r s d i s c u s s e d i n Chapter 2 a r e b u r n e r s . The two-region r e a c t o r h a s b e t t e r neutron economy, is b e t t e r f o r breeding, and, in l a r g e r installations, gives higher conv e r s i o n r a t i o and lower fuel-cycle c o s t s . The o r i g i n of the m o l t e n - s a l t concept i s not clear. E a r l y i n the 1950's, however, molten salts w e r e c o n s i d e r e d as r e a c t o r f u e l s to s a t i s f y the need f o r high t e m p e r a t u r e and e x t r e m e l y high power d e n s i t i e s needed f o r r e a c t o r s intended f o r n u c l e a r a i r c r a f t propulsion. Development work, p a r t i c u l a r l y at Oak Ridge National L a b o r a t o r y , r e s u l t e d i n s e v e r a l conc e p t s , and i n 1954 the A i r c r a f t R e a c t o r E x p e r i m e n t (ARE), p a r t of the A i r c r a f t Nuclear P r o p u l s i o n P r o j e c t (ANP), w a s o p e r a t e d . Since the cancellation, a s of October 1957, of work on circulating-fuel r e a c t o r s f o r a i r ~ r a f t work ,~ h a s continued a i m e d at developing power and b r e e d e r r e a c t o r s that utilize molten s a l t s . Molten-salt r e a c t o r s a r e a t t r a c t i v e concepts f o r s e v e r a l r e a s o n s . ' ~ ' ~They ~ provide high t e m p e r a t u r e s i n a l o w - p r e s s u r e s y s t e m to produce s t e a m a t t e m p e r a t u r e s high enough to give high t h e r m a l cycle efficiencies. They a r e v e r s a t i l e b e c a u s e of the r a n g e of solubilit i e s of different compounds of fissionable e l e m e n t s in salts. The s i m p l e ionic salts a r e stable under i r r a d i a t i o n . Such r e a c t o r s a l s o h a v e the advantages of other fluid-fueled r e a c t o r s ; f o r example, they have high negative t e m p e r a t u r e coefficients of r e a c t i v i t y , f i s s i o n p r o d u c t s c a n be r e moved continuously, fuel e l e m e n t s need not b e f a b r i c a t e d , and m a k e - u p fuel m a y be added as needed. According t o Weinberg," a g r e a t advantage is t h a t t h e fissionable m a t e r i a l s c a n be consumed at v e r y high thermal e f f i c i e n c i e s and with e x t r e m e l y high burnup. The m a j o r p r o b l e m with a salt-fueled r e a c t o r is that a l l the salt i n the s y s t e m m u s t be kept molten a t all times. In 1959, the Fluid F u e l R e a c t o r T a s k F o r c e c o m p a r e d the aqueous homogeneous, molten- s a l t , and l i q u i d - m e t a l fueled r e a c t o r s The p r i n cipal conclusions w e r e : the m o l t e n - s a l t r e a c t o r had the b e s t chance of achieving technical feasibility; only with the homogeneous aqueous r e a c t o r was t h e r e a possibility of achieving a r e a s o n a b l y s h o r t doubling t i m e ; and the total power c o s t s f o r the MSR w e r e between t h o s e f o r the aqueous r e a c t o r and the liquid-metal-fueled r e a c t o r e

Salt-fueled r e a c t o r s are advanced concepts, and t h e r e i s a s yet no adequate e x p e r i e n c e f o r building l a r g e - s c a l e power plants , although m a n y concepts have been developed f o r such plants e7 C u r r e n t development is r e p r e s e n t e d by the Molten Salt R e a c t o r E x p e r i m e n t , which achieved c r i ticality at ORNL i n m i d 1965.

9 References 1. H. G. M a c P h e r s o n , Molten Salt R e a c t o r s , Chapter 21 i n Reactor Handbook, Vol. IV, Engineering, S t u a r t McLain and J. H, M a r t e n s , e d s . , I n t e r s c i e n c e Division, John Wiley and Sons, New York, 1964, 2.

James A. Lane, H. G. MacPherson, and F r a n k Maslan, Fluid Fuel R e a c t o r s , Addison Wesley Publishing Co., Reading M a s s . , 1958.

3. W. S. Ginell, Molten Phosphate R e a c t o r F u e l . 5925, Atomics International, Sept. 30, 1961

P a r t I, NAA-SR-

4. R. C . C r o o k s , M. J. Snyder, and J. W. Clegg, F u s e d Salt Mixtures as Potential Liquid F u e l s f o r Nuclear Power R e a c t o r s , BMI-864, Del., Battelle Memorial Institute, Sept. 8, 1953. Decl. with del., F e b . 2 0 , 1957. 5. C. S . Dauwalter and J. Y . E s t a b r o o k , Circulating P o t a s s i u m Hydroxide R e a c t o r s , Y-F8-9, Del., ORNL, Dec. 19, 1950.

6, E. M. Simons and J. H. Stang, Engineering P r o b l e m s P e r t i n e n t to the Use of Sodium Hydroxide i n R e a c t o r s , Chemical Engineering P r o g r e s s Symposium S e r i e s . Nuclear Engineering, Part I, No. 11, Vol. 50, AIChE, New York, 1954, pp. 139-144. 7. H. G. M a c P h e r s o n to R. W. Ritzmann, Molten-Salt R e a c t o r s : R e p o r t f o r 1960 T e n - Y e a r - P l a n Evaluation, Unpublished r e p o r t , ORNL, July 25, 1960. 8. W. R. G r i m e s , F, F. Blankenship, G. W. Keilholtz, H. F. Poppendiek, and M. T. Robinson, Chemical A s p e c t s of Molten F l u o r i d e R e a c t o r s , P r o c . 2nd U.N. Int. Conf. on Peaceful Uses of Atomic EnerrTv, Geneva, 1958, 28, pp. 99-111, United Nations, New York, 1958,

9. A i r c r a f t Nuclear P r o p u l s i o n P r o j e c t . Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending D e c e m b e r 31, 1957, A. J. M i l l e r , P r o j e c t Coo r d i n a t o r , ORNL-2440, Del., ORNL, April 24, 1958, Decl. with del., Nov. 4, 1959.

1 0 . A. M, Weinberg, Advanced S y s t e m s - -A P e r s o n a l A p p r a i s a l , Nuclear Eng.- 5, No. 53, pp. 463-465, October 1960. -

11. R e p o r t of the Fluid F u e l R e a c t o r s T a s k F o r c e , TID-8507, USAEC, Feb. 1959. 1 2 . W. R. G r i m e s , Molten S a l t s as R e a c t o r M a t e r i a l s , Nuclear News 7, No. 5, pp. 3-8, May 1964.

Chapter 2. One-region R e a c t o r s Most of the one-region r e a c t o r s d i s c u s s e d in t h i s chapter a r e b u r n e r s , with highly e n r i c h e d u r a n i u m i n the molten fuel and no e x t e r n a l blanket. The c o n v e r t e r s have e i t h e r p a r t i a l l y e n r i c h e d u r a n i u m o r thor i u m salts a s f e r t i l e m a t e r i a l i n the f u e l - s a l t m i x t u r e . One-region r e a c t o r s have been c o n s i d e r e d both f o r a i r c r a f t propulsion and f o r the g e n e r a t i o n of h e a t and e l e c t r i c a l power. The ANP ( A i r c r a f t Nuclear Propulsion) P r o j e c t l e d to many concepts, and one r e a c t o r e x p e r i m e n t , ARE ( A i r c r a f t R e a c t o r E x p e r i m e n t ) , w a s o p e r a t e d f o r a s h o r t time. As p a r t of the A i r c r a f t Nuclear Propulsion P r o j e c t , s e v e r a l d e s i g n s f o r molten-salt-fueled a i r c r a f t r e a c t o r s w e r e proposed both b e f o r e and a f t e r the operation of the A i r c r a f t R e a c t o r E x p e r i m e n t . In addition to the s t u d i e s at ORNL, work w a s c a r r i e d out b y such c o n t r a c t o r s as the H. K. F e r g u s o n Company and the P r a t t & Whitney A i r c r a f t Company. In 1957, however, w o r k on circulating-fuel r e a c t o r s f o r a i r c r a f t w a s discontinued. The MSRE (Molten Salt R e a c t o r E x p e r i m e n t ) is the c u r r e n t m a j o r effort on t h i s type of r e a c t o r , with c r i t i c a l i t y achieved i n m i d 1965.

R e a c t o r s f o r Propulsion E a r l y Concepts Concepts r e p o r t e d by H. K. F e r g u s o n i n 1950 and 1951 included both r e a c t o r s fueled with molten f l u o r i d e s and a few fueled with s u s p e n s i o n s of u r a n i u m oxide i n molten sodium hydroxide. The s u s p e n s i o n s w e r e u s e d b e c a u s e of the difficulty of dissolving u r a n i u m compounds i n NaOH, T h e s e s u s p e n s i o n s are included h e r e , although they cannOt b e defined a s molten-salt solutions. In t h e Homogeneous Circulating Suspension R e a c t o r , the fuel i s a suspension of 2 . 2 wt. '70 u r a n i u m oxide i n sodium'hydroxide, which acts, as m o d e r a t o r . ' The fuel e n t e r s the top of the r e a c t o r , w h e r e a w h i r l ing motion i s i m p a r t e d t o it by v a n e s , and l e a v e s through t h e bottom to a h e a t exchanger. In a similar concept,' the fuel i s a c o a r s e s u s p e n s i o n of the 0 x i d . e i n sodium hydroxide, which c i r c u l a t e s through a s p h e r i c a l r e a c t o r . The oxide is r e m o v e d i n a cyclone s e p a r a t o r ; the liquid p a s s e s through a h e a t e x c h a n g e r , and then picks up the oxide b e f o r e r e t u r n i n g to the c o r e . c

The Circulating-fluoride Reactor, concept includes b e r y l l i u m r o d s as m o d e r a t o r and a m o l t e n fluoride fuel, which c i r c u l a t e s to a w r a p a r o u n d h e a t exchanger.' This concept w a s studied a s a v a r i a t i o n of a r e a c t o r f u e l e d with molten m e t a l .

In another concept,' the b e r y l l i u m m o d e r a t o r i s i n different f o r m s . In one, it is distributed throughout the c o r e ; in the o t h e r , it is a r e f l e c tor layer. The Circulating Moderator - coolant Reactor utilized u r a n i u m t e t r a f l u o r i d e dissolved i n a molten m i x t u r e of sodium and b e r y l l i u m fluoride^.^ Instead of a solid m o d e r a t o r , molten sodium hydroxide i s used a s m o d e r a t o r , coolant, and r e f l e c t o r . The sodium hydroxide flows downward through tubes i n the c o r e to cool the quiescent fuel s a l t . Secondary cooling is by exchange with sodium in a h e a t exchanger. The r e f l e c t o r is a jacket of the hydroxide around the c o r e . The d e s i g n power f o r this r e a c t o r is 140 MW(t). A v e r y similar r e a c t o r is the Circulatingm o d e r a t o r ARE.3 In 1952, Dayton and Chastain m a d e calculations f o r the design of one- and two-region circulating r e a c t o r s using hydroxides as m o d e r a t o r coolant^.^ The compounds studied w e r e sodium hydroxide, lithium- 7 hydroxide, and lithium-7 deuteroxide. Uranium-233 oxide, suspended i n the hydroxide within the s p h e r i c a l r e a c t o r , w a s the fuel specified. F o r the one-region r e a c t o r s , t h o r i u m oxide w a s added to the fuel f o r b r e e d ing. The conversion r a t i o s w e r e s o low that the a u t h o r s concluded that i n t e r n a l breeding would not b e f e a s i b l e if a small c r i t i c a l mass w e r e r e q u i r e d . If, however, c o s t and s i z e a r e not c o n s i d e r e d , L i 7 0 D a p p e a r s to b e the m o s t a t t r a c t i v e of the compounds. Two ORNL designs w e r e f o r a 2OO-MW(t) A i r c r a f t R e a c t o r (1951)5 and a Circulating-fuel Rea-ctor f o r D i r e c t Heat T r a n s f e r to Engines (1953).6 In the f i r s t r e a c t o r , the f u e l - - a molten m i x t u r e of b e r y l l i u m , sodiump and u r a n i u m f l u o r i d e s - - d o e s not c i r c u l a t e . It is contained i n U-tubes, which a r e within coolant tubes through which sodium c i r c u l a t e s . B e r y l l i u m oxide i s the m o d e r a t o r and r e f l e c t o r i n the cylindrical r e a c t o r . This w a s intended t o b e a f u l l - s c a l e r e a c t o r , and the ARE w a s to duplic a t e it a s f a r a s possible in m a t e r i a l s , t e m p e r a t u r e p a t t e r n , and k i n e t i c s , but not in fuel c i r c u l a t i o n o r power. In the second r e a c t o r , hot fuel c i r culates f r o m the c o r e d i r e c t l y to the a i r c r a f t engine; o t h e r w i s e t h i s r e a c t o r i s similar i n m a n y r e s p e c t s to the f i r s t . The A i r c r a f t R e a c t o r E x p e r i m e n t The ARE w a s built at Oak Ridge National L a b o r a t o r y as a circulating-fuel r e a c t o r of low power and high t e m p e r a t u r e , but materials suitable f o r u s e i n a r e a c t o r of high power w e r e employede7-9 According t o Weinberg, "The purpose of t h i s r e a c t o r e x p e r i m e n t w a s s i m p l y to gain e x p e r i e n c e i n handling salts i n a r e a c t o r at v e r y high t e m p e r a t u r e s , to s e e whether one could i n f a c t contain the intensely radioactive circulating fuel, and to study the kinetic behavior of the r e a c t o r . " "

Before the circulating fuel w a s decided upon, solid fuel pins and stagnant fluoride f u e l s w e r e considered.ll Stagnant f l u o r i d e fuel w a s u s e d i n the f i r s t design." The c o r e would have a cylindrical m o d e r a t o r matrix, containing v e r t i c a l h o l e s into which small fuel tubes would b e placed. This a s s e m b l y would be within a cylindrical p r e s s u r e s h e l l , through which sodium would b e p a s s e d . A s l a b of boron c a r b i d e would b e placed at the top of t h e l a t t i c e , and t h e fuel tubes would extend through the s l a b , which would a c t as a "neutron c u r t a i n " f o r control. S e v e r e p r o b l e m s , however, m a d e t h i s concept l e s s a t t r a c t i v e than a circulating-fuel r e a c t o r . The molten salts have poor t h e r m a l conductivity. The e x t r e m e l y l a r g e t h e r m a l g r a d i a n t at r e a s o n a b l y high power l e v e l s would m a k e the t e m p e r a t u r e of the fuel n e a r the c e n t e r of the tube prohibitively high. T h e r e would be difficult i e s i n loading the r e a c t o r . Also, during loading, l a r g e control r o d s would b e needed, and the h e a t cycling and draining of coolant between fuel additions would pose m a n y p r o b l e m s + Expansion during melting might b e a p r o b l e m r e l a t i v e to possible deformation (expansion) o r rupture The final fuel w a s u r a n i u m t e t r a f l u o r i d e dissolved i n a m i x t u r e of sodium and z i r c o n i u m f l u o r i d e s . B e r y l l i u m oxide w a s the m o d e r a t o r and r e f l e c t o r ; blocks of it w e r e stacked around the fuel t u b e s , tubes for. r e f l e c t o r cooling, and control a s s e m b l i e s t h a t p a s s e d v e r t i c a l l y through the c o r e . The fuel took a s e r p e n t i n e path through p a r a l l e l c i r c u i t s to the outside of the c o r e , finally leaving at the bottom. It c i r c u l a t e d to a n e x t e r n a l h e a t exchanger then back to the c o r e . Sodium p a s s i n g through tubes in the m o d e r a t o r cooled it. B a r r e n fuel salt a l s o had b e e n sugg e s t e d as coolant. The m a x i m u m d e s i g n power w a s 2-5 MW(t).lZ,l3 The r e a c t o r b e c a m e c r i t i c a l on November 11, 1954, and it w a s shut down the following evening. It had d e m o n s t r a t e d the feasibility of using a h i g h - t e m p e r a t u r e fluoride fuel i n a circulating-fuel r e a c t o r 14 e

A r e a c t o r with a t a n d e m h e a t exchanger w a s suggested as a modification of the ARE.15 The m o d e r a t o r - r e f l e c t o r i s w a t e r o r sodium hydroxide, with the c o r e and the tandem h e a t exchanger being s u r r o u n d e d b y a l a y e r of w a t e r at 300-350 p s i . The fuel e n t e r s the r e a c t o r at t h e top, m a k e s a loop through fuel tubes in the r e a c t o r , and exits t o h e a t exc h a n g e r s , The m o d e r a t o r e n t e r s the l a t t i c e around the p e r i p h e r y at thle r e a r of the r e a c t o r and flows to a n outlet at the f o r w a r d end. In another modification, the fuel-coolant salt c i r c u l a t e d through the coolant t u b e s i n the B e 0 r k f l & e t o r bk the ARE.'6 Iri this modification, t h e r e would b e a l a r g e r leakage of high-energy n e u t r o n s and of g a m m a radiation than with b a r r e n fuel s a l t as m o d e r a t o r coolant.

