ORNL-TM-1855 by Jon Morrow

. -

INTRA-LABORATORY CORRESPONDENCE OAK R I D G E NATIONAL L A B O R A T O R Y

October

To:

3, 1967

Recipients of the subject report.

Report No, :

Author(s): Subject:

ORNL-TM- 1855___-._-

Dunlap Scott and

CIassi f icat ion:

Unclassified

A.__ G. Grindell

Components and Systems Development for

Molten-Sa\-t Breeder Reactors

For your information: Reference 7, on page

52 of

subject report

is incorrect.

It should read as follows:

7P. G. Smith, Experience with High-Temperature Centrifugal Pumps i n Nuclear Reactors and Their Application to Molten-Sal t Thermal Breeder Reactors, ORNL-TM-1993 (September 1967).

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L.l,l’>gg# et..9,$‘t cd

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N. T. Bray, Supervisor Laboratory Records Department Technica I lnforma t ion D ivtsion NTB:WC 8:dbp

UCN-6638 (3 s-651

UCN-430 13 5-61)

iii

TABLE OF CONTENTS INTRODUCTION GENERAL STATUS OF TECKNOLOGY

PURPOSE AND SCOPE OF DEVELOPMXNT PROGRAM

mACTOR COm

Review of Hydraulic Tests o f t h e MSRE Core

Hydraulic T e s t s f o r t h e MSBE Core

Fuel C e l l Tests i n Molten S a l t

CONTROL ROD AND DRIVE

C o n t r o l Rod System f o r t h e K R E

C o n t r o l Scheme f o r t h e MSBR

SALT PUMPS FOR MOLTEN SALT

P r e s e n t Technology

Requirements f o r Pumps f o r Breeder R e a c t o r s

Program Scope

Design and Development Program

E f f e c t s of P h y s i c a l P r o p e r t i e s of Breeder S a l t s on Pump Design

S p e c i f i c Design Problems and Goals

S e p a r a t i o n Requirement

Hydraulic Design

Rotordynamic A n a l y s i s

Plastic Strain

Purge Gas Requirements

S i z e - S c a l i n g Requirements

S p e c i f i c Development Problems and Goals

iv TABLE -

OF CONTENTS ~

cont'd

F u e l m d Blanket Pumps

Page

S h a f t Damper T e s t e r

Molten-Salt Bearing T e s t e r

Pump T e s t F a c i l i t y

Coolant S a l t Punrps

HEAT EXCIIANGERS

Review o f Heat Exchangers i n t h e MSEE

Fundamental Molt en-Salt Heat Trans f e r

Heat Exchangers f o r Breeder R e a c t o r s

Fuel-Salt Heat Exchanger

Blanket-Salt Heat Exchanger

Steam Reheater

Reheat Steam P r e h e a t e r s

Boiler-Superheater

Heat Trans f e r Enhanc ernent

PRESSURE RELIEF I N COOLANT SYSTEM

DRAIN AND STOFUGE TANKS

Drain Tank System f o r t h e MSRE

Drain Tank System for t h e MSBE

VALVES FOR MOLTEN SALTS

SALT SAMPLERS

GAS SYSTEM

MSRE Cover and Offgas Systems

MSRE Gas System Performance

MSBH Offgas System

314

TABLE OF --.--CONTENTS - c o n t ' d __-l_l

MSBE Offgas System De ve Lopment Program

Gas S e p a r a t o r

Mass T r a n s f e r t o C i r c u l a t i n g Subbles

Salt-Powered I n j e c t o r

Cyclone S e p a r a t o r

S a l t - M i s t Removal

F i s s i o n Product F i l t e r

Kr-85 and T r i t i u m Removal System

Gas Compressor

G a s Sampler

MSBE Gas System T e s t Loop

CELL FURNACE AND SHIELDING

STEAM SYSTEM

TURBINE GENERATOR

ENGINEERING TEST UNIT

SCHEDULE AND COST

ACKNOWLEDGEMENTS

INTRODUCTION The c o n c e p t u a l d e s i g n of a lOOO-Mw( e ) Molten--Salt Breeder Reactor (MSBR) i s d e s c r i b e d i n 0 ~ ~ ~ - 3 9 9 6 The . Molten-Salt Reactor Experiment (MSRE) ,2now o p e r a t i n g , r e p r e s e n t s a f i r s t s t e p i n t h e development of such a r e a c t o r . A Molten-Salt Breeder Experiment (MSBE) i s proposed as t h e n e x t s t e p . This r e a c t o r would be a 100- t o 15O-Mw(th) model of t h e MSBR designed t o demonstrate a l l a s p e c t s of t h e b r e e d e r technology under c o n d i t i o n s at least as s e v e r e as t h o s e proposed f o r t h e f u l l - s c a l e b r e e d e r . Components and systems f o r t h e MSBE would i n c o r p o r a t e a l l t h e features o f t h e f u l l - s c a l e u n i t s s o t h a t "scaling-up" t h e equipment t o h i g h e r power l e v e l would be t h e major t a s k i n b u i l d i n g t h e r e f e r e n c e breeder. The purpose of t h i s r e p o r t i s t o d e s c r i b e t h e present; s t a t u s of development o f components and systems f o r m o l t e n - s a l t r e a c t o r s and t o p r e s e n t a development program f o s t h e MSBE. S i n c e no d e s i g n h a s been made f o r t h e b r e e d e r experiment, t h e program i s based on a s t u d y o f t h e problems of t h e r e f e r e n c e d e s i g n assuming t h a t t h e MSBE would b e a "scaled-down" v e r s i o n of t h e modular concept d e s c r i b e d i n t h e r e f e r e n c e r e p o r t . For purposes of o r g a n i z i n g t h i s r e p o r t and t h e development program, t h e p l a n t was s u b d i v i d e d i n t o components, systems, and g e n e r a l problem areas. The d e s i g n , t h e problems, t h e p r e s e n t s t a t u s of t h e t e c h n o l o g y , and t h e r e q u i r e d development are d i s c u s s e d f o r each subdivision.

GE3JERAL STATUS OF TECHNOLOGY --_---I_-.I_---.-_The i n i t i a l technology development f o r m o l t e n - s a l t r e a c t o r s w a s done i n t h e e a r l y 1950's i n t h e A i r c r a f t Nuclear P r o p u l s i o n (ANP) Program a t O a k Ridge N a t i o n a l Laboratory. I n c a r r y i n g o u t t h i s program, much i n f o r m a t i o n on t h e p h y s i c a l , chemical and e n g i n e e r i n g c h a r a c t e r i s t i c s of m o l t e n - s a l t systems w a s o b t a i n e d from s t u d i e s of f l u o r i d e salt c h e m i s t r y , and m a t e r i a l s c o m p a t i b i l i t y , and from development of compone n t s , materials, f a b r i c a t i o n methods, and r e a c t o r maintenance methods. I n 1954 t h e A i r c r a f t Reactor Experiment (ARE), a 2-1/2 Mw(th) moltens s l t r e a c t o r - - f u e l e d w i t h UF4 d i s s o l v e d i n a m i x t u r e of zirconium and sodium f l u o r i d e s , moderated w i t h b e r y l l i u m o x i d e , and c o n t a i n e d i n Inconel--was b u i l t and o p e r a t e d s u c c e s s f u l l y a t o u t l e t s d t t e m p e r a t u r e s up t o 1650째F. The p r e s e n t m o l t e n - s a l t r e a c t o r program w a s i n i t i a t e d i n 1957, draw i n g upon t h e i n f o r m a t i o n developed i n t h e ASJP program as w e l l as b e g i n n i n g new i n v e s t i g a t i o n s . By 1960 enough f a v o r a b l e e x p e r i m e n t a l r e s u l t s were o b t a i n e d t o s u p p o r t a u t h o r i z a t i o n for d e s i g n and c o n s t r u c t i o n of a lO-Mur(th) Molten-Salt R e a c t o r Experiment (MSRE'). The MSRE i n i t i a t e d power o p e r a t i o n i n e a r l y 1966, and p r o v i d e s f a c i l i t i e s for t e s t i n g f u e l s a l t , g r a p h i t e , and H a s t e l l o y N under a p p r o p r i a t e r e a c t o r o p e r a t i n g c o n d i t i o n s . The b a s i c r e a c t o r performance t o d a t e h a s been o u t s t a n d i n g , and i n d i c a t e s t h a t t h e d e s i r a b l e features o f t h e moltens d t concept can be embodied i n a p r a c t i c a l r e a c t o r t h a t can b? c o n s t r u c t e d , o p e r a t e d , and maintained with s a f e t y and r e l i a b i l i t y ,

The pu-rpose of t h e program i s t o p r o v i d e components and systems w i t h demonstrated r e l i a b i l i t y f o r u s e i n t h e MSHE. A l l components and systems niust be of a design. t h a t can be s c a l e d up t o t h e h i g h e r power l e v e l of t h e PEBR. The development of new t y p e s of equipment m d improvement of e x i s t i n g equipment r e q u i r e t h a t l i f e - t e s t s be performed. Such t e s t s p r o v i d e in:fomnat ion on l i m i t i n g o p e r a t i o n a l c h a r a c t e r i s t i c s and a s s i s t i n p r e d i c t i n g maintenance requirements. I n a d d i t i o n , c e r t a i n performance t e s t s must be made on components when o p e r a t e d as p a r t of a system t o p r o v i d e i n f o r m a t i o n f o r e v a l u a t i n g t h e c o m p a t i b i l i t y of t h e component w i t h t h e system. The devel.opment of new t y p e s of equipment such as t h e steam g e n e r a t o r , t h e off-gas d i s p o s a l system, t h e s a l t - c o o l e d c o n t r o l r o d , and. t h e l o n g s h a f t m o l t e n - s a l t pumps w i l l r e q u i r e s e p a r a t e t e s t f a c i l i - t i e s of s i g n i f i c a n t s i z e . I n a d d i t i o n , t h e r e w i l l b e numerous s m a l l t e s t s conducted t o a a s i . s t i n r e s o l v i n g d e s i g n f e a t u r e s as w e l l as t o e s t a b l i s h t h e expected l i f e of sOme components. These s m a l l t e s t s may b e conducted i n s e p a r a t e f a c i l i t i e s b u t i n many c a s e s t h e y can be i n c o r p o r a t e d i n t o one of t h e l a r g e r t e s t f a c i l i t i e s . In many areas t h e technology i s reasona.bly w e l l e s t a b l i s h e d , b u t c o n s e r v a t i v e e n g i n e e r i n g r e q u i r e s performance and l i f e t e s t i n g of t h e components t o m a k e s u r e t h e y w i l l operate s a t i s f a c t o r i l y with t h e reactor.

For a f i n a l demonstration of t h e r e l i a b i l i t y and c o m p a t i b i l i t y of a l l m o l t e n - s a l t connect,ed componenLs and systems, an Engineering T e s t Unit ( E T U ) , a f u l l - s c a l e o p e r a t i n g model of t h i s MSBE, w i l l b e c o n s t r u c t e d and o p e r a t e d , e s s e n t i a l l y i s o t h e r m a l l y , o v e r t h e ranges o f temperature and s a l t flow proposed f o r t h e PEBE. A s d e s c r i b e d i n t h e a p p r o p r i a t e s e c t i o n s , t h e f i n a l e v a l u a t i o n of t h e components w i l l be made w h i l e o p e r a t i n g as a p a r t of t'nis system. The model xi11 a l s o b e used t o t r a i n o p e r a t o r s f o r t h e r e a c t o r and t o demonstrate t h e maintenance procedures and equipment. REACTOR CORE Iieview of Hydraulic 'Tests --.I_____. of t h e MSRE Core

_ _ I -

The M S R 3 r e a c t o r v e s s e l i s a 5 - f t - d i m by 8-ft-high t a n k t h a t cont a i n s a 55-in - d i m by 6 7 - h . -high g r a p h i t e c o r e s t r u c t u r e . Under design c o n d i t i o n s o f 1 0 Mw o f r e a c t o r h e a t , t h e f u e l salt would e n t e r t h e flow d i s t r i b u - L o r a t t h e t o p o f t h e v e s s e l a.t ll'75'F and 20 p i g . Tne f u e l i s d i s t r i b u t e d evenly around t h e circumference of t h e v e s s e l and then flows t u r b u l e n t l y downward i n a s p i r a l p a t h throuzh a 1-in. annulus between t h e v e s s e l wall and t h e core can. The salt, l o s e s i t s r o t a t i o n a l motion i n t h e s t r a i g h t e n i n g vanes i n t h e lower plenum and t u r n s and flows upward through t h e g r a p h i t e m a t r i x i n the c o r e can. The g r a p h i t e m a t r i x i s an assembly of v e r t i c a l b a r s , 2 i n . by 2 i n . by about 67 i n . l o n g . The f u e l flows i n 0.4-in- by 1 . 2 - i n . channels t h a t are formed by grooves i n t h e s i d e s of t h e b a r s . There are about 11.40 of t h e s e e

3 p a s s a g e s . F u e l w a s t o l e a v e t h e t o p of t h e r e a c t o r a t 1225'F. Add.it i o q a l d e s c r i p t i o n of t h e MSRE c o r e i s g i v e n i n t h e MSRE Design Report, 2 The c o r e development program w a s divid-ed i n t o two p h a s e s . The f i r s t phase c o n s i s t e d of b u i l d i n g and t e s t i n g a 1/5 l i n e a r l y s c a l e d p l a s t i c model. T h i s model w a s o p e r a t e d w i t h w a t e r and w a s r e l a t i v e l y i n e x p e n s i v e . It w a s used as a r a p i d method of checking t h e p r e l i m i n a r y design t o e s t a b l i s h t h e a c c e p t a b i l i t y o f major c o n c e p t s . The second phase c o n s i s t e d o f b u i l d i n g and t e s t i n g a f u l l - s c a l e model o f t h e c o r e a t t h e r a t e d flow. T h i s model w a s used t o e s t a b l i s h t h e d e s i g n . The c o r e vessel w a s made of carbon s t e e l and t h e moderator b a r s were e x t r u d e d from aluminum. T h i s model was used f o r a f i n a l and much more d e t a i l e d look a t t h e h y d r a u l i c and t h e r m a l c h a r a c t e r i s t i c s of t h e c o r e . Some of t h e major i t e m s s t u d i e d were:

1. O v e r d l p r e s s u r e drop and d i s t r i b u t i o n of t h i s p r e s s u r e drop among t h e c o r e components. 2.

Flow d i s t r i b u t i o n by t h e v o l u t e .

E f f i c i e n c y of t h e s w i r l k i l l e r s i n t h e lower v e s s e l head.

4. Heat transfer c o e f f i c i e n t s i n t h e lower and upper heads t o a s s u r e adequate v e s s e l w a l l c o o l i n g . 5. Flow d i s t r i b u t i o n s i n t h e lower and. upper h e a d t o a s s u r e t h a t no s t a g n a n t s a l t p o c k e t s were p r e s e n t .

Tendency of p a r t i c u l a t e matter t o s e t t l e out i n t h e lower v e s s e l h e a d , on t h e t o p s o f t h e c o r e b a r s , and on t h e c o r e s u p p o r t flange.

Various o t h e r more minor phenomena.

Most o f t h e measurements were made w i t h water i n t h e loop, and a t flow r a t e s from t h e d e s i g n flow down t o 25% of t h e d e s i g n flow. With water, however, t h e Reynolds number vas several t i m e s h i g h e r t h a n would be e x p e c t e d f o r f u e l s a l t a t t h e n o t e d flow r a t e . To a t t a i n Reynolds s i m i l a r i t y , a t h i c k e n i n g a g e n t was added t o t h e water t o i n c r e a s e i t s v i s c o s i t y , and t h e r e f o r e d e c r e a s e t h e Reynolds number. S e v e r a l a f t h e i t e m s i n t h e above l i s t were t h e n rechecked. The agreement between measurements i n t h e 1/5 s c a l e model, t h e f u l l - s c a l e model w i t h water, and t h e f u l l - s c a l e model w i t h t h i c k e n e d w a t e r , was good where e q u i v a l e n t measurements were made. None of t h e s e measurements were checked i n a m o l t e n - s a l t system. It w a s b e l i e v e d t h a t t h e h e a t and momentum t r a n s f e r a n a l o g i e s were a d e q u a t e l y w e l l e s t a b l i s h e d t o e x t r a p o l a t e w a t e r d a t a t o a m o l t e n - s a l t system w i t h a d e g r e e of r e l i a b i l i t y much g r e a t e r t h a n was r e q u i r e d t o i n s u r e adequate performance of t h e MSRX. During t h e c o u r s e o f MSRE c o r e development, s e v e r a l s m a l l models were made t o check some h y d r a u l i c phenomena. G e n e r a l l y , t h e s e models were made of p l a s t i c and o p e r a t e d w i t h t a p water.

4 Hydraulic T e s t s f o r t h e MSBE Core The r e a c t o r core for t h e MSBE i s e x - p e c t e d t o be about 4 - f t - d i m by 5-ft-high and composed of r e - e n t r a n t t y p e g r a p h i t e f u e l c e l l s t h r o u g h which -the f u e l sa1.t f l o w s . The g r a p h i t e t u b e s a r e a t t a c h e d t o two plenum chambers at t h e bottom of t h e r e a c t o r w i t h g r a p h i t e - t o - m e t a l t r a n s i t i o n s l e e v e s . Fuel from t h e e n t r a n c e plenum flows up through t h e o u t e r annulus o f t h e f u e l c e l l and down through t h e c e n t r a l passage t o t h e e x i t plenum. The f u e l flows from t h e e x i t pl.enum t o t h e pump t h e n through t h e h e a t exchanger and back t o t h e r e a c t o r . A 2-f't-thick b l a n k e t of a thorium-containing s a l t and g r a p h i t e surrounds t h e c o r e . The b l a n k e t s a l t a l s o permeates -the i n t e r s t i c e s o f t h e c o r e l a t t i c e s o f e r t i l e m a t e r i a l flows through t h e c o r e without mixing w i t h t h e f i s s i l e fuel salt. Generally s p e a k i n g , t h e MSRE c o r e w i l l be t h a n t h e MSRE c o r e because of i t s much h i g h e r posed development program for t h e MSBE core w similar t o t h a t f o r t h e MSRE c o r e , and can b e program.

s t u d i e d more c r i t i c a l l y power d e n s i t y . The proi l l b e , i n many r e s p e c t s , t h o u g h t o f as a two-phase

The f i r s t phase w i l l b e d i r e c t e d toward making p l a s t i c models as n e c e s s a r y f o r r a p i d and p r e l i m i n a r y checks on major design c o n c e p t s . This could t a k e t h e form of a complete scaled-down p l a s t i c model as i n t h e MSRE, but probably n o t . Xather, s m a l l p l a s t i c models o f i n d i v i d u a l c o r e components w i l l be b u i l t and t e s t e d . Probable examples a r e : 1. A small model of t h e f u e l s a l t d i s t r i b u t i o n plenums would b e b u i l t and t e s t e d for p r o p e r flow d i s t r i b u t i o n t o t h e f u e l c e l l s . 2 . A s m a l l model of t h e b l a n k e t s a l t d i s t y i b u t o r wou1.d be b u i l t and t e s t e d f o r pl-oper flow d i s t r i b u t i o n .

3. A s i n g l e f u l l - s c a l e model of a f u e l c e l l would be b u i l t and t e s t e d w i t h t a p water t o measure t h e p r e s s u r e drop and check f o r adeq u i t e degassing on s t a r t u p .

Other models as needed t o p r o v i d e confidence i n t h e d e s i g n .

Assembled u n i t s do n o t always behave as one might expect from o b s e r v i n g i n d i v i d u a l components. It i s t h e r e f o r e n e c e s s a r y t o t e s t h y d r a u l i c a l l y a complete p r o t o t y p e of t h e c o r e . A f u l l - s c a l e p r o t o t y p e i s a v a i l a b l e i n t h e ETU and it i s planned t o run t h e ETU w i t h water for a p e r i o d of t i m e , t h u s f l i i i d measurements c o u l d be e a s i l y o b t a i n e d . However, it may t a k e 6 montins t o a y e a r t o make a l l t h e measurements n e c e s s a r y i n t h e c o r e . It would c e r t a i n l y be u n d e s i r a b l e t o r e s t r i c t t h e ETU t o water o p e r a t i o n f o r t h i s long a p e r i o d of t i m e . We t h e r e f o r e plan, as phase two, t o b u i l d a n o t h e r and much l e s s expensive prototype o f t h e core s u i t a b l e f o r operating i n a c i r c u l a t i n g water loop. This s p e c i a l loop w i l l a l s o a l l o w u s t o s t a r t t e s t i n g t h e core sooner t h a n i n -theETU, p o s s i b l y i n FY 1969. The l o o p w i l l s i m u l a t e b o t h s a l t systems. The core s i z e w i l l b e h a l f t o f u l l s c a l e , although f u l l s c a l e

i s p r o b a b l y more d e s i r a b l e . will b e :

The p r i n c i p a l o b j e c t i v e s of t h i s model

1. To demonstrate t h e r e q u i r e d flow d i s t r i b u t i o n of f u e l and b l a n k e t s a l t throughout t h e c o r e . 2.

To i n s u r e adequate flow f o r c o o l i n g s t r u c t u r a l members of t h e

To demonstrate t h a t no s t a g n a n t f u e l and b l a n k e t s a l t r e g i o n s

core. exist.

To i n s u r e complete d e g a s s i n g o f a11 f u e l t u b e s d u r i n g f i l l i n g and s t a r t u p .

