metal transfer process for extraction of re

8/7/2019 Metal Transfer Process for Extraction of RE

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ORNL-517. . *. .

Engineering Tests of the M etal TransferProcess for Extraction of Rare-EarthFission Products from a Molten-SaltBreeder Reactor Fuel SaltH. C.SavageJ. R . Hightower, Jr.

HOM

HEL
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Printed in the United States of America. Available fromNational Technical Information ServiceU.S. Department of Commerce5285 Port Royal Road, Springfield, Virginia 22161Price: Printed Copy $4,50; Microfiche $3.00.

This report was prepared as an account of work sponsored by the United StatesGovernment. Neither the United States nor the Energy Research and DevelopmentAdministratiodUnited States Nuclear Regulatory Commission, nor any of theiremployees, nor any of their contractors, subcontractors, or their employees, makesany warranty, express or implied, or assumes any legal iability or responsibili ty or theaccuracy, completeness or usefulness of any information, apparatus, product orprocess disclosed, or represents that its use would not infringe privatelyowned ights.

Y


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ORNL-5176D i s t . C a t e g o r y UC-76

C o n t r a c t N o. W-7405-eng-26

CHEMICAL TECHNOLOGY DIVISION

ENGINEERING TESTS OF THE METAL TRANSFER PROCESS FOR EXTRACTION OFRARE-EARTH FISSION PRODUCTS FROM A MOLTEN-SALTBREEDER REACTOR FUEL SALT

H . C . SavageJ . R . H i g h t o w e r , Jr.

Date Published: February 1977

OAK ZIDGE NATIONAL LABORATORYOak R i d g e , T e n n e s s e eoperated byUNION CARBIDE CORPORATIONfor the

ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION


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t/ TABLE OF CONTENTSPage

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 12. METAL TRANSFER PROCESS . . . . . . . . . . . . . . . . . . 33. DESCRIPTION OF METAL TRANSFER EXPERIMENTS MTE-3 AND MTE.3B . 6

3.1 Process Vessels and Equipment . . . . . . . . . . . . 63.2 Experimental Proce dures . . . . . . . . . . . . . . . 114. ANALYSIS OF DATA . . . . . . . . . . . . . . . . . . . . . 145. EXPERIMENTAL RESULTS . . . . . . . . . . . . . . . . . . . 185.1 Overall Mass-Transfer Co eff ici en ts and EquilibriumDi st r i bu ti on C oeff icie nts f o r Neodymium . . . . . . . 1 95.2 Entrainment Studies i n Experiment MTE-3B . . . . . . . 36

Contactor and Str ipper . . . . . . . . . . . . . . . . 405.5 System Performance . . . . . . . . . . . . . . . . . . 426. DISCUSSION OF RESULTS . . . . . . . . . . . . . . . . . . . 447. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . 5 1

5.3 Neodymium and 147Nd I nventory i n Ex periment MTE-3B . . 385.4 Lith ium Reductant i n t he Bismuth So lu t ion s i n the..

8. ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . 53. . . . . . . . . . . . . . . . . . . . . . . .. REFERENCES 54APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56


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ENGINEERING TESTS OF THE METAL TRANSFER PROCESS FOR EXTRACTION OFRIIW-EARTH FISSION PRODUCTS FROM A MOLTEN-SALTBREEDER REACTOR FUEL SALT

H. C. SavageJ . R. Hightower, J r .

ABSTRACT

I n t h e metal t r a ns fe r p rocess f o r removal o f r a re -ear thf i s s i o n p r o du c t s from th e f u e l s a l t of a molten-sal t breederreactor (MSBR),the rare e a r t h s are ex t r ac t ed from th e moltenf u e l s a l t i n t o a molten bismuth solu t i on contai ning l i t h iu m andthorium m e t a l r educ tan ts , t r ans fe r red f rom the b ismuth in tomolten l i th ium ch lo r i de and , f i na l l y , r ecovered f rom thel i th iu m ch lo r ide by ex t rac t ion in to molten b i smuth con ta in ingl i th ium reduc tan t .

Engineering experiments using mechanically agi ta te d, non-d isper s ing con tac to r s wi th s a l t and bismuth flow rates [Q 1%ft h o s e r eq u i red f o r p r oces sin g t h e f u e l s a l t from a 1000-MW(e)MSBR] have been conducted (1) t o stu dy t h i s pro ces s, (2) t o measurethe removal rate of a r ep r e s en t a t i v e r a r e- ea r t h f i s s i o n p r od u ct(neodymium) from MSBR f u e l s a l t , and (3) t o evalu ate t he mechanical lya g i t a t e d c o n t a ct o r f o r u s e i n a p lan t p r o ces s in g f u e l s a l t froma 1000-MW(e) FISBR.