The F i r e b a l l and Related Concepts A concept that originated before the operation of the ARE and w a s scheduled f o r u s e i n l a t e r developments w a s a circulating-fuel, r e f l e c t o r m o d e r a t e d r e a c t o r , known originally a5 the F i r e b a l l . I 7 , l 8 In t h i s r e a c t o r t h e r e a r e no fuel tubes. The fuel c i r c u l a t e s i n a n annulus between a central i s l a n d of b e r y l l i u m m o d e r a t o r and a n outer shell of m o d e r a t o r and r e f l e c t o r . In the e a r l i e s t design the c e n t r a l i s l a n d w a s s p h e r i c a l , but l a t e r development r e s u l t e d in a v a s e - s h a p e d is1and.l8 This shape, a c cording t o F r a a s , r e d u c e s the c r i t i c a l mass, i m p r o v e s power d i s t r i b u tion, and hydrodynamically gives the b e s t p a s s a g e f o r fuel.â&#x20AC;? Cooling is by circulating the fluid s a l t to a c i r c u m f e r e n t i a l wraparound h e a t exchanger between the m o d e r a t o r s h e l l and the p r e s s u r e s h e l l . T h e r e h e a t t r a n s f e r to sodium o r sodium-potassium t a k e s place. The fuel p a s s e s downward i n the annulus, then outward. The m o d e r a t o r is cooled by sodium flowing downward between the b e r y l l i u m and the enclosing s h e l l . Fraas and Savolainen have d i s c u s s e d eight c o r e designs f o r the s p h e r i c a l r e f l e c t o r - m o d e r a t e d r e a c t o r , with a wraparound h e a t exchanger, that a r e r e l a t e d to the F i r e b a l l . â&#x20AC;? The s i m p l e s t design is the c o r e in which a thick s p h e r i c a l m o d e r a t o r shell s u r r o u n d s a s p h e r i c a l c h a m b e r f o r liquid fuel. The s h e l l h a s t o p and bottom ducts f o r fuel to p a s s i n and out of the c o r e . B e c a u s e of a b s o r p t i o n of n e u t r o n s n e a r the f u e l - r e f l e c t o r i n t e r f a c e , power density d e c r e a s e s t o a c o m p a r a t i v e l y low value n e a r the c e n t e r . A l s o , the flow p a t t e r n is i n d e t e r m i n a t e . Vanes o r s c r e e n s at the i n l e t might i m p r o v e the flow. Adding a c e n t r a l i s l a n d r e d u c e s c r i t i c a l mass and gives a m o r e u n i f o r m power distribution. The m o d e r a t o r , however, m u s t be cooled i n this design. Liquid b i s m u t h o r l e a d could b e c i r c u l a t e d between the fuel and m o d e r a t o r regions to r e m o v e the heat. Graphite w a s suggested i n two o t h e r modifications. A block of graphite containing p a r a l l e l p a s s a g e s f o r fuel flow i s placed i n the c e n t r a l zone t o give a n e a r l y homogeneous m i x t u r e of fuel and graphite i n the c o r e . Concentric s h e l l s of graphite could b e u s e d as m o d e r a t o r and as guides f o r the fuel flow. The a u t h o r s concluded t h a t t h e s e d e s i g n s w e r e l i t t l e b e t t e r , f r o m the n u c l e a r standpoint, than the s i m p l e c o r e with no moderator structure. T h r e e designs w e r e f o r the u s e of molten sodium hydroxide a s a liquid m o d e r a t o r . In onet the m o d e r a t o r p a s s e s through coiled tubes i n the c o r e . The tubes would both s e r v e as m o d e r a t o r i n the c o r e and improve distribution of fuel velocity. It would, however, be difficult to avoid l o c a l hot s p o t s , and the s t r u c t u r a l m a t e r i a l would c a p t u r e a high

p e r c e n t a g e of n e u t r o n s , so t h a t the c r i t i c a l mass would b e i n c r e a s e d . In two other modifications, fuel p a s s e s through tubes and the hydroxide m o d e r a t o r c i r c u l a t e s through s p a c e s between fuel p a s s a g e s , In one design, the tubes a r e s t r a i g h t . In the o t h e r , they a r e c u r v e d to f i t the shell cont o u r s , i n o r d e r to r e d u c e the volume of h e a d e r regions and to give a m o r e n e a r l y s p h e r i c a l c o r e shape, with lower shield weight. 4

Some concepts t h a t have employed the F i r e b a l l d e s i g n with little change a r e the A i r c r a f t R e a c t o r T e s t , â&#x20AC;? The Circulating F l u o r i d e - fuel High F l u x R e a c t o r , â&#x20AC;? and a modified F i r e b a l l concept of G e n e r a l E l e c t r i c . 22 In the High-flux Rea-ctor,, which includes a c e n t r a l i s l a n d of graphite, u s e of a l a y e r of bismuth between the c e n t r a l island and the fuel l a y e r was suggested by the author to r e s i s t flow of t h e r m a l n e u t r o n s f r o m the c e n t r a l island, w h e r e they a r e c r e a t e d , to the s h e l l , w h e r e they a r e a b s o r b e d , It would a l s o p r o t e c t the i n t e r n a l island f r o m g a m m a radiation. Pratt & Whitney concepts w e r e originally v a r i a t i o n s and developm e n t s of the F i r e b a l l design, with changes i n the dimensions and o t h e r f a c t o r s to give r e a c t o r s of different power levels.23924In two s i m p l i f i e d v e r s i o n s z 5 the annulus of the F i r e b a l l is r e p l a c e d by five tubes i n the c e n t e r of the c o r e . In one, the c o r e i s a graphite cylinder and i n the o t h e r it i s a b e r y l l i u m s p h e r e . The d e s i g n w a s intended to give m o r e s t r u c t u r a l stability and to alleviate p r o b l e m s of flow sepasation. G r a p h i t e w a s u s e d to obtain m o r e favorable c r i t i c a l mass And power d i s t r i b u tion. The b e r y l l i u m - m o d e r a t e d concept w a s developed into a m o r e c o m p l e t e d e s i g n O z 6In another modification, the i s l a n d is cylindrical, r a t h e r than v a s e shaped a s i n the original Other v a r i a t i o n s c o n s i d e r e d b r i e f l y w e r e the u s e of b e r y l l i u m , b e r y l l i u m oxide, o r graphite f o r the island and f o r the r e f l e c t o r , and using and not using a r e f l e c t o r Alterriative f u e l s c o n s i d e r e d w e r e lithium o r b e r y l l i u m f l u o r i d e s as b a s e s f o r f u e l s , and s l u r r i e s of u r a n i u m dioxides i n alkali metalsmZ4 Lithium-7 w a s c o n s i d e r e d a s a coolantJz4and z i r c o n i u m hydride a s a m o d e r a t o r .

The u s e of z i r c o n i u m hydride as a m o d e r a t o r w a s i n c o r p o r a t e d i n one concepte2* The c o r e c o n s i s t s of fuel tubes and z i r c o n i u m hydride r o d s , with l i t h i u m - 7 flowing p a r a l l e l to the t u b e s , Two a r r a n g e m e n t s clf fuel tubes w e r e studied. In one, a multitube a r r a n g e m e n t , , the fuel flows down through the i n n e r tubes then r e t u r n s through the o u t e r t u b e s , In the o t h e r , a thimble-tube design, the fuel flows through a n i n n e r tube and r e t u r n s through the annulus between t h i s tube and a n enclosing o u t e r tube. Lithium-7 could c i r c u l a t e d i r e c t l y t o the engine r a d i a t o r The hydride m o d e r a t o r , which would b e clad with molybdenum, is c l a i m e d to permit. high t e m p e r a t u r e without t h e need f o r e x c e s s i v e cooliag o r s t r u c t u r a l support. In 1955, staff m e m b e r s at the W a l t e r Kidde Nuclear L a b o r a t o r i e s , Inc ., published d e s i g n s f o r y e a c t o r s f o r a i r c r a f t p r o p u l ~ i o n . ~ ~

One r e a c t o r w a s s i m i l a r to a n e a r l i e r concept of H. K, F e r g u s o n Co. The fuel i s stationary, within t u b e s . A g r e a t m a n y t u b e s a r e r e quired b e c a u s e they m u s t b e small to avoid e x c e s s i v e i n t e r n a l t e m p e r a t u r e s . Heat r e m o v a l would be difficult b e c a u s e of the poor conductivity of the molten salts. T h r e e w e r e c i r c u l a t i n g - m o l t e n - s a l t r e a c t o r s , two c l o s e l y r e sembling e a r l i e r concepts. They included a r e a c t o r having the F i r e b a l l s t r u c t u r e , with a modification in which the c o r e i s cylindrical r a t h e r than s p h e r i c a l ; a circulating-fluoride r e a c t o r with r o d s of b e r y l l i u m m o d e r a t o r i n the c o r e ; and a circulating-fluoride r e a c t o r with molten sodium hydroxide a s m o d e r a t o r and r e f l e c t o r An ORSORT concept, the Screwball (1953), differed f r o m the F i r e ball chiefly i n that helical fuel tubes r e p l a c e d the annular p a s s a g e b e tween the c e n t r a l i s l a n d , which w a s eliminated, and the m o d e r a t o r shellO3' Thus it somewhat r e s e m b l e s the Pratt & Whitney concept d e s c r i b e d i n Ref. 26. The m o d e r a t o r is circulating NaOD. According to the a u t h o r s , p r o b l e m s with the F i r e b a l l design indicated need f o r changes. The S c r e w ball design is c l a i m e d to eliminate o r alleviate all but one, namely, p r e s s u r e s u r g e s . Use of fuel tubes r e d u c e s uncertainty of sustained i n s t a b i l i t i e s i n fuel region. "Self-shielding" should be l e s s with the tubes than with the s p h e r i c a l fuel annulus of the F i r e b a l l . L o w e r power density (2.5 kW/cm3) was chosen to a i d p r o b l e m s of questionable fuel density. Removal of the solid island e l i m i n a t e s the need to cool it. The p r e s s u r e s u r g e p r o b l e m w a s not alleviated. S u r g e s m a y be l a r g e r with Screwball b e c a u s e of the tortuous expansion path out of the c o r e , but p r e s s u r e is not expected to be g r e a t enough to c a u s e difficulty. Substitution of c i r c u lating NaOD l e a d s to p r o b l e m s with c o r r o s i o n ; stagnant o r low-velocity l a y e r s of NaOD next to hot fuel tubes o r containing s h e l l , t h e r e f o r e , m u s t not o c c u r R e a c t o r f o r Ship Propulsion ORSORT students designed a molten- salt r e a c t o r f o r s h i p propulsion, which contained m a n y of the f e a t u r e s of the a i r c r a f t r e a c t o r conc e p t ~ . ~A' compact, h i g h - p e r f o r m a n c e r e a c t o r w a s sought i n o r d e r to r e d u c e weight. In the cylindrical r e a c t o r c o r e , the m o d e r a t o r i s a n a r r a y of Inconel-clad b e r y l l i u m oxide r o d s tipped with poison material to r e d u c e end leakage and fissioning in the e n t r a n c e and exit plenums f o r the fuel. The fuel flows up through the c e n t r a l c o r e region, then down through a n annular downcomer at the c o r e p e r i p h e r y . T h e r e it e n t e r s a wraparound h e a t exchanger, which i s cooled by molten salt. This 125-MW(t) r e a c t o r h a s a nickel r e f l e c t o r , as well as extensive shielding.

An advanced design of t h i s type of r e a c t o r w a s conceived by the s a m e group to i m p r o v e r e a c t o r p e r f o r m a n c e and r e d u c e weight. To improve moderation i n the c o r e , the d e s i g n e r s substituted z i r c o n i u m hydride

f o r b e r y l l i u m oxide a s m o d e r a t o r and used a beryllium-containing fuel. Nickel-molybdenum cladding was substituted f o r Inconel cladding i n the c o r e b e c a u s e thinner cladding could be used to r e d u c e the amount of poison i n the c o r e . In the r e s u l t i n g design, dimensions and power level w e r e reduced.

R e a c t o r s f o r E l e c t r i c a l Power and Heat Even b e f o r e the A i r c r a f t R e a c t o r E x p e r i m e n t was c a r r i e d out, s o m e o n e - r e g i o n r e a c t o r s had been proposed f o r p u r p o s e s other than a i r c r a f t propulsion. Development of such r e a c t o r s h a s continued. They include s o m e designs that g e n e r a l l y r e s e m b l e the ARE i n c o r e s t r u c t u r e . E a r l y Concepts An e a r l y concept, on which l i t t l e h a s been published, i s f o r a t h o r i u m c o n v e r t e r f o r e l e c t r i c a l power production, which was developed by Davidson and R ~ b b .In~t h~i s c o n v e r t e r , the fuel i s a solution of 93 p e r c e n t e n r i c h e d U235F4i n molten f l u o r i d e s containing t h o r i u m fluor i d e f o r conversion. F o u r concepts, by students at the Oak Ridge School of R e a c t o r Technology, a r e intended f o r power and h e a t , and one is a b r e e d e r . The F u s e d Salt R e a c t o r f o r P o w e r and Heat, proposed i n 1953, could be e i t h e r a b u r n e r o r c o n v e r t e r , with t h o r i u m fluoride added to the molten salt if conversion is d e s i r e d . 3 3 The c o r e i s a graphite s p h e r e , t h r o u g h which fuel c i r c u l a t e s f r o m the bottom through chann e l s cut into the graphite. The graphite is clad with a n Inconel shell and is contained i n a n Inconel p r e s s u r e v e s s e l . The r e a c t o r i s designed f o r installation at r e m o t e locations to produce power--about 5 MW(t)-and heat. The h e a t is produced by w a t e r heated by l o w - p r e s s u r e w a s t e g a s f r o m the turbine. In the F u s e d Salt B r e e d e r R e a c t o r (FSBR),34the f u e l i s a solution of u r a n i u m - 2 3 3 fluoride and t h o r i u m fluoride i n fused l i t h i u m - 7 f l u o r i d e and b e r y l l i u m f l u o r i d e . Stacked graphite blocks f o r m the c o r e , , which h a s a s p h e r i c a l top, a f l a t bottom, and cylindrical s i d e s . The fuel p a s s e s through p a s s a g e s i n the g r a p h i t e and through h e a t e x c h a n g e r s in the g r a p h i t e surrounding the c o r e . The fuel p a s s e s to inter'mediate h e a t e x c h a n g e r s cooled by sodium. Two s i z e s w e r e c o n s i d e r e d , one f o r 125 MW(e') and ohe f o r 250 MW(e). The 6 0 0 - M W F u s e d Salt Homogeneous R e a c t o r P o w e r u t i l i z e s a fuel salt of f l u o r i d e s of uranium-235, z i r c o n i u m , and sodium. The r e a c t o r i s s t a t e d to b e self-moderating b e c a u s e of the fluorine.

The r e a c t o r v e s s e l i s a v e r t i c a l cylinder, with a dished bottom, of s t a i n l e s s s t e e l . The fuel c i r c u l a t e s through the m u l t i p a s s v e s s e l upward to a sodium loop within the v e s s e l , to a n annular U-tube h e a t e x c h a n g e r s and to a secondary heat exchanger. The desigsL of this b u r n e r could be a l t e r e d s o a s to b r e e d uranium-235. The F u s e d Salt R e a c t o r f o r P r o c e s s Heat (1956)36h a s two f e a t u r e s that differ somewhat f r o m previous d e s i g n s . The aim w a s to g e n e r a t e as m u c h heat as possible i n the regions of the r e a c t o r not b e a r i n g f u e l and to u s e a c e r a m i c as both m o d e r a t o r and heat-exchange m e d i u m f o r hight e m p e r a t u r e heat e x c h a n g e r s . Magnesium oxide w a s chosen as the b e s t available m a t e r i a l to m e e t both r e q u i r e m e n t s , even though it is not a v e r y good m o d e r a t o r . The r e a c t o r c o n s i s t s of a cylindrical m a t r i x of hexagonal m a g n e s i u m oxide blocks p e n e t r a t e d by Inconel tubes i n a triangular a r r a y . Fuel c i r c u l a t e s through t h e s e tubes B e r y l l i u m oxide r e f l e c t o r s u r r o u n d s the c o r e , and a s t e e l p r e s s u r e v e s s e l i s the cont a i n e r . Of the 400 Ivfw(t) produced by the r e a c t o r , 35 Mw is g e n e r a t e d i n the MgO m o d e r a t o r and is u s e d to h e a t s t e a m f r o m h e a t e x c h a n g e r s . The m o d e r a t o r is p e r f o r a t e d to allow p a s s a g e of s t e a m . The r e m a i n i n g heat i s r e m o v e d by the fuel circulating t o e x t e r n a l h e a t e x c h a n g e r s . The d e s i g n is f o r four r e a c t o r s to b e used i n conjunction with a c o a l hydrogenation plant. The h i g h - t e m p e r a t u r e s t e a m f r o m the m o d e r a t o r would b e u s e d t o gasify coal to produce hydrogen f o r the hydrogenation. The remaining s t e a m , a t a lower t e m p e r a t u r e , would be u s e d to d r i v e turbines e

The u s e of n a t u r a l convection h a s been suggested to e l i m i n a t e the p r o b l e m of providing r e l i a b l e , long-lived pumps f o r fuel c i r c u l a t i o n , 37,38 This advantage is a t the c o s t of a g r e a t e r fuel volume. The fuel c i r c u l a t e s by n a t u r a l convection through the c o r e , v e r t i c a l convection r i s e r s , and p r i m a r y h e a t e x c h a n g e r s . In the design suggested, the c o r e i s s p h e r i c a l , with the p r i m a r y h e a t exchanger above the c o r e . The heat-exchange m e d i u m m a y b e e i t h e r molten salt o r h e l i u m . E i t h e r would give a power of 2 2 MW(e). This s y s t e m m a y b e a t t r a c t i v e f o r s o m e applications b e c a u s e of e a s y maintenance and good reliability. Molten l e a d i s suggested as coolant i n a n ORNL concept of 1958039 The only m o d e r a t o r i s the fluorine i n the fuel salt--NaF-ZrF$-,UF4. The molten l e a d c i r c u l a t e s the fuel salt b y d i r e c t mixing with a j e t pump. Heat exchange is r a p i d and no p r i m a r y exchanger i s needed. The l e a d i s s e p a r a t e d f r o m the s a l t d o w n s t r e a m by a pipeline s e p a r a t o r ; the f u e l goes to the c o r e , the l e a d to a h e a t exchanger. The d e s i g n power i s 194 MW(e).

The MSRE and Related Concepts B e f o r e the design of the MSRE w a s decided upon, o t h e r concepts originated f r o m the Molten Salt R e a c t o r P r o j e c t at Oak Ridge National

I 1

L a b o r a t o r y . Two that w e r e developed furthe st w e r e the Slightly Enriched, Fused-Salt-Fueled R e a c t o r and the Experimental Molten-Salt-Fueled 30 MW(t) Power R e a c t o r . P r e d e c e s s o r s to MSRE The Slightly Enriched, Fused-Salt-Fueled R e a ~ t o r ~ O -i ~ s ’a c o n v e r t e r fueled with slightly e n r i c h e d u r a n i u m t e t r a f l u o r i d e dissolved i n molten lithium fluoride and b e r y l l i u m fluoride. It w a s proposed i n 1958, and a p r e l i m i n a r y d e s i g n w a s published i n 1959. The cylindrical c o r e i s of unclad g r a p h i t e , which s e r v e s a s m o d e r a t o r . The fuel flows upward through holes i n the graphite. Highly enriched u r a n i u m is added a s m a k e u p fuel. The r e a c t o r produces 315 MW(e). The E x p e r i m e n t a l Molten-Salt- Fueled 30 - MW(t) Power R e a ~ t o r ~ ” ’ ~ ~ is a b u r n e r fueled with highly e n r i c h e d u r a n i u m t e t r a f l u o r i d e dissolved in molten l i t h i u m fluoride and b e r y l l i u m fluoride. T h e r e i s no o t h e r m o d e r a t o r . The c o r e i s a s p h e r e of INOR-8. The fuel c i r c u l a t e s to a h e a t exchanger. B a r r e n molten s a l t - - l i t h i u m f l u o r i d e - b e r y l l i u m fluoride- -is the s e c o n d a r y coolant. MSRE The Molten Salt R e a c t o r E ~ p e r i m e n t is ~ ~the - ~ f~i r s t of the t h r e e s t a g e s i n the development of m o l t e n - s a l t r e a c t o r s d i s c u s s e d by M a c P h e r s o n i n 1960.47 After t h i s one-region r e a c t o r , a two-region r e a c t o r e x p e r i m e n t w a s planned, and a high-power prototype of a m o l t e n - s a l t r e a c t o r would follow. The MSRE h a s the objectives of showing that a c i r c u l a t i n g moltensalt-fuel s y s t e m w i l l o p e r a t e s u c c e s s f u l l y and demonstrating a reactor type t h a t c a n be developed into a n advanced c o n v e r t e r o r t h e r m a l b r e e d e r . It a l s o is intended to d e m o n s t r a t e that unclad graphite is a s a t i s f a c t o r y m o d e r a t o r that c a n b e u s e d i n contact with molten s a l t s f o r extended p e r i o d s and that o n - s i t e hydrofluorination p r o c e s s i n g c a n c l e a n up contaminated fuel. The MSRE i s a c o n v e r t e r , with the possibility of i n t e r n a l b r e e d i n g . In s t r u c t u r e i t r e s e m b l e s t h e A i r c r a f t R e a c t o r E x p e r i m e n t m o r e c l o s e l y than such later a i r c r a f t r e a c t o r developments as the F i r e b a l l . The mocte r a t o r c o n s i s t s of v e r t i c a l s t r i n g e r s of g r a p h i t e , which f o r m a c’y1indric:al c o r e within a r e a c t o r v e s s e l . The fuel p a s s e s downward i n a n annulus between the g r a p h i t e cylinder and the contkining v e s s e l . It then flows upward i n channels f o r m e d between the s t r i n g e r s , out the top to a h e a t exchanger ( i n which the i n t e r m e d i a t e coolant is L i F - B e F 2 ) , and back to the c o r e .