To show t h a t f l u i d induced v i b r a t i o n s are below a c c e p t a b l e

levels. These measurements w i l l be made over a range of flow r a t e s both above and below t h e d e s i g n v a l u e s . Water w i l l be t h e f l u i d u s e d i n most of t h e s e t e s t s and Reynolds s i m i l a r i t y w i l l n o t h o l d . Where n e c e s s a r y , t h e measurements w i l l be r e p e a t e d w i t h a t h i c k e n i n g agent added t o t h e w a t e r t o a t t a i n Reynolds s i m i l a r i t y . Measurements made i n t h e ETU would t h e n be l i m i t e d t o t h o s e thought n e c e s s a r y t o confirm r e s u l t s of t h e water model. C e r t a i n l y some d a t a w i l l be t a k e n w i t h water i n t h e system. Some d i r e c t measurements w i t h s a l t i n t h e system may b e n e c e s s a r y , a l t h o u g h t h i s w i l l be a more d i f f i c u l t t a s k and might have t o a w a i t development of a d d i t i o n a l i n s t r u m e n t a t i o n . N e v e r t h e l e s s , i f some f l u i d dynamic c h a r a c t e r i s t i c of t h e c o r e i s s u f f i c i e n t l y c r i t i c a l , it c o u l d be checked out i n t h e ETU while c i r c u l a t i n g s a l t . Fuel -

C e l l Tests i n Molten S a l t

Demonstration of t h e performance o f f u l l - s c a l e MSBE f u e l c e l l s w i t h o u t r a d i a t i o n i s an important p a r t of t h e e a r l y phases of core development f o r t h e MSBE. A s soon as p r a c t i c a b l e , r e p r e s e n t a t i v e g r a p h i t e f u e l c e l l s w i l l be o p e r a t e d w i t h t h e f u l l design s a l t f l o w s , t e m p e r a t u r e s and p r e s s u r e d i f f e r e n c e s . These t e s t s w i l l b e run i n t h e pump development l o o p and t h e o f f - g a s t e s t l o o p . Remo.rra.1 and r e p l a c e ment by t h e remote m e a n s w i l l be demonstrated as p a r t of t h i s t e s t pro-

gram.

CONTROL ROD AND DRIVE The d e s i g n of t h e MSBR t a k e s advantage of t h e e a s e of adding f u e l w h i l e t h e r e a c t o r i s o p e r a t i n g t o minimize t h e excess r e a c t i v i t y i n t h e c o r e , t h e a b i l i t y t o d r a i n t h e f u e l t o e f f e c t complete shutdown and s a f e t y f u n c t i o n s . However, a c o n t r o l r o d o r r o d s , as y e t undesigned, are included t o permit short-term adjustments t o t h e r e a c t o r temperature a

6 C o n t r o l Rod System f o r t h e MSRE -I

II.-

The c o n t r o l r o d system f o r t h e MSRE c o n s i s t s of a f l e x i b l e poison rod t h a t i s moved i n and out of a r e - e n t r a n t t h i m b l e by a continuous l i n k - c h a i n d r i v e mechanism. This chain d r i v e i s c o n t r o l l e d by a servomotor through a magnetic-clut ch arrangement which p e - m i t s r a p i d i n s e r t i o n of t h e poison r o d . I n a d d i t i o n t h e r e a r e e l e c t r i c a l synchros and p o t e n t i o m e t e r s f o r remote i n d i c a t i o n of p o s i t i o n , l i m i t s w i t c h e s f o r control. o f t h e range of motion, and a shock a b s o r b e r t o s t o p t h e r a p i d i n s e r t i o n . The d r i v e unit and t h e con-Lrol element are cooled by c i r c u l a t i n g a i r through t h e d r i v e housing and through t h e c e n t e r of t h e c o n t r o l rod. The poison elements o p e r a t e at a t e m p e r a t u r e i n t h e 1200 t o 1400'F r a n g e . The e l e c t r o m e c h a n i c a l d r i v e u n i t , mounted w e l l above t h e r e a c t o r v e s s e l , i s s l i g h t l y above ambient c e l l a i r t e m p e r a t u r e which does n o t exceed 150'F. Two c o n d i t i.ons dominated t h e d e s i g n , high-thinible t e m p e r a t u r e and maintenance-free o p e r a t i o n . The e l e c t r o m e c h a n i c a l design o f t h e d r i v e u n i t i s s t r a i g h t f o r w a r d , complicated p r i n c i p a l l y by space r e s t r i c t i o n s . It was n o t expected t o be troublesome. The s e r v i c e r e c o r d of t h e s e MSRE r o d s and a s s o c i a t e d d r i v e i n i . t s has been good b u t o n l y because t h e f i n a l design was preceded by o v e r a y e a r of concent r a t e d developmental t e s t i n g o f a p r o t o t y p e u n i t . A s e x p e c t e d , t h e s e t e s t s d i s c l o s e d a nunher of d e f e c t s and confirmed t h e q u a l i t y of t h e f i n a l version. C o n t r o l S s m e f o r t h e -MSBN Although experience w i t h t h e c o n t r o l r o d s f o r t h e MSF3 p r o v i d e s a u s e f u l background, t h e c o n t r o l rod and d r i v e f o r t h e MSBE w i l l b e c o n s i d e r a b l y d i f f e r e n t . Design of t h e d r i v e should be s t r a i g h t f o r w a r d b u t a i r c o o l i n g o f t h e rod would n o t s u f f i c e a t t h e much h i g h e r power d e n s i t y , and. t h e m e t a l t h i m b l e would absorb t o o many of t h e n e u t r o n s needed f o r b r e e d i n g 2 3 3 U . A l i k e l y c o n t r o l scherae f o r t h e MSBE i n v o l v e s t h e i n s e r t i o n of t h e c o n t r o l element d i r e c t l y i n t o t h e c e n t e r o f t h e r e a c t o r c o r e , without u s i n g a t h i m b l e , and l e t t i n g t h e f e r t i l e b l a n k e t s a l t p r o v i d e t h e n e c e s s a r y c o o l i n g . I f it groves n e c e s s a r y t o p r o v i d e c o o l i n g f o r t h e p o r t i o n of t h e g r a p h i t e r o d which i s i n t h e gas s p a c e above t h e f e r t i l e s a l t , a s m a l l stream can be d i v e r t e d from t h e i n l e t l i n e and d i r e c t e d over t h e r o d . One problem of t h i s scheme i s t h a t t h e d r i v e mechanism must a l s o be w i t h i n a g a s space d i r e c t l y connected t o t h e b l a n k e t s a l t . Not o n l y does t h i s r a d i o a c t i v e environment p r e s e n t a problem of e l e c t r i c a l design b u t it a l s o makes t h e r e p a i r of t h e d r i v e d i f f i c u l t . A system of gas seals and b u f f e r c o n t r o l should b e developed t o perrnit t h e d r i v e t o o p e r a t e i n a c l e a n gas atmosphere. A thorough development and. p r o t o t y p e t e s t i n g program w i l l b e yequired. Components o f t h e d r i v e and rod w i l l be t e s t e d s e p a r a t e l y , and t h e n t e s t e d i n assembly i n a s i m u l a t e d r e a c t o r environment. F i n a l l y , t h e r o d w i l l be o p e r a t e d i n t h e ETU.

7 SALT PUMPS FOR MOLTEN SA.LT The approach which w i l l be followed t o p r o v i d e t h e pumps r e q u i r e d f o r m o l t e n - s a l t b r e e d e r s i s o u t l i n e d . A b r i e f resume' i s p r e s e n t e d o f t h e p r e s e n t s t a t u s o f molten s a l t pump technology at ORNL and t h e cons i d e r a t i o n s given t o u s i n g t h e MSRE pump c o n f i g u r a t i o n i n t h e b r e e d e r c o n c e p t - A more d e s i r a b l e pump c o n f i g u r a t i o n i s broached, and t h e problems a n t i c i p a t e d w i t h it are l i s t e d . F i n a l l y , t h e s p e c i f i c design and development problems f o r t h e new c o n f i g u r a t i o n as t h e y are p r e s e n t l y e n v i s i o n e d are d i s c u s s e d i n more d e t a i l . P -----r e s e n t Technology The p r e s e n t s t a t u s of t h e technology of molten s a l t pumps at ORNL i s s e t f o r t h i n References 3, 4 , 5 and 6. I n b r i e f , w e have developed t h e sump pump c o n f i g u r a t i o n i n which t h e i m p e l l e r i s mounted on t h e lower end of t h e pump s h a f t below t h e lower s h a f t b e a r i n g . Conventional b a l l b e a r i n g s and s h a f t s e a l s , l u b r i c a t e d and c o o l e d w i t h a petroleum b a s e t u r b i n e o i l , are u t i l i z e d . The v e r t i c a l s h a f t i s mounted i n a b e a r i n g housing t o s u p p o r t and g u i d e t h e i m p e l l e r i n t h e pump v o l u t e , which i s an i n t e g r a l p a r t of t h e pump tank. The pump t a n k also s e r v e s as t h e expansion t a n k f o r t h e molten s a l t system and i s u s e d i n t h e MSRE f o r t h e removal of gaseous f i s s i o n p r o d u c t s such as 135Xe. These pumps have been b u i l t i n s i z e s from 2 t o 1600 gprn t o develop heads t o 400 f t o f f l u i d . They have been used t o pump molten s a l t s The MSRE f u e l s a l t pump and l i q u i d m e t a l s t o t e m p e r a t u r e s o f 1500'F. c i r c u l a t e s 1200 gpm normally a t 1210'F a g a i n s t 49 f t of head, and t h e c o o l a n t s a l t pump c i r c u l a t e s 850 g p m normally a t 1020'~ a g a i n s t 78 ft o f head. The MSRE p r o t o t y p e f i e 1 pump w a s o p e r a t e d a t t e m p e r a t u r e s up t o

1500'F

Four 5 gpm pumps, one 750 gpm and one 1200 gpm pump, were o p e r a t e d f o r p e r i o d s g r e a t e r t h a n one y e a r . The a t t e m p e r a t u r e s above 1200'F 750 gpm pump was o p e r a t e d w i t h molten s a l t f o r 25,000 h r a t 1200'F i n a regime of c a v i t a t i o n . Another t e s t pump which w a s equipped w i t h a submerged j o u r n a l b e a r i n g l u b r i c a t e d w i t h molten s a l t w a s o p e r a t e d f o r 12,000 h r , d u r i n g which it w a s s t a r t e d and s t o p p e d approximately 100 times . Two pump c h a r a c t e r i s t i c s of concern t o o p e r a t i o n of t h e MSRE were determined i n somewhat s p e c i a l f a s h i o n s . Techniques were developed u s i n g 8 5 K r t o measure t h e back d i f f u s i o n of gaseous f i s s i o n p r o d u c t s a g a i n s t a flow of purge g a s i n t h e s h a f t annulus of t h e MSRE f u e l pump. The conc e n t r a t i o n o f u n d i s s o l v e d gas i n t h e c i r c u l a t i n g molten s a l t w a s measured f o r t h e MSRE f u e l pump i n t h e p r o t o t y p e pump t e s t f a c i l i t y u s i n g r a d i a t i o n d e n s i t o m e t r y d e v i c e s and t e c h n t q u e s a d a p t e d t o t h e t a s k . Larger pumps, o f d e s i g n s s i m i l a r t o t h o s e proposed f o r l a r g e molten s a l t pumps, have been b u i l t and o p e r a t e d i n l i q u i d m e t a l cooled r e a c t o r s . Operating c o n d i t i o n s f o r t h r e e such pumps are g i v e n i n Table 1. Experience w i t h t h e s e pumps b e a r s d i r e c t l y on t h e development of pumps f o r t h e

8 molten s a l t b r e e d e r r e a c t o r s . A s u r v e y 7 o f t h e p e r t i n e n t design f e a t u r e s and t h e o p e r a t i n g e x p e r i e n c e s with t h e s e l a r g e r pumps i s being made t o s t i m u l a t e a n d enhance t h e i r c o n t r i b u t i o n t o t h e d e s i g n of t h e b r e e d e r s a l t pumps. Table 1. Pumps f o r L i q u i d Metal R e a c t o r s Hallam

~ - - - .

Fermi

Flow, gpm 7200 11,800 Head, f t 160 310 Temperature, OF 1000 1000 Speed, 1-;om 900 900 Pumping power, bhp 350 1060 Operating experi,ance : H a l l a m p m p s accumulated s e v e r a l thousand h r of pump o p e r a t i o n with sodium from 300 t o 95OoF, of which a t l e a s t 1000 h r w a s at 95OoF.

EBR-2 5500 200 So0

1035 350

Fermi pumps accumulated over 7000 h r o p e r a t i o n i n c l u d i n g two weeks a t 100O0F.

. l . l . _ _ _ l l l l

Requirements f o r Pumps flo.r- Breeder Reactors - _ . l ~ The p r e s e n t l y e n v i s i o n e d requirements of t h e f u e l , b l a n k e t , and coolant s a l t pumps f o r a 1000 Mw(e) Molten-Salt Breeder Reactor (MSBR) p l a n t , a n d f o r t h e Molten S a l t Breeder Experiment (MSBE) , a 1 5 0 Mw(th) experiment, a r e p r e s e n t e d i n Table 2 . T e n t a t i v e v a l u e s f o r p e r t i n e n t h y d r a u l i c design p a r a m e t e r s , e . g . , speed, s p e c i f i c s p e e d , a r e g i v e n also. The c e n t r i f u g a l sump pumps developed and used i n t h e A i r c r a f t Reactor Experiment ( m ) ,t h e A i r c r a f t Reactor T e s t program (ART), and t h e Molten-Salt Reactor Experiment (MSRE) r e c e i v e d f i r s t c o n s i d e r a t i o n f o r a p p l i c a t i o n t o t h e Molten-Salt Breeder Reactor (MSBR). There a r e a t l e a s t t h r e e d i f f e r e n c e s between t h e I%Yt?E and t h e MSBR concept whose e f f e c t s on t h e t h e r m a l and n u c l e a r r a d i a t i o n environments w i l l i n f l u e n c e t h e c h o i c e of t h e pump c o n f i g u r a t i o n f o r t h e bEBR. Depending on t h e t y p e of d e s i g n s , t h e power r a t i n g f o r t h e MSBR i s f i f t y t o 200 t i m e s g r e a t e r t h a n MSIZF: d e s i g n power. In addition, the s e p a r a t i o n d i s t a n c e s between i t s r e a c t o r , h e a t exchanger, and pump are e q u a l t o o r s m a l l e r t h a n t h e corresponding MSRE d i s t a n c e s . Thus t h e i n t e n s i . t y of t h e n u c l e a r r a d i a t i o n s i n t h e v i c i n i t y of t h e f u e l pump w i l l b e very much g r e a , t e r f o r t h e MSBR than t h e MSRE.

9 Table 2 .

Pumps for Breeder R e a c t o r s _l_l_l__

Fuel _ _ I _ -

lll_

Blanket

Coolant

-___-_.~__--

2225 Mw(th) MSBR

Number r e q u i r e d

Design t e m p e r a t u r e , OF

1300

11y 000

2000

16,000

150

1160

C a p a c i t y , gpm Heat, f't

Speed, rpm

2830

S p e c i f i c s p e e d , N,

2150

3400

NPSH, r e q u i r e d , f't (Net p o s i t i v e s u c t i o n head)

I m p e l l e r i n p u t power, hp

990

250

1440

1300

4500

540

150 Mwt MSBE Number r e q u i r e d Design t e m p e r a t u r e , OF C a p a c i t y , gpm

Heat, ft

150

Speed, rpm

1750

2730

1520

NPSH r e q u i r e d , ft ( N e t p o s j t i v e s u c t i o n head)

I m p e l l e r i n p u t power, hp

410

Specific speed, N

___--I__-

___

1300 4300

150

1750 2670 26 390

---

q h e same t o t a l number of pumps i s r e q u i r e d for a 1000 % ( e ) p l a n t of t h e MSBR r e f e r e n c e d e s i g n or modular d e s i g n .

10 Another d i f f e r e n c e concerns t h e manner o f h e a t i n g t h e IGBR.

One

of t h e f e a t u r e s o f t h e MSBR concept i s t h e u s e of l a r g e f u r n a c e s t o

c o n t a i n t h e f u e l , b l a n k e t and c o o l a n t s a l t systems and t o m a i n t a i n them at e l e v a t e d t e m p e r a t u r e s d u r i n g r e a c t o r power o p e r a t i o n . The t e m p e r a t u r e i n .the f u r n a c e for t h e f u e l and b l a n k e t s a l t systems w i l l range between 1050 and 1150'F. The t e m p e r a t u r e i n t h e c o o l a n t s a l t system f u r n a c e may range between 700 and 1150'F. A l i s t of t h e conditlions and circumstances under which t h e MSRE pump c o n f i g u r a t i o n may be u s e d i n t h e f u e l and b l a n k e t s a l t systems include : a.

Provide a s p e c i a l l y c o n s t r u c t e d and cooled p i t , b o t h t o m a i n t a i n t h e ,ambient t e m p e r a t u r e f o r t h e b e a r i n g housing i n t h e range 150 t o 175'F,and reduce i n t e n s i t y of nucl-ear r a d i a t i o n s .

Develop s u i t a b l e s h a f t b e a r i n g s and seals and t h e a s s o c i a t e d l u b r i c a n t f o r operat,ion at a h i g h e r ambient t e m p e r a t u r e which, although s t i l l requil-ing t h e cons t r u c t i o n of a pump p i t , would m a t e r i a l l y reduce t h e heat l o a d on t h e pump p i t c o o l i n g system.

Return t o t h e concept of l o c a l p r e h e a t i n g of t h e s a l t system components ,with a t t e n d a n t u s e o f l o c a l n u c l e a r r a d i a t i o n s h i e l d i n g and space c o o l i n g , t o m a i n t a i n t h e ambient t e m p e r a t u r e below 200'F.

I n a more d e s i r a b l e pump c o n f i g u r a t i o n , t h e t h e r m a l and r a d i a t i o n damage s e n s i t i v e d r i v e motor i s s e p a r a t e d from t h e pump, p e r s e , by a s u f f i c i e n t l y large d i s t a n c e t o p r o v i d e b o t h r e a s o n a b l e t h e r m a l g r a d i e n t s i n t h e pump s t r u c t u r e and adequate amounts of r a d i a t i o n a t t e n u a t i o n m a t e r i a l s . The approach i s t o s e p a r a t e t h e d r i v e motor froin t h e h o s t i l e environments by as l a r g e a d i s t a n c e 8s p r a c t i c a b l e w i t h i n t h e l i m i t s of rotordynamic, f a b r i c a t i o n , and r e a c t o r l a y o u t c o n s i d e r a t i o n s . P r e l i m i n a r y s t u d y i n d i c a t e s t h a t t h e r e q u i r e d s e p a r a t i o n probably cannot b e o b t a i n e d w i t h t h e PISRE: pump c o n f i g u r a t i o n u s i n g a r e a s o n a b l e s h a f t d i a m e t e r . Thus i n i t i a l c o n s i d e r a t i o n w i l l be g i v e n t o a pump conf i g u r a t i o n t h a t f e a t u r e s a r a t h e r l o n g s l e n d e r s h a f t and u t i l i z e s molten s a l t l u b r i c a t e d b e a r i n g s and probably s h a f t dampers.

Program Scope -.The pump program w i l l p r o v i d e f o r t h e s t u d y and design o f t h e f u e l , b l a n k e t , and c o o l a n t s a l t pumps for t h e l a r g e r MSBR, and f o r t h e d e s i g n and development of t h o s e pumps f o r t h e s m a l l e r MSBE. The s t u d y w i l l i n c l u d e t h e e v a l u a t i o n o f t h e f e a s i b i 1 . i . t ~of t h e l o n g s h a f t pump conf i g u r a t i o n and t h e p r a c t i c a b i l i t y o f s c a l i n g it down by a f a c t o r o f f o u r t o suit t h e MSBE pump r e q u i r e m e n t s .

Our p r e s e n t approach i s t o u s e one b a s i c pump r o t a r y assembly d e s i g n and t o accommodate t h e d i f f e r e n c e s i n t h e h y d r a u l i c requirements f o r t h e t h r e e pumps w i t h a p p r o p r i a t e changes i n t h e hydrauli.c d e s i g n s o f t h e i m p e l l e r arid v o l u t e and i n t h e c h a r a c t e r i s t i c s of t h e d r i v e motors.

11 I f , f o r r e a s o n s of r e a c t o r system l a y o u t t h e c o o l a n t s a l t pump r e q u i r e s s e p a r a t e treatment, then e i t h e r t h e long s h a f t Configuration w i l l b e modified o r t h e MSRE pump c o n f i g u r a t i o n w i l l be u s e d , depending upon t h e r e s u l t s o f f u r t h e r s t u d y ,

One each of t h e f u e l , b l a n k e t , and c o o l a n t s a l t p w p s w i l l be prov i d e d f o r 1) development, 2 ) t h e E n g i n e e r i n g Test U n i t , and 3 ) t h e MoltenS a l t Breeder Experiment.

I n e s s e n c e , t h e s t u d y p o r t i o n of t h e program w i l l b e f o c u s e d on i d e n t i f y i n g pump c o n f i g u r a t i o n s t h a t are f e a s i b l e f o r t h e MSBR, and t h e development p o r t i o n of t h e program w i l l b e concerned w i t h producing pumps for t h e MSBE, which w i l l b e scaled-down v e r s i o n s of t h e MSBR c o n f i g u r a t i o n s . During t h e development of t h e MSBE pumps, a t t e n t i o n w i l l be given t o t h e problems of s c a l i n g - u p components f o r use i n t h e MSBR pumps. Design and Development Prograru Because of t h e importance of t h e pumps and t h e c l o s e r e l a t i o n s h i p between t h e i r design and development, t h e s e two a c t i v i t i e s a r e c o n s i d e r e d t o b e one. I n t h i s a c t i v i t y t h e major problems are expected t o i n c l u d e : 1. 2.

4. 5.

6. 7. 8. 9.

selecting a hydraulic design, choosing a s a t i s f a c t o r y rotordynamic c o n f i g u r a t i o n , c o n t r o l l i n g t h e L o t a l p l a s t i c s t r a i n i n t h e pump caused by t e m p e r a t u r e c y c l i n g of t h e system, s p e c i f y i n g purge gas requirements t o p r e v e n t back d i f f u s i o n o f gaseous f i s s i o n p r o d u c t s t o r a d i a t i o n s e n s i t i v e r e g i o n s of t h e pump, c o n t r o l l i n g a d e q u a t e l y any flow which p a s s e s through t h e pump t a n k , a ) t o prevent t h e re-entrainment of xenon-laden g a s i n t h e r e c i r c u l a t i n g s a l t , and b) t o p r e v e n t stoppage o f purge gas flow by f r e e z i n g of s a l t s p l a s h o r a e r o s o l i n t h e pump s h a f t a n n u l u s , d e s i g n i n g and proof t e s t i n g an adequate s h a f t damper, a m o l t e n - s a l t l u b r i c a t e d b e a r i n g , and any s h a f t s e a l t h a t i s l a r g e r i n d i a m e t e r t h a n now u s e d , v e r i e i n g t h e adequacy of t h e h y d r a u l i c and r o t o r dynamic d e s i g n s , p r o v i d i n g pump r e l i a b i l i t y , and o b t a i n i n g confidence i n s c a l i n g - u p t h e MSBE pumps t o f i t t h e requirements of l a r g e - s c a l e p l a n t s .