The experimental equipment and procedures are descr ibed.Resu l t s ob ta ined dur ing f i ve exper iments i n which the rare e a r t hneodymium w a s ex tra ct ed from MSBR f u e l s a l t are presented.Removal rates and mass- t ransfer co eff ic ien ts between the s a l t andbismuth phases were dete rmin ed f o r neodymium and are discussed interms of th e process ing requirements fo r a 1000-MW(e) MSBR.

1. INTRODUCTION

The Oak Ridge Nati ona l Labora tory h as been engaged i n developing232m-233ua mol ten-sa l t b reeder r eac to r th a t would opera te on th e

fu el cyc le t o produce low-cos t power while producing more f i s s i l ematerial than i s consumed.s a l t mixture as t h e f u e l an d g r ap h i t e as the moderator.t h e r e a c t o r t o be operated as a breeder , i t would be necessar y t oremove the rare-ear th f i ss io n products on a 25- t o 100-day cycl e andis o la te 233Pa f rom the region of h igh neutron f l ux dur ing i t s decay

The reactor would use a mol ten f luor ideI n o r d er f o r

"


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t o 233U. Thus an on- site process ing pl an t t h a t contfnuously removesthe protact in ium and rare e a r t h s i s r equ i red f o r t h e r eac to r t operform as a breeder .

71.6746-12-0.33 mole % LiF-BeF2-ThF4-UF4 and conta ins 233PaF andr a r e -ea r t h f l u o r id e f i s s i o n pr od uc t s.f o r t h e pr o ces sin g p l an t , f u e l s a l t i s removed from the reactor a ta rate of about 0.9 gpm. The s a l t i s f i r s t fed t o a f l u o r in a to rwhere-about 99% of th e uranium i s removed as UF6.l e av in g t h e f l u o r in a to r i s contacted with bismuth that con ta insl i th ium and thorium reduc tan ts i n o rder t o ex t ra c t p ro tac t inium andt h e remaining uranium. The salt stream, ess en t ia l ly f r e e o f u ran iumand protact in ium but containing th e rare-ear th f i ss io n products , i sthen fed to a rare-ear th removal system where th e rare-ear th f i ss io nproducts are ex t rac ted before r e tu rn ing the fu e l s a l t t o t h e r e a c t o r.The equi l ibr ium concentrat ion of th e rare e a r th s i n t h e s a l t fromth e r eac to r i s . ab o u t 100 ppm f o r a 1000-MW(e) MSBR; ra re -ear thremoval times ran ge from 25 t o 100 days.

1The fuel s a l t f o r a si n g le -f lu id MSBR has th e composi t ion4

In the re fe rence f lowshee t

The s a l t stream

~

Engineering experiments t o s tud y a recent ly developed rare-ear thremoval ca ll ed th e metal t r an s f e r p rocess , have beenconducted over th ep as t sev era l years . I n t h i s method, t he rare e a r t h sare ex t rac ted f rom the fue l s a l t in to bismuth contain ing l i th ium andthor ium reductan ts , t ran sfer red from the.bismuth in to molten l i th iumchlo r ide and, f in al ly , recovered from the l i th ium chlo r ide byex t r ac t i on in to molten b ismuth con ta in ing l i th ium reduc tan t .

495Mechanically agitated salt-metal cont acto rs have been inves t igat edfo r use i n th e MSBR process ing systems based on reduc tiv e ex tra cti on .This type of c ontacto r i s of p a r t i c u l a r i n t e r e s t f o r t h e metal t r a n s f e rprocess since adequate mass-transfer rates may be po ss ib le with outd i s p e r s a l o f the s a l t and bismuth phases.consid erably reduces t he problem of entrainment of bismuth i n t he

E l imina t ing phase d i sp er s a l

processed fuel carr ier sa l t and subsequen t t r a ns f e r to the r e ac to r ,which i s cons tructed of a nicke l -base a l lo y th a t i s sub je ct t o damageby metal l ic bismuth.a near- i so thermal , in t e rn a l l y c i r cu l a ted , cap t ive phase tha t wouldminimize th e occurrence of mass-transfer corrosio n. Also, it i s bel ieved