Advanced Concept The u s e of molten f l u o r i d e s as fuel i n a lO-MW(e) f a s t r e a c t o r f o r s p a c e c r a f t was considered by Allen.48 Calculations w e r e m a d e to e s t i m a t e the s i z e and weight of such a r e a c t o r and to c o m p a r e t h e m with those of a r e a c t o r fueled with u r a n i u m c a r b i d e . Highly e n r i c h e d (93.5 p e r c e n t ) u r a n i u m tetrafluoride w a s the fuel, with fluorides of sodium, b e r y l l i u m , lithium, and zirconium c o n s i d e r e d as solvents. The fuel m i x t u r e f o r which calculations w e r e m a d e is 70 p e r c e n t UF4, 30 p e r c e n t NaF. Lithium is the coolant, and the r e a c t o r is unmoderated, with a n inner r e f l e c t o r of zirconium and an outer r e f l e c t o r of b e r y l l i u m . The author concluded that u r a n i u m fluoride does not have a n a p p a r e n t a d vantage o v e r u r a n i u m c a r b i d e ; it d o e s not achieve the full potential of liquid f u e l s f o r the purpose; and other liquid f u e l s , such as liquid m e t a l s , should b e studied.

Status The Molten Salt R e a c t o r E x p e r i m e n t apparently is the only c u r r e n t active p r o g r a m f o r developing molten- salt r e a c t o r s . Construction is i n p r o g r e s s , and c r i t i c a l i t y w a s achieved i n 1965.49 The one-region r e a c t o r i s m e a n t as a n i n t e r m e d i a t e s t e p in developing a l a r g e tworegion b r e e d e r , but one-region r e a c t o r s have a l s o b e e n suggested f o r u s e s i n t h e i r own right, especially i n s m a l l e r power s t a t i o n s . 47

DATA SHEETS

ONE -REGION REACTORS

No. 1 Homogeneous Circulating Suspension R e a c t o r b

H. K. F e r g u s o n Co.

R e f e r e n c e : Unpublished r e p o r t , H. K. F e r g u s o n Co., Dec. 12, 1950. Originators: Staff of Atomic E n e r g y Division, K a r l Cohen, D i r e c t o r . Status: Design, 1950. Details: Thermal. n e u t r o n s , steady s t a t e , b u r n e r . Fuel-coolant: suspension of 2.2 wt 70 U23502i n NaOH. Moderator: NaOH. F u e l suspension c i r c u l a t e s to e x t e r n a l h e a t exchanger; s e c o n d a r y coolant: Na. Reflector: 6 in. Iriconel in 3 laminated s h e l l s around c o r e . Core: cylinder, within s p h e r i c a l p r e s s u r e v e s s e l . F u e l suspension e n t e r s t o p of r e a c t o r , where whirling motion is imp a r t e d to it, and l e a v e s through opening in bottom of c o r e , to shell-and-tube heat exchanger. Shielding: tank of b o r a t e d H20; Pb; plastic. Control: negative t e m p e r a t u r e coefficient; s h i m r o d - - 3 concentric c y l i n d e r s of boron s t e e l , H20 filled, located in nickel-plated Z r thimble through v e r t i c a l a x i s of c o r e . Power: 270 MW(t>. P r o b l e m s : high f r e e z i n g point of NaOH delays s t a r t u p and shutdown; NaOH c o r r o s i v e ; stability of s l u r r y under i r r a d k t i o n questionable. Code: 0313 17 31312 44 637 711 84677 921 101 81111

No. 2 Homogeneous Circulating F u e l - m o d e r a t o r S l u r r y R e a c t o r H. K. F e r g u s o n Co. R e f e r e n c e : Unpublished r e p o r t , H. K. F e r g u s o n Co., 1950. o r i g i n a t o r s : Staff of Atomic E n e r g v Division, K a r l Cohen, D i r e c t o r . Status: P r e l i m i n a r y study 1950; abandoned. Details: S i m i l a r t o concept in Data Sheet No. 1. C o a r s e suspension of UOZ in molten NaOH c i r c u l a t e s through s p h e r i c a l r e a c t o r . Fuel is r e m o v e d in cyclone s e p a r a t o r . Liquid goes through h e a t exchanger, then picks up fuel and r e t u r n s to c o r e . Secondary coolant: Na, NaK, o r NaOH. 921 101 Code: 0313 17 31312 44 637 711 84677 81111 v

No. 3 Circulating-fluoride R e a c t o r

H.K. F e r g u s o n Co. Reference: Unpublished r e p o r t , J u n e 1, 195 1. Originators: Staff of Atomic E n e r g y Division, K a r l Cohen, D i r e c t o r . Status: Design, 1951. Details: T h e r m a l neutrons, steady s t a t e , b u r n e r . Fuel-coolant: UF, d i s solved in molten N a F - B e F , 3.4 wt 70 U. Moderator: Be r o d s , 2 in. d i a m e t e r , clad with s t a i n l e s s s t e e l . F u e l c i r c u l a t e s to w r a p around heat exchanger. Core: cylinder, 42 by 4 2 in. Reflector: 2 in. of m o d e r a t o r r o d s . Control: negative t e m p e r a t u r e coefficient, v e r t i c a l l y moving c o n t r o l r o d s ; e a c h r o d filled with molten P b - C d alloy; r o d s i n t h i m b l e s . P o w e r (Max.): 152 MW(t). Code: 0313 15 31211 44 627 711 81112 921 104 . 84679

No. 4 Circulating-fuel, Disper s e d - m o d e r a t o r R e a c t o r

H. K. F e r g u s o n Co. Reference: Unpublished r e p o r t , H. K. F e r g u s o n Co., 1950. Originators: Staff of Atomic E n e r g y Division, K a r l Cohen, D i r e c t o r . Status: P r e l i m i n a r y study, 1950; abandoned. Details: T h e r m a l n e u t r o n s , steady s t a t e , b u r n e r . V a r i a t i o n of a liquidmetal-fueled r e a c t o r . Fuel-coolant: molten m i x t u r e of U, Na, and Be fluorides. Moderator: Be o r B e 0 d i s t r i b u t e d throughout c o r e . F u e l c i r c u l a t e s through r e a c t o r to heat exchanger cooled by Na, K, o r Li. P o w e r (for liquid-metal fuel): 200 MW(t). Code: 0 3 1 3 15 31211 4X 627 7XX 84679 9X 104

No. 5 Circulating-fuel, R e f l e c t o r - m o d e r a t o r R e a c t o r

H. K. F e r g u s o n Co. Reference: Unpublished r e p o r t , H.K. F e r g u s o n Co., 1950. O r i g i n a t o r s : Staff of Atomic E n e r g y Division, K a r l Cohen, D i r e c t o r . Status: P r e l i m i n a r y study, 1950; abandoned. Details: S a m e a s concept i n Data Sheet No. 4 except t h a t Be o r B e 0 m o d e r a t o r is r e f l e c t o r l a y e r in the s p h e r i c a l r e a c t o r . 15 31211 4X 627 7XX 84679 921 104 Code: 0313

25 No. 6 Circulating Moderator -coolant R e a c t o r H. K. F e r g u s o n Co. Reference: HKF--112. Originators: Staff of Atomic E n e r g y Division, K a r l Cohen, D i r e c t o r . Status: Design, August 1951. Details: T h e r m a l neutrons, steady s t a t e , b u r n e r . Fuel: UF, (18 wt 70 U235) dissolved in molten s a l t - - 4 0 m o l 7'0 NaF-60 m o l % ' BeF2. Moderator-coolant: molten NaOH. R e a c t o r : v e r t i c a l cylinder, 32 in. d i a m e t e r , 32 in. high, with small, c l o s e l y spaced Inconel tubes in t r i a n g u l a r -pitch lattice. F u e l expansion c h a m b e r connected to top and bottom of c o r e . Reflector: 4-in. jacket of NaOH around c o r e ; 10 in.. NaOH i n top and bottom h e a d e r s . NaOH coolant flows downward through tubes i n c o r e . F u e l is in s p a c e between tubes. NaOH goes to heat exchanger f o r h e a t exchange with Na. Control: s h i m control- -negative t e m p e r a t u r e coefficient; fine control- - single r o d , along axis of c o r e , consisting of v e r t i c a l annular r o d filled withmolten Pb-Cd. Power: 140 MW(t). Code: 0313 17 31112 44 627 711 84677 921 106 81112

No. 7 C i r c u l a t i n g - m o d e r a t o r ARE H. K. F e r g u s o n Co. Reference: H K F - 112. Originators: Staff of Atomic E n e r g y Division, K a r l Cohen, D i r e c t o r Status: Design, August 1951. Details: C l o s e l y r e s e m b l e s "Circulating Moderator -coolant R e a c t o r , I' Data Sheet No. 6. T h e r m a l n e u t r o n s , steady s t a t e , b u r n e r . Fuel: m o l t e n UF,NaF - B e F z containing 3 4070 uranium. Moderator - coolant: circulating m o l t e n NaOH. Reflector: NaOH, 8 in. thick top and bottom, 4 in. thick at circ:umf e r e n c e . R e a c t o r : cylinder, 32 by 32 in. Quiescent fuel is on s h e l l s i d e of coolant t u b e s , through which NaOH flows at 890 gpm. Inlet t e m p e r a t u r e : 1409OF; outlet: 14 19'F ( a v e r a g e ) . NaOH g o e s to h e a t exchangers. Control: s h i m - -negative t e m p e r a t u r e coefficient, varying l e v e l of fuel; fine - -axial c o n t r o l rod. Power: 1 MW(e). Code: 0313 17 31112 44 627 711 84677 921 106 8111X e

No. 8 Unreflected Homogeneous R e a c t o r Moderated bv Sodium Hydroxide Battelle M e m o r i a l Institute Reference: BMI - 746. Originators: R. W. Davton and J . W. Chastain. Status: Design calculations, 1952. Details: Steady s t a t e , t h e r m a l n e u t r o n s , c o n v e r t e r . F u e l - m o d e r a t o r - coolant: homogeneous m i x t u r e of U23302, NaOH, and T h o z . Mixture p r e s u m a b l y c i r c u l a t e s to e x t e r n a l heat exchanger. C o r e container: z i r c o n i u m s p h e r e . C o r e t e m p e r a t u r e : 1100'F. No r e f l e c t o r . Calculations indicated that i n t e r n a l breeding not f e a s i b l e i f small c r i t i c a l mass is r e q u i r e d . Code: 0311 17 31312 45 637 756 84677 91 101 v

No. 9 Unreflected Homogeneous R e a c t o r Moderated by Lithium- 7 Hydroxide Battelle M e m o r i a l Institute R e f e r e n c e : BMI-746. O r i g i n a t o r s : R. W. Dayton and J . W. Chastain. Status: Design calculations, 1952. Details: S a m e as concept i n Data Sheet No. 8, except t h a t Li70H is used ins t e a d of NaOH. Code: 0312 17 31312 45 637 756 84677 9 1 ' 101

No. 10 Unreflected Homogeneous R e a c t o r Moderated b y Lithium- 7 Deuteroxide Battelle M e m o r i a l Institute R e f e r e n c e : BMI-746. O r i g i n a t o r s : R. W. Dayton and J . W. Chastain. Status: Design calculations, 1952. Details: S a m e a s concept in Data Sheet No. 8, except t h a t Li70D is u s e d ins t e a d of NaOH. Code: 0312 17 31312 45 637 756 84677 91 101

No. 11 200-MW(t) A i r c r a f t R e a c t o r ORNL

R e f e r e n c e : Unpublished r e p o r t , ORNL, 195 1. Originators: StafE of ORNL ANP P r o j e c t . Status: P r e l i m i n a r y design, 195 1, P r o j e c t cancelled, 1957. Details: I n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . Fuel: molten BeF2NaF-UF,. M o d e r a t o r and r e f l e c t o r : BeO. Coolant: Na, p r i m a r y and second a r y . Core: 3 f t s q u a r e cylinder with ellipsoidal ends. Inconel p r e s s u r e shell. 2268 p a r a l l e l coolant tubes, spaced b y p e r f o r a t e d and dimpled d i s k s , r u n along long axis of c o r e . In e a c h coolant tube a r e 3 U-tubes (0.100 in. d i a m e t e r ) containing fuel. L e g s of e a c h U-tube connected to s e p a r a t e inlet and outlet h e a d e r s . F u e l does not c i r c u l a t e . Control: negative t e m p e r a t u r e coefficient; s h i m control by varying volume of fuel. P o w e r : 200 MW(t). T h i s r e a c t o r intended to b e f u l l - s c a l e r e a c t o r for which the ARE was to duplicate, as far as possible, m a t e r i a l s , t e m p e r a t u r e p a t t e r n , and kinetics. 15 31103 44 627 711 84679 921 106 Code: 0213 83 189

No. 12 Circulating-fuel R e a c t o r f o r D i r e c t Heat T r a n s f e r to Engine ORNL R e f e r e n c e : Unpublished r e p o r t , 1953. O r i g i n a t o r s : R. W. Schroeder and B. Lubarsky. Status: P r e l i m i n a r y design, 1953. P r o j e c t cancelled, 1957. Details: I n t e r m e d i a t e n e u t r o n s , s t e a d y s t a t e , b u r n e r Fuel-coolant: molten f l u o r i d e s containing UF,. Moderator: BeO. Reflector: BeO, cooled b y c i r culating b a r r e n molten fluorides. Core: p a r a l l e l tubes a r r a n g e d i n concent r i c c i r c l e s within a cylinder, 40.4 in. d i a m e t e r , with conical and truncated ends. E a c h c o r e tube is s u r r o u n d e d by h o t - p r e s s e d BeO. Around c o r e is B e 0 r e f l e c t o r . C o r e h a s two manifolds to allow two-pass flow of fuel. Incone1 s t r u c t u r a l m a t e r i a l f o r all m e t a l l i c p a r t s i n contact with fuel o r with m o d e r a t o r coolant. F u e l flows i n through c e n t e r of inlet, p a s s e s through tubes, and l e a v e s through annuli between f u e l inlet and wall. Control: negative t e m p e r a t u r e coefficient; power demand; fuel d r a i n a g e for shutdown. Shielding: P b , plastic, HZO. P o w e r : 640 MW(t)o D i r e c t flow of hot fuel to engine e l i m i n a t e s liquid-liquid h e a t exchanger but m a k e s p r o b l e m s i n shielding. 15 31211 44 627 711 84679 921 104 Code: 0213 e

No. 13 A i r c r a f t R e a c t o r E x p e r i m e n t with Stagnant F u e l ORNL R e f e r e n c e : Nuclear Sci. and Eng. 2,No. 6, pp. 804-825, Nov. 1957. Originators: E. S. Bettis, R. W. S c h r o e d e r , G. A. C h r i s t y , H. W. Savage, R. G. Affel, and L. F. Hemphill. Status: Design; abandoned f o r circulating-fuel r e a c t o r . Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . Fuel: molten- salt m i x t u r e containing UF,. Moderator: BeO. Coolant: Na. Core: c y l i n d r i c a l matrix of B e 0 with small v e r t i c a l h o l e s f o r fuel tubes. C o r e within p r e s s u r e shell. F u e l r e m a i n s within tubes. Na pumped through p r e s s u r e shell. Control: poison r o d s within matrix; s l a b of B4C at top of l a t t i c e . F u e l t u b e s a r e not completely filled at design p r e s s u r e and z e r o power, but f u e l l e v e l extends above B4C. I n c r e a s e i n t e m p e r a t u r e expands m o r e fuel above B4C f o r fast control. Difficulties: at r e a s o n a b l y high power, high t h e r m a l gradient in molten salt c a u s e s fuel i n c e n t e r of t u b e s t o r e a c h p r o hibitively high t e m p e r a t u r e s ; difficulties in loading fuel at r o o m t e m p e r a t u r e - - p h a s e changes of fuel during heating might r u p t u r e fuel tubes, l a r g e c o n t r o l r o d s would be needed, and heat cycling and draining of coolant between f u e l additions would pose m a n y p r o b l e m s . 627 711 8111X 921 106 Code: 0413 15 31103 44 83 189

No. 14 A i r c r a f t R e a c t o r E x p e r i m e n t (ARE) '

ORNL

2, No. 1, F e b . 1'357, R e f e r e n c e s : ORNL-1845, Del.; Nuclear Sci. and Eng. ppo 797-853, C F - 5 3 - 12-9. Originators: First suggested by R. C. B r i a n t . P r o j e c t d i r e c t e d by h i m until h i s death, and subsequently d i r e c t e d b y W. H. J o r d o n and S. J . C r o m e r . Status: C r i t i c a l , October 1954. F i n a l shutdown, November 1954, Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r s F u e l coolant: circulating m i x t u r e of 93-470 e n r i c h e d U235as U F 4 in N a F and Z r F 4 . M o d e r a t o r and r e f l e c t o r : B e 0 blocks stacked around fuel tubes, r e f l e c t o r cooling t u b e s , and c o n t r o l a s s e m b l i e s . I n n e r m o s t section: about 3 ft diame t e r x 3 f t high c y l i n d r i c a l c o r e . B e 0 in f o r m of small hexagonallymachined blocks, split axially. F u e l c i r c u l a t e d i n closed loop through 6 p a r a l l e l c i r c u i t s a t inlet f u e l header at top of r e a c t o r c o r e ; each c i r c u i t m a k e s 11 s e r i e s of p a s s e s through c o r e , s t a r t i n g at c o r e axis and p r o g r e s s i n g i n s e r p e n t i n e fashion to p e r i p h e r y of c o r e , finally leaving at the bottom of the c o r e . F u e l c i r c u l a t e d to e x t e r n a l heat exchanger and back to c o r e . Reflector coolant: Na, p a s s e d up through r e f l e c t o r tubes, cooling r e f l e c t o r and Inconel p r e s s u r e s h e l l and filling m o d e r a t o r i n t e r s t i c e s b e f o r e leaving c o r e . Na a l s o h e l p s t r a n s f e r h e a t r e a d i l y f r o m m o d e r a t o r t o fuel stream. Control: one r e g u l a ting and 3 v e r t i c a l s h i m r o d s of s l u g s of h o t - p r e s s e d B4C c l a d in s t a i n l e s s s t e e l ; negative t e m p e r a t u r e coefficient. M a x i m u m power: 2.5 MW(t). 15 31211 44 627 711 81161 921 104 Code: 0413 84679