E f f e c t s of P h y s i c a l P r o p e r t i e s of Breeder S a l t s on Pimp Design Density and v i s c o s i t y are t h e two p h y s i c a l p r o p e r t i e s of molten s a l t s which s t r o n g l y a f f e c t pump d e s i g n . S a l t d e n s i t y mainly a f f e c t s t h e t o r q u e requirements f o r the pump i m p e l l e r and r e q u i r e s t h a t t h e s h a r t has s u f f i c i e n t t o r s i o n a l s t r e n g t h and t h a t t h e d r i v e motor produces t h e r e q u i r e d t o r q u e . Both of t h e s e i t e m s , which are under t h e c o n t r o l of t h e pump d e s i g n e r , s h o u l d p r e s e n t no untoward problem i n t h e d e s i g n of t h e b r e e d e r pumps.

1.2 V i s c o s i t y s t r o n g l y a f f e c t s t h e l i f e c h a r a c t e r i s t i c s of t h e hydrodynamic b e a r i n g s , which we a n t i c i p a t e w i l l be used i.n t h e b r e e d e r pumps. The v a l u e s o f t h e v i s c o s i t y f o r a l l t h r e e b r e e d e r r e a c t o r s a l t s a x e s i m i l a r and g r e a t e r t h a n vater and s h o u l d p r e s e n t no untoward problem i n t h e d e s i g n o f molten s a l t l u b r i c a t e d b e a r i n g s . S p e c i f i . c - - - c e s i p Problems and Coa,ls

S e z a-__ r a t i o n Requiremait. The p r i n c i p a l f e a t u r e of t h e long s h a f t punip c o n f i g u r a t i o n i s t h e u s e of s u f f i c i e n t s e p a r a t i o n d i s t a n c e and s h i e l d i n g t o p r o v i d e f o r t e n y e a r s of o p e r a t i o n of' t h e d r i v e motor. Such a c o n f i g u r a t i o n r e q u i r e s a l o n g , s l e n d e r s h a f t guided a t i t s lower end by a m o l t e n - s a l t b e a r i n g and a t i t s upper end by a more c o n v e n t i o n a l b e a r i n g and usirig , h o p e f u l l y , a c o n v e n t i o n a l , e a s i l y r e p l e n i s h a b l e l u b r i e a n t A s h a f t damper w i l l probably be n e c e s s a r y t o p r o v i d e f o r o p e r a t i o n a t a speed above t h e f i r s t c r i t i c a l frequency of t h e s h a f t - b e a r i n g system.

E s t i m a t e s of t h e s e p a r a t i o n d i s t a n c e between t'ne pump i m p e l l e r and d r i v e motor w i l l be made based on t h e a n t i c i p a t e d f l u x o f n e u t r o n s and garnms r a d i a t i o n a t t h e motor and t h e s h i e l d i n g r e q u i r e d t o p r o v i d e ten-year l i f e f o r t h e r a d i a t i o n damage s e n s i t i v e m a t e r i a l s i n t h e f u e l and b l a n k e t pumps. Bydraulic Design. We p l a n t o s e l e c t t h e h y d r a u l i c design which w i l l p r o v i d e t h e r e q u i r e d head (H) and c a p a c i t y ( Q ) a t as h i g h s h a f t speed (M) as good p r a c t i c e and t h e a v a i l a b l e n e t p o s i t i v e s u c t i o n head (NPSH) i n t h e system w i l l p e r m i t . This approach should permit t h e u s e o f a r e l a t i v e l y small diameter i m p e l l e r and v o l u t e and s h o u l d minimize t h e p a r a s i t i c volume of s a l t . Vanes f o r t h e back s i d e of t h e i m p e l l e r , s u i t a b l e f o r reducing h y d r a u l i c t h r u s t , w i l l r e c e i v e c o n s i d e r a t i o n . Rotordynamic Analysis. The p r i n c i p a l a n a L y t i c a l problem w e a n t i c i p a t e concerns t h e s e l e c t i o n o f s a t i s f a c t o r y pump rotordynamic c o n f i g u r a t i o n s . These should p r o v i d e r e l i a b l e and economic pumps f o r t h e f u e l , b l a n k e t , and c o o l a n t s a l t c i r c u i t s i n t h e MSBR, which can be s c a l e d do5m by a f a c t o r of approximately f o u r f o r u s e i n t h e FSBE. The rotordynamics o f t h e proposed "long s h a f t " c o n f i g u r a t i o n are n e w t o u s zrld w i l l be analyzed e x t e n s i v e l y t o determi-ne a s u i t a b l e arrangement or" s h a f t , bearrings, and s h a f t danipw. We plan t o s e l e c t two or t h r e e o u t of s e v e r a l promising s h a f t - b e a r i n g e o n f i g u r a t i o n s which p r o v i d e t h e r e q u i r e d s e p a r a t i o n , and t o s u b j e c t them t o rotordynamic a n a l y s i s . The l o c a t i o n and performance c h a r a c t e r i s t i c s of b o t h s h a f t dampers and b e a r i n g s necessa-ry t o p r o v i d e a s a f e margin of f a t i g u e l i f e f o r t h e shaf't d u r i n g ten-year o p e r a t i o n w i l l be determined f o r several v a l u e s of s h a f t d i a m e t e r . The c o n f i g u r a t i o n which has the b e s t char-ce of providring r e l i a b l e pumps w i l l . b e chosen f o r development" Appropriate r o t o r d y n m i c a n a l y s i s of a reduced scope w i l l b e performed f o r t h e c o o l a n t s a l t punp, i f a d i f f e r e n t c o n f i g u r a t i o n i.s r e q u i r e d .

13 P l a s t i e S t r a i n . Temperature c y c l e s i n a s a l t system can impose inerements of p l a s t i c s t r a i n i n t h e high-temperature p o r t i o n s of t h e pump due t o changes i n e i t h e r t h e r m a l s t r e s s e s a s s o c i a t e d w i t h st*eep t e m p e r a t u r e g r a d i e n t s o r mechanical s t r e s s e s a s s G c i a t e d w i t h p i p e anchor f o r c e s and moments e x e r t e d on pump n o z z l e s . We n o t e d t h a t t h e l a r g e s t t e m p e r a t u r e g r a d i e n t s a s s o c i a t e d w i t h t h e n u c l e a r o p e r a t i o n of t h e MSRE f u e l pump were caused by h e a t d.eposited i n t h e pump w a l l s by gaseous f i s s i o n p r o d u c t s . It i s l i k e l y t h a t more f i s s i o n p r o d u c t s w i l l be p r e s e n t and h e a t w i l l be d e p o s i t e d i n l a r g e r q u a n t i t i e s i n t h e s a l t r e s e r v o i r i n t h e MSBR f u e l pump. We p l a n t o u s e a s m a l l p o r t i o n of t h e c i r c u l a t i n g f u e l s a l t t o remove t h e h e a t . The t o t a l p l a s t i c s t r a i n i n t h e pump n o z z l e s , r e s u l t i n g from t h e f o r c e s a s s o c i a t e d w i t h h e a t i n g and c o o l i n g t h e system and changing r e a c t o r power l e v e l s , w i l l b e e s t i m a t e d f o r a, s p e c i f i e d number of c y c l e s . Measures w i l l b e t a k e n t o keep t h e t o t a l s t r a i n w i t h i n t h e p l a s t i c f a t i g u e s t r e n g t h of t h e cont a i n e r material. Purge Gas Requirements. An i n e r t purge gas w i l l b e used i n t h e MSBR, as i n t h e MSRE, t o : (1) remove, d i l u t e , and t r a n s p o r t t o an a p p r o p r i a t e t r a p system t h e xenon and o t h e r gaseous f i s s i o n p r o d u c t s from t h e f u e l s a l t ; ( 2 ) reduce t h e back d i f f u s i o n of t h e s e gaseous f i s s i o n p r o d u c t s i n t o r a d i a t i o n s e n s i t i v e r e g i o n s of t h e pump; and ( 3 ) remove any l u b r i c a n t t h a t l e a k s p a s t a s h a f t s e a l w i t h o u t perm i t t i n g t h e l e a k a g e t o e n t e r t h e pumped s a l t . The amount of purge g a s r e q u i r e d for t h e f u e l arid b l a n k e t s a l t pumps w i l l be much l a r g e r t h a n f o r t h e MSRE fâ&#x20AC;&#x2122;uel pump, and a r e c y c l e system w i l l be used t o conserve g a s . The r e c y c l e system i s t r e a t e d i n t h e s e c t i o n on t h e o f f g a s system. The s m a l l e r purge gas flow f o r t h e coolant s a l t pwnp may p e r m i t open-cycle o p e r a t i o n .

Size-ScaliXRequirements. Pumps f o r t h e NSBR and MSBE s h o u l d u s e t h e same g e n e r a l c o n f i g u r a t i o n s . The f e a s i b i l i t y o f s c a l i n g up t h e MSBE pumps by a f a c t o r of f o u r f o r a p p l i c a t i o n t o t h e MSBR w i l l be one c r i t e r i o n f o r acceptance of MSBE pump d e s i g n . The s c a l i n g of t h e r o t o r dynamic c o n f i g u r a t i o n w i l l be made a p a r t o f t h e a n a l y s i s of t h e MSBR pumps, which, i n t u r n , s h o u l d e s t a b l i s h t h e requirements f o r s c a l i n g t h e molten s a l t b e a r i n g s and dampers. F a b r i c a t i o n , i n s p e c t i o n , h a n d l i n g , assembly, and i n s t a l l a t i o n of t h e MSBR pumps w i l l r e c e i v e s t u d y t o determine t h a t t h e long s h a f t c o n f i g u r a t i o n w i l l n o t impose expensive s o l u t i o n s f o r l a r g e m o l t e n - s a l t systems. We p l a n t o have t h e MSBE pumps f a b r i c a t e d by i n d u s t r y , and t o discuss e x t e n s i v e l y with them d u r i n g t h i s t i m e t h e f a b r i c a t i o n problems of t h e MSBR pumps. The necess i t y f o r p r o o f - t e s t i n g t h e l a r g e pumps i n molten s a l t xi11 r e c e i v e much a t t e n t i o n d u r i n g s i m i l a r t e s t s with t h e PSBE pumps. S p e c i f i c Development Problems and Goals The development of t h e and c e r t a i n pump components t e s t s t o pump d e s i g n , and w ware f a b r i c a t i o n . The main pump c o n f i g u r a t i o n i n c l u d e :

MSBE pumps w i l l e n t a i l t h e t e s t i n g of pumps

and t h e feedback of i n f o r m a t i o n from t h e s e i l l i n c l u d e a l l t h e a s p e c t s of d e t . a i l e d hardproblems a n t i c i p a t e d w i t h t h e l o n g s h a f t (1) demonstrating t h e adequacy of t h e design

14 and the r e l i a b i l i t y - of t h e s h a f t damper and t h e molten-sal-t b e a r i n g i n component t e s t e r s ; ( 2 ) p r o v i d i n g adequate c o n t r o l of t h e bypass s a l t flow which c a r r i e s f i s s i o n - p r o d u c t l a d e n helium i n t o t h e pump t a n k ; and ( 3 ) v e r i f y i n g t h e adequacy of t h e h y d r a u l i c , rotordynamic, and purge g a s d e s i g n s f o r each conipl-ete pump. Th-e long-time r e l i a b i l i t y ( a , v a i . l a b i l i t y ) of t h e pumps w i l l be demonstrated i n endurance t e s t s . The f e a s i b i l i t y of v e r i f y i n g the rotordynamic c h a r a c t e r i s t i c s of l a r g e pumnps i.n room t e m p e r a t u r e s h a k e r t e s t s of s m a l l models of shaft-bearing-damper conf i g u r a t i o n s w i l l be stu.di.ed a l s o . S i n c e many of t h e s e development t a s k s a r e of routi-ne n a t u r e , o n l y t h o s e problems whose r e s o l u t i o n meets s p e c i f i c and s i g n i f i c a n t goals a r e d i s c u s s e d 'oe1.oi.j.:

S h a f t Damper 'Tester. The h y d r a u l i c performance and t h e mechanical design of t h e damper x i l l b e v e r i f i e d i n what we a n t i c i p a t e will be a room-temperature t e s t e r u s i n g a f l u i d which approximates t h e kinematic v i s c o s i t y - of t h e daiiper working f l u i d . The damping c o e f f i c i e n t r e q u i r e d t o reduce s h a f t f l e x u r e s t r e s s t o a v a l u e s a t i s f a c t o r y t o p r o v i d e t e n y e a r pump l i f e w i l l b e deduced d u r i n g rotordynamic a n a l y s i s of t h e pumps. I n t h e t e s t e r , we a n t i c i p a t e i-mposing on t h e damper a s i n u s o i d a l t r a n s v e r s e motion of known amplitude and frequency and deducing t h e damping c o e f f i c i e n t from measurements of t h e f o r c e n e c e s s a r y t o s u s t a i n t h a t motion. S a t i s f a c t o r y c o r r e l a t i o n between p y e d i c t e d and experimental v a l u e s o f t h e damping c o e f f i c i e n t would p r o v i d e confidence i n extrapol a t i n g t h e hydrau1i.c and mechanj-cal d e s i g n s of s h a f t dampers t o pumps f o r t h e l a r g e - s c a l e systems. Molten-Salt B e a r i n g-T ~ e s t.e r-. - Tine o p e r a t i n g s t a b i l i t y of t h e b e a r i n g and t h e s t a r t - s t o p wear r e s i s t a n c e of Yne b e a r i n g m a t e r i a l s w i l l b e v e r i f i e d i n a component t e s t e r . W e anticipate f i r s t operating a suitable b e a r i n g c o n f i g u r a t i o n a t room temperature w i t h a f l - u i d having tine approximate kiiiematic v i s c o s i t y of tile a p p r o p r i a t e s a l t i i l o r d e r t o i n s u r e s t a b l e o p e r a t i o n of t h e b e a r i n g . Next, t h e b e a r i n g w i l l be o p e r a t e d i n t h e a p p r o p r i a t e molten s a l t i n .the t e s t e r f o r more t h a n t h e a n t i c i p a t e d number of s t a r t s and s t o p s f o r t h e pump i n t h e MSBE. Then, t h e b e a r i n g wi.3-1 b e t h e r m a l l y c y c l e d over t h e t e m p e r a t u r e range and t h e number of c y c l e s a n t i c i p a t e d f o r t h e MSBE and o p e r a t e d i n an endurance t e s t t o o b t a i n conf'i-dence i n t h e adequacy and r e l i a b i l i t y o f i t s mechanical d e s i g n , Tlne t e s t e r w i l l be designed t o accommodate t h e l a r g e r diameter b e a r i n g s a n t i c i p a t e d f o r pumps f o r l a r g e - s c a l e systems. Sufficien-l; t e s t s w i l l b e inade w i t h mockup f l u i d t o e s t a b l i s h t h e s t a b i l i t y of t h e l a r g e r bearings. We p l a n t o v e r i f y t h e h y d r a u l i c and r o t o r Pump T e s t 3 ' a c i l i : z d.yn,Unic d e s i g n s m d t o e s t a b l j - s h c o n t r o l o f s a l t bypass f l o w , i . e . , t o e l i m i n a t e s a l t s p l a s h amd re^-entrainment of xenon-laden gas i n t h e r e c i r c u l a t e d s a l t u s i n g a f l u i d which has kinematic v i s c o s i t y s i m i l a r t o the a p p r o p r i a t e s a l t . Then t h e h y d r a u l i c and rotoi-dynamic d e s i g n s and t h e f u n c t i o n s of t h e purge gas system will b e checked i n molten s a l t o p e r a t i o n , a f t e r which t h e r e l i a b i l i t y of t h e pump w i l l be i n v e s t i g a t e d d u r i n g endurance t e s t s . M a L n t a i n a b i l i t y of t h e puni~)w i l l b e demonstrated d u r i n g t h e s e t e s t s also.

It w i l l be n e c e s s a r y t o perform s e v e r a l k i n d s of room t e m p e r a t u r e t e s t s w i t h each of t h e t h r e e s a l t pump d e s i g n s u s i n g a s u i t a b l e f l u i d . These t e s t s i n c l u d e : 1) checking t h e h y d r a u l i c d e s i g n performance, 2 ) developing a p p r o p r i a t e c o n t r o l s f o r r e q u i r e d bypass flows through t h e pump t a n k , 3) p r o v i d i n g adequate c a p a c i t y f o r d e g a s s i n g t h e l i q u i d , and 4) d e t e r m i n i n g t h e adequacy o f t h e pump d e s i g n t o meet s p e c i a l , t r a n s i e n t o r emergency c o n d i t i o n s encountered i n r e a c t o r o p e r a t t o n o r of r e v i s i o n s t o pump d e s i g n deemed n e c e s s a r y . P r e l i m i n a r y s t u d y i n d i c a t e s t h e s e t e s t s can be performed f o r a l l t h r e e pumps i n a s i n g l e room t e m p e r a t u r e f a c i l i t y u s i n g an a p p r o p r i a t e f l u i d . The d i f f e r e n c e s i n t h e chemistry and p h y s i c a l p r o p e r t i e s of t h e t h r e e s a l t s and i n t h e flow s a t e requirements f o r t h e i n d i v i d u a l s a l t c i r c u i t s i n d i c a t e t h e d e s i r a b i l i t y of u s i n g t h r e e h i g h t e m p e r a t u r e pump t e s t f a c i l i t i e s , one each f o r t h e f u e l , b l a n k e t , and c o o l a n t salt pumps *

A f a c i l i t y f o r making a room temperature rotordynamic t e s t of t h e f u l l - s c a l e r o t a r y assembly w i l l also be p r o v i d e d , i f t h e r e s u l t s o f t h e rotordynamic a n a l y s e s i n d i c a t e t h i s n e c e s s i t y . Coolant Salt Pumps. I n t h e event t h a t t h e MSRE pump c o n f i g u r a t i o n i s chosen o v e r t h e l o n g shafâ&#x20AC;&#x2122;t c o n f i g u r a t i o n f o r t h e coolaxit s a l t pump, t h e f o l l o w i n g development program w i l l be c a r r i e d o u t . The leakage performance and l i f e c h a r a c t e r i s t i c s of t h e s h a f t s e a l

w i l l b e o b t a i n e d a t an e a r l y p r a c t i c a b l e d a t e . The b e a r i n g - s h a f t - s e a l c o n f i g u r a t i o n w i l l be mocked up and o p e r a t e d a t design speed and t e m p e r a t u r e u s i n g a good g r a d e t u r b i n e o i l t o l u b r i c a t e t h e s e d . Followon t e s t s w i l l be made w i t h l a r g e r d i a m e t e r s h a f t s e a l s s u i t a b l e for t h e c o o l a n t s a l t pumps i n l a r g e - s c a l e systems. I n a d d i t i o n t o t h e molten s a l t pump t e s t f a c i l i t y a l l u d e d t o p r e v i o u s l y , a room t e m p e r a t u r e pump t e s t f a c i l t t y s u i t e d t o t h e w a t e r t e s t development o f t h e MSRE pump c o n f i g u r a t i o n w i l l be p r o v i d e d . The h y d r a u l i c d e s i g n of t h e pump w i l l b e checked and s a t i s f a c t o r y c o n t r o l s f o r t h e bypass flow of s a l t i n t h e pump t a n k w i l l be developed, Subseq u e n t l y , performance and endurance t e s t s w i l l be p e r f o r n e d w i t h molten salt i n t h e high temperature f a c i l i t y . HEAT EXCHANGERS Review o f Heat Exchangers i n t h e MSRE Although 10 Mw(th) was t h e nominal power l e v e l for t h e design e a l c u l a t i o n s f o r t h e %RE, t h e a c t u a l c a p a b i l i t y i s l h i t e d t o about Both t h e primary h e a t exchanger ( f u e l salt t o c o o l a n t s a l t ) 7.5 M w ( t ) and t h e r a d i a t o r ( c o o l a n t salt t o a i r ) c o n t r i b u t e t o t h i s reduced c a p a c i t y . A review a t each h e a t exchanger w i l l be v e r j b r i e f l y summarized.

The primary h e a t exchanger i s a c o n v e n t i o n a l c r o s s b a f f l e s , U-tube exchanger, w i t h f u e l s a l t on t h e s h e l l s i d e and c o o l a n t s a l t on t h e t u b e

16 s i d e . For a more d e t a i l e d d e s c r i p t i o n see Ref. 8. The observed o v e r a l l h e a t t r a n s f e r c o e f f i c i e n t w a s about 60% of t h e e s t i m a t e d design c o e f f i c i e n t ( r e t s . 9 and 1.0). The i n i t i a l design of t h i s h e a t exchanger w a s revriewed i n d e t a i l and t h e f o l l o w i n g s i g n i f i c a n t items n o t e d : 1. Heat t r a n s f e r c o e f f i c i e n t s and p r e s s u r e drops were computed from conventional- r e l a t i o n s h i p s f o r normal f l u i d s . 2.

The p h y s i c a l p r o p e r t i e s of s a l t used i n t h e design were t h o s e b e l i e v e d t o be c o r r e c t a t t h a t t i m e .

A t o t a l contingency f a c t o r of something over 20% w a s included i n t h e h e a t t r a n s f e r area.

I n t r y i n g t o determine why t h e measured c o e f f i c i e n t was s o low, mmy t h i n g s were c o n s i d e r e d . The f o l l o w i n g a r e t h e most p e r t i n e n t . 1.

S i n c e s a l t does not wet H a s t e l l o y N , t h e q u e s t i o n of a helium gas f i l m on t h e t u b e s w a s c o n s i d e r e d . This was d i s c o u n t e d by p r e s s u r e r e l e a s e t e s t s d i s c u s s e d i n r e f . 9 and o t h e r c o n s i d e r a t j - o n s .

The q u e s t i o n of an i n s u l a t i n g s c a l e was c o n s i d e r e d . The very h i g h r e s i s t a n c e of H a s t e l l o y N t o a t t a c k by f u e l s a l t i n a good many l o o p s and t h e r e a c t o r made t h i s a n e g l i g i b l e c o n s i d e r a t i o n . Also, t h e r e h a s been very l i t t l e , i f .any, drop i n U w i t h t i m e i n t h e r e a c t o r .