No. 15 A i r c r a f t R e a c t o r with T a n d e m Heat Exchanger ORNL Reference: ORNL- 1227, O r i g i n a t o r s : ANP staff. Status: Pr e l i m i n a r y de sign, 1952; discontinued. Details: T h e r m a l and i n t e r m e d i a t e neutrons, s t e a d y s t a t e , b u r n e r Fuel: molten f l u o r i d e s . M o d e r a t o r - r e f l e c t o r : HZO or NaOH. Cooling: c i r c u l a tion of fuel t o h e a t exchanger. R e a c t o r and h e a t exchanger in tandem. R e a c t o r h o r i z o n t a l cylinder. C o r e and heat exchanger s u r r o u n d e d by 1/2-in. l a y e r o f H z 0 at 300-350 p s i . F u e l e n t e r s r e a c t o r at top r e a r , m a k e s a c o m plete loop through fuel t u b e s i n c o r e , and d i s c h a r g e s to h e a t exchanger. F u e l tubes: s t a i n l e s s s t e e l , 1$ in, ID, 0,015 in. wall thickness. M o d e r a t o r e n t e r s a c t i v e lattice a r o u n d p e r i p h e r y at r e a r of r e a c t o r and flows toward outlet at f o r w a r d end. If HzO is m o d e r a t o r , double-wall construction i s used. R e a c t o r v e s s e l s u r r o u n d e d b y about 4 ft HZO. Control: 2 c u r t a i n s of 5 0 Cd r o d s mounted on two e n d l e s s t r a c k s ; c u r t a i n s m o v e f r o m r e f l e c t o r into a c t i v e lattice; e a c h r o d is cylinder, 12 in. long, 1/2 in. OD, 1/4 in. ID. P o w e r : 400 M W ( t ) . 711 84677 921 104 Code: 0413 13 31211 44 627 8 12 12 17

No. 16 F i r e b a l l , E a r l y Design ORNL Reference: Y - F 1 0 - 104. Originators: Suggested b y R. C. B r i a n t t o A. P. Fraas, who worked out details. Status: P r e l i m i n a r y design calculations; p r o j e c t cancelled 1957. Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . F u e l coolant: molt en fluoride s containing u r a n i u m . Moderator - ref lector: Be 0, graphite, o r circulating m o d e r a t o r of NaOD. F u e l c i r c u l a t e s to e x t e r n a l heat exchanger. Structure: 3 concentric s p h e r e s of B e 0 o r graphite. BeO: (90% BeO, 10% Na) c e n t r a l s p h e r e , 14 in. d i a m e t e r ; fuel-coolant shell, 4 in. thick, 22 in. OD. Reflector: 1 f t thick, 46 in. OD. Graphite: c e n t r a l s p h e r e 18 in. d i a m e t e r ; fuel-coolant shell: 6 in. d i a m e t e r . Reflector: 12 in. d i a m e t e r . Graphite r e d u c e s moderating power, with m o r e leakage of fast neut r o n s . Deuterium-bearing compound could be added to graphite to m a k e it equivalent to BeO, o r circulating r e f l e c t o r of NaOD might be used. Island d e c r e a s e s c r i t i c a l mass and i n c r e a s e s uniformity of fissioning density. Control: negative t e m p e r a t u r e coefficient. 12 31211 44 627 711 84677 923 104 Code: 0413 15 17

No. 17 Reflector -moderated Circulating-fuel R e a c t o r ( F i r e b a l l ) ORNL

R e f e r e n c e s : Y - F 1 0 - 104; ORNL- 1515. O r i g i n a t o r s : Suggested by R . C. B r i a n t to A. P oF r a a s , who worked out de tails Status: Design i n c o r p o r a t e d in A i r c r a f t R e a c t o r T e s t ; project cancelled 1957. Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , one-region b u r n e r Fuel-coolant: molten fluorides containing about 2 m o l % uranium. Moderator: Be shell. F u e l c i r c u l a t e s to heat exchanger; s e c o n d a r y coolant: NaK; m o d e r a t o r cooled by Na. Reflector: Be m o d e r a t o r shell, 12 in. thick. Around r e f l e c t o r is 1 in. boron c a r b i d e . R e a c t o r v e s s e l : four c o n c e n t r i c s h e l l s . Two i n n e r s h e l l s s u r r o u n d c o r e region and s e p a r a t e it f r o m va.seshaped island of Be i n c e n t e r of r e a c t o r . Outer Be m o d e r a t o r - r e f l e c t o r s h e l l s u r r o u n d e d by m a i n p r e s s u r e shell. F u e l - r e g i o n d i a m e t e r : 21 in. f o r 200 MW(t) r e a c t o r . P r i m a r y construction m a t e r i a l : Inconel. F u e l c i r c u l a t e s downward through annulus between two i n n e r m o s t s h e l l s , where f i s s i o n o c c u r s , then downward and outward to c i r c u m f e r e n t i a l s p h e r i c a l heat exchanger that is between m o d e r a t o r s h e l l and p r e s s u r e shell. F u e l flows upward i n heat exchanger t o top, where it e n t e r s the t o p of the annular p a s s a g e leading back t o the c o r e . M o d e r a t o r cooled by Na flowing downward in annulus b e between Be and enclosing s h e l l s and back upward through p a s s a g e s i n the Be to e x t e r n a l h e a t e x c h a n g e r s . V a s e - s h a p e d island used b e c a u s e it r e d u c e s c r i t i c a l mass, i m p r o v e s power distribution in fuel region, and hydrodynami c a l l y gives b e s t p a s s a g e f o r fuel. Shielding: p r e s s u r e s h e l l , P b shielding, t h e r m a l insulation, and b o r a t e d water in self- sealing r u b b e r tank. C o n t r o l (suggested): fine--one o r two r o d s i n c e n t r a l r e g i o n o r i n r e f l e c t o r ; c o a r s e s h i m - -negative t e m p e r a t u r e coefficient. Power: 200 MW (t). Code: 0413 15 31211 44 627 711 8111X 923 104 84679

No. 18 F i r e b a l l without C e n t r a l Island ORNL R e f e r e n c e : Unpublished r e p o r t , ORNL, Dec. 3, 1954. O r i g i n a t o r s : A. P. Fraas and A. W. Savolainen. Status: Part of g e n e r a l design survey; p r o j e c t discontinued, 1957. Details: S a m e as F i r e b a l l , but without c e n t r a l island. Code: 0413 15 31211 44 627 711 8111X 921 104 84679

No. 19 F i r e b a l l Cooled by Lead o r Bismuth ORNL Reference: Unpublished r e p o r t , ORNL, Dec. 3, 1954. Originators: A. P. Fraas and A. W. Savolainen. Status: Part of g e n e r a l design survey; p r o j e c t discontinued, 1957. Details: S a m e as F i r e b a l l , except that liquid P b o r B i coolant c i r c u l a t e s between f u e l and m o d e r a t o r regions. Code: 0413 15 31211 44 627 711 8111X 923 104 31105 84679 31106

No. 20 G r a p h i t e - m o d e r a t e d F i r e b a l l ORNL R e f e r e n c e : Unpublished r e p o r t , ORNL, Dec. 3, 1954. Originators: A. P. Fraas and A. W. Savolainen. Status: P a r t of g e n e r a l design survey; p r o j e c t discontinued, 1957. Details: S a m e as F i r e b a l l , except that g r a p h i t e is m o d e r a t o r , e i t h e r as block i n c e n t r a l zone with holes f o r fuel p a s s a g e , o r a s concentric shell. 12 31211 44 627 711 8111X 923 104 Code: 0413 84679

No. 21 F i r e b a l l Moderated with Sodium Hvdroxide ORNL R e f e r e n c e : Unpublished r e p o r t , ORNL, Dec. 3, 1954. Originators: A. P. Fraas and A. W. Savolainen. Status: Part of g e n e r a l design survey; p r o j e c t discontinued, 1957. Details: S a m e a s F i r e b a l l , except that m o l t e n NaOH is m o d e r a t o r NaOH e i t h e r c i r c u l a t e s through coiled t u b e s i n c o r e o r through s p a c e s between f u e l p a s s a g e s . T u b e s a r e e i t h e r s t r a i g h t o r c u r v e d to f i t s h e l l contours. 17 31211 44 627 711 8111X 923 109 Code: 0213 84679

No. 22 A i r c r a f t R e a c t o r T e s t ORNL Reference: ORNL- 1835. Originators: R. C. B r i a n t , A. P. Fraas, e t al. Status: Design, 1953; project cancelled 1957. Details: T h e r m a l and i n t e r m e d i a t e neutrons, steady s t a t e , b u r n e r . Fulelcoolant: m o l t e n N a F - Z r F - U F 4 (50-46-4 m o l yo) o r N a F - K F - L i F - U F 4 (1 1-42-44-3 m o l yo); enrichment: 93.570 U235. Secondary coolant: NaK. M o d e r a t o r - r e f l e c t o r : Be, 12 in. thick. Reflector coolant: Na. S t r u c t u r e of r e a c t o r s a m e as for F i r e b a l l , with s p h e r i c a l c e n t r a l island of Be and outer Be r e f l e c t o r , and out of c o r e . F u e l c i r c u l a t e s downward between inner Be island and o u t e r Be r e f l e c t o r , and out of c o r e . Then fuel flows upward through h e a t exchanger region, which is around s p h e r i c a l c o r e . F u e l is d i s c h a r g e d downward into c o r e . Heat is t r a n s f e r r e d i n heat e x c h a n g e r s to1 the s e c o n d a r y coolant. Reflector cooled by Na flowing downward through p a s s a g e s in Be andupward through annular s p a c e between Be and enclosing s h e l l s . C e n t r a l Be island cooled s i m i l a r l y except that the Na e n t e r s through bottom of i s l a n d and r e t u r n s to top of r e a c t o r through cooling p a s s a g e s in m a i n p r e s s u r e shell. C o r e d i a m e t e r : 21 in.; island d i a m e t e r : 11 in. F u e l r e g i o n thickness: 4.5 in. Reflector thickness: 72 in. Shielding: 7 in. b o r ated HZO; 3 1 in. HZO. Control: negative t e m p e r a t u r e coefficient; s h i m control: one r o d , 5yo Ak/k. P o w e r : 60 MW(t). Code: 0413 15 31211 44 627 711 84679 923 104 81XlX

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No. 23 Circulating F l u o r i d e - f u e l High-flux R e a c t o r ORNL \ J

Reference: CF-56-6-9 Rev. 2. Originator: W. K. E r g e n . Status: P r e l i m i n a r y design data, 1956. Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . Fuel: solution of 0.167 m o l 70 U235F4i n NaZrFt;. M o d e r a t o r - r e f l e c t o r : graphite. Coolant: p r e s u m a b l y , c i r c u l a t i o n of fuel solution t o e x t e r n a l h e a t exchanger. Core: s p h e r i c a l s h e l l embedded in infinite m o d e r a t o r . C e n t r a l island of graphite. C o r e radius: 50 c m . F l u x at c e n t e r of s p h e r e : 3 x neutrons/ cmz. Contr 01: negative t e m p e r a t u r e coefficient; p r e poisoning o r c o n t r o l x c e s s reactivity. L a y e r of B i between c e n t r a l island and f u e l l a y e r suggested t o r e s i s t flow of n e u t r o n s f r o m c e n t r a l island, where they a r e c r e a t e d , to s h e l l , w h e r e they a r e a b s o r b e d . It would a l s o s e r v e as a g a m m a shield f o r protecting the i n t e r n a l column. P o w e r : 444 MW(t). Code: 0413 12 31211 44 627 711 84679 923 104 8 15XX 81XlX

No. 24 R e f l e c t o r - m o d e r a t e d L F - 1 through LF-6 G e n e r a l E l e c t r i c . Company Reference: APEX- 135. Originators: W. C. Coolev and C. Hussev, , -ANP P r o i e c t . Status: De sign study, 19 53. Details: F i r e b a l l modification. T h e r m a l and i n t e r mediate neutrons , steady s t a t e , b u r n e r . Fuel-coolant: m i x t u r e of f l u o r i d e s , e i t h e r "Fulinak" (Li, Na, K, and U f l u o r i d e s ) o r "Fubeli" (Be, Li, and U f l u o r i d e s ) containing 93.470 e n r i c h e d U235 as UF,. M o d e r a t o r - r e f l e c t o r : Be. Annular c o r e region b e tween 9-in. OD i n t e r n a l Be m o d e r a t o r island and 18-in. ID e x t e r n a l Be r e flector. Reflector: 12-in. thick, with 48 in. d i a m e t e r s p h e r i c a l contour, around which i n t e r m e d i a t e h e a t exchanger is located. Secondary coolant: Na o r NaK. S t r u c t u r a l m a t e r i a l : Inconel. F u e l flows downward through annitlar c o r e passage and r e t u r n s upward outside the NaK tubes i n the i n t e r mediate h e a t exchanger to the pump section. F u e l inlet t e m p e r a t u r e : 1000'F; outlet: 1500'F. Reflector and m o d e r a t o r cooled by Na. Control: negative t e m p e r a t u r e coefficient; c o n t r o l r o d in the c e n t r a l Be island for fine control; a n additional r o d m a y be installed. Concept is identical f o r L F - 1 , - 2 , -3, -4, -5, and -6, except f o r power produced: L F - 1 , 76 MW; LF-2, 1 0 1 MW; L F - 3 , 115 MW; L F - 4 , 135 MW; L F - 5 , 180 MW; and LF-6, 232 MW. Code: 0413 15 31211 44 627 711 81111 923 104 84679 v

No. 25 300-MW Circulating-fuel R e a c t o r

Pratt & Whitney A i r c r a f t Division, United A i r c r a f t C o r p . R e f e r e n c e s : Unpublished r e p o r t s , 1953-54. Originators: Staff m e m b e r s . Status: Design calculations; work discontinued 1957. Details: Modification of F i r e b a l l . I n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . Fuel-coolant: molten NaUF5 NaZrF, (3.26 mol 7'0 UF,). Modera t o r : Be. F u e l c i r c u l a t e s to c i r c u m f e r e n t i a l heat exchanger. F i r e b a l l s t r u c t u r e with i n t e r n a l island of Be and Be m o d e r a t o r - r e f l e c t o r . C o r e volume: 127 l i t e r s . Be island: 6.69 in. OD. Inconel-clad p r e s s u r e shell: 34.3 in. OD. Shield: Inconel, with boron t h e r m a l shield. Control: probably negative coefficient of r e a c t i v i t y and probably v e r t i c a l l y moving c o n t r o l r o d in m o d e r a t o r , as with F i r e b a l l . Power: 300 MW(t). Code: 0 2 1 3 , 15 31211 44 627 711 84679 923 104 8 lXlX

No. 26 C o r e - m o d e r a t e d R e a c t o r (PWAR-7) Pratt & Whitney A i r c r a f t Division, United A i r c r a f t Corp.

i I

Reference: Unpublished r e p o r t , 1957. Originators: Staf:f m e m b e r s . Status: P r e l i m i n a r y design, 1956; work discontinued, 1957. Details: ' F i r e b a l l type. Intermediate neutrons, steady s t a t e , b u r n e r . F u e l coolant: N a F - Z r F - U F , , containing 3 m o l 70 UF,. Moderator: Be. F u e l c i r c u l a t e s to c i r c u m f e r e n t i a l NaK heat exchanger. Be island. Reflector: 7 in. Be. C o r e d i a m e t e r : 29 in.; length: 37 in. P r e s s u r e shell: o v e r a l l height, 5 ft; OD, 6 2 in. Inconel s t r u c t u r e . Max. fuel t e m p e r a t u r e : 1600'F. Control: p r e s u m a b l y negative t e m p e r a t u r e coefficient. Power: 190 MW(t). Design f o r twin r e a c t o r s . Suggestions to i n c r e a s e power and d e c r e a s e weight. F u e l s : LiF- o r B e F i - b a s e d fluorides, o r s l u r r i e s of u r a n i u m oxide in alkaline- e a r t h m e t a l s . Coolant: Li7. S t r u c t u r a l m a t e r i a l s : Mo; Mo0.4570 Ti; Nb-0.6570 Z r ; FP-16 (2370 Ni, 1470 Mo, 870 C r , 170 Al, 2.570 T i ) . Code: 0213 15 31211 44 627 711 84679 923 104

No. 27 Modified F i r e b a l l ( E a r l v Concept f o r C o r e - m o d e r a t e d R e a c t o r ) P r a t t & Whitney A i r c r a f t Division, United A i r c r a f t Corp. Refe r enc e s: Unpublished r e p o r t s , 19 54. O r i g i n a t o r s : Staf.f m e m b e r s . Status: Design calculations, 1954; project discontinued, 1957. Details: Same as F i r e b a l l , except t h a t fuel annulus is r e p l a c e d by five tubes with end d i f f u s e r s , in a c i r c u l a r p a t t e r n , which p a s s through the c o r e . In one, the t u b e s p a s s through a graphite cylinder within a Be c o r e . Graphite is believed to give b e t t e r c r i t i c a l mass and power distribution. In the (other design, the fuel p a s s a g e s a r e through the s p h e r i c a l Be c o r e , which is within a n Inconel p r e s s u r e v e s s e l . T h i s modification of the fuel p a s s a g e is believed to r e d u c e flow- s e p a r a t i o n p r o b l e m s and t o give m o r e s t r u c t u r a l stability. Code: 0213 15 31211 44 627 711 81XlX 923 104 84679

No. 28 Circulating F u e l C o r e - m o d e r a t e d R e a c t o r (CMR)

Pratt & Whitney A i r c r a f t Division, United A i r c r a f t Corp. Reference: PWAC- 186. Originators: Staff m e m b e r s . Status: Design, 1956; project discontinued, 1957. Details: Intermediate neutrons, steady s t a t e , b u r n e r . Fuel-coolant: enriched U F 4 in molten NaF-ZrF4. Moderator: Be. F u e l c i r c u l a t e s to wraparound NaK heat exchanger between r e f l e c t o r and p r e s s u r e shell. Reflector: Be. Core: e s s e n t i a l l y cylinder of Be (29.1 in. d i a m e t e r , 37 in. high) through which 30 s t r a i g h t p a r a l l e l tubes (3 in. ID) p a s s . F u e l e n t e r s c o r e f r o m plenum c h a m b e r above, p a s s e s downward through f u e l tubes, e n t e r s plenum at bottom, and flows on s h e l l side of h e a t exchanger. F u e l e n t e r s c o r e at 1200'F; l e a v e s at 1600'F. C o r e and r e f l e c t o r cooled by Na flow. I n t e r n a l shield: c e r m e t of Bi째C and Cu, clad with Inconel, between r e f l e c t o r s h e l l and r e f l e c t o r support shell. Control: c e n t r a l v e r t i c a l r o d , in thimble, for r e a c t o r s h i m and c o n t r o l - - r o d is clad c e r m e t of Bi째C and Cu cooled with He; negative t e m p e r a t u r e coefficient. P o w e r : 190 MW(t>. Two r e a c t o r s t o be u s e d i n t a n d e m .