The p h y s i c a l p r o p e r t i e s of s a l t were looked a t c r i t i c a l l y , and h e r e i n l i e s what w e b e l i e v e t o b e t h e discrepancy.

S p e c i f i c a l l y ,it i n v o l v e s t h e t h e r m a l c o n d u c t i v i t y . Shown i n t h e t a b l e are v a l u e s of t h e r m a l c o n d u c t i v i t y used i n t h e h e a t exchanger d e s i g n . These values were e s t i m a t e d from d a t a on s i m i l a r b u t n o t i d e n t i c a l s a l t s . Also shown a r e r e c e n t l y measured v a l u e s ( r e f . l i . ) f o r f u e l s a l t and an e s t i m a t e d v a l u e f o r cool-ant s a l t . Thermal Conductivity (Btu/hr f t O F ) Fuel S a l t Values used in o r i g i n a l design Measured v a l u e ( r e f . 11) Estimated f o r coolant s a l t = ( 0 . 8 3 ) ( 3 . 5 / 2 . 7 5 )

2.75 0.83 --

C o o l a n t Sa1t

3.5

Not y e t measured

1.06

Now i f t h e o v e r a l l heat t r a n s f e r c o e f f i c i e n t of t h e primary h e a t exchanger is recomputed w i t h t h e s e new v a l u e s of thermal c o n d u c t i v i t y , t h e n t h e measured and computed v a l u e s a g r e e q u i t e w e l l .

The primary h e a t exchanger w a s t e s t e d w i t h w a t e r a f t e r it w a s b u i l t . The t u b e s v i b r a t e d e x c e s s i v e l y i n t h e b a f f l e s a t flows g r e a t e r t h a n about 2 / 3 o f t h e design flow t h r o u g h t h e s h e l l , and t h e s h e l l s i d e p r e s s u r e drop w a s e x c e s s i v e . M o d i f t e a t i o n s were rnade t o t i g h t e n t h e t u b e s i n t h e b a f f l e s and t o reduce t h e p r e s s u r e drop a t t h e o u t l e t n o z z l e , The exchanger has been apex-ateed f o r about 9OGG h r at h i g h temp e r a t u r e w i t h s a l t without obvious d i f f i c u l t y . The r a d i a t o r c o n s i s t s of 120 t u b e s , each about 30 f t l o n g , i n t h e form of an S-shaped b u n d l e . A i r blows a c r o s s t h e t u b e bundle a t r i g h t a n g l e s t o remove t h e h e a t . For a more d e t a i l e d d e s c r i p t i o n , see r e f . 3 The observed o v e r a l l h e a t t r a n s f e r c o e f f i c i e n t w a s about 68% of t h e d e s i g n c o e f f i c i e n t ( r e f s . 9 and 1 0 1 . The i n i t i a l design of t h e r a d i a t o r w a s reviewed i n d e t a i l and t h e followj-ng s i g n i f i c a n t i t e m s n o t e d :

1. The s a l t s i d e C o e f f i c i e n t w a s computed from con-rrentional r e l a t i o n s h i p s f o r normal f l u i d s . I n t h e r a d i a t o r t h i s i s a n e g l i g i b l e c o n s i d e r a t i o n , however, because o n l y about 2% o f t h e r e s i s t a n c e t o h e a t t r a n s f e r i s through t h e s a l t film. 2.

A d e s i g n error was found i n t h e c a l c u l a t i o n of t h e a i r

c o e f f i c i e n t . This r e s u l t e d i n t h e e s t i m a t e d o u t s i d e c o e f f i c i e n t b e i n g about 111%t o o h i g h .

A contingency f a c t o r of o n l y about

t h e h e a t t r a n s f e r area.

4% w a s i n c l u d e d i n

If t h e o v e r a l l c o e f f i c i e n t i s recomputed t o account f o r t h e e r r o r mentioned i n i t e m 2 , t h e n t h e observed c o e f f i c i e n t i s about 75% of t h e design c o e f f i c i e n t . W e b e l i e v e t h a t a d i s c r e p a n c y of t h j s magnitude i s not unreasonable when t h e unconventional c o n f i g u r a t i o n of t h e r a d i a t o r i s c o n s i d e r e d . A 20 t o 30% continF5ency f a c t o r should have been i n c l u d e d i n t h e d e s i g n h e a t t r a n s f e r arca t o be c e r t a i n o f 10 Mw capacity. The c o n c l u s i o n we have a r r i v e d at , a f t e r l o o k i n g a t t h e performance o f b o t h h e a t exchangers i n d e t a i l , i s t h a t no unique heat, t r a n s f e r problems e x i s t i n t h e MSRE t h a t e m be a t t r i b u t e d t o some unusual b e h a v i o r of t h e molten s a l t . Fundamental Molten S a l t Heat T r a n s f e r Heat t r a n s f e r w i t h m o l t e n - s a l t m i x t u r e s d u r i n g t h e p e r i o d 1950-2.957as a p a r t of t h e 1958-1961 as a pa,rt o f t h e MSR program. The t a b u l a t e d below a l o n g w i t h c e r t a i n p e r t i n e n t

was e x t e n s i v e l y s t u d i e d

ANP e f f o r t , and t h e p e r i o d m i x t u r e s i n l r e s t i g a t e d are parameters :

18 S a l t Mixture

N a011 N aF-KF-LiF

Compo sit i o n (azole%)

Reyno1d s Modulus

Test Section Mater i a1

100.0

6000-12,000 2300-9000

Nickel Nickel, Inconel,

2800-13,OOO

Inconel,

11.5-42.0-46.5

316

NaF-KF-Li F-UF),

N ab'-7, rF4-UF4

N aF-ZrF4-UF)+ LiF-B e F;?-UFq L i F-B eF2 -UF L ri F-BeF2 -UF4 -T'nF4

50.0-46.0-4.0 53.5-40.0-6.5 53.0-46 +0.-1.0 62.0-37.0-1.0 67.0-18.5-0.5-1b.

L iC1-KC1

41.2-58.8

ss,

6000-18,000

Hastelloy B Inconel Inconel I n c on el I n cone 1 Inconel, Hastelloy N Inconel,

4900-25,OOO

Inconel,

~~000-10,000 3500-14,000

4000-5000

316

3000-7000

6500-25,000

347 ss 316

While t h e s e experiments i n d i c a t e d t h a t t h e molten s a l t s have t h e h e a t t r a n s f e r and f l u i d mechanical p r o p e r t i e s of common f l u i d s ( 0 . 5 < Npr i 1 0 0 ) ,* t h e same s t u d i e s showed t h a t such phenomena as non-wetting and i n t e r f a c i a l d e p o s i t s c o u l d d r a s t i c a l l y reduce t h e h e a t t r a n s f e r . S i n c e t h e s e e f f e c t s a r e d i f f i c u l t t o p r e d i c t , t h e h e a t t r a n s f e r charact e r i s t i c s of t h e molten s a l t s f o r c r i t i c a l a p p l i c a t i o n s s h o u l d be exp e r i m e n t a l l y e s t a b l i s h e d . R b i b l i o g r a p h y covering ORNL s t u d i e s on m o l t c n - s a l t h e a t t r a n s f e r i s given i n r e f e r e n c e s 1 . t h i - o u g h 8 . 1. H . W. Hoffman, T u r b u l e n t Forced Convection Heat T r a n s f e r i n C i r c u l a r Tubes Containing Molten Sodium Xydroxide , USAEC Report ORNL-1370, ORNL (1952) ; s e e a l s o _-IHeat I. T r a n s f e r and F l u i d_.IMechanics _..__ ____ I n s t i t u -..-..-, t e P 83, S t a n f o r d U n i v e r s i t y P r e s s , Stanford, Calif. (1953). _ I _

H . W. Hoffman and J. Lones , Fused S a l t Heat 'TransferP a r t 11: Forced Convection IIeat T r a n s f e r i n C i r c u l a r Tubes Containing bTaF-KF-LiF E u t e c t i c , USAEC Report OIQiL-1777,

O W L (1955).

H. W . Hoffman and S . I. Cohen, Fused S a l t Heat TransferP a r t 111: Forced Convection Heat T r a n s f e r i n C i r c u l a r Tubes Containing t h e S a l t Mixture NaN02-NaN03-KN03, USAEC Report ORNL-2433, ORNL (1960)

H . W . Hoffman, Fused S a l t Heat Transfer, Reactor Heat T r a n s f e r Information Meeting Oct. 18-19, 1954, p . 23, USAEC Report BNL-311, Brookhaven N a t i o n a l Laboratory (classified).

#The P r a n d t l modulus

Npr f o r t h e t a b u l a t e d mixtures ranges from 1 t o 1 0 .

H . W. Hoffman, Molten S a l t Heat Transfer, Reactor Heat Transfer Conference of 1956, p . 5 0 , USmC Report TID-7329 (Pt. 3), (classified).

H . W. Hoffman, Molten S a l t Heat T r a n s f e r , USAEC RepoPt OEWL-CF-58-2-40? OFXL (1958)

ANP Quart. Prog. Repts. P e r i o d Ending S e p t . 10, 1955, p. 149, USAEC Report OFLNL-1947; P e r i o d Ending Dec. 1 0 , 1955, p . 170, USAEC Report ORNL-2012; P e r i o d Ending Mar. 1 0 , 1956, p . 171, USAEC Report O P J V L - ~ O ~P~e;r i o d Ending June 30, 1957, p. 99, USMC Report ORTJL-2340; P e r i o d Ending S e p t . 30, 1957, p . 103, USAEX Report 0m-~-2387; P e r i o d Ending Dec. 31, 1957, p . 57, USAEC Report O R N L - ~ ) - ~ L O .

MSR Quart. Prog. Repts. P e r i o d Ending J a n . 31, 1958, p . 37, USAEC Report OWL-2474; P e r i o d Ending June 30, 1958, p . 43, USAEC Report ORNL-2551; P e r i o d Ending Oct. 31, 1958, p. 46, USAEC Report om1;-2626; P e r l o d Ending Jan. 31, 1959, p. 67, USAEC Report ORNL-2684; P e r i o d Ending Apr. 30, 1959 p. 41, USAJ3C Report ORNL-2773; P e r i o d Ending ,July 31, 1959, p. 39, USAEC Report ORNL-2799; P e r i o d Ending Oct. 31, 1959, p. 2 3 , USAEC Report O R N L - ~ ~ ~ PO e; r i o d s Ending J a n . 31 and Apr. 30, 1960, p . 27, USAEC Report OWL-2973; P e r i o d Ending J u l y 31, 1960, p . 86, USAEC Report ORNL-3014; P e r i o d Ending Feb. 28, 1961, p. 140, USAEC Report ORNL-3122; P e r i o d Ending Aug. 31, 1961, p . 1 3 2 , USAEX Report ORNL-3215.

For added a s s u r a n c e arid for o t h e r r e a s o n s , a molten salt h e a t t r a n s f e r loop w i l l b e b u i l t . G e n e r a l l y t h e l o o p w i l l b e s m a l l and o r i e n t e d toward fundamental h e a t transfer r a t h e r t h a n toward component t e s t i n g . It w i l l be c a p a b l e o f o p e r a t i n g w i t h a v a r i e t y o f salts osld c o n t a i n e r materials. Some o f i t s o b j e c t i v e s w i l l b e t o e v a l u a t e :

1, T r a n s f e r c o e f f i c i e n t s and pressure drop w i t h salt, flowing a x i a l l y on t h e i n s i d e and o u t s i d e of t h e t u b e s .

2. Thermal, e f f e c t s of p o s s i b l e corrosion and s c a l e d e p o s i t s on t h e t u b e s .

E f f e c t s of c i r c u l a t i n g gas bubbles on h e a t t r a n s f e y . This c o u l d be s i g n i f i c a n t i f t h e s a l t does n o t wet t h e t u b e s , and i s of concern i n t h e MSBE because gas bubbles w i l l b e i n t e n t i o n a l l y i n j e c t e d i n t o t h e f u e l salt a t t h e i n l e t t o t h e primary h e a t exchanger t o a i d i n s t r i p p i n g Xenon-135.

20 Heat Exchangers f o r Breeder Reactors

_ I

Molten-salt b r e e d e r r e a c t o r s of t h e r e f e r e n c e d e s i g n m a k e use of f i v e d i f f e r e n t h e a t exchangers: (1.) t h e fuel s a l t h e a t exchanger, ( 2 ) t h e b l a n k e t s a l t h e a t exchanger, ( 3 ) t h e b o i l e r s u p e r h e a t e r , (4) t h e steam r e h e a t e r , and ( 5 ) t h e r e h e a t steam p r e h e a t e r . These h e a t exchangers w i l l be l a r g e l y designed and b u i l t by commercial manufacturers. F a b r i c a t i o n procedures w i l l . be devglo ed by t h e manufacturers o r as p a r t of t h e m a t e r i a l s development program.”However, any h e a t t r a n s f e r o r f l u i d flow s t u d i e s n e c e s s a r y t o assure adequate performance of t h e u n i t s i s a p a r t of t h i s component development program.

The m n c t i o n o f t h i s h e a t exchanger i s t o t r a n s f e r h e a t from t h e f u e l s a l t t o t h e c o o l a n t s a l t . The h e a t exchangers i n each of t h e MSBR c i r c u i t s has a c a p a c i t y of 528 Mw. The MSBE w i l l have one h e a t exchanger w i t h a c a p a c i t y of 1 5 0 Mw. The f’uel s a l t i s i n t h e t u b e s and makes two p a s s e s t‘nrough t h e exchanger. F i r s t it goes doTwnward through an a n n u l a r bundle of t u b e s n e a r t h e c e n t e r . It r e v e r s e s d i r e c t i o n i n a f l o a t i n g head and t h e n p a s s e s up through a n o t h e r a n n u l a r t u b e bundle at t h e o u t e r p e r i p h e r y . The coolant s a l t on t h e s h e l l s i d e flows g e n e r a l l y c o u n t e r c u r r e n t t o t h e f u e l s a , l t . B a f f l e s a r e i n c o r p o r a t e d t o a t t a i n c r o s s flow. The c o o l a n t s a l t o u t l e t i s through a p i p e l o c a t e d a t t h e c e n t e r o f t h e h e a t exchanger and running i t s e n t i r e l e n g t h . This h e a t exchanger, and a l l o t h e r h e a t exchangers i n t h i s r e p o r t , a r e i n t h e c o n c e p t u a l design s t a g e and s u b j e c t t o change as more design work i s done on t h e r e a c t o r . A h e a t exchanger of f’ull MSBE s i z e w i l l be b u i l t and t e s t e d i n t h e ETTJ. The ETU i s conceived of as an i s o t h e r m a l l o o p ; n e v e r t h e l e s s , it w i l l have a l a r g e c a p a c i t y f o r h e a t i n g f l u j . d s . With t h i s h e a t s o u r c e a v a i l a b l e and with w a t e r i n t h e system, we expect t o measure r e a s o n a b l y w e l l t h e o v e r a l l heat t r a n s f e r c o e f f i c i e n t . This w i l l c h a r a c t e r i z e t h e h e a t exchanger p h y s i c a l l y ; t h a t i s , -the combined e f f e c t s of b a f f l e s , unc o n v e n t i o n a l geometry, e t c . T’ne o v e r a l l h e a t t r a n s f e r c o e f f i c i e n t can t h e n be e x t r a p o l a t e d t o a s a l t - s a l t system. Wnile w a t e r i s i n t h e ETU, t h e p r e s s u r e drop through t h e h e a t exchanger w i l l be measured. I n a d d i t i o n , t h e u n i t w i l l b e checked for f l u i d induced v i b r a t i o n s . A s many o f t h e measurements as p o s s i b l e w i l l b e checked a g a i n w i t h s a l t i n t h e system. Because of t h e unconventional c o n f i g u r a t i o n of t h i s h e a t exchanger, v a r i o u s s m a l l models may have t o b e b u i l t t o s e r v e as a check of t h e h y d r a u l i c and s t r u c t u r a l d e s i g n . For i n s t a n c e , a r e l a t i v e l y s m a l l p l a s t i c model t o run on w a t e r would b e used t o l o o k a t t h e adequacy o f t h e flow d i s t r i b u t i o n produced by t h e c o o l a n t s a l t i n l e t v o l u t e . A l s o , because of t h e complexity i n t r o d u c e d by combining t h e pump w i t h t h e h e a t exchanger, models may have t o be b u i l t t o measure t h e r m a l l y induced stresses.

21 Blanket S a l t Heat ExchanggP The purpose o f t h i s exchanger i s t o t r a n s f e r h e a t from t h e b l a n k e t

s a l t t o t h e c o o l a n t s a l t . The MSBR exchangers each have a. c a p a c i t y o f 28 Mw. The MSBE would have a 5- t o 8-MW exchanger. They a r e similar t o t h e f u e l s a l t h e a t exchangers and t h e same comments and program apply. Steam R e h e a m The f u n c t i o n of t h i s exchanger i s t o r e h e a t steam from t h e highp r e s s u r e t u r b i n e b e f o r e it i s a d m i t t e d t o t h e i n t e r m e d i a t e p r e s s u r e t u r b i n e . The MSBR p l a n t h a s e i g h t r e h e a t e r s each r a t e d a t 36 Mw; t h e MSBE would have a 12- t o 18-Mw u n i t . ' The r e h e a t e r would b e s i n g l e pass of steam and c o o l a n t s a l t w i t h t h e steam i n t h e t u b e s and t h e s a l t flowing c o u n t e r c u r r e n t l y t h r o u g h t h e d i s c-and-doughnut - b a f f l e d s h e l l Control of t h e steam o u t l e t t e m p e r a t u r e i s o b t a i n e d by v a r y i n g t h e s a l t flow. G e n e r a l l y , t h i s h e a t exchanger i s c o n v e n t i o n a l , and no fundmnental h e a t t r a n s f e r problems are f o r e s e e n , Again, t h e o v e r a l l h e a t t r a n s f e r c o e f f i c i e n t s h o u l d b e measured i n t h e ETU, p o s s i b l y with s a l t on t h e s h e l l s i d e and low-pressure s u p e r h e a t e d steam on t h e t u b e s i d e . Reheat Steam P r e h e a t e r s The f u n c t i o n of t h i s h e a t exchanger i s t o p r e h e a t t h e h i g h p r e s s u r e t u r b i n e exhaust t o 6 5 0 b~e f~o r e it r e a c h e s t h e r e h e a t e r s . T h i s i s n e c e s s a r y t o minimize t h e chances o f f r e e z i n g t h e c o o l a n t s a l t i n t h e r e h e a t e r s . The h e a t i n g f l u i d i s steam a t 3500 p s i a and 1000째F. The exchanger i s U-shaped c o n t a i n i n g a s i n g l e p a s s of U t u b e s . Exhaust steam from t h e h i g h - p r e s s u r e t u r b i n e m a k e s a s i n g l e pass through the s h e l l s i d e ; it is s u p e r h e a t e d t h r o u g h o u t . T h r o t t l e steam makes a s i n g l e p a s s t h r o u g h t h e t u b e s c o u n t e r c u r r e n t l y ; it i s s u p e r c r i t i c a l t h r o u g h o u t . The h e a t t r a n s f e r c o e f f i c i e n t on t h e tube s i d e i s h i g h compared t o t h e o v e r a l l c o e f f i c i e n t , s o t h a t even t h e boundary l a y e r t e m p e r a t u r e i s f a i r l y w e l l above t h e c r i t i c a l p o i n t . No development work i s planned f o r t h i s h e a t exchanger. The u n i t f o r t h e MSBE w i l l be designed w i t h ample c a p a c i t y and t h e o v e r a l l h e a t transfer c o e f f i c i e n t w i l l be measured during t h e operation of t h e r e a c t o r . Boiler-Superhe a t e r The f u n c t i o n o f t h e s e h e a t exchangers i s Lo Lake h e a t from t h e c o o l a n t s a l t and g e n e r a t e s u p e r c r i t i c a l steam for t h e t u r b i n e s . Each of 1 6 exchangers i n t h e MSBR p l a n t h a s a c a p a c i t y of 1 2 1 Mw. % d o exchangers o f about 60-MW c a p a c i t y each or one o f 120 M , c a p a c i t y would b e u s e d i n t h e JGBE. P h y s i c a l l y , t h e heat exchangers are U s h e l l wish a s i n g l e p a s s of U t u b e s . The s h e l l s i d e has c r o s s flow b a f f l e s w i t h a v a r i a b l e p i t c h . The p i t c h i s g r e a t e s t i n t h e c e n t r a l p o r t i o n of t h e exchanger where t h e bulk f l u i d t e m p e r a t u r e d i f f e r e n c e i s h i g h e s t . S a l t on t h e s h e l l s i d e and s u p e r c r i t i c a l w a t e r on t h e t u b e s i d e flow c o u n t e r c u r r e n t l y . T h i s h e a t exchanger t s c o n v e n t i o n a l except f o r t h e s u p e r c r i t i c a l a s p e c t of t h e w a t e r . Coolant s a l t i s s u p p l i e d t h r o u g h a t h r o t t l i n g v a l v e which p e r m i t s c o n t r o l o f t h e o u t l e t steam t e m p e r a t u r e .

22 The choice of tlie s u p e r c r i t i c a l steam c y c l e f o r t'ne MSBR steam g e n e r a t o r w a s based on c o n s i d e r a t i o n s of t h e h i g h m e l t i n g p o i n t of the m e 1 .and c o o l a n t s a l t , t h e l a r p t h e r m a l s L r e s s e s which a r e produced i n the t u b e w a l l during normal o p e r a t i o n , and t h e h i g h e r t h e r m a l e f f i c i e n cy which may b e o b t a i n e d w i t h t h e s u p e r c r i t i c a , l c y c l e .

We p r e f e r t o o p e r a t e t h e f u e l and c o o l a n t s a l t system such t h a t even 1.ocal f r e e z i n g would n o t o c c u r . The f u e l s a l t , which f r e e z e s at about 85OoF, w i l l be k e p t from f r e e z i n g i n 'Ale fuel. h e a t exchanger by m a i n t a i n i n g t h e t e m p e r a t u r e of .the coolant s a l t above 850OF. and t h e c o o l a n t s a l t will be k e p t from f r e e z i n g by m a i n t a i n i n g t h e feedwater t e m p e r a t u r e a t about TOOOF. Conventionally, a feedwater temperature of l e s s t h a n 575OF i s u s e d b u t 'the h i g h e r t e m p e r a t u r e i s p o s s i b l e with .tile s u p e r c r i t i c a l system. Also, by r a i s i n g the feedwater temperatui-e, t h e t e m p e r a t u r e g r a d i e n t a c r o s s t h e t u b e wa1.l i s reduced t o about 1/2 w i t h a corresponding reduct i o n i n t h e t h e r m a l s t r e s s f o r normal o p e r a t i o n . Rapid thermal c y c l i n g of t h e t u b e wall which i s produced by a r a p i d o s c i l l a t i o n of t h e steam-water i n t e r f a c e i n s u b c r i t i c a l systems w i l l b e g r e a t l y reduced by t h e v i r t u a l e l i m i n a t i o n o f t h e phase change i n going through t h e c r i t i c a l tempera.ture i n t h e s u p e r c r i t i c a l p r e s s u r e system. The t h e r m a l e f f i c i e n c y c o n s i d e r a t i o n i s c o n s i s t e n t w i t h t h e t r e n d of the power i n d u s t r y toward t ' n e u s e o f s u p e r c r i t i c a l steam systems t o obtain t h e highest e f f i c i e n c y f o r t h e temperature. Since t h e high n i c k e l a l l o y i s t o b e used t o c o n t a i n t h e coolant, s a l t myway, t h e r e w i l l b e no a d d i t i o n a l p e n a l t y from t'ne m a t e r i a l s s t a n d p o i n t . The s t u d y of t h e c o m p a t i b i l i t y of H a s t e l l o y N w i t h s u p e r c r i t i c a l steam w i l l be done as a p a r t of tile m a t e r i a l s program. 1 2 S e v e r a l i n v e s t i g a t i o n s OP h e a t t r a n s f e r t o s u p e r c r i t i c a l water have been r e p o r t e d i n t h e l i t e r a t u r e . Notably a r e two i n v e s t i g a t i o n s one by Babcock and Wilcox ( r e f . 1 3 ) and t h e o t h e r by Westinghouse ( r e f . 1 4 ) . Both programs are q u i t e e x t e n s i v e . The programs were c a r r i e d out independently and y i e l d e d p r a c t i c a l l y i d e n t i c a l h e a t t r a n s f e r c o e f f i c i e n t c o r r e l a t i o n s . A s a r e s u l t of t h i s , we belj.eve t h a t e x t e n s i v e work d i r e c t e d toward f i n d a m e n t a l l y measuring and c o r r e l a t i n g c o e f f i c i e n t s i s unwarranted a t t h i s t i m e . N e v e r t h e l e s s tlie technology of s u p e r c r i t i c a l hea.t t r a n s f e r j.s r e l a t i v e l y new and t h e r e a r e q u e s t i o n s of c o r r o s i o n , s c a l e d e p o s i t s , t h e r m a l s t r e s s e s , e t c . and how t h e s e a f f e c t t u b e performance. One of' t h e most p o t e n t i a l l y s e r i o u s unknowns concerns superc r i t i c a l h e a t t r a n s f e r w h i s t l e . "Whistle" i s a phenomenon much l i k e t h e more c o n v e n t i o n a l b o i l i n g songs, b u t c o n f i n e d t o s u p e r c r i t i c a l s y s t e m . Sometimes t h i s w h i s t l e i s a s s o c i a t e d w i t h e x t e n s i v e t u b e v i b r a t i o n s and flow o s c i l l a t i o n s . L i t t l e i s known about t h e cause ant1 e f f e c t of t h i s phenomenon.

Two developmental programs a r e planned concerning s u p e r c r i t i c a l h e a t t r a n s f e r . The f i r s t w i I . 1 be a r a t h e r fundamentally o r i e n t e d study i n a s m a l l l a b o r a t o r y l o o p . One o r p o s s i b l y two s u p e r c r i t i c a l steam g e n e r a t i n g loops w i l l be i n v o l v e d . This program i s i n t e n d e d p r i m a r i l y t o l o o k a t w h i s t l e from a m e c h a n i s t i c p o i n t of view. C a l c u l a t e d heat t r a n s f e r c o e f f i c i e n t s w i l l a l s o be confirmed.

23 The second program i n v o l v e s a l a r g e r two f l u i d ( s a l t 2nd water) system, and can be t h o u g h t of as 8. component dEvel.oprnerit loop. This loop w i l l f e a t m e two o r t h r e e f i l l - s i z e d ttibes from t h e b o i l e r s;;lperheat;er. The t u b e s w i l l be o p e r a t e d at t h e i r r a t e d heai l o a d xi-th c i ~ c u l a t i a gsalt on t h e s h e l l s i d e t r a n s f e r r i n g h e a t t o weker. i n the tubps xt s u p e r c r i t i c a l c o n d i t i o n s . Some of t h e p r i n c i p a l objectives of t h i s 10~75are s follows :

1. To assure t h e absence of s u g e r c r i t f c a l w h i s t l e i n a n e a r l y e x a c t d u p l i c a t e of t h e boiler s u p e r h e a t e r tubes and under similar conditions

To confirm t h e o v e r a l l h e a t t r a n s f e r c o e f f i c i e n t ( : a l e d a t e d for t h e b o i l e r s u p e r h e a t e r . .

To g a i n e x p e r i e n c e 111 cDrrosion aid s c a l e b u i l d u p liu a once-through system of t h i s t y p e , and t o obscrve the feedwater chemical c o n t r o l n e c e s s a r y ~ C I acccptzkL P e results. A d d i t i o n a l i n f o r m a t i o n 1~211b e g o t t e n ?n the c o m p a t i b i l i t y of K a s t e l l o y N in steam, howzvex, t h y maJor program f o r t h i s s t u d y i s a p a r t of t h e m h t e r i a l s development program.

C i r c u l a t i n g bubbles would be add& t o t h e sant loop t o see i f any r e d u c t i o n in o v e r a l l 'reat transfer c o e f f i c i e n t results.

A s one of t h e f i n d e x p e r i m e n t s , one of t h e s u p e r c r t t i c a l steam t u b e s would b e intentionally r i q t u r e d Lo see i f t b z s a l t s i d e p r e s s u r e r e l e a s e system i s a d e q u a t e . This t e s t s h o u l d y i e l d v a l u a b l e i n f o r m a t i g n on t h e ef"fect o f a similar i n c i d e n t i n t h e S E E .

F i g u r e 1 i s a diagram of t h i s l o o p , The above program s h o u l d provide an adcquaxe d e m o n s t r a t i m of the h e a t t r a n s f e r performance o f t h e b o i l e r s u p e r h e a t e r , ever1 though IC i s c o n f i n e d t o two o r t h r e e t u b e s . The e n t i r e b o i l e r superbeater w i l l be t e s t e d i s o t h e r m a l l y i n t h e ITTU. A s i n the case of all o t h e r beat exchangers, i t s p r e s s u r e d r o p , f l u i d induced t u b e ? r i b r a t i o n s an2 o v e r a l l h e a t t r a n s f e r c o e f f i c i e n t (salt to a i r or low p i c s s u ~ e stnani) will b e measured. Heat T r a n s f ~ E r n h m c emenl;

1 _ _

A s a long-range g o d , h e a t t r m s f e r enhancement may he a method of r e d u c i n g c a p i t a l c o s t and f u e l salt inv-entvry P a r t i c u l a r reference i s made to a t u b e shape d e v i s e d by C . G. Lawson ( r e f . 151. 'This t u b e f e a t u r e s a "wavy" s u r f a c e and i s unique i n t h a t i a s i d e heat, t r a n s f e i = c o e f f i c i e n t s have been doubled i n such a way t h a t C'olbum's mslopy h o l d s . That i s t o s a y , t h e inside h e a t t r m s f e r coefficicAn+ i n c r c a ; c s i n t h e same p r o p o r t i o n 8s t h e f " l u i d f r i c t i o n factor, A ( i , ~ v e i ienhaqced t u b e w i l l t r a n s f e r t h e same q u a n t i t y of h e a t RS a longer saool-b t u b e %

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25 i f b o t h have t h e same flow and p r e s s u r e drop. Both t u b e s wov.ld r r ; q u i r e t h e same pumping power. The t u b e s t e s t e d s o f a r a r e of" brass and t h e "waves" are s p i r a l grooves produced by drawing t h e tubes t h r o u g h a p l a n e t a r y swaging head c o n t a i n i n g four b a l l s o r n e e d l e s The i n d e n t i o n s l e f t b y t h e b a l l s a r e t h e s p i r a l grooves. Tests have been conducted o n i y w i t h water. Tubes of t h i s t y p e s h o u l d b e useful i n any heat exchancer i n t h e r e a c t o r system i n c l u d i n g t h e t u r b i n e condenser, bua, would be vcxy i m p o r t a n t i n t h e f u e l t o c o o l a n t s a l t h e a t exchanger i n provTcling a s i g n i f i c a n t decrease i n t h e f u e l inventory.

A s t u d y w i l l be made of t h e u s e of t h e enhanced heat, transfer i n t h e f u e l h e a t exchanger and i f t h e coneept i s compatible t h e n measurements w i l l b e made u s i n g s a l t i n t h e s p e c i a l t u b e s .

One of t h e purposes o f u s i n g an i n t e r m e d i a t e s a l t t o s e p a r a t e t h e f i e 1 and steam systems i s t o p r e v e n t -the high-pressure steam from leaking i n t o t h e h i g h l y r a d i o a c t i v e f u e l r e g i o n and c r e a t t n g a g r o s s r a p t u r e cf t h e low-pressure p i p e o r v e s s e l walls. A p r e s s u r e r e l i e f system i s proposed f o r t h e c o o l a n t s a l t s i d e o f t h e steam g e n e m t o r and r e h e a t e r bo handle t h e t o t a l flow of steam r e s u l t i n g from t h c r u p t u r e of s e v e r a l steam t u b e s w i t h o u t p u t t i n g an e x c e s s i v e p r e s s u r e on t'ne h e a t exchangers. There i s no e q u i v a l e n t requirement i n t h e MSm. This problem can be mostly s o l v e d by design s t u d i e s *mid t e s t s nsing compressed gas and w a t e r . However, some t e s t s may b e required of t h e d i s c h a r g e of s u p e r c r i t i c a l steam i n t o c o o l a n t s a l t and t h e r e l e a s e of s%emand s a l t m i x t u r e s t h r o u g h r u p t u r e d i s c s and blow-down l i n e s ,

DRAIN AND STORAGE TANKS The d r a i n and s t o r a g e t a n k system p r o v i d e s f o r t h e s a f e storage of t h e f u e l , b l a n k e t , and c o o l a n t s a l t s when t h e y are not i n t h e c i r c u l a t i n g systems. I n a d d i t i o n t o m a i n t a i n i n g t h e s a l t s above t h e i i q u d u s temp e r a t u r e , t h e r e are p r o v i s i o n s f o r removing t h e af"ter.-'neat; from Gh-e f u e l and b l a n k e t s a l t s and for m a i n t a i n i n g an i n e r t cover gas o v e r p r e s s u r e t o p r e v e n t t h e i n l e a k a g e of m o i s t u r e and oxygen. A metnod f o r detrrmindng t h e l e v e l of s a l t i n t h e t a n k i s a l s o provided. Drain Tank System f a r t h e Ea Four t a n k s a r e p r o v i d e d f o r storage of t h e s a l t r n i x t u ~ e swhen t h e y are not i n u s e in t h e f u e l - and c o o l a n t - s a l t -1reinZatiny; system of t h e MSRE. Two f u e l - s a l t d r a i n t a n k s and a f l u s h - s a l t t a n k arc connected ta t h e r e a c t o r by means o f t h e fill and drair? l i n e which contains Yreeze v a l v e s t o c o n t r o l t h e s a l t flow. One d r a i n t a n k i s p r o v i d e d f o r the coolant salt I

26 A f u e l d r a i n t a n k i s 50 i n . i n d i a n e t e r by 86 i.n. h i g h and has a volume of about 80 F t 3 , s u f f i c i e n t t o h o l d i n a n o n c r i t i c a l geometry a l l t h e s a l t t h a t can be c o n t a i n e d i n t h e f u e l c i r c u l a t i n g system. The t a n k i s provided w i t h a c o o l i n g system c a p a b l e of removing 1 0 0 kw of f i s s i o n - p r o d u c t decay h e a t ? t h e c o o l i n g b e i n g accomplished by b o i l i n g water i n 32 bayonet t u b e s t h a t w e j - n s e r t e d i n t h i m b l e s i n t h e t a n k . The f l u s h - s a l t t a n k i s s i m i l a i - t o t h e f u e l - s a l t t a n k except t h a t it has no t h i m b l e s o r cooling system. New f l u s h salt i s l i k e me1 salt b u t w i t h o u t f i s s i l e o r f e r t i l e maLeria1. It, i s used t o wash t h e f u e l c i r c u l a t i n g system b e f o r e fuel i s added and a f t e r file1 i s d r a i n e d , and t h e only decay h e a t i n g i s by t h e s m a l l q u m t i t y o f f i s s i o n p r o d u c t s t h a t i t removes f r o m t h e equi.pinent

The c o o l a n t - s a l t tank resembles t h e f l u s h - s a l t t a n k ? b u t it i s 40 i n . i n diameter by 78 i n . high and t h e volume i s 50 f t 3 . The t a n k s a r e provided w i t h d e v i c e s t u j n d i c a t e high and low l i q u i d l e v e l s , w i t h v e i g h c e l l s t o i n d i c a t e t h e weight of t h e t a n k s and t h e l i r c o n t e n t s ? arid w i t h the-mocouples t o i n d i c a t e t h e t e m p e r a t u r e s at' s e v e r a l p o i n t s on t h e tank s u r f a c e . These t a n k s a r e i n s t a l l e d i n i n s u l a t e d f u r n a c e s which a r e h e a t e d with e l e c t r i c a l r e s i s t a n c e h e a t e r s . The e x p e r i e n c e w i t h t h e e l e c t r i c a l l y h e a t e d f u r n a c e s i-n t,he MSiiE has been very good. A t e s t u n i t w a s brought i n 1963 and has o p e r a t e d e s s e n t i a l l y without up t o a t e m p e r a t u r e of 1200'F i n t e r r u p t i o n for 25,600 h o u r s . The f a i l u r e of an e l e c t r i c a l l e a d , which o c c u r r e d s h o r t l y a f t e r t h e s t a r t u p , w a s t r a c e d t o a poor weld a t a j u n c t i o n . This j u n c t i o n was r e d e s i g n e d t o permit i n s p e c t i o n and no f u r t h e r t r o u b l e has been encountered from e i t h e r t h e t e s t unit o r t h e h e a t e r s i n t h e d r a i n taiiks of t h e E R E . Another probl-ern encountered w i t h t h e MSRE d r a i n t a n k s w a s t h e s t a r t u p of t h e steam c o o l i n g system. I n t h e standby condiLion, t h e bayonet t u b e s are a t t h e d r a i n t a s k temperature of g r e a t e r t h a n 1000'F. To s t a r t t h e c o o l i n g system, w a t e r i s allowed t o run down t h e c e n t e r most t u b e , c o o l i n g as it goes. There i s no method i n t h e p r e s e n t system of r e d u c i n g t h e thermal. shock to t h e t u b e t h a t r e s u l t s from this sudden c o o l i n g . The t e s t s r u n on MSilF! p r o t o t y p e c o o l i n g tubes demonstrated (1) t h a t t h e r e w a s 11.0 s i g n i f i c a n t h a z a r d even i f one of t h e 'ii.ibes d i d f a i l s i n c e i t w a s e a s i l y d e t e c t e d , and (2) t h x t t h e r e were s u f f i c i e n t t h e r m a l c y c l e s a v a i l a b l e b e f o r e f a i l u r e t o o p e r a t e thmugh the expected li.fe of t h e MSRE.

The f u e l , b l a n k e t ? and c o o l a n t system; w i l l r e q u i r e s e p a r a t e d r a i n or storage areas Because o f c - r i t jc a l mass considera,tions , t h e f u e l s t o r a g e area w i l l c o n t a i n s e v e r a l tanks each of which w i l l have a c o o l i n g system t h a t may be similar t o t h e one i n t h e MSRE d r a i n t a l k sysiem. Although t h i s c o o l i n g system would n o t be n e c e s s a r y i f t h e f u e l could be h e l d i n t h e h e a t exchmger-fuel piimp system f o r a f t e r h e a t decay, j t would

n o t b e p r a c t i c a l t o d e l a y a mainzenance ope r a tion j u s t for this purpose. T h e r e f o r e , t h e s t o r a g e t a n k c o o l i n g system must have s u f f i c i e n t c a p a c i t y t o t a k e 6a.m o f t h e heat e x i s c i n g s h o r t l y after reactor shutdown. The blankec salt system does n o t have $J? a-stomatic d r a i n feat-ire i n t h e c i r c u l a t i n g system b u t will have a d r a i n t a n k system sfmilar to t h e fuel s t o r a g e system. The m o u n t o f a f t e r - h e a t removal needed w i l l be c o n s i d e r a b l y l e s s t h a n f o r t h e IkeL system but scme p r o v i s i o n must b e made. The c o o l a n t s a l t d r a i n tank area will be separate from t n ~ fuel b l a n k e t s a l t s t o r a g e area t o take advantage of t h e lower tempera+;ure r e q u i r e d f o r t h e c o o l a n t s a l t e The in-trentory for b D t h %he blanket, and c o o l a n t s a l t i s l a r g e enough t o require several t a n k s . The design o f t h e d r a i n i;mk system f o r t h e MZBR baa n o t been c a m i e d f a r enough to g i v e good defLnxtion t o t h e devel.opmt3n-t program, If t h e MSFE d r a i n t a n k system can be u s e d , 3 n e ~ rmethod ~ of s t a r t - i l p and o p e r a t i o n must be developed. The maJcr thermal shoek in t h e MSEE aoo1.ing system occurs when t h e water i s first i n t r o d u c e d i n t o %he centermost t u b e t h e r e b y suddenly r e d u c i n g t h e tube temperatiire f r o m a b w e lOOO'F t o t h e o p e r a t i n g t e m p e r a t u r e of about 212". A more g e n t l e s t a r t u p c o u l d b e accomplished by r e p i p i n g t h e system t o permit t h e ?;-,e o f 10-w p r e s s u r e steam i n i t i a l l y , a n d t h e n by r e d u c i n g t h e s t e m q u a l i t y a t r a r l s i t , z o n t o water c o u l d b e made, The use of water as t h e normal o p e r a t i n g c o u l a ~ l would permit t h e u s e of a s t o r a g e system for emergency c m l i n g . , If a d i f f e r e n t system i s d e v i s e d f o r t h e MSBR, some devFelopment and t e s t i n g , as y e t u n d e f i n e d , w i l l undoubtedly be r e q u i r e d , In any e v e n t , t h e t e s t s t a n d used f o r t h e MSRE coolers will be r e a c t i v a t e d o r a new test s t a n d w i l l be b u i l t f o r t h i s program. Another area which must be i n v e s t i g a t e d is the method of masnLafni n g t h e d r a i n t a n k s a t t e m p e r a t u r e . The s y s t m i n t h e MSRE: used a f u r n a c e f o r each t a n k , removable h e a t e r - l n s u l a t i o n packages for the p i p i n g , and space c o o l e r s to remove t h e h e a t whneh leaks through t h e i n s u l a t i o n , t h e r e b y m a i n t a i n i n g a low terapersture in t h e drain cellOne advantage o f t h i s arrangement i s t h a t i t allowed much leewzy ;E t h e c h o i c e o f materials and equipment t h a t would be u s e d i n The ce31 The d i s a d v a n t a g e s are t h a t a f a i l u r e of t h c apare conier ~n t h e e e l 1 would permit t h e c e l l t e m p e r a t u r e t o rise exc~ss;vely and % h a t t;he h e a t e r - i n s u l a t i o n packages i n v o l v e many i n t r i c a t e shapes w h i c h are d i f f i c u l t t o f a b r i c a t e and maintadin.. The MSBE proposes k > i n s t a l l t h e t a n k s and p i p i n g i n h e a t e d e e l l s , one cell f o r tAhe fuel and. blankery d r a i n t a n k s and one c e l l f o r t h e c o o l a n t salt t a n k s I n additton t o t h e cell. w a l l , i n s u l a t i o n and containment membrane, there are cell h e a t e r s , v e s s e l s u p p o r t s , i n s t r u n e n t a t i o n , and service line disconnects a l l of" which must be examined f o r e o m p a t 2 b i l i t y with t h e h i g h temperat u r e environment, Many of t h e s e problems aye common t o t h o s e found i n the reactor c e l l ,

vAr,vEs FOR MOLTEN SALTS --.-

Means o f c o n t r o l l i n g t h e flow of molten s a l t w i l l be needed i n a l l of t h e systems of t h e MSBR. The requ.irements range from a b s o l u t e s h u t o f f of t h e flow i n t h e f i l l , d r a i n , and t r a n s f e r I.i.nes of t h e f u e l , b l a n k e t , and c o o l a n t sysLems t o t h e t h r o t t l i n g of - t h e flow of t h e c o o l a n t s a l t -to t h e s t e m r e h e a t e r and t o t h e b o i l e r - s u p e r h e a t e r . The c o o l a n t s a l t flow w i . 1 1 be normally 14,600 gpm to -the b o i l e r s u p e r h e a t e r s and 2200 gpm t o t h e r e h e a - t e r s . The c o n t r o l scheme for o p e r a t i n g t h e p l a n t d u r i n g s t a r t u p a n d o t h e r o f f d e s i g s c o n d i t i o n s has n o t been f i r m l y e s t a b l i s h e d , b u t it i s e s t i m a t e d t h a t t h e t h r o t t l i n g range may be down t o about 20% of t h e f U l flow b u t i n no c a s e w i l l it have t o go t o z e r o fl.ow. Methods of a c h i e v i n g t h e s e requirements i n c l u d e v a r i a b l e flow pumps, mechanical L h r o t t l i n g and c u t o f f v a l v e s , f r o z e n s a l t c u t o f f v a l v e s , and b a l a n c e d p r e s s u r e b a r o m e t r i c l e g s t o p r o v i d e and m a i n t a i n flow i n t e r r u p t i o n . A b r i e f d i s c u s s i o n of t h e s t a t u s o f t h e s e methods i s given below. Some development work was done on an emergency d r a i n o r dump v a l v e f o r use i n t h e molten s a l t of t h e A i r c r a f t Reactor ‘Test. This v a l v e cons i s t e d of a s p h e r i c a l metal p l u g which f i t t e d i n t o a s i m i l a r m e t a l s e a t t o form a s e a l . The l e a k a g e p e r m i t t e d .tinrough t h i s v a l v e w a s less t h a n 1 c c / h r . The p o s i t i o n i n g of t h e p l u g w a s accomplished by t h e movement o f a s t e m through a bellows s e a l . The g u i d i n g w a s done on t h e helium gas s i d e of t h e b e l l o w s . Among t h e accomplishments of t h i s work w a s t h e development of a method of a t t a c h i n g a Kenametal p l u g and s e a t t o an I n c o n e l stem and v a l v e body. One of t h e d i f f i c u l t i e s encountered w a s t h e tendency of t h e v a l v e t o s t i c k a f t e r an extended p e r i o d i n t h e c l o s e d p o s i t i o n . Although t h e v a l v e t e n d e d t o s t i c k even a f t e r t h e Kenametal was adopted, t h e r e were i n d i c a t i o n s t h a t t h e s t i c k i n g then was due t o g a l l i n g of t h e e x t e r i o r g u i d e s . IJnfortunately , t h i s program w a s t e r m i n a t e d b e f o r e it w a s completed and t h e q u e s t i o n was n o t resolved.. During t h e t e s t s i n connection w i t h t h i s d-evelopment, none of t h e v a l v e s would c o n s i s t e n t l - y l e a k leks than’l0c c / h r , .although some of them d i d approach this

Valves f o r u s e w i t h l i q u i d metal. systems have been developed and s u c c e s s f u l l y demonstrated. One f e a t u r e of t h e s e v a l v e s which p r e v e n t s t h e i r b e i n g adopted d i r e c t l y f o r u s e w i t h molten s a l t i s t h e f r o z e n m e t a l s h a f t s e a l . S t a t i c s e a l s u s i n g f r o z e n molten s a l t s have been used w i t h f r e e z e f l a n g e s , a c c e s s p o r t s , and f r e e z e va.l.ves, however, t h e g l a s s l i k e c h a r a c t e r of t h e f r o z e n s a l t makes i t s u s e i n a dynamic s e a l doubtful. An a l . t e r n a t e t o t h e mechanica.l t h r o t t l i n g v a l v e f o r c o n t r o l l i n g s a l t flow would be t o p r o v i d e v a r i a b l e flow s a l t pumps, one f o r t,’ne s t e m r e h e a t e r , and a second f o r t‘ne b o i l e r - s u p e r h e a t e r . While it appears t h a t such a scheme i s f e a s i b l e , t2here a r e o t h e r c o n s i d e r a t i o n s which make t h e use of a mechanical v a l v e more a t t r a e t i v e f o r c o n t r o l l i n g tjhe sa1.t flow t o t h e steam r e h e a t e r , and. a variab1.e flow pump f o r c i r c u l a t i n g t h e coola,nt s a l t .