U s e of m o d e r a t o r in c o r e expected t o

lower fuel r e q u i r e m e n t s . Using tubes instead of annulus f o r fuel expected to eliminate unpredictable and possibly unfavorable flow and h e a t - t r a n s f e r c h a r a c t e r i s t i c s of the o r i g i n a l F i r e b a l l c o r e . A c y l i n d r i c a l r a t h e r than s p h e r i c a l c o r e should simplify s t r u c t u r a l and f a b r i c a t i o n p r o b l e m s . Code: 0213 15 31211 44 627 711 81111 923 104 84679

No. 29 Circulating F u e l , Reflector - m o d e r a t e d , Epithermal, Aircraft Reactor ~

P r a t t & Whitney A i r c r a f t Division, United A i r c r a f t Corp. Reference: PWAC- 189. Originators: Staff m e m b e r s . Status: Design, 1956; discontinued, 1957. Details: F i r e b a l l s t r u c t u r e . I n t e r m e d i a t e n e u t r o n s , s t e a d y s t a t e , b u r n e r . Fuel-coolant: N a F - Z r F , - U F 4 (56.3, 37.2, 6.570); u r a n i u m 93.570 e n r i c h e d . Moderator: Be. C o r e components cooled by Na. Reflector: Be, 48 in. OD. F u e l annulus: 6 in. thick. Inner island is cylindrical, 8 in. d i a m e t e r . P r e s s u r e shell: s p h e r e , 70 in. d i a m e t e r . F u e l e n t e r s c o r e at 1200째F, c i r c u l a t e s downward then outward and upward and l e a v e s at 1600'F t o NaK wraparound h e a t exchanger. I n t e r n a l shielding: s h e l l s containing B1'. Control: c e n t r a l v e r t i c a l rod, cooled by He, consisting of r a r e e a r t h oxides in Ni matrix, clad with Hastelloy-X; negative t e m p e r a t u r e coefficient. Power: 194 MW(t). Two r e a c t o r s to be used in t a n d e m f o r a i r c r a f t propulsion. 15 31211 44 627 711 81114 923 104 Code: 0213 84679

No. 30 D i r e c t - c i r culating, Zirconium Hydride - m o d e r a t e d R e a c t o r

Pratt & Whitney A i r c r a f t Division, United A i r c r a f t Cprp. R e f e r e n c e : Unpublished r e p o r t , 19 56. Originators: Staff m e m b e r s . Status: Design, 1956; p r o j e c t discontinued, 1957. Details: T h e r m a l and i n t e r m e d i a t e neutrons, steady s t a t e , b u r n e r Fuel: u r a n i u m salt in molten fluorides, possibly LiF- o r B e F - b a s e d . Moderator: ZrHX. Coolant: Li7. Core: fuel t u b e s and Z r H r o d s , clad with Mo. Coolant flows p a r a l l e l t o t u b e s . In one design, the fuel flows down through t u b e s in c e n t e r , goes to a h e a d e r , and r e t u r n s through outer tubes. In a l t e r n a t i v e , f u e l flows down through inner tube and up through annulus f o r m e d by e n c l o s ing i n n e r tube with a n outer one. Li7 coolant could flow d i r e c t l y to a n engine r a d i a t o r . Use of ZrHX p e r m i t s high t e m p e r a t u r e without need f o r e x c e s s i v e cooling o r s t r u c t u r a l support. Code: 0413 17 31106 44 627 711 84679 9XX 106 e

No. 31 Stationary F l u o r i d e F u e l , Sodium Cooled, Reflector - m o d e r a t e d R e a c t o r Walter Kidde Nuclear L a b o r a t o r i e s , Inc. R e f e r e n c e : WKNL-42. O r i g i n a t o r s : Staff m e m b e r s . Status: Design f o r evaluation, 1955. P r o j e c t discontinued, 1957. Details: S i m i l a r to H. K. F e r g u s o n concept in Data Sheet No. 6. T h e r m a l n e u t r o n s , steady s t a t e , b u r n e r . Fuel: e i t h e r U235 o r U233 in m o l t e n KF-'7 UF,). Stationary fuel is i n t u b e s . Using N a F - Z r F 4 - U F 4 m i x t u r e (4 m o l 0 u233 i n s t e a d of U235 i n c r e a s e s coolant volume and r e d u c e s fuel r e q u i r e d , but increases a v e r a g e h e a t flux excessively. I n c r e a s i n g U235 concentration to 27.5 m o l 70 a l s o would i n c r e a s e fuel volume, but b e c a u s e of d e c r e a s e d t h e r m a l conductivity would r e q u i r e m o r e than t h r e e t i m e s as m a q y f u e l e l e m e n t s , 68,400 instead of 20,400. Supporting s o m a n y with p a r a l l e l flow of coolant would be v e r y difficult. Coolant: Na. Difficulties: difficult h e a t r e m o v a l b e c a u s e of poor t h e r m a l conductivity of the molten salts; b e c a u s e t u b e s m u s t be small to avoid e x c e s s i v e i n t e r n a l t e m p e r a t u r e s , m a n y tubes a r e required. 1X 31103 44 627 711 8XXXX 9XX 106 Code: 0313

No. 32 B e r y l l i u m C o r e Moderated, Circulating F l u o r i d e - f u e l R e a c t o r Walter Kidde Nuclear L a b o r a t o r i e s , Inc. Reference: WKNL-42. Originators: Staff m e m b e r s . Status: Design for evaluation, 1955. P r o j e c t discontinued. Details: T h e r m a l neutrons, steady s t a t e , b u r n e r . Fuel-coolant: molten f l u o r i d e s - - 5 0 . 8 m o l 70 NaF, 46.8 m o l 70 Z r F 4 , 2.4 m o l 70 UF,. M o d e r a t o r : 1630 Inconel-clad Be r o d s , 0.88 in. OD, 42 in. long, i n c o r e . Annular h e a t exchanger. R e a c t o r container: 64-in. ID multiwall Inconel s h e l l with dished bottom; cooling channels i n wall. Core: c i r c u l a r cylinder, 72 in. by 72 in. F u e l flows downward p a r a l l e l to r o d s , upward through Na-cooled h e a t exchanger, and back to c o r e through pumps. Reflector: 4-in. blanket of 885 Be r o d s cooled by fuel. F u e l inlet t e m p e r a t u r e : 1500째F, outlet (max), 1150'F. Control: negative t e m p e r a t u r e coefficient; 13 b o r a t e d s t e e l c o n t r o l r o d s i n Inconel t h i m b l e s extending f r o m t o p of r e a c t o r s h e l l into c o r e , replacing like number of m o d e r a t o r r o d s . P o w e r : 300 MW(t). 15 31211 44 627 711 81111 921 104 Code: 0313 84679

No. 33 B e r y l l i u m Reflector Moderated, Circulating F l u o r i d e - f u e l R e a c t o r Walter Kidde Nuclear L a b o r a t o r i e s , Inc. Reference: WKNL-42. Originators: Staff m e m b e r s . Status: Design f o r evaluation, 1955; p r o j e c t discontinued. Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . F u e l coolant: m o l t e n fluorides--50 m o l 70 NaF, 46.2 m o l 70 Z r F 4 , 3.8 mol 70 UF,, M o d e r a t o r - r e f l e c t o r : clad Be. F i r e b a l l s t r u c t u r e . Island: 12 in. OD; R e f l e c t o r : 24.4 in. ID, 48.4 in. OD; Inconel p r e s s u r e shell: 69 in. OD. F u e l c i r c u l a t e s f r o m c o r e annulus, up through wraparound Na-cooled heat exc h a n g e r , and back to top of c o r e . Island and r e f l e c t o r cooled by s e p a r a t e Na s y s t e m . Control: negative t e m p e r a t u r e coefficient; v e r t i c a l r o d through c e n t e r of island. P o w e r : 300 MW(t). Alternative design: c y l i n d r i c a l r e f l e c t o r to avoid difficulties of fabricating s p h e r i c a l r e f l e c t o r . M o d e r a t o r shell, island, and fuel annulus as i n s p h e r i c a l design. 711 8111X 923 104 Code: 0413 15 31211 44 627 84679

No. 34 Sodium Hvdroxide C o r e Moderated, Circulating Fluoride-fuel R e a c t o r

. i

Walter Kidde Nuclear L a b o r a t o r i e s , Inc Reference: WKNL- 42. Originators: Staff m e m b e r s . Status: Design f o r evaluation, 1955. P r o j e c t discontinued. Details: T h e r m a l neutrons, steady s t a t e , b u r n e r . Fuel-coolant: molten f l u o r i d e s - - 5 1 . 1 m o l 70 NaF, 47.0 m o l 70 Z r F 4 , 1.0 m o l 70 UF,. F u e l c i r c u l a t e s to Na-cooled heat exchanger. Moderator: m o l t e n NaOH in 98 Inconel U - t u b e s , 2 in. OD, 42 in. long. Moderator c i r c u l a t e d to e x t e r n a l Na-cooled h e a t exchanger. Reflector: 4 in. thick annulus containing NaOH. Core: c i r c u l a r cylinder, 42 by 42 in. P r e s s u r e shell: 70 in. OD. F u e l inlet t e m p e r a t u r e : 1150OF; outlet (max) 1765OF. Control: negative t e m p e r a t u r e coefficient; 4 v e r t i c a l b o r a t e d s t e e l c o n t r o l r o d s . P o w e r : 300 MW(t). Code: 0313 17 31211 44 627 711 81111 921 104 84677

No. 35 R e f l e c t o r - m o d e r a t e d , Circulating-fuel A i r c r a f t R e a c t o r (Screwball) ORSORT Reference: CF-53-9-84. Originators: J . H. MacMillan e t all Status: P r e l i m i n a r y design study f o r feasibility; ORSORT t e r m paper, 1953. Details: Modification of F i r e b a l l . T h e r m a l and i n t e r m e d i a t e neutrons, steady s t a t e , b u r n e r . Fuel: molten m i x t u r e of 50 m o l yo NaF, 47 m o l 70 ZrF,, and 3 m o l 70 enriched UF,. Moderator: circulating molten NaOD. Coolant: NaK. Reflector: s p h e r i c a l Be shell, 11 in. thick, 2 in. OD. Structure: s p h e r i c a l , with Be shell, p r e s s u r e shell, and h e l i c a l f u e l tubes in annular f o r m . Inconel s t r u c t u r a l m a t e r i a l ; clad with nickel where in cont a c t with NaOD. H e l i c a l tubes used to r e d u c e u n c e r t a i n t i e s of unstable flow in r e a c t o r s of high power density. F u e l e n t e r s c o r e at n o r t h pole and flows downward through six 3.5 in. ID Inconel t u b e s . F i v e t u b e s a r e wrapped i n a v a r i a b l e - p i t c h helix to f o r m a s p h e r i c a l annulus of fuel. Sixth p a s s e s through c e n t e r of s p h e r e , forming s m a l l e r - d i a m e t e r helix. In returning, fuel flows over p r i m a r y NaK-cooled heat exchanger. NaK coolant in c i r c u m f e r e n t i a l heat exchanger, s p h e r i c a l s h e l l . F u e l and coolant flow c o u n t e r c u r r e n t l y . NaOD, which cools r e f l e c t o r , flows downward through s p h e r i c a l cavity in r e f l e c t o r and s u r r o u n d s fuel tubes; a c t s as m o d e r a t o r "island. 'I R e t u r n s to top through holes i n r e f l e c t o r , through s p h e r i c a l cavity outside r e f l e c t o r , through a shell-and-tube heat exchanger and back to c o r e . NaOD cooled i n exchanger by exchange with NaK t h a t is r e t u r n i n g to r e a c t o r . NaK then goes to p r i m a r y heat exchanger to cool fuel. Control s y s t e m needed to k e e p t e m p e r a t u r e of r e t u r n i n g NaOD constant to p r e v e n t c o r r o s i o n f r o m over-heating o r f r e e z i n g f r o m cooling. Heat-exchange s y s t e m u s e s only one i n t e r m e d i a t e h e a t - t r a n s f e r m e d i u m and e l i m i n a t e s need f o r additional r a d i a t o r s to cool p a r t of NaK, a s proposed f o r F i r e b a l l . Control: negative t e m p e r a t u r e coefficient; s h i m control- -adding e n r i c h e d fuel; v a r i a b l e b y - p a s s i n xenon s e p a r a t o r would add xenon to provide fine adjustment i n r e a c t i v i t y between additions of e n r i c h e d fuel. No r o d s . Basically, power e x t r a c t e d is d e t e r mined solely by demand of propulsion s y s t e m . P o w e r : 200 MW(t). Code: 0413 17 31204 44 627 711 84677 923 107 83789 81596

No. 36 High-performance M a r i n e R e a c t o r

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ORSORT R e f e r e n c e : Unpublished ORSORT t e r m p a p e r , August 1957. O r i g i n a t o r s : K. H. Dufrane, T. G. B a r n e s , C. Eicheldinger, W. D. Lee, N. P. Otto, C. P. P a t t e r s o n , T. G. P r o c t o r , R. W. Thorpe, and R. A. Watson. Status: Design and feasibility study, 1957. Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b u r n e r . F u e l coolant : u 2 3 5 i n molten-salt m i x t u r e containing 49 m o l 70NaF, 4570 Z r F , , 670 UF4. M o d e r a t o r : c y l i n d r i c a l Be r o d s , clad with Inconel, equally spaced throughout c o r e region in t r i a n g u l a r pitch a r r a y and extending length of c o r e . Rods tipped with poison m a t e r i a l ( B e 0 plus B1') to r e d u c e end leakage, as well as to r e d u c e fissioning in exit and e n t r a n c e plenums f o r fuel. F u e l c i r c u l a t e s to s e c o n d a r y h e a t exchanger. Reflector: Ni blanket, 6 in. thick, around c o r e . It is s u r r o u n d e d by 5+-in. thick region of c y l i n d r i c a l r o d s , 3/4-in. thick, containing m i x t u r e of B e 0 and B1'. Boron-bearing Inconel r o d s in i n t e r s t i c e s of c y l i n d e r s . R e a c t o r v e s s e l : cylinder, 80 by 80 in., containing expansion tank for fuel and coolant c o i l s in head f o r rem0vin.g i n t e r n a l l y g e n e r a t e d heat by flow of portion of fuel. Shielding: p r i m a r y - s t r u c t u r a l s t e e l plus 5 in. P b plus 39 in. H,O; s e c o n d a r y - - 4 - 6 + in. P b ; thin s l a b of B4C in. Cu matrix s u r r o u n d s t h i s region. P r i m a r y construction m a t e r i a l : Inconel. F u e l flows up through c e n t r a l c o r e r e g i o n (75 cm d i a m e t e r , 80 c m high) and down through annular downcomer at p e r i p h e r y containing p r i m a r y (fuel-to- s e c o n d a r y fluid) wraparound heat exchanger cooled by m o l t e n salt (30 m o l 70 NaF, 2070 LiF, 5070 B e F 2 ) . Heat exchanger of oncethrough, shell-and.-tube, counterflow design; fuel g o e s to s h e l l s i d e , coolant to tube side. F u e l r e t u r n s to c o r e , coolant to s t e a m - g e n e r a t i n g equipment. In a modification, an i n t e r m e d i a t e heat exchange with a t e r t i a r y fluid sugg e s t e d t o r e d u c e shielding weight. Control: negative t e m p e r a t u r e coefficient; varying coolant flow; single v e r t i c a l c o n t r o l r o d (Inconel -BeO-Ni- 1 vol. 70 B1') in thimble extending length of c o r e a t c o r e c e n t e r l i n e f o r r e a c t o r shutdown, change in m e a n t e m p e r a t u r e , and f u e l burnup; r o d thimble about 4 in. d i a m e t e r , with g a p f o r cooling by m o l t e n salt o r m e t a l ; provision f o r e m e r gency fuel dumping. P o w e r : 125 MW(t). Code: 0413 15 31211 44 627 711 81111 921 104 83789 84679

i 1

No. 37 Modified High-performance M a r i n e R e a c t o r ORSORT R e f e r e n c e : Unpublished ORSORT t e r m p a p e r , August 1957. Originators: K. H. Dufrane, T . G. B a r n e s , C. Eicheldinger, W. D. Lee, N. P. Otto, C. P. P a t t e r s o n , T. G. P r o c t o r , R. W. T h o r p e , a n d R . A. Watson. Status: P r e l i m i n a r y study, 1957. Details: Modification of design i n Data Sheet No. 36 to give advanced design that would r e d u c e weight and improve p e r f o r m a n c e . Fuel-coolant: molten salt, 42 wt 70BeF-3870 NaF-2070 UF,; Be salt to i n c r e a s e moderation in c o r e . Moderator: ZrHX r o d s , 0 . 5 in. d i a m e t e r , instead of B e 0 t o i n c r e a s e m o d e r a tion. Ni-Mo cladding ( 0 . 0 1 in.) used on r o d s i n s t e a d of Inconel. Ni-Mo c o r r o s i o n r e s i s t a n c e p e r m i t s thinner cladding on m o d e r a t o r and t h u s l e s s poison i n c o r e . Core: 40 c m d i a m e t e r by 78 c m high. F u e l c i r c u l a t e s to Na-cooled U-tube h e a t exchanger. F u e l e n t e r s c o r e at l l O O ° F , l e a v e s at 1300’F. I n t e r m e d i a t e heat exchanger used to r e d u c e amount of shielding n e c e s s a r y . Shielding: p r i m a r y - - 1 in. s t r u c t u r a l s t e e l j u s t outside insulation of c o r e v e s s e l ; next 15.7 in.HzOand 6 in. P b ; finally 70 in. HzO i n 1/2-in. thick s t e e l v e s s e l . Power: 100 MW(t). Other d e t a i l s same as o r i g i n a l design. Code: 0413 17 31211 44 627 711 81111 921 104 83789 84679

NO. 38 Molten- salt T h o r i u m C o n v e r t e r f o r E l e c t r i c a l P o w e r Production Knolls Atomic P o w e r L a b o r a t o r y Reference: KAPL-M-JKD- 10. Originators: J. K. Davidson, W. L. Robb, L. B e r n a t h , W. H. Horton, R. P. Schuman, R . H. Simon, and A. D. Tevebaugh. Status: I n f o r m a l r e a c t o r evaluation, 1952- 53; no f u r t h e r work. Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , c o n v e r t e r Fuel: solution of 9370 U235F3o r UF, i n L i F - B e F z - T h F 4 . C o r e : Inconel, 5.77 f t r a d i u s . Up t o 8570 a v e r a g e conversion of ThZ3’ t o U233is possible; conversion r a t i o would b e 0.73 to 0.905. F u e l would have to b e added periodically. Code: 0411 1X 31211 44 627 746 84679 9XX 104