An a l t e r n a t i v e to t h e mechanical c u t o f f valve is 3 Yreeze valve. Freeze v a l v e s f o r u s e i n 1-1/2 i n . ps.pes were developed for u s e i n -the MSRE and, except f o r a p o s s i b l e l i m i t a t i o n cm t h e elcgezt>edl i f e because of t h e s t r e s s produced i n t h e r m a l c y c l i n g d u r i n g t h e freeze-thaw opera,t i o n , t h e s e valves have performed w e l l and should be adtLptabLe f o r use i n t h e MSBR. The t h e r m a l c y c l i n g problem w i l l have to be s t u d f e d . B r i e f l y , t h e valve Consists of a f l a x t e n e d s e c t - i o n o f p q i e , c o o l e d at t h e c e n t e r by an i n s u l a t e d a i r s-tream, and 8, h e a t e d ?urnace which e n c l o s e s t h e e n t i r e v a l v e . T h i s arrangement c c n t r o l s t h e manner i n which t h e s a l t f r e e z e s and thaws s o as -Lo p r e v e n t damage r e s u l t i n g from t r a p p e d l i q u i d expaision d u r i n g t h c thaw. Modes of o p e r a t i o n possible for t h e s e v a l v e s i n c l u d e : (1)open, ( 2 ) c l o s e d b u t ready t o open on 8 power f a i l u r e , ( 3 ) c l o s e d m d t o remain c l o s e d on a power f a i l u r e , and (4) closed b u t ready t o open r a p i d l y ( l e s s t h a n 15 m i n u t e s ) on demand. The t i m e r e q u i r e d t o f r e e z e a v a l v e v a r i e s from 5' t o 30 minutes depend-ing on t h e s t a r t i n g t e m p e r a t u r e and t h e t i m e r e q u i r e d t o thaw v a r i e s from l e s s t h a n 1 5 minutes up t o several hours depending an t h e Inode of' o p e r a t i o n at t h e t i m e of t h e demand. Another method of c o n t r o l l i n g t h e flow i s t h e use of t h e balanced p r e s s u r e b a r o m e t r i c l e g t o provSde and m a i n t a i n t h e flow i n t e r r u p t L o n except when a c o n t r o l l e d zransfer i s needed. B r i e f l y , t h e f l 5s~ c o n t r o l l e d by d i f f e r e n t i a l gas p r e s s u r e s between t h e S Q W C ~ and t h e r e c e i v e r and t h e q u a n t i t y t r a n s f e r r e d i s l i m i t e d by t h e volumes a v a i l a b l e t o t h e t r a n s f e r l i n e s . This system i s p a r t i c u l a r l y a t t r a c t i v e f o r use i n e l i m i n a t i n g t h e t h e r m a l stress a s s o c i a t e d w i t h f r e e z e ~alveswhere t r a n s f e r s are v e r y f r e q u e n t but i n v o l v e o n l y a s m a l l q u m t l t ; y o f s a l t i n each transfer. The development program i n i t i a l l y w i l l c o n s i s t of a design s t u d y to determine more e x a c t l y t h e requirement of %he system f o r flow c o n t r o l , A mechanical t h r o t t l e v a l v e f o r u s e in h i g h flow streams will be designed and t e s t e d i n connection with one of the salt pump Loops. A mechanicaL v a l v e f o r t h e s h u t o f f of small flows will b e designed and s t u d i e d f o r p o s s i b l e use i n t r a n s f e r l i n e s , The developrcent, of t h e be made of v a l v e o p e r a t o r w i l l b e a p a r t o f t h i s pragramo A study .i~i1l t h e f i l l , d r a i n , and t r a n s f e r flow r a t e requirements t o d e l e m i n e t h e s i z e of v a l v e s needed and t h e a p p r o p r i a t e f r e e z e v a l v e w i l l b e designed and t e s t e d . F i n a l l y , a s t u d y w i l l be made of t h e u s e 3f b*druneed p r e s s u r e method of' flow c o n t r o l to d e t e m r n e t h e lsmitations and i f the problems a r e r e a s o n a b l e , a system f o r c o n t r o l l e d transfer wiC2.g b e developed f o r p r o c e s s s y s t e m s ,

The salt sampler c o n s i s t s cf a mechanism f o r Powering a capsule i n t o a f r e e s u r f a c e o f t h e s a l t frora which t h e sample i s to be taken, S i n c e t h e sample c a p s u l e must pass t h r o u g h both t h e primary and recond a r y containment boundaries , it i s n e c e s s a r y %hat s u i t a b l e v a l v e s , a c c e s s p o r t s , and t r a n s p o r t mechanisms be provided t o prpvpnt the a e c i d e n t a l r e l e a s e of a e t T v i t y . I n a d d i t i o n , it i s nec5e,:sary- t h a t a

30 h i g h l e v e l of r e l i a b i l i t y of t h e mechanisms i n v o l v e d be e s t a b l i s h e d , and t h a t a r e l i a b l e maintenance scheme b e d e v i s e d t o r e p l a c e a l l components of t h e sampler system w i t h a minimum de1a.y. The sampler i n t h e MSEE c o n t a i n s t h r e e primary s e a l c l o s u r e s t h r o u g h which t h e sample i s t r a n s f e r r e d i n sequence. The f i r s t c l o s u r e c o n s i s t s of two g a t e v a l v e s w i t h helium b u f f e r and l e a k d e t e c t o r s a t t h e v a l v e s e a t s . This c l o s u r e i s o l a t e s t h e sampler from t h e t a n k t h a t i s b e i n g sampled except when t h e samp1.e i s a c t u a l l y b e i n g withdrawn. These v a l v e s are r e p l a c e a b l e b u t r e q u i r e t h a t t h e r e a c t o r be s h u t down d u r i n g replacement.

'Cine second c l o s u r e c o r i s i s t s of a s i n g l e door w i t h a helium b u f f e r e d and leak d e t e c t e d s e a l . This door p r o v i d e s a c c e s s t o t h e c a p s u l e lowering mechanism and i s opened o n l y a f t e r t h e f i r s t c l o s u r e i s c l o s e d and s e a l e d . The sample c a p s u l e i s i n s e r t e d and removed through t h i s door w i t h a hand-operated mechanical m a n i p u l a t o r . The t h i r d c l o s u r e i s a b a l l v a l v e w i t h a helium b u f f e r e d and. leak d e t e c t e d s e a l . A c y l i n d r i c a l t r a n s p o r t c o n t a i n e r i s lowered throu,oh t h i s v a l v e , t h e sampler i n s t a l l e d , and t h e s e a l e d c o n t a i n e r i s removed i n t o a shielded carrier. The c a p s u l e lowering mechanism, which i s between t h e f i r s t and second c l o s u r e s , c o n s i s t s of s e v e r a l e l e c t r i c a l l y o p e r a t e d components i n c l u d i n g a motor and a c a b l e drum w i t h c a b l e and c a p s u l e l a t c h . I n g e n e r a l , t h e sampler system has o p e r a ' b i d s a t i s f a c t o r i l y through .the removal of 239 samples and t h e i n s e r t i o r i o f SG e n r i c h i n g c a p s u l e s . The only d i f f i c u l t y w i t h t h e system, which r e q u i r e d complete s h u t t i n g down of t h e r e a c t o r t o r e p a i r , o c c u r r e d when an e l e c t r i c a l connection on t h e innermost c l o s u r e opened due t o a s h o r t e d c o n n e c t o r . T h i s equipment w a s designed t o i n s u r e t h a t it c o u l d b e maintained b u t w i t h no s t r o n g emphasis on speed of maintenance. Approximately one week w a s r e q u i r e d t o d i s a s s e m b l e , r e p a i r , and r e p l a c e t h e f a u l t y i t e m , under c o n d i t i o n s of medium r a d i o a c t i v e contamination ( 6 0 R/hr a t s u r f a c e of t h e component).

A more o b j e c t i v e approach i s needed f o r t h e maintenance of t h e sampler f o r t h e MSBE. F i r s t , it s h o u l d not be n e c e s s a r y t o s h u t down t h e r e a c t o r t o reparir t h e sampler. Seconaly, t h e time r e q u i r e d t o r e p a i r any p o r t i o n o f t h e sampler system s h o u l d b e l e s s t h a n t h e r e q u i r e d sampling i n t e r v a l . With t h e e x p e r i e n c e g a i n e d from t h e MSRE sampler as a g u i d e , t h e e n t i r e sampler d e s i g n w i l l b e reviewed f o r changes which w i l l improve t h e m a i n t a i n a b i l i t y .,and t h e s u c c e s s of t h e s e changes wi.11 be demonstrated i n a p r o t o t y p e sampler t o b e used on t h e ETU. One s i m p l i f y i n g f e a t u r e of t h e MSBE i s Lhat t h e samplirig need not be c a r r i e d . out i n t h e r e a c t o r c e l l . S i n c e a p o r t i o n of t h e f u e l and b l a n k e t s t r e a m w i l l b e bypassed c o n t i n u o u s l y t o t h e chemical p r o c e s s p l a n t , t h e sampling s t a t i o n might be i n s t a l l e d i n a c e l l a d j a c e n t t o t h e a n a l y t i c a l f a c i l i t y such t h a t t h e s a l t coming from t h e r e a c t o r t o t h e

p r o c e s s p l a n t and from t h e p r o c e s s p l a n t back t o t h e r e a c t o r could be analyzed f o r m a t e r i a l c o n t r o l and i n v e n t o r y purposes. Development needed i s t o e n a b l e one sampler t o s e r v e s e v e r a l s t a g e s i n t h e chemical process plant. GAS SYSTEM The design of t h e MSBR gas system w i l l be based i n p a r t on experience g a i n e d from p r e v i o u s l i q u i d fuel. r e a c t o r s , t h e ART, t h e HRT, and t h e MSRE, and i n p a r t on design c r i t e r i a p e c u l i a r t o t h e MSBR.

A s i n t h e MSRE, t h e MSBR gas system w i l l : 1. S t r i p xenon-135 from t h e f u e l system. 2.

Dispose of r a d i o a c t i v e f i s s i o n gases and d a u g h t e r s .

P r o t e c t t h e s a l t from o x i d i z i n g atmospheres.

Provide motive power f o r salt t r a n s f e r .

F u r n i s h miscellaneous s e r v i c e s such as p u r g i n g , v e n t i n g , and l e a k d e t e c t i o n .

Compared w i t h t h e MSRE, t h e MSBR cover gas supply system w i l l . have a l a r g e r c a p a c i t y and w i l l u t i l i z e helium r e c y c l e d from t h e o f f g a s system. The MSBR o f f g a s system plans or contemplates t h e f o l l o w i n g f e a t u r e s which were not; a p a r t of t h e MSRE system. 1. Rapid s t r i p p i n g of xenon-135 from t h e f u e l system by i n j e c t i n g helium a t t h e h e a t exchanger i n l e t and removing xenon-enriched helium by means of a gas s e p a r a t o r downstream of t h e h e a t exchanger. The helium from t h e s e p a r a t o r w i l l be r e t u r n e d t o t h e fie1 s t r e a m a f t e r p a s s i n g through a holdup system designed t o reduce t h e c o n c e n t r a t i o n of Xe-135 by a f a c t o r of 40. 2.

Removal of Kr-85 and tri2;ium from t h e c h a r c o a l bed e f f l u e n t , with c o l l e c t i o n , recompression and r e u s e of t h e helium, and c o n c e n t r a t i o n and s t o r a g e o f t h e Kr-85 and tritium.

E R E Cover and Offgas Systems A d e t a i l e d d e s c r i p t i o n of t h e MSFG cover and o f f g a s system may b e found i n t h e EasRE Design and Operations Report.2 Only a b r i e f d e s c r i p t i o n w i l l be p r e s e n t e d h e r e .

A helium cover-gas system p r o t e c t s t h e oxygen-sensitive fuel from c o n t a c t wit'n a i r arid m o i s t u r e . Commercial helium i s s u p p l i e d i n a t a n k t r u c k and i s passed through a p u r i f i c a t i o n system t o reduce t h e oxygen and water c o n t e a t below 1. pprn b e f o r e it i s a d m i t t e d t o t h e r e a c t o r systems. A flow of 200 f t 3 / d a y (STP) i s passed c o n t i n u o u s l y through t h e f u e l pump bowl. t o t r a n s p o r t t h e f i s s i o n product g a s e s t o a c t i v a t e d c h a r c o a l a d s o r b e r beds. The r a d i o a c t i v e xenon i s r e t a i n e d on t h e c h a r c o a l f o r a minimum of 90 d a y s , and -the k:rypton f o r 7--l/2 d a y s , which i s s u f f i c i e n t f o r a l l b u t t h e 8 5 K r t o decay t o i n s f - g n i f i c a n t l e v e l s . The 8 5 K r i s maintained well w i t h i n t o l e r a n c e , t h e e f f l u e n t gas b e i n g d i l u t e d with 21,000 c f m of a i r , f i l t e r e d , moni.tored, and d i s p e r s e d from a 3-ft-dixm by 100 f t h i g h s t a c k . Some tritium i s a l s o produced i n t h e r e a c t o r . I t s b e h a v i o r has n o t been s t u d i e d b u t we assume t h a t i t t o o i s d i s c h a r g e d t o t h e atmosphere. The q u a n t i t y produced i s such t h a t t h e c o n c e n t r a t i o n i n t h e a i r does n o t exceed AEC limits

A s d e s c r i b e d i n t h e s e c t i o n on pump development;, t h e MSRE pump also c o n t a i n s an arrangement for s p r a y i n g t h e s a l t i n t o t h e gas s p a c e of t h e pump i n f i n e streams such t h a t t h e g a s i s p e r m i t t e d t o s e p a r a t e from t h e s a l t . Experiments conducted on t h i s arrangement i n a small t e s t loop i n d i c a t e d .tihat t h e e f f i c i e n c y of t h i s s e p a r a t i o n would b e l e s s t h a n l 5 % , probably due t o t h e extremely s h o r t c o n t a c t i n g time a v a i l a b l e i n t h e gas s p a c e . The e x p e r i e n c e g a i n e d i n t h e MSRE has i n d i c a t e d t h a t t h e apparent e f f i c i e n c y may be as h i g h as 75%. It i s b e l i e v e d t h a t t h e apparent h i g h e r s e p a r a t i o n e f f i c i e n c y i s t h e r e s u l t of a small volume f r a c t i o n of gas bubbles c i r c u l a t i n g i n t h e s a l t . On t h e average t h e s e bubbles make 20 t r i p s around t h e f u e l l o o p and t h e n p a s s through t h e s p r a y r i n g i n t o t h e pump bowl where t h e y can s e p a r a t e from i'ne s a l t . The xenon c o n c e n t r a t i o n i n t h e bubbles should be i n e q u i l i b r i u m w i t h t h e c o n c e n t r a t i o n of xenon d i s s o l v e d i n t h e s a l t . S i n c e t h e s o l u b i l i t y i n s a l t i s very l o w , most of t h e xenon w i l l be i n t h e b u b b l e s . This type of b u b b l e - l i q u i d c o n t a c t o r i s proposed f o r use i n t h e MSBH except t h a t a bubble w i l l not r e s i d e i n t h e l o o p f o r more t h a n 1 c i r c u i t . The cover gas system i s a l s o used t o p r e s s u r i z e tile d r a i n t a n k s t o move molten s a l t s i n t o t h e f u e l and c o o l a n t c i r c u l a t i n g systems. Gas from t h e s e o p e r a t i o n s i s p a s s e d through c h a r c o a l beds and f i l t e r s b e f o r e it i s d i s c h a r g e d through t h e o f f g a s s t a c k .

MEHE G a s System Performance ---I-__.

Performmce of t h e cover gas supply and d i s t r i b u t i o n system h a s been s a t i s f a c t o r y . Buildup of oxide tn t h e f u e l s a l t duri.ng % l O , O O O hours of o p e r a t i o n has been n e g l i g i b l e , i n d i c a t i n g t h a t t h e p u r i t y of t h e helium gas has been adequate. The helium p u r i f i e r system, t h e p r e s s u r e and flow c o n t r o l s , and t h e leak d e t e c t o r system have o f f e r e d no mechanical. problems. M k o r d i f f i c u l t i e s have been experienced as f o l l o w s :

- t h e i n d i c a t e d moisture c o n t e n t of t h e p u r i f i e d gas has v a r i e d from l e s s t h a n t h e 1 ppm c o n t r o l p o i n t t o as h i g h as 10 ppm. It i s not known i f t h e v a r i a t i o n i s r e a l or perhaps i s a s y s t e m a t i c e r r o r i n t h e a n a l y t i c a l i n s t r u m e n t . Some development work i s under way t o e v a l u a t e t h i s problem f o r t h e MSRE.

1. Gas p u r i f i c a t i o n

Back d i f f u s i o n - p r e s s u r e v a r i a t i o n s i n t h e d r a i n t a n k s caused back d i f f u s i o n of a c t i v i t y i n t o t h e helium supply l i n e w i t h r e s u l t a n t h i g h r a d i a t i o n l e v e l i n t h e a d j a c e n t work a r e a . The s i t u a t i o n was c o r r e c t e d by p r o v i d i n g a s m a l l , continuous purge of c l e a n gas through t h e l i n e s . Rupture d i s c s - t h e supply l i n e r u p t u r e d i s c ( p r o t e c t s s a l t v e s s e l s from excess p r e s s u r e ) f a i l e d s e v e r a l t i m e s d u r i n g t h e pre-nuclear o p e r a t i n g p e r i o d . The t r o u b l e vas a s c r i b e d t o t h e lower r a t i o of r u p t u r e t o o p e r a t i n g p r e s s u r e s , and t h e problem w a s c o r r e c t e d by reducing t h e header operating pressure.

Delay t e s t s were run on t h e MSRE c h a r c o a l beds during t h e pren u c l e a r p e r i o d . The krypton d e l a y time was found t o a g r e e w i t h t h e p r e d i c t e d v a l u e w i t h i n a c c e p t a b l e l i m i t s . T h i s f a c t , coupled with e x p e r i e n c e d u r i n g MSRE power o p e r a t i o n , i n d i c a t e s t h a t t h e b a s i c technology of c h a r c o a l bed design i s adequate. The f o l l o w i n g d i f f i c u l t i e s were experienced w i t h t h e MSRF: o f f g a s system :

1. Foreign m a t t e r , which r e s u l t e d from i n l e a k a g e of o i l

from t h e f u e l pump l u b r i c a t i n g system, caused plugging of c o n t r o l v a l v e s , flow r e s t r i c t o r s , and f i l t e r s . The r e s u l t i n g l o s s of c o n t r o l of pump bowl over-pressure and off-gas flow caused s e v e r a l i n t e r r u p t i o n s i n r e a c t o r o p e r a t i o n s . The problem i s being c o r r e c t e d by modific a t i o n s i n f u e l pump d e s i g n and by t h e use of f i l t e r s of improved d e s i g n . The i n v e s t i g a t i o n of t h i s problem y i e l d e d v a l u a b l e e x p e r i e n c e i n t h e d e s i g n of f i l t e r s for r a d i o a c t i v e gases ( e . g . , t h e importance of adequate h e a t t r a n s f e r ) , and i n t h e hot c e l l examination of components. The work a l s o s e r v e d t o emphasize t h e p o t e n t i a l problem of salt-mist c a r r y o v e r i n t h e offgas

A flow r e s t r i c t i o n r e s u l t e d i n t h e d r a i n t a n k vent h e a d e r when t h e poppet i n an i n - l i n e r e l i e f valve became disengaged from t h e v a l v e body and became lodged i n t h e p i p i n g a t t h e i n l e t t o t h e a u x i l i a r y c h a r c o a l bed.

Control v a l v e s , which o p e r a t e d i n t h e very l o w flow o f 4 l i t e r s / m i n o f dry helium, tended t o gall. i n t h e SI i djng s u r f a c e s between t h e v a l v e p l u g and t h e v a l v e seat. This problem has been reduced by u s i n g d i f f e r e n t m a t e r i a l s and by opening t h e c l e a r a n c e s between t h e p l u g and seat.

I n t e r m i t t e n t plugging o c c u r r e d a t t h e i n l e t t o t h e main c h a r c o a l beds. T'nis t r o u b l e , whi ch has p e r s i s t e d throughout t h e power o p e r a t i o n , w a s a t f i r s t r e l i e v e d p e r i o d i c a l l y by blowing back from t h e charcoal bed i n t o t h e holdup volume. A s a r e s u l t of h o t cell e x a x i n a t i o n of o f f g a s system components, tine d i f f i c u l t y w a s a s c r i b e d t o accumuations o f polymerized organic s o l i d s . I n r e c e n t mont'ns t h e r a t e of p l u c g i n g h a s been a p p r e c i a b l y lower, p o s s i b l y due t o t h e improved f i l t e r s mentioned i n 1. above, and r e s t r i c t i o n s when e x c e s s i v e , have been c l e a r e d by h e a t i n g t h e c h a r c o a l b e d i n l e t l i n e s t o about 800'F.

MSBH Offgas System

-..-

I -

T n e o f f g a s system proposed t o r t h e MSBR i s shown s c h e m a t i c a l l y on F i g u r e 2 . The f u e l system o f f g a s s t r e - m i s a combination o f helium flows from the gas s e p a r a t o r m d from t h e pump bowl vapor space. The pump bowl e f f l u e n t i s a c o l l e c t i o n of m i s c e l l a n e o u s purge g a s e s from p l a c e s such as t h e pump shaft; annulus and t h e l e v e l i n d i c a t o r instrument b u b b l e r s . The t w o o f f g a s s t r e a m s combine a t t h e cyclone separator. where e n t r a i n e d sa1.t i s removed. The o f f g a s s t r e a m t h e n combines w i t h s i m i l a r s t r e a m s from t,he o t h e r t h r e e r e a c t o r modul.es,* and t h e t o t a l offgas stream p a s s e s through t h e 48-hr holdup system where t h e gas i s f i l t e r e d to remove so1i.d daughter p r o d u c t s and t h e xenon-135 c o n c e n t r a t i o n i s reduced by r a d i o a c t i v e decay t o about 2-1/2% of i t s i n i - t i a l v a l u e . A t t h e o u t l e t of t h e 1-18-hr holdup system, t h e o f f g a s i s s p l i t i n t o t w o streams. One, comprising about 96% o f t h e t o t a l f l o w , i s r e t u r n e d t o the f u e l system a t t h e f u e l pump suctj-on l i n e by means of a gas i n j e c t i o n system. The i n j e c t i o n ra%e i s c a l c u l a t e d t o maintain t h e volume f r a c t i o n of gas a t t h e p o i n t of injectrion e q u a l t o 1%of t h e f i e 1 flow. This v a l u e f o r t h e c i r c u l a t i n g void f r a c t i o n i s t e n t a t i v e , however, pending r e s u l t s of developrnent s t u d i e s .to be made on t h e d i f f u s i o n r a t e o f xenon from t h e s a l t t o t h e c i r c u l a t i n g b u b b l e s .

The balance of t h e f u e l system o f f g a s flow i s combined w i t h b l a n k e t piarlp o f f g a s from t h e f o u r inodules and t h e conibined s t r e a m p a s s e s i n o r d e r

Lhrough long d e l a y c h a r c o a l b e d s , a tritium removal system and a krypton-85 t r a p p i n g system, and i s t h e n recompressed and r e t u r n e d t o t h e purge gas supply system. -

____I__

1-11____

-..-

,#The t e r m module i s used i n t e r c h a n g e a b l y i n t h i s d i s c u s s i o n t o r e p r e s e n t one h e a t exchanger and pump c i r c u i t i n t h e 1000 Mw(e) MSBR of r e f e r e n c e do?-,,~gri o r one complete r e a c t o r systgm i n a 1000 M w ( ~ ) M5BR p l a n t containi.ng f o u r r e a c t o r s of modular d e s i g n s . c

3.5

E-

-. .

36 Thus, t h e o f f g a s system c o n s i s t s of two r e c i r c u l a t i n g l o o p s , one a h i g h flow system f o r r a p i d removal of xenon-135 from t h e r e a c t o r f u e l stream, and t h e o t h e r a low flow system f o r removal of l o n g - l i v e d a c t i v i t y and recovery of hel.j_urn. Current e s t i m a t e s of t h e v a r i o u s flow r a t e s are as f o l l o w s : Flo~w Rate, -.-----

One Module

scfm -F_______ Ielium Four ModuAles

________c

I n p u t to Fuel System S t r i p p e r Gas M i s cel.1 an eou s Purge Tot a 1 Inpu-t

6.5 0.25

6.75

E f f l u e n t from Fuel System Gas S e p a r a t o r Miscellaneous Purge Tot a1 E f f l u e n t

26 1 27

0.25

26 1

Throughput f o r 48 h r Holdup System

---.-

S t r i p p e r Gas Recycle

6.5

Throughput f o r Blanket System

0.25

Throughput f o r Long Delay Charcoal. Bed

----

I---

6.5

6.75

Throughput f o r ' T r i t i u m and Krypton Removal Sys t era Clean Helium Recycle ~

-I.--

..~-.--.______-___-

Y"ne a n t i c i p a t e d t e m p e r a t u r e and p r e s s u r e l e v e l s a t v a r i o u s p o i n t s i n t h e system a r e t a b u l a t e d on Figure 2. I n a d d i t i o n t o t h e main o f f g a s system, p r o v i s i o n i s made f o r h a n d l i n g tine f o l l o w i n g gas strecams: 1.

I n t e r m i t t e n t v e n t i n g o f l a r g e volumes of helium f r o m t ' n e f u e l b l a n k e t and c o o l a n t system d r a i n t a n k s .

A continuous flow of about 0.8 scfm of helium f r o m t h e c o o l a n t pumps. T h i s stream w i l l c o n t a i n some s h o r t Lived, induced a c t i v i t y p l u s a high p a r t i a l p r e s s u r e of YF3.

A more-or-less continuous low flow o f f g a s s t r e a m cont a i n i n g gaseous f i s s i o n p r o d u c t a c t i v i t y from t h e chemical processing p l a n t .

37 These g a s e s are p r e t r e a t e d t o remove u n d e s i r a b l e contaminants such as BF3 and f l u o r i n e and t h e n d i r e c t e d t h r o u g h a high f l o w , a u x i l i a r y c h a r c o a l bed. Depending on t h e outcome of f u t u r e f e a s i b i l i t y s t u d i e s , t h e e f f l u e n t from t h e a u x i l i a r y c h a r c o a l b e d may b e d i l u t e d w i t h a i r from t h e b u i l d i n g v e n t i l a t i o n system and d i s c h a r g e d t o t h e atmosphere through an i o d i n e t r a p and a b s o l u t e f i l t e r system, or it may b e p u r i f i e d , recompressed and r e t u r n e d t o t h e helium supply h e a d e r . The p r e s e n t flow s h e e t shows t h i s material as b e i n g v e n t e d t o t h e s t a c k .

MSBE Offgas System The MSBE o f f g a s system w i l l b e a s c a l e model. of t h e proposed MSBR system and as such w i l l s e r v e as a f i n a l proving ground t o check t h e adequacy of t h e i n d i v i d u a l components and of t h e i n t e g r a t e d system. S i n c e t h e f u e l flow r a t e i n t h e MSBE i s about 40% o f t h e flow i n one MSBR module, components common t o each module, such as t h e gas s e p a r a t o r and t h e g a s i n j e c t o r , w i l l b e about 2 / 5 MSBR s c a l e . T h e s c a l e of t h e o t h e r components will v a r y from 1/4 t o 1 / 1 0 as shown on Table 3. Table

MSBE Offgas System S c a l i n g F a c t o r s

System

Flow Rate SBR MSBE

MSBE

F u e l , gpm

ll,OOO* 4400

6.5*

2.6

2/5

6.5"

2.6 20

2/5

48-hr holdup system, s c f

21 2

1/10

Biological charcoal beds, s c h

2.85

G a s i n j e c t i o n & s t r i p p i n g , scfm

Cyclone s e p a r a t o r : Gas, scfm Salt, a m

50n

Kr-85 t r a p p i n g system, scfm H e l i u m compressor, scfm

0.5

0.. 5

0.75

Scale

2/5

215

1/4 1/4 1/4

*Per r e a c t o r module. Development Program

G a s system components which r e q u i r e development are t h e g a s separat o r , t h e s a l t powered gas i n j e c t o r , t h e cyclane s e p a r a t o r , t h e f i l t e r system f o r f i s s i o n p r o d u c t s , t h e gas compressor, t h e 85Ky. s t r i p p i n g system, t h e t r i t i u m removal system and t h e gas sampler.

38 Gas S e p a r a t o r

_ II.

The gas s e p a x a t o r wi.11 b e l o c a t e d i n t h e fu.el p i p e between t h e h e a t exchanger outt;l.et and t h e r e a c t o r i n l e t . i n t h i s reg.i.on t h e r e a c t o r i n l e t l i n e s u r r o u n d s , and i s c o n c e n t r i c w i t h , t h e r e a c t o r o u t l e t l i n e , forming an a n n u l a r d u c t . The s e p a r a t o r f o r t'ne MSBR w i l l c o n s i s t of about 15 i d e n t i c a l v o r t e x bubble s e p a r a t o r u n i t s of t h e same diameter as t h e annulus width and d i s t r i b u t e d about t h e annulus as shown i n F i g u r e 3. The s e p a r a t o r f o r t h e MSBE w i l l u s e tiie f u l l - s c a l e IGBR s e p a r a t o r u n i t , b u t only s i x of t h e v o r t e x u n i t s w i l l . b e r e q u i r e d because of t h e lower s a l t flow r a t e .

For t h e MSER, each i n d i v i d u a l uni.t should have t h e c a p a b i l . i t y of removing a l l bubbles l a r g e r than 0 . 0 1 i n . dia.m and the c a p a c i t y t o s e p a r a t e 0.44 s c f m of gas from a flow o f 750 gpm. o f s a l t . The gas t a k e o f f l i n e s w i l l b e connected t o a ccmrfl~nheader l e a d i n g t o t h e cyclone s e p a r a t o r . About 50 gpm of s a l t , e q u a l t o about 40% o f t h e t o t a l volume flow w i l l be d i s c h a r g e d t o t h e cyclone s e p a r a t o y a l o n g w i t h t h e g a s . A c o n s i d e r a b l e amount o f t h e o r e - t i c a l and experimental work w a s done i n connection with t h e gas s e p a r a t i o n problem i n t h e aqueous homogeneous r e a c t o r s . 16,17,18,19 The program w i l l incl.ude (I.) a p p l i c a t i o n of t h o s e r e s u l t s t o t h e design of a f u l l - s c a l e u n i t , and ( 2 ) proof t e s t i n g of a p r o t o t y p e u n i t i n water and s a l t l o o p s .

Mass T r a n s f e r -LIJ-

Ci rcul

Bubble s

One o f t h e m c e r t a i n t i . e s i n e s t i m a t i n g t h e e f f i c i e n c y of t h e proposed system f o r removing 1 3 5 X e and a l l o t h e r noble gases .from tiie system i s t h e r a t e of mass t r a n s f e r f r o m t i i e f u e l s a l t t o t h e c i r c u l a t i n g bubbles. This r a t e ris i n t i m a t e l y a s s o c i a t e d w . t b t h e mass ti-ansfel- c o e f f i c i e n t t o t h e bubbles. Only a moderate amount of i n f o r m a t i o n on thj.s mechanism i s a v a i l a b l e from t h e L i t e r a t u r e and g e n e r a l l y it i s n o t d i r e c t l y a p p l i c a b l e . A program involvi-ng a w a t e r 10o:p and soiiie r e l a t i v e l y i n s o l u b l e gas (perh!zps oxygen) w i l l b e u s e d t o measure t h e mass t r a n s f e r c o e f f i c i e n t t o s m a l l bubbles c i r c u l a t i n g i n a t u r b u l - e n t stream. T'nis information w i l l . t h e n be e x t r a p o l a t e d t o t h e f u e l s a l t - h e l i u m bubble system by mass t r a n s f e r analogy. I t is hoped t o b e a b l e t o confirm t h e s e r e s u l t s i n tiie gas system t e s t l o o p and t h e e n g i n e e r i n g t e s t u n i t . Salt-Powered -.l r i j e c t o r The Xe--135 s t r i p p i n g system r e q u i r e s i n j e c t i o n of helium i.nto t h e f u e l stream a t t h e h e a t exchanger i n l e t . 'Fne r e q u i r e d gas flow i s about 6.5 scfm. The a v a i l a b l e gas h e a d , which i s t h e p r e s s u r e a t t h e outl.et o f t h e 48-hr holdup system, i s about 2 p s i g . T'ne s t a t i . c p y e s s u r e of t h e s a l t at t h e p o i n t o f i n j e c t i o n i s about 9 p s i g . We b e l i e v e t h a t t h e gas i n j e c t i o n can 'oe e f f e c t e d by u t i l i z i n g t h e energy i n t h e ss1.t) stream. The d e v i c e might be e i t h e r a commercial, l i q u i d powered gas i n j e c t o r or a f u l l - f l o w v e n t u r i s e c t i o n . A s a backup, t'ne p o s s i b E l i t y o f u s i n g a mechanical compressor w i l l a l s o b e i n v e s t i g a t e d . The program rv.il.1 i n c l u d e s m a l l - s c a l e z e s t s t o e v a l u a t e t h e a l t e r n a t e s followed by c o n s t r u c t i o n

,- -. .....

.. .

2 -

40 and t e s t i n g of an PEBE protoLype u n i t . The main problems w i l l b e t o demonstrate (1) a b i l i t y t o perform a t t h e p r e s c r i b e d MSSE d e s i g n cond i t i o n s ( 2 ) c o m p a t i b i l i t y w i t h t h e o v e r a l l gas h a n d l i n g sys ten1 , ( 3 ) adequate s e r v i c e l i f e and ( 4 ) r e p l a c e a b i l i t y . Âś

A cyclone s e p a r a t o r i s provided t o remove s a l t which i s e n t r a i n e d by t h e g a s coming from t h e gas s e p a r a t o r . The underflow i s r e t u r n e d t o t h e f i e 1 s t r e a m by way o f t h e pump bowl. The design o f t h e u n i t w i l l be based on existring t e c h n o l o g y , b u t t h i s work w i l l b e d e f e r r e d pending development of d a t a on t h e o p e r a t i n g c h a r a c t e r i s t i c s of t h e gas s e p a r a t o r . The program will. c o n s i s t merely of p r o o f - t e s t i n g t h e f i n a l design I

Salt-Mist Removal. Offgas system components must b e p r o t e c t e d from s a l t m i s t . A program w i . 1 1 be r e q u i r e d t o determine t h e n a t u r e and s e v e r i t y o f t h e salt-mist problem, and t o develop a s a t i s f a c t o r y e n t r a i n m e n t s e p a r a t i o n system. Tests w i l l b e conducted i n a l o o p i n c o r p o r a t i n g flow of f u e l and o f f g a s a t design c o n d i t i o n s . The program w i l l i n c l u d e ( I ) c h a r a c t e r i z a t i o n of o f f g a s c o n t a ~ n i n m t sand ( 2 ) p r o o f - t e s t i n g of v a r i o u s p o s s i b l e m i s t t r a p p i n g d e v i c e s . The MSSX m i s t tra.p w i l l b e l o c a t e d a t t h e o u t l e t of t h e cyclone s e p a r a t o r . 'The problem with t h e entrainment o f a s a l t m i s t i n t h e g a s l i n e s o f t h e MSRE w a s f i r s t encountered i n one of t h e o f f g a s l i n e s coming from t h e pump bowl. The gas flows from t h e pump bowl a t about 4 l i t e r s / min and t r a v e l s through a ho1du.p vol.ume of 170 l i t e r s b e f o r e e n t e r i n g a f i l t e r and v a l v e assembly. It was found t h a t very f i n e p a r t i c l e s o f salt were car-rying through t h e holdup volume, going through t h e f i l t e r and d e p o s i t i n g i n t h e opening of t h e v a l v e u l t i m a t e l y causi-ng a flow stoppage. S i n c e t h e q u a n t i t y of s a l t w a s very s m a l l and di.d not seem to p r e s e n t o t h e r problems the d i f f i c u l t y w a s s o l v e d by changing t h e p o r e srize of t h e f i l t e r from 2 5 1-1 t o one c l o s e r t o 1 0 u . A t tiie same t i . m e t e s t s were i n i t i a t e d t o c h a r a c t e r i z e t h e p a r t i c l e s coming from the bowl o f a s i m i l a r pimp b e i n g o p e r a t e d i n 8. t e s t loop. It was found t h a t t h e p a r t i c l e s were formed as a m i s t of .the c i r c u l a t i n g s a l t and were n o t t h e r e s u l t of condensation of a s a l t vapor. The proposed solution t o t h i s problem, which i s t o D ' e t e s t e d f o r use i n t h e %RE: r e p l a c e ruent pump, i s t o i n s t a l l a h e a t e d m e t a l l i c f i l t e r element i n t h e pinip bowl such t h a t any s a l t caught on t h e f i l t e r w i l l . run back i n t o t h e pump h o w l . The %BE could p o t e n t i a l l y have a more s e v e r e probl-em s i n c e t h e gas l e a v e s tiie pump bowl a t about, 30 t i m e s t h e r a t e f o r tiie PGRE. A s i m i . l . a r s o l u t i o n i s proposed f o r t h e MSBE but it must be t e s t e d a t t h e h i g h e r g a s flow.

41 F i s s i o n Product F i l t e r

At a power l e v e l of 2200 Mw thermal, f i s s i o n p r o d u c t s w i l l . b e produced at a rate of &out 0 . 1 y gm-moles/day , where y i s t h e y i e l d i n p e r c e n t . S i n c e y i e l d s of kryptons and xenons range up t o &5%, t h e t o t a l p r o d u c t i o n of xenon and k r y p t o n will be on t h e o r d e r of s e v e r a l hundred grams p e r day ( s e e T a b l e 4 ) Except f o r Kr-85, e s s e n t i a l l y 100% of t h e r a d i o a c t i v e kryptons and xenons w i l l deeay t o s o l i d daughter p r o d u c t s which w i l l d e p o s i t i n t h e r e a c t o r system o r a t some p o i n t i n t h e o f f g a s system. The l o c a t i o n and r a t e o f d e p o s i t i o n w i l l b e a fâ&#x20AC;&#x2122;unction of t h e decay c o n s t a n t and t h e l o c a l flow r a t e and geometry. I n t h e MSBR, a f i l t e r system i s r e q u i r e d upstream of t h e 48-hr c h a r c o a l beds t o remove s o l i d daughters f r o m t h e o f f g a s stream. The purpose i s to minimize t h e d e p o s i t i o n o f s o l i d s i n u n d e s i r e d p l a c e s , such as on valve t r i m , and t o minimize t h e c a r r y - o v e r o f s o l i d s i n t o t h e c h a r c o a l b e d s . The e q u i v a l e n t system f o r t-he MSBE w i l l be designed u t i l i z i n g e x p e r i e n c e g a i n e d i n t h e d e s i g n and o p e r a t i o n of f i l t e r s f o r t h e KYRE o f f g a s system. The prime cons i d e r a t i o n s are (1) adequate h e a t d i s s i p a t i o n , ( 2 ) adequate s e r v i c e l i f e and ( 3 ) ease of r e p a i r o r replacement I

Table

P r o d u c t i o n o f Gaseous F i s s i o n P r o d u c t s i n M B R * Power Level - 2200 Mwt Isotope, i

(tlmi _l___ll_

K r 87 K r 88

78 m

K r 90 K r 91

33 s 9*8 s

Kr 89

Xe Xe Xe Xe Xe Xe

133

135 137 138 139

140

Yi 1 1 -

2.77 h r

3.18 m

5.27 d 9.13 h r

3.9 m

17 m 41 s 16 s

gms /day

2.7 3.7 4.6

3.7

6.5

4.7

76 65

5.2

6.2 5.9 5-5

3.7

41 47

52 443 621

T o t a l K r and Xe

*Kr-85 and s h o r t lived (t l / 2 < 5

s e c s ) a r e n o t shown.

Kr-85 and T r i t it? Remova&.-.Sj-st em

-_s_____-

A t a powel. of 2200 Mw thermal., t h e MSBR w i l l produce an e s t i m a t e d 2000 c u r i e s / d a y OS Kr-85 ( 1 0 . 2 7 y r h a l f - l i f e ) and 2800 curi.es/day of t r i t i u . m (12.26 y r h a l f - l i f e ) . About, 25% of t h e tritium 1 r i l . l b e produced l i i t h e bl-anket. S i n c e t h e r e i s no i n f o r m a t i o n a v a i l a b l e a t p r e s e n t which would i n d j - c a t e an a l t e r n a t e f s t e f o r t h e tritiim, it i s assumed t h a t i t , as w e l l as t h e Kin-85, w i l l pa,ss e s s e n t i . a l l y undecayed through t h e c h a r c o a l bed r e t e n t i o n system. A cleanup system - w i _ l l b e provided which w i J . 1 reduce t h e Kr-85 and t r i t i u m - t o a level which w i l l permit helium .Lo b e r e t u r n e d t o t h e purge gas system o r vented t o t h e s t a c k . The c u r r e n t concept of t h e cleanup system p r o v i d e s f o r a s e r i e s o p e r a t i o n wherein t h e helium will. pass f i r s t through a t r i t i u m removal s t a t t o n and t h e n t h r o u g h a cryogenic a b s o r b e r t o remove Kr-85. The Kr-85 system w i l l be of t h e r e g e n e r a t l v e t y p e , w i t h p e r i o d i c t r a n s f e r of t h e s t r i p p e d material t o storage cylinders.