No. 39 F u s e d Salt R e a c t o r for P o w e r and Heat ORSORT

Reference: C F - 5 3 - 10-26 Originators: Theodore J a r v i s e t al. Status: Conceptual design, 1953; ORSORT t e r m p a p e r . Details: T h e r m a l and mixed neutrons, steady s t a t e , b u r n e r o r c o n v e r t e r . Fuel: UZ35F4(0.3 m o l 70);t h o r i u m fluoride might be added for conversion. C r i t i c a l mass U235: 2.7 kg. Moderator: graphite, of high density to avoid penetration of fuel. Reflector: graphite s p h e r e . Containment: graphite s p h e r e i n Inconel shell, surrounded by Inconel p r e s s u r e v e s s e l . F l u o r i d e fuel c i r c u l a t e s f r o m bottom through m a n y p a r a l l e l channels cut d i r e c t l y into the g r a p h i t e m o d e r a t o r out the top of t h e r e a c t o r to e x t e r n a l h e a t e x c h a n g e r s , in which n i t r o g e n is the heat-exchange medium. Channels of different length s o t h a t c o r e a p p r o a c h e s shape of s p h e r e . No provisions f o r cooling chatnnels i n graphite m o d e r a t o r b e c a u s e its t e m p e r a t u r e will not exceed 2000'F at m a x i m u m power l e v e l and with s u r f a c e cooling. R e a c t o r p r e s s u r e shell, h e a t exchanger, and piping a r e Inconel. Control: negative t e m p e r a t u r e coef ficient; dumping as additional e m e r g e n c y control; no c o n t r o l r o d s . P o w e r : 5.3 MW(t). R e a c t o r designed f o r installation at r e m o t e location to produce e l e c t r i c a l power, as well as power f o r station heating. Heat provided by water heated by l o w - p r e s s u r e w a s t e g a s f r o m the turbine exhaust. 921 104 Code: 0411 12 31211 44 627 711 84679 0413 746 83189

No. 40 F u s e d Salt B r e e d e r R e a c t o r (FSBR) ORSORT Reference: C F - 5 3 - 10-25. Originators: D. B. Wehmeyer e t a l . Status: Design study, 1953; ORSORT t e r m p a p e r . Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , steady s t a t e , b r e e d e r . F u e l c o o l a n t - f e r t i l e m a t e r i a l : solution of U233F4and T h F 4 in molten Li7F and BeF2. I n t e r m e d i a t e coolant: Na. Moderator - r e f l e c t o r : stacked graphite blocks, which contain t h e salt. F u e l is pumped through graphite p a s s a g e s and through h e a t exchangers located i n the graphite mass surrounding c:ore. C r i t i c a l r a d i u s of c o r e : 160 c m . C o r e h a s s p h e r i c a l top, flat bottom, and c y l i n d r i c a l s i d e s . Average operating t e m p e r a t u r e : 1400'F. Control: iiegative t e m p e r a t u r e coefficient; c o n t r o l of fuel concentration. Breeding ratio: 1.0. Two s i z e s of r e a c t o r s : 310 MW(t), 125 MW(e); 616 MW(t), 250 MW(e). 921 104 Code: 0412 12 31211 45 627 746 83789 84679

No. 41 600-MW F u s e d S a l t Homogeneous R e a c t o r P o w e r P l a n t ORSORT R e f e r e n c e : C F - 56 - 8 - 20 8, Del. O r i g i n a t o r s : R . W. Davies e t al. Status: Design and feasibility study, 1956; ORSORT t e r m p a p e r . Details: I n t e r m e d i a t e neutrons, s t e a d y s t a t e , + b u r n e r . Fuel-coolant: solution of highly enriched U235F4 in m o l t e n N a F and Z r F . No m o d e r a t o r o t h e r than fluorine in solution. Reflector: c o r e v e s s e l . C o r e : cylinder, 2 f t d i a m e t e r by 10 f t high, s u r r o u n d e d by tube bundles of p r i m a r y h e a t exchanger. R e a c t o r v e s s e l : m u l t i p a s s c y l i n d r i c a l c o n t a i n e r . F u e l flows up through c o r e and U-tube heat e x c h a n g e r s and through annular downcomer at p e r i p h e r y of the v e s s e l . Eight pumps c i r c u l a t e the fuel. Inlet t e m p e r a t u r e : 1050'F; outlet: 1200'F. Control: negative t e m p e r a t u r e coefficient. I n t e r m e d i a t e coolant: Na. Ni-Mo alloys f o r c o n s t r u c t i o n materials. R e a c t o r designed t o b u r n U235,but design could be a l t e r e d to b r e e d U233. P o w e r : 600 MW(t). Code: 0213 17 31211 44 627 711 84677 921 101

No. 42 F u s e d Salt R e a c t o r f o r P r o c e s s Heat ORSORT Reference: CF-56-8-211. Originators: J. T. Roberts e t al. Status: Conceptual design, 1956; ORSORT term p a p e r . Details: T h e r m a l and i n t e r m e d i a t e n e u t r o n s , s t e a d y state, b u r n e r . F u e l coolant: 9370 e n r i c h e d U F 4 i n NaF-ZrF,. M o d e r a t o r : MgO c e r a m i c . Reflector: BeO. F u e l c i r c u l a t e d at 17.4 ft/sec through 90 2-in. ID Inconel t u b e s in t r i a n g u l a r a r r a y on 12-in. c e n t e r s . T u b e s a r e i n a 10-ft-diameter by 12-ft-high c y l i n d r i c a l matrix of hexagonally shaped blocks of MgO. Mode r a t o r p e r f o r a t e d t o allow p a s s a g e of s t e a m through t u b e s i n s e r t e d i n holes. 35 MW(t) is g e n e r a t e d in the MgO and u s e d to h e a t s t e a m f r o m 2040'F to 3000'F. Annulus between tubes and w a l l s of MgO m a y be filled with aluminum s i l i c a t e "wool" a s a t h e r m a l b a r r i e r . F u e l heated f r o m 1050'F to 1200'F in a single p a s s upward through t h e c o r e by i n t e r n a l h e a t generation; d e l i v e r s the h e a t t o Na i n a n e x t e r n a l h e a t exchanger. C o r e r e f l e c t e d on s i d e s with 8-in. B e 0 and contained in a 12-ft-diameter by 18-ft-long steel p r e s s u r e v e s s e l . Control: r o d s included, but no d e t a i l s given; p r e s u m a b l y a l s o negative t e m p e r a t u r e coefficient. Design includes 4 s u c h r e a c t o r s f o r a n i n t e g r a t e d coal-hydrogenation plant. E a c h p r o d u c e s 400 MW(t); 123 MW(e). Code: 0413 17 31211 44 627 711 81XXX 921 104 84679

No. 43 Molten Salt N a t u r a l Convection R e a c t o r A m e r i c a n Standard and ORNL R e f e r e n c e s : CF-58-2-46; T r a n s . ANS, 1, No. 1, p. 64. Originators: F. E. R o m i e ( A m e r i c a n Standard) and B. W. Kinyon (ORNL). Status: P r o p o s a l , 1958. Details: I n t e r m e d i a t e neutrons, steady s t a t e , p r e s u m a b l y b u r n e r . F u e l moderator-coolant: solution of U F 4 i n LiF-BeF,. C o r e v e s s e l : s p h e r e , 8 ft d i a m e t e r . F u e l solution c i r c u l a t e s by n a t u r a l convection through the c o r e f r o m the bottom, through v e r t i c a l convection r i s e r s , to p r i m a r y heat exchangers above the c o r e . M a x i m u m fuel t e m p e r a t u r e : 1225'F; minimum: 975- 1025'F. P r i m a r y h e a t exchanger m a y be cooled by e i t h e r molten s a l t o r helium. Control: p r e s u m a b l y negative t e m p e r a t u r e coefficient. Power: 60 MW(t); 22 MW(e). Code: 0213 17 31211 44 627 711 84677 9X 101

No. 44 Homogeneous F u s e d Salt P o w e r R e a c t o r ORNL Reference: T r a n s . ANS, 1, No. 1, pp. 63-64. Originators: W. A. Box e t al. Status: F e a s i b i l i t y study, 1958. Details: I n t e r m e d i a t e neutrons, steady state, burner.. F u e l - m o d e r a t o r : highly e n r i c h e d U F 4 dissolved i n molten N a F - Z r F 4 (57 m o l 70-43 m o l 70). Coolant: m o l t e n P b . Core: cylinder, 10 f t d i a m e t e r , 10 f t high. P b c i r c u l a t e s m o l t e n salt by d i r e c t mixing b y m e a n s of j e t pump. Heat exchange is v e r y r a p i d ; no p r i m a r y heat exchanger needed. F u e l and coolant seF)ar a t e d d o w n s t r e a m f r o m the j e t pump by pipeline s e p a r a t o r . F u e l g o e s to c o r e , P b to s t e a m g e n e r a t o r . Heat e x t r a c t e d f r o m P b by six h e a t - t r a n s f e r loops that supply turbine g e n e r a t o r s . P r e s s u r e : 140 psi. Control: negative t e m p e r a t u r e coefficient. P o w e r : 600 MW(t); 194 MW(e). Code: 0213 17 31106 44 711 84677 9X 105

i 1

No. 45 Slightly E n r i c h e d , F u s e d - salt-fueled R e a c t o r ORNL R e f e r e n c e s : ORNL-2684, pp. 18-22; C F - 5 8 - 10-60; C F - 5 9 - 1-26. O r i g i n a t o r s : H. G. M a c P h e r s o n and C. E. Guthrie. Status: P r o p o s a l , 1958; p r e l i m i n a r y design, 1959. Details: N e a r - t h e r m a l n e u t r o n s , s t e a d y s t a t e , c o n v e r t e r . Fuel-coolant: slightly-enriched 1.3- 1.870 U235F4i n m o l t e n L i F - B e F 2 . M o d e r a t o r : g r a p h i t e . Unclad g r a p h i t e m o d e r a t o r c o r e , 12; f t i n d i a m e t e r and height, is contained i n a c y l i n d r i c a l INOR-8 v e s s e l . F u e l flows at 35,470 g p m f r o m bottom t o t o p of c o r e through 3.6 in. h o l e s on 8-in. c e n t e r s i n t h e g r a p h i t e . Highly e n r i c h e d u r a n i u m added as m a k e -up fuel. Control: controlling t e m p e r a t u r e and f u e l concentration. I n i t i a l c o n v e r s i o n r a t i o of U t o P u : about 0.79. P o w e r : about 775 MW(t); 315 MW(e). Code: 0311 12 31211 42 627 743 84679 922 104 83789

No. 4 6 E x p e r i m e n t a l Molten-salt-fueled 30 MW(t) P o w e r R e a c t o r ORNL R e f e r e n c e s : ORNL-2796; ORNL-2684, pp. 3- 17. O r i g i n a t o r s : L. G. Alexander -e t al. Status: P r e l i m i n a r y design, 1960. Details: I n t e r m e d i a t e n e u t r o n s , s t e a d y s t a t e , b u r n e r . F u e l - m o d e r a t o r coolant: solution of 90% e n r i c h e d U235F4i n m o l t e n L i F - B e F 2 . C o r e : s p h e r e , 6 f t d i a m e t e r . Secondary coolant: m o l t e n L i F - B e F z . Single s t r u c t u r e con-. t a i n s c o r e , h e a t exchanger, expansion tank, and f u e l pump volute. F u e l c i r c u l a t e s at 1480 gpm through bottom of c o r e , flows upward a t w a l l s of c o r e to h e a t exchanger and back to c o r e , w h e r e i t flows down. S t e a m produced a t l O O O O F and 1450 p s i . Exit t e m p e r a t u r e of fuel: 1235OF. S t r u c t u r a l m a t e r i a l : INOR-8. Control: negative t e m p e r a t u r e coefficient; c o n t r o l of f u e l concent r a t i o n . P o w e r : 30 MW(t); 10 MW(e). Code: 0213 17 31211 44 627 711 84677 9XX 101 83789

No. 47 Molten Salt R e a c t o r E x p e r i m e n t (MSRE) ORNL

R e f e r e n c e s : P r o c . Symp. P o w e r R e a c t o r E x p e r i m e n t s 1 .IAEA, Vienna, 1962, pp. 247-92; Nucleonics 22, No. 1, pp. 67-70, J a n u a r y 1964. Originators: MSR p r o j e c t , ORNL. Status: Conceptual design, 1960. C r i t i c a l i t y achieved in 1965. Details: T h e r m a l n e u t r o n s , steady s t a t e , c o n v e r t e r (possibly with i n t e r n a l breeding). Fuel-coolant: solution of 93.570 enriched U235F4 in L i F - B e F 2 Z r F4-ThF4. I n t e r m e d i a t e coolant: Li7F- BeF2. Moderator: unclad g r a p h i t e , 1064 s t r i n g e r s (2 x 2 x 63 in. long) loosely pinned t o r e s t r a i n i n g b e a m s at c o r e bottom; f o r m c y l i n d r i c a l c o r e (about 5 f t d i a m e t e r by 7.5 f t high) contained i n a r e a c t o r v e s s e l . Annulus between t h i s inner cylinder and o u t e r s h e l l provides cooling for the shell. Flow is l a m i n a r at 1200 gpm; fuel, blanketed by helium g a s , e n t e r s top of c o r e at 635OC, flows i n a s p i r a l path downward i n annulus along the wall to the bottom where a dished head r e v e r s e s the flow. It then flows up through channels in the graphite c o r e matrix f o r m e d b y machining the f a c e s of the s t r i n g e r s . All components i n contact with the fuel a r e of INOR-8. Exiting at 663OC the fuel e n t e r s the sump-type pump f r o m which it is d i s c h a r g e d through the s h e l l side of the h e a t exchanger b a c k t o the c o r e inlet. Control: negative t e m p e r a t u r e c o e f ficient; 3 s h i m c o n t r o l rods--thin-walled c y l i n d e r s of B4C m a d e of stacked s h o r t s e c t i o n s clad in INOR-8. P o w e r : 10 MW(t). 12 31211 44 627 746 84679 923 104 Code: 0311 0312 81111

No. 48 Uranium Fluoride-fueled Fast R e a c t o r f o r S p a c e c r a f t J e t P r o p u l s i o n L a b o r a t o r y , Calif. Inst. Tech,

Reference: J P L - T R - 3 2 - 198. Originator: L. S. Allen. Status: Calculations, 1962. Details: Fast n e u t r o n s , steady s t a t e , b u r n e r . Fuel: u r a n i u m as 93.5% enr i c h e d UF, dissolved in molten-salt mixture--7070 UF,, 3070 NaF. No m o d e r a t o r . Coolant: Li, which flows t o engine. Core: s p h e r e , 2 1 in. d i a m e t e r , 40 l i t e r s vol. C o r e composition: 42% UF,, 1870 N a F , and 10% Z r by volume. R e f l e c t o r : i n t e r n a l , Z r ; e x t e r n a l , 3 in. Be. Control: p r e s u m a b l y negative t e m p e r a t u r e coefficient. P o w e r : 10 MW(t). Code: 0113 11 31106 44 627 711 84679 923 109

References 1. Unpublished r e p o r t , H. K. F e r g u s o n Company, Dec. 12, 1950.

2. Ibid., June 1, 1951, 3. Circulating M o d e r a t o r -coolant R e a c t o r f o r Subsonic A i r c r a f t , HKF- 112, â&#x201A;Ź3. K. F e r g u s o n Co., Aug. 29, 1951. Decl. J u l y 8 , 1964.

4. R . W. Dayton and J . W. Chastain, Hydroxides as M o d e r a t o r - c o o l a n t s in P o w e r - b r e e d e r R e a c t o r s , BMI-746, Del., Battelle M e m o r i a l Institute, May 26, 1952. 5. Unpublished r e p o r t , ORNL, 195 1.

6. R . W e S c h r o e d e r and B. L u b a r s k y , unpublished r e p o r t , ORNL, 1953. 7. E. S. B e t t i s , W. B o C o t t r e l l , E. R. Mann, J. L. Meem, and G. D. Whitman, T h e A i r c r a f t R e a c t o r E x p e r i m e n t - -Operation, N u c l e a r Sci. Eng. 2, NO. 6, pp. 841-853, NOV. 1957. 8. R . C. B r i a n t and A. M. Weinberg, Molten F l u o r i d e s as P o w e r R e a c t o r F u e l s , Ibid., pp. 797-803.

9. W. K. E r g e n , A. D. Callihan, C. B. M i l l s , and Dunlap Scott, T h e A i r c r a f t Reactor Experiment- -Physics, Ibid., pp. 826-840.

10. A. M. Weinberg, Some A s p e c t s of F l u i d F u e l R e a c t o r Development, Ibid., - 8, pp. 346-360, Oct. 1960. 11. E. S. B e t t i s , R. W. S c h r o e d e r , G. A. C h r i s t y , H. W. Savage, R . G. A.ffe1, and Lo F. Hemphill, The A i r c r a f t R e a c t o r E x p e r i m e n t - - D e s i g n and Construction, Ibid., - 2, No. 6, pp. 804-825, Nov. 1957. 12. W. B o C o t t r e l l , H.E. Hungerford, J . K. L e s l i e , and J . L. Meem, O p e r a t i o n of t h e A i r c r a f t R e a c t o r E x p e r i m e n t , ORNL-1845, ORNL, Sept. 6, 1955. Decl. with del., F e b . 12, 1959. 13. W. B. C o t t r e l l , ARE Design Data, CF-53-12-9, ORNL, Dee. 1, 1953. Decl., Oct. 9, 1959. 14. E. S. B e t t i s and W. K. E r g e n , A i r c r a f t R e a c t o r E x p e r i m e n t , in -.F l u i d F u e l R e a c t o r s , J. A. Lane, H. G. M a c P h e r s o n , and Frank M a s l a n , e d s . , Addison-Wesley Publishing Co., Reading, M a s s . , 1950, pp. 673-680. 15. A i r c r a f t N u c l e a r P r o p u l s i o n P r o j e c t Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending M a r c h 10, 1952, ORNL-1227, W. B. C o t t r e l l , ed,, ORNL, M a y 7, 1952.

16. C. B. M i l l s , ARE with F u e l - c o o l a n t i n t h e R e f l e c t o r , Y-F10-91, ORNL, F e b . 27, 1952. 17. C . B. M i l l s , T h e F i r e b a l l , A R e f l e c t o r M o d e r a t e d C i r c u l a t i n g - f u e l R e a c t o r , Y-F10-104, ORNL, J u n e 20, 1952.

49 !

18. A. P. Fraas, Design C h a r a c t e r i s t i c s of the R e f l e c t o r - m o d e r a t e d R e a c t o r , i n A i r c r a f t Nuclear P r o p u l s i o n P r o j e c t Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending M a r c h 10, 1953, W. B. C o t t r e l l , ed., ORNL-1515, A p r i l 16, 1953.

19. A. P. Fraas and A. W. Savolainen, Unpublished r e p o r t , ORNL, 1954. 20.

W. B. C o t t r e l l , W. K. E r g e n , A. P. Fraas, F. R . McQuilkin, and J . L. M e e m , A i r c r a f t R e a c t o r T e s t . H a z a r d s S u m m a r y R e p o r t , ORNL- 1835, ORNL, Jan. 19, 1955. Decl., Oct. 9, 1959.

21. W. K. E r g e n , P r e l i m i n a r y Design Data f o r a Circulating F l u o r i d e - f u e l High-fluxReactor, CF-56-6-9, Rev. 2, ORNL, J a n . 28, 1958. 22.

W. C. Cooley, Nuclear A i r c r a f t P o w e r P l a n t s Utilizing Liquid C i r c u lating F u e l R e a c t o r s , APEX- 135, ANP P r o j e c t , G e n e r a l E l e c t r i c Company, June 1, 1953. Decl., J u n e 9, 1961.

23. Unpublished r e p o r t s , Pratt & Whitney A i r c r a f t Division of United A i r c r a f t Corporation, 1953-54.

24. Ibid., 1957.

1 -

25. Ibid., 1954.

26. R e a c t o r Study, PWAC- 186, Pratt & Whitney A i r c r a f t Division of United A i r c r a f t Corporation, J u l y 15, 1957. 27. The P & WA Circulating F u e l R e f l e c t o r - m o d e r a t e d R e a c t o r , PWAC- 189, Pratt & Whitney A i r c r a f t Division of United A i r c r a f t Corporation, Nov. 15, 1957.

28. Unpublished r e p o r t , Pratt & Whitney A i r c r a f t Division of United A i r c r a f t C o r p o r a t i o n , 1956.

29. K. H. P u e c h l , A l t e r n a t e R e a c t o r Concepts f o r A i r c r a f t P r o p u l s i o n , WKNL-42, Walter Kidde Nuclear L a b o r a t o r i e s , Inc., F e b . 1, 1955. Decl. J a n . 19, 1965. 30. J . H. MacMillan, C. B. Anthony, K. Guttmann, C. P. M a r t i n , J. L. Munier, and R. D. Worley, A R e f l e c t o r Moderated, Circulating F u e l , A i r c r a f t R e a c t o r , CF-53-9-84, ORSORT, Aug. 14, 1953. 31. K. H. Dufrane, T . G. B a r n e s , C.. Eicheldinger, W. D. Lee, N. P. Otto, C. P. P a t t e r s o n , T . G. P r o c t o r , R . W. T h o r p e , a n d R . A. Watson, Unpublished ORSORT t e r m p a p e r , Aug. 1957.

32. J . K. Davidson and W. L. Robb, A M o l t e n - s a l t T h o r i u m C o n v e r t e r f o r P o w e r Production, KAPL-M-JKD- 10, K A P L , Oct. 31, 1956. Decl., F e b . 26, 1957.

33. Theodore J a r v i s , L. L. Brown, D. L. Conklin, F. 0. Ewing, R. 0. Lowrey, C. M. R i c e , G. E. Tate, and R. E. Wascher, R e a c t o r Design and F e a s i bility P r o b l e m . F u s e d Salt Package, C F - 5 3 - 10-26, ORSORT, Aug. 1953. Decl., J a n . 20, 1964. 34. D. B. Wehmeyer, J . A. B a r a , J r . , D. J . C o c k e r a m , R. B. Donworth, L. B. Holland, R. S . Hunter, P. J . M r a z , W. P a r k , and W. L. Webb, Study of a F u s e d Salt B r e e d e r R e a c t o r f o r P o w e r Production, CF-53-1025, ORNL, Sept. 1953. Decl., J u l y 5, 1957. 35. R. W. Davies, D. H. F e e n e r , W. A. F r e d e r i c k , K. R . Goller, I. Granet, G. R. Schneider, and F. W. Shutko, 600 MW F u s e d Salt Homogeneous R e a c t o r P o w e r P l a n t , CF-56-8-208, Del., ORNL, Aug. 1956. Decl. with del., M a r c h 4, 1957. 36. J . T . R o b e r t s , J . S. Lagarias, F. J . Remick, R. W. Ritzmann, J . 0. R o b e r t s , W. J . R o b e r t s , J . E. Schmidt, and P. R . Kasten, R e a c t o r P r o ducing 3000'F S t e a m for P r o c e s s Heat, CF-56-8-211, ORSORT, Aug. 6, 1956. Decl., Sept. 15, 1959. 37. F. E. R o m i e and B. W. Kinyon, A Molten Salt N a t u r a l Convection R e a c t o r System, CF-58-2-46, ORNL, F e b . 5, 1958. 38. F. E. R o m i e and B. W. Kinyon, Design Study of a Molten Salt N a t u r a l Convection R e a c t o r , T r a n s . ANS, 1, No. 1, p. 64, 1958. 39. W. A. Box, C . S. B a r n e t t , R. Bean, S. J . Ditto, F. A. Hazenkamp, L. R. P o l l a c k , and M. L. Winton, F e a s i b i l i t y Study of a Homogeneous, F u s e d 1, No. 1, Salt, Molten Metal Cooled, P o w e r R e a c t o r System, T r a n s . ANS, pp. 63-64, 1958. 40. H. G. M a c P h e r s o n , Survey of Low-enrichment Molten-salt R e a c t o r s , CF-58-10-60, ORNL, Oct. 17, 1958. 41. H. G. M a c P h e r s o n , A P r e l i m i n a r y Study of a Graphite Moderated Molten Salt P o w e r R e a c t o r , Unpublished r e p o r t , ORNL, J a n . 13, 1959. 42. Molten Salt R e a c t o r P r o j e c t Q u a r t e r l y R e p o r t f o r P e r i o d Ending Jan. 31, 1959, ORNL-2684, ORNL, M a r c h 17, 1957. 43. L. G. Alexander, B. W. Kinyon, M, E. Lackey, H. G. M a c P h e r s o n , J. W. M i l l e r , F. C. VonderLage, G. D. Whitman, and J . Z a z l e r , E x p e r i m e n t a l Molten-salt-fueled 30-MW P o w e r R e a c t o r , ORNL-2796, ORNL, M a r c h 24, 1960. 44. A. L. Bock, E. S. B e t t i s , and W. B. McDonald, The Molten-salt R e a c t o r E x p e r i m e n t , P r o c . Symp. on P o w e r R e a c t o r E x p e r i m e n t s , 1, IAEA, Vienna, 1962, pp. 247-292.

51 1

45. H. G. M a c P h e r s o n , Molten Salt R e a c t o r P r o g r a m Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending J u l y 31, 1960, ORNL-3014, ORNL, pp. 1-23, Dec. 22, 1960. 46. E. S. B e t t i s and W. B. McDonald, M o l t e n - s a l t R e a c t o r E x p e r i m e n t , 22, No. 1, pp. 67-70, Jan. 1964. Nucleonics, 47. H. G. M a c P h e r s o n , M o l t e n - s a l t R e a c t o r s : R e p o r t f o r 1960 T e n - y e a r plan Evaulation, Unpublished r e p o r t , ORNL, J u l y 25, 1960. 48. L. S. Allen, A P a r a m e t r i c S u r v e y of C r i t i c a l i t y - l i m i t e d Fast R e a c t o r s Employing U r a n i u m F l u o r i d e F u e l s , J P L - T R - 3 2 - 198, Calif. Inst. T e c h . , M a r c h 15, 1962. 49. W. R. G r i m e s , Molten Salts a s R e a c t o r M a t e r i a l s , N u c l e a r News, .-7, No. 5, pp. 3-8, May 1964.

1 ' 1

Chapter 3 .

Two-region R e a c t o r s

In the development of p r a c t i c a l molten-salt-fueled r e a c t o r s , tworegion r e a c t o r s r e p r e s e n t a m o r e advanced s t a g e of development than one-region r e a c t o r s . A two-region power b r e e d e r is the goal. Work on two-region MSR's h a s been n e a r l y a l l concentrated a t Oak Ridge National Laboratory. Most r e a c t o r s d e s c r i b e d i n this c h a p t e r have graphitem o d e r a t e d c o r e s and fluoride fuels , although two concepts utilize c h l o r i d e fuels and no m o d e r a t o r .

In 1960, M a c P h e r s o n d e s c r i b e d t h r e e p o s s i b l e types of r e a c t o r construction f o r breeding. 1 The first, the unit fuel tube, was believed to be the m o s t p r a c t i c a l . The fuel p a s s e s through the r e a c t o r in graphite tubes, which a r e enclosed by graphite m o d e r a t o r . The blanket, which contains a t h o r i u m s a l t , s u r rounds the c o r e , The blanket s a l t a l s o p a s s e s through small p a s s a g e s i n the g r a p h i t e a s a coolant. The graphite c o r e s h e l l c o n s i s t s of t h r e e blocks of g r a p h i t e - - a top h e a d e r , a c e n t e r section, and a bottom h e a d e r , The blocks should be of graphite that is n e a r l y i m p e r v i o u s to the fuel solution. The t h r e e blocks a r e e i t h e r clamped, cemented, o r held together by p o s t s .

In the i n t e r n a l l y cooled r e a c t o r , the fuel is i n graphite tubes extending through the m o d e r a t o r into the blanket. The tubes a r e connected a t e a c h end to a h e a d e r s y s t e m , s o that the f u e l can be slowly c i r c u l a t e d to keep it uniform, to r e m o v e gaseous f i s s i o n p r o d u c t s , and to allow f o r the fuel concentration to be adjusted f o r burnup. The h e a t is t r a n s f e r r e d through the tube wall to the blanket salt, which thus a c t s as a coolant. Graphite i n s e r t s i n the tubes f o r c e the fuel to the o u t e r portion of tubes to i n c r e a s e h e a t t r a n s f e r . A p r o b l e m with this s t r u c t u r e is t h a t it is unlikely t h a t all of the 10,000 tubes needed f o r a 200 MW(e) r e a c t o r would keep t h e i r i n t e g r i t y f o r a long r e a c t o r lifetime. Hvdr oxi de - mode rat e d React o r

4 3 '

In considering hydroxide-moderated two-region r e a c t o r s , Dayton and Chastain emphasized lithium-7 hydroxide and lithium-7 deuteroxide.' The s p h e r i c a l r e a c t o r , consisting of c o n c e n t r i c s h e l l s of z i r c o n i u m , has a n o u t e r annulus, which contains a suspension of t h o r i u m oxide i n heavy waker. This suspension s e r v e s both as a breeding blanket and as a r e f l e c t o r . The specified c o r e t e m p e r a t u r e of l l O O O F w a s a s s u m e d to b e high enough fo:r efficient power production but low enough to avoid e x c e s s i v e c o r r o s i o n . Breeding gains g r e a t e r than 0.2 w e r e postulated f o r r e a c t o r s with e i t h e r lithium compound. The authors concluded that the r e a c t o r m o d e r a t e d with

Li70D would be p r e f e r a b l e . The r e a c t o r m o d e r a t e d with Li70H has a l o w e r c o s t m o d e r a t o r , s m a l l e r c o r e r a d i u s , and s m a l l e r fuel r e q u i r e m e n t s . T h e s e advantages, however, a r e m o r e than offset by those of the r e a c t o r m o d e r a t e d with Li70D. This r e a c t o r , because of i t s l a r g e r c o r e r a d i u s , would o f f e r a l a r g e r breeding gain and would have i m p r o v e d h e a t - r e m o v a l p r o p e r t i e s . Also, although m o r e fuel is r e q u i r e d , i t i s a much s m a l l e r p e r c e n t a g e of the total m a s s than i s r e q u i r e d with the r e a c t o r m o d e r a t e d with Li70H. MIT F a s t R e a c t o r A r e a c t o r designed in e a r l y 1952 that differed f r o m m o s t two-region r e a c t o r s was the MIT Fluid Fuel F u s e d - s a l t R e a c t o r r e p o r t e d by Goodman -e t al.3â&#x20AC;&#x2122;4 Instead of f l u o r i d e s , the fuel i s u r a n i u m t e t r a c h l o r i d e , which is dissolved i n a molten m i x t u r e of l e a d chloride and sodium chloride. The higher t h e r m a l neutron-absorption c r o s s section of the chlorides r e q u i r e s this to be designed as a f a s t r e a c t o r . The blanket c o n s i s t s of u r a n i u m t e t r a c h l o r i d e containing depleted uranium. A l e a d r e f l e c t o r around the s e m i s p h e r i c a l c o r e i s used f o r s h i m control. ORSORT F a s t B r e e d e r A s i m i l a r design f o r a f a s t r e a c t o r was employed by B u l m e r , e t a l . , students a t the Oak Ridge School of R e a c t o r Technology, i n 1956.5 Again the fuel s a l t w a s a chloride i n s t e a d of a fluoride, with both plutonium and depleted u r a n i u m chlorides dissolved in sodium and m a g n e s i u m c h l o r i d e s , The depleted u r a n i u m p e r m i t s i n t e r n a l breeding. The blanket, a p a s t e of depleted u r a n i u m oxide powder in sodium, i s divided into two regions by a graphite m o d e r a t o r , which m a k e s p o s s i b l e a s m a l l e r blanket. A moltenl e a d r e f l e c t o r is between the c o r e and the blanket. A g r a p h i t e r e f l e c t o r s u r r o u n d s the second blanket region. A power of 2 6 0 MW(e) was given. Internallv Cooled Molten - s a l t R e a c t o r Lackey calculated the n u c l e a r c h a r a c t e r i s t i c s f o r this r e a c t o r , which u s e s molten fluorides of u r a n i u m , t h o r i u m , lithium, and b e r y l l i u m a s fuel. The blanket and coolant a r e the molten-salt solutions without u r a n i u m , 6 Graphite i s the m o d e r a t o r . Cylindrical p a s s a g e s f o r coolant a r e in a t r i angular l a t t i c e within the graphite, with the fuel i n the annular s p a c e between the coolant tube and the graphite. The f e r t i l e s a l t i s in a blanket around the graphite. A different c o r e a r r a n g e m e n t , to r e d u c e doubling t i m e , would u s e two concentric tubes with fuel i n the annulus and coolant flowing through the i n n e r tube and outside the o u t e r tube. This design w a s f o r a r e a c t o r of high power--1563 MW(t).

T h e r m a l Convection R e a c t o r Z a s l e r h a s proposed a r e a c t o r , 7 J 8f o r which few details a r e given, in which circulation of fuel could be e i t h e r b y n a t u r a l convection f o r a 5-MW e x p e r i m e n t a l r e a c t o r , o r by fuel pumps f o r a 50-MW(t) pilot plant. In the s p h e r i c a l r e a c t o r , which i s s u r r o u n d e d by a blanket, f u e l flows f r o m the r e a c t o r to a shell-and-tube heat exchanger. Molten Salt R e a c t o r (MSR) 1

This ORNL, concept9-” h a s been given m a n y n a m e s : MSR; I n t e r i m Design R e a c t o r ; Molten F l u o r i d e C o n v e r t e r ; Molten Fluoride P o w e r R.ea c t o r ; R e f e r e n c e Design R e a c t o r ; RDR; MSR R e f e r e n c e Design; and Homogeneous , Two- region, Molten-fluoride-salt R e a c t o r . It underwent s e v e r a l modifications, p a r t i c u l a r l y i n the c o r e design. The fuel is highly e n r i c h e d u r a n i u m t e t r a f l u o r i d e i n a eutectic of lithium, b e r y l l i u m , and t h o r i u m fluorides. Plutonium-2 39 h a s been suggested a s an a l t e r n a t i v e fuel.” A f e r t i l e bl.anket of the s a m e composition a s the fuel s a l t but without the u r a n i u m s u r r o u n d s the fuel region. The c o r e h a s the shape of a n i n v e r t e d p e a r . The fuel e n t e r s the bottom of the r e a c t o r , p a s s e s to the top, goes to the p r i m a r y h e a t exchangers, and r e t u r n s to the r e a c t o r . The r e a c t o r , designed f o r c e n t r a l - s t a t i o n power, would produce 2 6 0 MW(e).

Two- region, Graphite-moderated, Molten-salt B r e e d e r R e a c t o r M e m b e r s of the MSR P r o j e c t staff s e l e c t e d a typical design f o r calculation of r e a c t o r p e r f 0 r m a n ~ e . l ~The c o r e is a g r a p h i t e s h e l l s t r u c t u r e with a single cylinder of graphite a s the m a i n p a r t and two graphite end p i e c e s . The t h r e e pieces a r e held together by r o d s of INOR-8 or o t h e r alloy. The fuel, u r a n i u m - 2 3 3 in a molten fluoride c a r r i e r containing thorium, p a s s e s downward through channels i n the c o r e then back upward to a n e x t e r n a l h e a t exchanger. The blanket, which contains t h o r i u m i n molten salt, i s kept a t a slightly h i g h e r p r e s s u r e than the c o r e . The power would be 125 MW(t).

Molten Salt B r e e d e r R e a c t o r (MSBR)

A r e a c t o r c o n s i d e r e d i n 1961 i n a c o m p a r i s o n of homogeneous r e a c t o r s f o r t h o r i u m breeding was the MSBR,’4’15 which w a s b a s e d on a design by M a c P h e r s o n i n 1959.l In both the 1959 and 1961 designs, the fuel is a solution of e n r i c h e d u r a n i u m t e t r a f l u o r i d e i n L i F - B e F Z , the blank e t surrounding the c o r e is m o l t e n s a l t containing thorium, and the fuel p a s s e s through tubes i n the g r a p h i t e m o d e r a t o r . In the 1959 design, the c o r e is of the unit-fuel-tube construction, in which o n e - p a s s g r a p h i t e tubes go through the g r a p h i t e m o d e r a t o r . In the 1961 design, the c o r e is cons t r u c t e d of g r a p h i t e p r i s m s , machined a t the c o r n e r s to f o r m v e r t i c a l

p a s s a g e s , into which two-pass bayonet graphite tubes f o r fuel flow a r e i n s e r t e d . Both designs a r e f o r u s e in groups of r e a c t o r s f o r power production. The 1959 concept is f o r t h r e e r e a c t o r s producing 333 MW(e) each, the 1961 concept f o r two r e a c t o r s producing 5 0 0 MW(e) each.