The development program w i l l i n c l u d e :

I. An e v a l u a t i o n of possi‘nle methods o f t r i t i u m removal followed by mocki.rp and t e s t i n g o:C s e l e c t e d w i t s . Two systems a r e c u r r e n t l y under corisideratiori: (1) an o x i d i z e r , such as hot C i i O , followed by a chemical trap t o remove t h e 3 H 2 0 and ( 2 ) a chemical r e a c t o r which w i l l . b i n d t h e t r i t i u m i n - t h e form o f a, h y d r i d e . 2.

Mockup and t e s t i n g of t h e Kr-85 removal system.

It i s planned t o use t h e MERE offgas systeui as a t e s t s t a t i o n f o r t h i s work

Gas Compressor

The helium e f f l u e n t from t h e ~ r - 8 5t r a p p i n g system will be r e c y c l e d t o t h e purge gas h e a d e r . A compressor w i l l b e r e q u i r e d t o recompress t h e gas t o about 30 p s i g i n o r d e r t o permit adequate flow c o n t r o l t o t h e v a r i o u s purge and ‘oubbler l i n e s . Operating condj.tions f o r t h e MSBR a r e : flow .__3 scfm, i n l e t p r e s s u r e - 0 p s i g , d i s c h a r g e p r e s s u r e - 30 p s i g . One of t h e m a h problems w i l l b e t o p r o v i d e a system which will n o t add contahinan-ts t o t h e gas. IS, i s a n t T c i p a t e d t h a t requirements w i l l b e met by a coIiimePcially-available diaphragm compressor. The program w i l l i n c l u d e (I) a su:rvey and paper cval.u.ati~onof commercial u n i t s and (2) p r o o f - t e s t i n g of s e l - e c t e d units b o t h on t e s t s t a n d and as p a r t o f t h e i n t e g r a t e d gas system. Gas Sarnpl.er --

Control 01” check samples wi1.1 b e r e q u i r e d from t h e r e c i r c u l a t i n g gas and t h e main o f f g a s stream. Analyses of t h e s e gas samples w i l l b e used t o provide a d d i t i o n a l information about t h e chemisLry of moltensalt reactors. The major problem w i l l be t o develop and p r o o f - t e s t adequate sampling technj-ques The o f f g a s sample u n i t c u r r e n t l y b e i n g i n s t a l l e d a:i; Lhc MSRE wj.l.1. provide t h e bas5.c technology for ’~1ii.swork.

43 MSBE Gas System T e s t Loop

It w i l l be n e c e s s a r y t o demonstrate t h e adequacy and r e l i a b i l i t y of t h e xenon s t r i p p i n g and o f f g a s system components when o p e r a t i n g as an i n t e g r a t e d system. 8uch a demonstration can b e s t be made by means of a t e s t system i n c o r p o r a t i n g a s a l t c i r c u l a t i n g l o o p w i t h s K i t a b l e connect i o n s f o r t h e v a r i o u s gas c i r c u l a t i n g l o o p s . F i g u r e 4 shows a schemakic diagram of t h e proposed l o o p l a y o u t . Provis-ions are made f o r : 1. G a s i n j e c t i o n and s e p a r a t i o n . 2 , S a l t powered gas c i r c u l a t i o n . 3. Recompression-recycle system,

The s a l t l o o p c o n t a i n s an e x t r a t e s t s e c t i o n f o r materials t e s t i n g and a t a n k t o s i m u l a t e r e a c t o r holdup. The g a s system c o n t a i n s t e s t s e c t i o n s f o r component t e s t o r component s i m u l a t i o n . The salt flow r a t e w i l l b e 1000 gpm. T h i s l o o p w i l l a l s o b e used to e v a l u a t e t h e performance o f s c a l e models of t h e components. The n e t m a s s t r a n s p o r t of t h e g a s t o t h e e n t r a i n e d bubbles i n j e c t e d i n t o t h e s a l t w i l l be determined and t h e e f f i c i e n c y f o r removal of t h e bubbles by t h e s e p a r a t o r w i l l be measured. The u s e o f t h e s a l t d r i v e n e x h a u s t e r as a prime mover f o r the gas r e c i r c u l a t i o n system w i l l be demonstrated as w i l l t h e ef'fect o f t h e gas i n j e c t i o n system on t h e s t a b i l i t y oi" t h e Liquid l e v e l , t h e s t a b i l i t y of t h e gas r e c i r c u l a t i o n , and t h e xenon removal r a t e . I n s h o r t , t h i s t e s t l o o p w i l l s e r v e t o proof t e s t t h e concept. CELL FURNACE __AND SHIELDING The c e l l c o n t a i n i n g t h e f u e l and b l a n k e t s a l t s i s t o be maintained above t h e l i q u i d u s t e m p e r a t u r e of b o t h s a l t s ( a b o u t 1 O 4 O 0 F ) . The cells c o n t a i n i n g c o o l a n t s a l t o n l y a r e t o b e o p e r a t e d above t h e l i q u i d u s t e m p e r a t u r e of t h e c o o l a n t ( a b o u t TOOOF) However, t h e r e are t i m e s when t h e c o o l a n t c e l l must aLso o p e r a t e above 1040째F S O t h e f u r n a c e w i l l b e designed for 1150'F. The c e l l t e m p e r a t u r e s are t o be m a i n t a i n e d by r a d i a n t h e a t i n g s u r f a c e s . Thermal i n s u l a t i o n and c o o l i n g w i l l be a p p l i e d as r e q u i r e d t o p r o t e c t c o n c r e t e , equipment s u p p o r t s , i n s t r u m e n t a t i o n '1 e t c .

The concept of m a i n t a i n i n g t h e e n t i r e e e l 1 a t the e l e v a t e d temperat u r e d i f f e r s from t h e method used i n p r e v i o u s molten s a l t work. The c l o s e s t approach t o t h e proposed method i s i n t h e t h e r m a l - s h i e l d r e a c t o r f u r n a c e arrangement i n t h e MSRE. Here t h e reactol- i s i n s t a l l e d i n a. water-cooled t h e r m a l s h i e l d t h a t has t h e r m a l i n s u l a t i o n on t>he i n n e r s u r f a c e s . The h e a t f o r t h e f u r n a c e i s s u p p l i e d by e l e c t r i c a l h e a t e r s which are i n s e r t e d t h r o u g h t h e t o p of t h e f u r n a c e . The c o o l i n g system i n t h e t h e r m a l s h i e l d removes t h e heat d e p o s i t e d by t h e n u c l e a r sowrce and a l s o t h e heat t h a t leaks t h r o u g h t h e t h e r m a l LnsulaLion, This system h a s o p e r a t e d s a t i s f a c t o r i l y except f o r t h e minnl- problem of keeping r a d i o l y t i c gas from accumulating i n some par't*s of t h e t'nermal

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45 s h i e l d . T h i s problem was a t l e a s t p a r t i a l l y s o l v e d by i n s t a l l i n g an a d d i t i o n a l c i r c u l a t i n g pump t o i n c r e a s e t h e flow t h r o u g h t h e water p a s s a g e s and by making p r o v i s i o n s f o r t h e removal o f t h e e n t r a i n e d g a s . One b a s i c problem which evolves from t h i s system r e s u l t s from t h e n e c e s s i t y o f u s i n g water as %he h e a t removal medium. The maximum c r e d i b l e a c c i d e n t f o r t h e MSRE i n v o l v e s t h e i n t i m a t e mixing of s a l t l e a k i n g from t h e f u e l system i n t o w a t e r l e a k i n g from t h e t h e r m a l s h i e l d system. Steam i s g e n e r a t e d and t h i s produces a h i g h p r e s s u r e i n t h e r e a c t o r c e l l , I n t h e MSRE:, a p r e s s u r e s u p p r e s s i o n system i s u s e d t o l i m i t t h e p r e s s u r e and t o c o n t a i n t h e f i s s i o n p r o d u c t s s h o u l d such an a c c i d e n t occur. S t u d i e s w i l l be made of d e s i g n s of f u r n a c e arid s h i e l d combinations f o r t h e MSBE w i t h t h e o b j e c t i v e of e l i m i n a t i n g t h e p o s s i b i l i t y of mixing o f s a l t and water. The h e a t f o r t h e s e c e l l s might be s u p p l i e d by gas o r o i l b u r n e r s mounted o u t s i d e t h e c e l l but w i t h t h e h o t g a s e s p a s s i n g t h r o u g h t h e c e l l i n r a d i a t i n g f i n t u b e s o r e l e c t r i c a l hea'cers mounted i n r e - e n t r a n t t u b e s i n t h e c e l l . The s e l e c t e d method and t h e proposed d e s i g n w i l l require t e s t i n g . The arrangement f o r c o o l i n g t h e s u p p o r t s f o r t h e r e a c t o r v e s s e l must be t e s t e d . The e f f e c t of t e m p e r a t u r e changes i n t h e s u p p o r t s on t h e v e s s e l alignment must be examined under t h e c o n d i t i o n s expected d u r i n g t h e system s t a r t u p and d u r i n g a f a i l u r e of t h e s u p p o r t c o o l i n g system. Some s m a l l s c a l e mockups w i l l be b u i l t t o g i v e a i d i n design arrangement and e v a l u a t i o n . The f i n a l checkout of t h e system w i l l be done i n t h e ETU. STEAM SYSTEM The s t e m c o n d i t i o n s i n t h e MSBR steam c y c l e a r e almost i d e n t i c a l t o t h o s e i n t h e B u l l R u n P l a n t of t h e TVA e x c e p t t h a t a r e h e a t steamp r e h e a t e r , a mixing t e e on t h e f e e d w a t e r l i n e , and a feedwater p r e s s u r e b o o s t e r pump have been added. The t e c h n o l o g y i n v o l v e d i n t h e s e t h r e e components i s such t h a t t h e d e s i g n and c o n s t r u c t i o n s h o u l d be s t r a i g h t forward. These u n i t s w i l l be s p e c i f i e d i n s u f f i c i e n t d e t a i l s o thaz; t h e y can be designed and f a b r i c a t e d by an . e x p e r i e n c e d manufacturer. While some t e s t i n g would b e done by t h e m a n u f a c t u r e r , t h e f i n d t e s t i n g f o r performance and s e r v i c e a b i l i t y c o u l d be done e l s e w h e r e , perhaps a t t h e B u l l R u n P l a n t . P r e l i m i n a r y i n q u i r i e s t o vendors have been m e t w i t h s u f f i c i e n t i n t e r e s t and confidence t o i n d i c a t e t h a t t h i s approach t o t h e procurement problem i s a r e a s o n a b l e one.

46 A 60 Mve t u r b i n e - g e n e r a t o r i s s m a l l e r t h a n i s normally s u p p l i e d by t h e major manufacturers f o r a 3500 psi--lOOO째F ^. IOOO'F' r e h e a t c y c l e . Here t o o , a, p r e l i m i n a r y i n q u i r y i n d i c a t e d t h a t such a u n i t i s t e c h n i c a l l y f e a s i b l e and. could be made, however, i n t e r s t a g e leakage i n t h e srriall high p r e s s u r e end would reduce t h e e f f i c i e n c y . The c o s t f o r t h i s small s u p e r c r i t i c a l p r e s s u r e u n i t would run from 1 0 % t o 25% more t h a n for a comparable u n i t at a 1.over, more c o n v e n t i o n a l p r e s s u r e . It i s desira'ole t o produce s u p e r c r i t i c a l steam i n o r d e r to reduce s o m e of t h e t;hermal s t r e s s problems i n t h e steam g e n e r a t o r . A s t u d y w i l l be r e q u i r e d t o decide whether t o use a s u p e r c r i t i c a l t u r b i n e o r t o t h r o t t l e t h e s t e m t o lower p r e s s u r e and use t h e more c o n v e n t i o n a l u n i t .

In summary, it appears t h a t t h e steam s y s t e r i i can 'oe i a i l o r e d t o f i t t h e bEBE requirements and t h a t no e x t e n s i v e developmeni i s n e c e s s a r y t o produce t h e equipment o r t o i n s u r e t h a t it meet:; t h e program r e q u i r e ment s . ENGINEERING.-.ITEST .I-___- UNIT

The . f i n a l demonstration o f tile components and systems f o r t h e MSBE w i l l b e done i n a f u l l s c a l e e n g i n e e r i n g t e s t u n i t modeled a f t e r t h e r e a c t o r . The components f o r t h i s model a r e t o be e x a c t l y -the same as t h o s e i n t e n d e d f o r u s e i n t h e %BE and i n f a c t some of t h e s e u n i t s , a f t e r demonstrating a s a t i s f a c t o r y performance i n t h e ETU, might s e r v e as s p a r e p a r t s for t h e r e a c t o r experiment. It i s expec-ted t h e experience g a i n e d i.n b u i l d i n g and operaking t h e ETU w i . 1 1 c o n s i d e r a b l y s h o r t e n t h e s t a r t u p t i m e f o r t h e MSHE. The primary purposes Tor t h e Engineering 'Test Unit a r e t h r e e : 1. I t w i l l provide an i n t e g r a t e d t e s t a-t f'u1.1. t e m p e r a t u r e s , p r e s s u r e s , and f l o w s , but i.n m u n r a d i o a c t i v e environment of t h e r e a c t o r f u - e l , b l a n k e t , and coolant systems ; t h e fuel.. and b l a n k e t p r o c e s s i n g systems ; and t h e i r major a u x i l i a , r i e s .

2. The equipment will b e t h e f i r s t manufactured of H a s t e l l o y i\J by commercial f a b r i c a t o r s . T h i s wi1.I p r o v i d e an o p p o r t u n i t y t o q-ualifyt h e manufacturers t o b u i l d r e a c t o r equipment and t h e m3dified E a s t e l l o y N as a s t r u c t u r a l m a t e r i a l . The same manufacturers will make a second group of components f o r t h e MSBE, and t h e y should be o f super.ior q u a l i t y .

3. It w i l l provide a p l a n t f o r thoroughly t r a i n i n g t h e o p e r a t i o n s and mai-ntenance s t a f f and f o r thoroughly t e s t i n g t h e maintenance equipment and procedures b e f o r e t h e s t a r t u p of tile MSBZ.

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The design of t h e E'TU w i l l be based on t h e MSRF: flowshee'; shorn i n F i g u r e 5 . The t e s t u n i t w i l l b e complete through the boil.er-super.h e a t e r and t h e steam r e h e a t e r b u t w i l l n o t i n c l u d e t h e s u p e r c r i t i c a l . steam system. It -wi1.1. i n c l u d e t h o s e p a r t s of t h e o f f g a s syskem t h a t a r e r e q u i r e d t o i n j e c t gas i n t o t h e c i r c u l a t i n g f u e l s t r e a m , remove gas from t h e f u e l stream, and s e p a r a t e entrainment from t h e gas b e f o r e it goes t o t h e carbon beds. 'The f u e l s a l t , b l a n k e t s a l t y and cool.mt s a l t drain t a n k system w i l l be i n c l u d e d . A p i l o t p l a n t w i l l be provided f o r p r o c e s s i n g the f u e l and bl.anket s a l - t s . How complete t h a t p l a n t w i l l be has n o t been (3.eci.ded. The equipment t o be used f o r e f f e c t i n g t r a n s f e r s between t h e r e a c t o r and t h e p r o c e s s i n g p l a n t w i l l c e r t a i n l y be included.. W e a l s o expect t o p r o v i d e equipment f o r f l u o r i n a t i n g , d i s t i l l i n g , and r e c o n s t i t u t i n g t h e s a l t s b u t have n o t y e t h l l y decided whether t h i s i s f u l l y n e c e s s a r y . W e p l a n t o i n s t a l l the E'YU i n an e x i s t i n g b u i l d i n g , probab1.y i n t h e Y-12 a r e a . This w i l l i n v o l v e removing e x i s t i n g equipment and f l o o r s , i n s t a l l i n g t h e c e l l l i n e r s and c o o l i n g system, i n s u l - a t i o n , vessel. s u p p o r t s and c o o l e r s c e l l h e a t e r s and r e p r e s e n t a t i v e s e c t i o n s o f w a t e r cooled c o n c r e t e s h i e l d i n g . The method of p e n e t r a t i n g t h e furiiacecontainment wall w i l . 1 b e used i n r e p r e s e n t a t i v e l o c a t i o n s such as s a l t pi.ping, instrument l j . n e s , and gas supply and v e n t l i n e s .

The program w i l l u s e t h e d e s i g n s and drawings p r e p a r e d f o r t h e r e a c t o r and. w i 1 - l p r e p a r e only t h o s e a d d i t i o n a l d e s i g n s n e c e s s a r y t o adapt t h e r e a c t o r t o t h e experimental i n s . t a l l a , t i o n s . Much o f t h e v e n d o r ' s development and t e s t i n g of f a b r i c a t i o n methods w i l l be done i n b u i l d i n g components f o r t h e ET'U. The systems w i l l o p e r a t e isothermal-ly d u r i n g most of t h e i r e x p e r i mental l i f e although it i s planned t h a t some r e p r e s e n t a t i v e t e m p e r a t u r e d i f f e r e n c e s a c r o s s components may be g e n e r a t e d by g r e a t l y reducing t h e s a l t flow and t h r o t t l i n g s m a l l q u a n t i t i e s of steam out of t h e steam g e n e r a t o r s . I n a d d i t i o n , some t h e r m a l t r a n s i e n t s w i l l be produced -Lo h e l p i n developing a s t a r t u p procedure which w i l l minimize t h e thermal shock t o t h e system. A s ou-tl.i.ned i n t h e program on h e a t t r a n s f e r equipment, it i s planned t h a t j - n i t i a l l y t h e i n d i v i d u a l s a l t l o o p s w i l l be o p e r a t e d w i t h w a t e r s o t h a t 'tile h y d r a u l i c c h a r a c t e r i s t i c s of t h e 1.00ps may be e v a l u a t e d . Since t h e r e w i l l be considerable heat input capacity a v a i l a b l e t o t h e l o o p s , it i s pl.aiined t h a t some h e a t t r a n s f e r d a t a w i l l be o b t a i n e d d u r i n g t h e p e r i o d of o p e r a t i o n w i t h w a t e r .

Another a r e a , i n which some preI.j.minary experieiice w i l l . be g a i n e d , i s t h e c o n t r o l of t h e c o o l a n t s a l t flow through t h e two steam g e n e r a t o r s a n d r e h e a t e r t o h e l p a d j u s t t h e system f o r c a r r y i n g reduced power l o a d s . A s d e s c r i b e d i n t h e design p r o p o s a l , t h i s w i l l be done by v a r y i n g Lhe c o o l a n t pump speed a n d . the p o s i t i o n o f t h e v a l v e whi.ch contro1.s t h e sa1.t flow t o t h e r e h e a t e r .

49 The adequacy o f t h e r e a c t o r and component support system will be e v a l u a t e d d u r i n g t h e r m a l s t a r t u p . The s t r e s s e s a t c r i t i c a l v e s s e l n o z z l e s and p e n e t r a t i o n s w i l l be measured with the system at reduced t e m p e r a t u r e by r e p r o d u c i n g s t r a i n s measured d u r i n g thermal s t a r t u p . While t h e purpose o f t h e ETU w i l l be t o e v a l u a t e as many of t h e components and systems as are ready a t t h e t i m e t h e u n i t i s scheduled t o s t a r t u p , it i s a n t i c i p a t e d t h a t some e x p e d i e n t s w i l l b e n e c e s s a r y t o meet t h e s t a r t u p date. Such t h i n g s a5 d i r e c t a c c e s s maintenance w i l l b e u s e d i n i t i a l l y w i t h demonstration of t h e remote t e c h n i q u e developed f o r r a d i o a c t i v e systems t o be made a t a l a t e r d a t e . Where a v a i l a b l e , r e p r e s e n t a t i v e r e a c t o r - g r a d e i n s t r u m e n t a t i o n w i l l be u s e d , however, if t h e a c t u a l i n s t r u m e n t i s n o t r e a d y , some s u b s t i t u t e measure w i l l be t a k e n w i t h p r o v i s i o n made t o i n s t a l l t h e r e a c t o r grade equipment l a t e r . The o p e r a t i o n of t h e ETU w i l l b e continuous d u r i n g t h e t e s t i n g p e r i o d w i t h molten s a l t s . During t h i s t i m e t h e p l a n t w i l l be s t a f f e d l a r g e l y by o p e r a t o r s and e n g i n e e r s i n t r a i n i n g f o r assignment t o t h e MSBE. T h i s w i l l p r o v i d e a w e l l t r a i n e d s t a f f f o r t h e s t a r t u p of t h e b r e e d e r experiment. SCHEDULE AND COST The s c h e d u l e and c o s t s a r e shown on T a b l e 5 and were e s t i m a t e d on t h e b a s i s t h a t t h e program b e g i n s w i t h F71 1968 and t h a t t h e ETU and MSBE i n s t a l l a t i o n s s h o u l d be completed by t h e end o f M 1971 and FY 1974, r e s p e c t i v e l y . The main e f f o r t o f t h e development program i s c e n t e r e d on b u i l d i n g components o f N5BE s i z e , assembling them i n t o systems and t e s t i n g them i n t h e Engineering T e s t U n i t .

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ACKNOWLEDGEMENTS The work of assembling t h e program for e n g i n e e r i n g development of components and systems for t h e Molten-Salt Breeder Reactor w a s done by some o f t h e same people who have had t h e j o b of developing e q u i v a l e n t components for t h e MSRE and even f o r t h e o r i g i n a l Aircrafâ&#x20AC;&#x2122;t Reactor Experiment. T h i s c o n t i n u i t y i s c o n s i d e r e d v e r y important i n t h e success of a f u t u r e program. P. G. Smith and L . V . Wilson p r e p a r e d t h e s e c t i o n on pumps. R. J . Ked1 and A . N . Smith p r e p a r e d a s u b s t a n t i a l p o r t i o n o f t h e remainder. R. B. Briggs provided guidance and e d i t o r i a l h e l p i n t h e p r e p a r a t i o n o f t h e document.

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