DATA SHEETS

TWO-REGION REACTORS

i No, 1 Reflected Homogeneous R e a c t o r Moderated by Lithium-7 Hvdroxide 4

Battelle M e m o r i a l Institute

Reference: BMI-746, O r i g i n a t o r s : R. W. Dayton and J. W. Chastain. Status : Design calculations, 1952. Details: T h e r m a l neutrons s t e a d y s t a t e , c o n v e r t e r . F u e l - m o d e r a t o r coolant: Homogeneous suspension of Uz330z i n LiOH. Minimum fuel f o r criticality: about 2.5 kg Uz33. Reflector-breeding blanket: circulating suspension of T h o z i n DzO, about 1 g/cm3, in s p h e r i c a l annulus. Blanket thickness: 6 0 c m . C o r e contained by 2 concentric Z r s h e l l s , 0.5 c m thick. Shells s e p a r a t e d by a i r s p a c e 1 c m thick, which i s t h e r m a l b a r r i e r . Z r foil i n a i r s p a c e to i m p r o v e t h e r m a l b a r r i e r . C o r e t e m p e r a t u r e : 1100째F. Blanket t e m p e r a t u r e : 250째F. Breeding gain: m o r e than 0.2. Code: 0311 17 31312 45 637 756 84677 941 101

7 I

No. 2 Reflected Homogeneous R e a c t o r Moderated by Lithium - 7 Deut e roxi de

Battelle M e m o r i a l Institute

Reference: BMI-746. Orig - i n a t o r s : R, W. Dayton and J. W. Chastain. Status : Design calculations 1952. Details: S a m e a s Data Sheet No. 1, except that Li70D is u s e d i n s t e a d of Li 70H. 84677 941 101 Code: 0311 .17 31312 45 637 756

No. 3 MIT Fluid F u e l F u s e d - s a l t R e a c t o r MIT

R e f e r e n c e s : MIT-5000, pp. 12-19, 25-150; MIT-5001, pp. 11-37. O r i g i n a t o r s : C l a r k Goodman et al. Status: Design adopted f o r study of n u c l e a r p r o b l e m s of nonaqueous fluid-fuel r e a c t o r s , 1952. Details: F a s t n e u t r o n s , s t e a d y s t a t e , c o n v e r t e r . Fuel-coolant: m i x t u r e of molten UCl, ( 2 2 % U235)JPbC12, and NaC1. No m o d e r a t o r . Reflector: I'b, i m m e d i a t e l y s u r r o u n d i n g s e m i s p h e r i c a l c o r e . Fertile material: blanket of depleted U (containing 0.3% U235) a s UCl,, around r e f l e c t o r . Fuel-coolant is c i r c u l a t e d to e x t e r n a l h e a t e x c h a n g e r s . S t r u c t u r a l m a t e r i a l s : Ni o r F e . Control: r e f l e c t o r for s h i m control; negative t e m p e r a t u r e coefficient. Conversion r a t i o of UZ3*to Pu239: about 1.15. No power given. Code: 0111 11 31211 43 627 735 84679 941 108 82x88

No. 4 F u s e d Salt F a s t B r e e d e r R e a c t o r ORSORT Reference: C F - 56 -8-204, Del. Originators: 5. J. B u l m e r -,et al. Status: Design and feasibility study, 1956. ORSORT t e r m p a p e r . Details: F a s t n e u t r o n s , s t e a d y s t a t e , b r e e d e r . F u e l coolant: circulating m i x t u r e of molten NaC1, MgCl,, PuCl,, and U238C13; PuC13 i s a s s u m e d to be i n solution with UCl,; depleted U is f o r i n t e r n a l breeding. F e r t i l e m a t e r i a l : blanket of p a s t e of depleted UOz powder i n Na. F u e l contained in a 72.5 in. ID, n e a r l y s p h e r i c a l , v e s s e l , t a p e r e d a t the top and bottom to 24 in. f o r pipe connections. V e s s e l is of Ni-Mo alloy-clad s t a i n l e s s s t e e l . Reflector: 1 in. liquid P b i m m e d i a t e l y surrounding c o r e . Around r e f l e c t o r i s blanket, under 1 0 0 p s i p r e s s u r e . Stationary blanket i s divided into 2 regions by a 5t-in. s t a i n l e s s s t e e l - c l a d graphite m o d e r a t o r . An 8 in. graphite r e f l e c t o r s u r r o u n d s second blanket region. U s e of g r a p h i t e m o d e r a t o r i n middle of blanket r e d u c e s s i z e of blanket n e c e s s a r y . Blanket cooled by Na flowing through tubes. F u e l e n t e r s r e a c t o r c o r e a t bottom a t 105O0F and l e a v e s through the top at 1350Â°F, then i s pumped through an e x t e r n a l loop and tube s i d e of Na h e a t exchanger. Control: m a i n l y through negative t e m p e r a t u r e coefficient. Shim control by changing level of P b r e f l e c t o r . E s t i m a t e d breeding r a t i o : 1.09. P o w e r : 700 MW(t), 2 6 0 MW(e). Code: 0112 11 31211 46 627 755 84679 941 108 82188

No, 5 Internally Cooled Molten-salt R e a c t o r ORNL Reference: C F - 5 9- 6 - 89. Originator: M. E. Lackev. u Status: Calculations of n u c l e a r c h a r a c t e r i s t i c s ? 1959. Details: T h e r m a l n e u t r o n s , s t e a d y s t a t e , b r e e d e r . Fuel: UZ3,F4 i n molten m i x t u r e - - T h F 4 - L i F - B e F Z . Two compositions: ThF4--7, 13%; LiF--67.25, 71%; BeFZ--25.75, 16%. Coolant: molten fuel c a r r i e r . Moderator: graphite. F e r t i l e m a t e r i a l : blanket, 2.5 f t thick, of molten fuel c a r r i e r . Core: cylinder, 19.15 f t d i a m e t e r , 19.15 f t high, s u r r o u n d e d by blanket, i n INOR-8 p r e s s u r e s h e l l , 1.5 in. thick. Cylindrical p a s s a g e s f o r fuel and coolant i n m o d e r a t o r , p a r a l l e l to c o r e a x i s , i n t r i a n g u l a r lattice. Coolant tube i n each p a s s a g e . F u e l in annular s p a c e between coolant tube and m o d e r a t o r . No r e f l e c t o r . Control: negative t e m p e r a t u r e coefficient. P o w e r : 1563 MW(t). Doubling t i m e s : with 7 m o l % ThZ3â&#x20AC;&#x2122;, 27.5 y e a r s ; with 13 m o l %, 22.5 y e a r s . The Paz3, f o r m e d could b e diluted by mixing the fuelc a r r i e r s a l t with the blanket and coolant s a l t s . This should r e d u c e doubling t i m e s . F u r t h e r reduction p o s s i b l e by different c o r e a r r a n g e m e n t : 2 conc e n t r i c tubes, with fuel in the annulus and coolant flowing through the i n n e r tube and on outside of o u t e r tube. Code: 0312 12 31211 44 627 746 84679 931 106

61 No. 6 5 MW(50 MW) Thermal-convection Molten Salt Reactor ORNL R e f e r e n c e s : ORNL-2551, pp. 49-51; ORNL-2626, p. 48. Originator: J. Z a s l e r . Status: P r o p o s a l f o r p r e l i m i n a r y design, 1958. Details: T h e r m a l n e u t r o n s , s t e a d y s t a t e , b r e e d e r , S p h e r i c a l c o r e , 5 f t d i a m e t e r , s u r r o u n d e d by 0.5 f t blanket. Fuel-coolant: flows a t 158 gpm through r e a c t o r and shell-and-tube h e a t exchanger, cooled by N a y e n t e r i n g the h e a t exchanger a t 1210'F and leaving a t 1010'F. 5-MW(t) e x p e r i m e n t a l r e a c t o r could b e converted to 50-MW(t) pilot plant by adding fuel pumptj (to i n c r e a s e flow to 1515 gpm) and i n c r e a s i n g capacity of the fuel pumps. Code: 0312 1X 31211 4X 627 7XX 84679 9XX 106 No. 7 Molten Salt R e a c t o r (MSR; I n t e r i m Design R e a c t o r ; MoltenF l u o r i d e C o n v e r t e r ; Molten F l u o r i d e P o w e r R e a c t o r ; R e f e r e n c e Design R e a c t o r , RDR; MSR R e f e r e n c e Design; Homogeneous , Two-region Moltenfluoride -s alt Reactor) ORNL

R e f e r e n c e s : ORNL-2751; P r o c . 2nd U.N. Int. Conf. 9, 1958, pp. 188-2,Ol; e t -a l . , Fluid F u e l R e a c t o r s , pp. 657, 681-696. Lane A O r i g i n a t o r s : H. G. M a c P h e r s o n e t al. Status: Conceptual design, 1959; w o r k continuing. Details: I n t e r m e d i a t e n e u t r o n s , s t e a d y s t a t e , c o n v e r t e r . Fuel-coolantm o d e r a t o r : m i x t u r e of 90% e n r i c h e d U235F4 with LiF-BeF2-ThF4; a l t e r n a t e fuel: Pu239i n s t e a d of U235.Neutrons with this fuel a r e t h e r m a l . F e r t i l e m a t e r i a l : 2-ft-thick blanket, of T h F 4 a s eutectic of LiF-BeFz-ThF4, completely s u r r o u n d i n g fuel region. Both fluids c i r c u l a t e d to e x t e r n a l s h e l l and-tube h e a t e x c h a n g e r s , w h e r e h e a t is t r a n s f e r r e d to Na. S e v e r a l c o r e configurations considered: 1 ) s t r a i g h t - t h r o u g h flow, 2 ) c o n c e n t r i c irtlet ( i n n e r pipe)-outlet (outer annulus) flow, 3) concentric inlet (outer anrtu1us)outlet ( i n n e r pipe) flow. Core: i n v e r t e d - p e a r - s h a p e d , Ni-Mo alloy, 8 - f t i n d i a m e t e r (6-ft i n e a r l y d e s i g n s ) , s u r m o u n t e d by expansion c h a m b e r containing fuel pump. F u e l t e m p e r a t u r e : a p p r o x i m a t e l y 1200'F. Control:. n e g a t i v e t e m p e r a t u r e coefficient. Blanket produces U233 at conversion r a t i o of 0.6 to 0.8, depending upon p r o c e s s i n g . R e a c t o r designed as c e n t r a l - s t a t i o n power plant to p r o d u c e 6 0 0 MW(t), 260 MW(e). Code: 0211 17 312 44 627 746 84677 931 101 0311 46

No. 8 Two-region, Graphite-moderated Molten-salt B r e e d e r R e a c t o r ORNL Reference: ORNL- 2 7 9 9. O r i g i n a t o r s : MSR p r o j e c t staff. Status: Typical design f o r calculation of p e r f o r m a n c e , 1959. Details: T h e r m a l n e u t r o n s , steady s t a t e , b r e e d e r . Fuel-coolant: Uâ&#x20AC;?â&#x20AC;&#x2122;, p r e s u m a b l y a s UF4, dissolved i n molten LiF-BeFZ-ThF4. Moderator: graphite. Reflector: graphite. F e r t i l e m a t e r i a l : 30-in. blanket of 13 m o l % Th i n molten LiF-BeFz-ThF4. Core: m a i n p a r t m a d e f r o m single cylinder of graphite, about 5 f t d i a m e t e r , 5 f t long, and two end p i e c e s . T h r e e p i e c e s held together by r o d s of INOR-8 o r other alloy. P a r a l l e l v e r t i c a l channels f o r fuel flow, 1/2 in. max. r a d i u s . Molten fuel s a l t p a s s e s downward through c o r e then back upward to ext e r n a l h e a t exchanger. Blanket, which s u r r o u n d s c o r e , is kept a t slightly higher p r e s s u r e . P r e s s u r e : 1 0 0 0 p s i max. Control: p r e s u m a b l y negative t e m p e r a t u r e coefficient. P o w e r : 125 MW(t). Code: 0312 12 31211 45 627 746 84679 941 104

No. 9 Molten Salt B r e e d e r Reactor (MSBR) ORNL R e f e r e n c e s : CF-61-3-9, pp. 68-81; CF-61-8-86. et al. O r i g i n a t o r s : H. G. M a c P h e r s o n , L. G. Alexander, Status: R e f e r e n c e design f o r evaluation of t h o r i u m b r e e d e r r e a c t o r s , 1961. Details: N e a r - t h e r m a l n e u t r o n s , s t e a d y s t a t e , b r e e d e r . Fuel-coolant: UF4 i n LiF and BeF2. Moderator: graphite. F e r t i l e m a t e r i a l : blanket of ThF4 in L i F and BeF2. Reflector: graphite. C o r e cylinder 7-$-ft x 7+ft. of graphite m o d e r a t o r p r i s m s , 7.5 in. s q u a r e by approx. 7 f t long. C o r n e r s machined to f o r m v e r t i c a l p a s s a g e s of about 5 in. d i a m e t e r c i r c u l a r c r o s s section. F u e l flows through 90 2 - p a s s bayonet g r a p h i t e tubes i n s e r t e d into t h e s e v e r t i c a l p a s s a g e s . C o r e s u r r o u n d e d on a l l s i d e s by 3-ft blanket, which i s then s u r r o u n d e d by the 1-ft g r a p h i t e r e f l e c t o r , Heat exchanger and fuel pump mounted d i r e c t l y above the r e a c t o r . Maximum fuel t e m p e r a t u r e : 1300OF; m i n i m u m 1125OF. Operating p r e s s u r e : 1 0 0 p s i . Control: through negative t e m p e r a t u r e coefficient. P o w e r station would include 2 s u c h r e a c t o r s to produce 2364 MW(t) o r 1 0 0 0 MW(e)--1182 MW(t) and 500 MW(e) each. Code: 0312 12 31211 44 627 746 84679 941 104

No. 1 0 G r a p h i t e - m o d e r a t e d , Circulating F u e l , Molten Salt R e a c t o r P l a n t ORNL Reference: CF-59-12-64 Rev. Originator: H. G. M a c P h e r s o n . Status: R e f e r e n c e design, 1959. Details: T h e r m a l n e u t r o n s , s t e a d y s t a t e , b r e e d e r . Fuel-coolant: UZ35F4 in L i F - B e F Z , a t m i n i m u m t e m p e r a t u r e of 975째F and m a x i m u m of 1300째F, circulating at 2 0 fps. Moderator: graphite. F e r t i l e m a t e r i a l : blanket of Th, p r e s u m a b l y a s ThF4, in L i F - B e F Z . Core: 5.3 f t in d i a m e t e r ; blanket: 2.5 ft thick. Graphite m o d e r a t o r c o r e contains g r a p h i t e tubes through which fuel p a s s e s (unit fuel tube construction). Blanket s a l t a l s o p a s s e s through s m a l l p a s s a g e s in m o d e r a t o r f o r cooling. F u e l inlet and outlet at bottom of c o r e , although straight-through flow is possible. Control: p r e s u m a b l y b y negative t e m p e r a t u r e coefficient. P o s s i b l e breeding r a t i o : 1.06. Each of 3 r e a c t o r s in plant produces 815 MW(t), 333 MW(e). 11, 31211 44 627 746 84679 931 104 Code: 0312

References 1. H. G. M a c P h e r s o n , Molten-salt B r e e d e r R e a c t o r s , CF-59-12-64 Rev., ORNL, J a n . 12, 1960. 2. R. W. Dayton and J. W. Chastain, Hydroxides as Moderator-coolants in P o w e r - b r e e d e r R e a c t o r s , BMI-746, Del., BMI, May 26, 1952.

3 . C l a r k Goodman, J. L. G r e e n s t a d t , R. M. Kiehn, A b r a h a m Klein, M. M. Mills, and Nunzio T r a l l i , N u c l e a r P r o b l e m s of Nonaqueous Fluid-fuel R e a c t o r s , MIT-5000, MIT, Nucl. Eng. P r o j e c t , Octo 15, 1952. Decl., F e b . 28, 1957. 4. G e o r g e S c a t c h a r d , H. M. C l a r k , Sidney Golden, Alvin Boltax, and R e i n h a r d t Schuhmann, J r . , C h e m i c a l P r o b l e m s of Nonaqueous F l u i d f u e l R e a c t o r s , MIT-5001, MIT, Nucl. Eng. P r o j e c t , Oct. 15, 1952. Decl., Oct. 7, 1959. 5. J. J, B u l m e r , E. H. Gift, R. H. Holl, A. M. J a c o b s , S. J a y e , E. Koffman, R. L. McVean, R. G. Oehl, a n d R. A. R o s s i , F u s e d Salt Fast B r e e d e r , CF-52-8-204, Del., ORSORT, Aug. 1956.

6. M. E. Lackey, I n t e r n a l l y Cooled Molten-salt R e a c t o r s , CF-59-6-89, ORNL, J u n e 22, 1959. 7. M o l t e n - s a l t R e a c t o r P r o g r a m Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending J u n e 30, 1958, ORNL-2551, ORNL, Sept. 24, 1958. 8. M o l t e n - s a l t P r o g r a m Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending October 31, 1958, ORNL-2626, O R N L , Jan. 23, 1959.

9. L. G. Alexander, D. A. C a r r i s o n , H. G. M a c P h e r s o n , and J. T . R o b e r t s , N u c l e a r C h a r a c t e r i s tics of S p h e r i c a l , Homogeneous , Two-region, M o l t e n - f l u o r i d e - s a l t R e a c t o r s , ORNL-2751, ORNL, Sept. 30. 1959. 10. H. G. M a c P h e r s o n , H. W. Savage, R. C. B r i a n t , W. H. J o r d a n , L. G. Alexander, W. F. Boudreau, E. J. Breeding, W. G. Cobb, B. W . Kinyon, M. E. Lackey, L. A. Mann, W. B. McDonald, J. T . R o b e r t s , A. W. Savolainen, E. S t o r t o , F. C. VonderLage, G. D. Whitman, and J. Z a s l e r , Molten F l u o r i d e P o w e r R e a c t o r , P r o c . 2nd U.N, Int. Conf. on P e a c e f u l U s e s of Atomic E n e r g y , Geneva, 1958, 9, pp. 188-201, U n i t e d N a t i o n s , New York, 1958.

11. L. G. Alexander, B. W. Kinyon, M. E. Lackey, H. G. M a c P h e r s o n , L. A. Mann, J. T. R o b e r t s , F. C. VonderLage, G. D. Whitman, and J. Z a s l e r , Conceptual Design of a P o w e r R e a c t o r , in F l u i d F u e l R e a c t o r s , J. A. Lane, H. G. M a c P h e r s o n , and F r a n k Maslan, e d s . , Addison-Wesley Publishing Company, Reading, M a s s . , 1958, pp. 681-696.

12. Ibid., p. 657. 13. M o l t e n - s a l t R e a c t o r P r o g r a m Q u a r t e r l y P r o g r e s s R e p o r t f o r P e r i o d Ending J u l y 31, 1959, ORNL-2799, ORNL, Oct. 8, 1959.

14. L. G. Alexander, W. L. C a r t e r , R. H. Chapman, B. W. Kinyon, J. W. M i l l e r , and R e Van Winkle, T h o r i u m B r e e d e r R e a c t o r Evaluation. P a r t I. F u e l Yield and F u e l Cycle Costs in F i v e T h e r i n a l B r e e d e r s , CF-61-3-9, ORNL, May 24, 1961. 15. W. L. C a r t e r and L. G. Alexander, T h o r i u m B r e e d e r R e a c t o r Evaluation. P a r t I. F u e l Yields and F u e l Cycle C o s t s of a Twor e g i o n p Molten Salt B r e e d e r R e a c t o r , CF-61-8-86, ORNL, Aug. 18, 1961.

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