The bismuth i n th i s ty pe of con tac tor would be


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t h a t a process ing system employing t h i s type of cont acto r can be moreeas i ly f ab r i c a ted o f g r ap h i t e , which i s required for bismuth containment,than one using packed columns.I

peration and t e s t re s u l t s o f eng ineer ing-sca le exper iments ,u t i l i z i n g t h e metal t ransfer p rocess and mechanica l ly ag i ta ted con tac tors ,are d es cr ib ed i n t h i s r e p or t .s t e p s i n t he metal t r an s f e r p ro cess u s in g s a l t flow rates t h a t wereabout 1%f t h o se r eq u i r ed fo r p ro cess in g th e f u e l s a l t from a 1000-MW(e) MSBR. The g o a l s of t h e ex pe rime nt s were (1) to s tu d y th e v a r io u ss t e p s of t h e p ro cess , (2) t o measure t h e rate of removal of representat iver a r e - ea r th f i s s io n p rod u ct s from th e mo l ten -sa l t r eac to r f u e l , and (3)t o d ete rmine th e su i t ab i l i t y of mechanical ly ag i t a t ed co n tac to r s f o rt h i s p r o c e s s .t h e s a l t and metal p hases i n t h e sys tem w e r e determined us ing represen ta t iver a r e - ea r th f i s s io n p ro d uc t s .

These experiments incorporated a l l t h e

For th i s eva lua t i on , mass- t ransfer coe f f i c ie n ts be tween

2. METAL TRANSFER PROCESSI n t h e metal t r a n s f e r p r oc e ss , f l u o r i d e f u e l s a l t t h a t - i s f r e e

of uranium and protactinium is f i r s t co n tac ted wi th mol ten b ismu thconta in i ng l i th ium and thor ium as r ed u c tan t s a t concen tra t ions o fabout 0.002 and 0.0025 m.f. , respectively. The rare e a r t h s areex t ra c ted in to th e b ismuth . The b ismuth th a t con ta ins th e rare e a r t h sand thorium is then con tac ted wi th molten l i t h iu m ch lo r id e ; an d ,because of highly f a vo r ab l e d i s t r i b u t i o n c o e f f i c i e n t s , t h e raree a r t h s d i s t r i b u t e s e l e c t i v e l y, r e l a t i v e t o t horium , i n t o t h e L i C 1 .The f i n a l s t e p of t h e p ro c es s c o n s i s t s of e x t r a c t i n g t h e rare e a r t h sfrom the L i C l by c on ta c t wi t h molten b ismuth con ta in ing l i th i umred u c tan t a t concen tra t ions o f 5 t o 50 a t . %.

The chemical reac t ions th a t represen t each s tep of th e processare give n below, usi ng a t r i v a l e n t rare e a r t h as an example:Reduct ive ex t r ac t i on : (1) I

Re3+(fuel s a l t ) + 3Li(Bi)Bi--0*2 a t ' % Li+ 3 Li+( fu e l sa l t ) + RE(Bi);T ran s f e r t o L i C 1 :RE (B i ) + 3Li+(LiC1) L i C l 3 Li (B i ) + RE3+ (LiC1);


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S t r i p p in g i n to Bi - L i :F S 3+(LiC1) + 3 L i ( B i ) Bi--5 a t ' % Li b 3Li+(LiC1) + RE(Bi).

(3)

The eq ui l i br ia fo r the se r ea ct i on s have been measured and expressedas d i s t r i b u t i o n c o e f f i c i e n t s f o r t h e rare ea r th s be tween the f ue lcarr ier s a l t and bismuth conta ining l i th iu m as a reductant and asd i s t r i b u t i o n co e f f i c i en t s o f t ho rium an d rare ea r t hs between l i th i umchlor ide and bismuth containing l i th ium. y 7c o e f f i c i e n t i s defined as

T h e d i s t r i b u t i o n

whereDM = d i s t r i b u t i o n c o e f f i c i e n t ,5 = mole f ract ion.of metal M i n th e b ismuth phase ,hn mole f ra c t i on of th e metal h a li d e i n t h e s a l t phase.Under conditions of in terest , t h e d i s t r i b u t i o n c o e f f i c i e n t s h av e

been found t o be dependent on the l i th ium conce ntrat i ons as follows:*log DM = n log s i+o g %, (5)where

n = valence of metal Mn+ i n t he s a l t phase,si mole f ra c t i on o f l i th iu m i n th e b i smuth phase,$ = cons tan t a t a given temperature .Ca lcu la ted va lues o f rare earth-- thorium sep ara t io n fa ct or s

8between the bismuth and L i C l s a l t range from about l o 4 t o 10d iv a l en t an d t r i v a l en t rare ea r th s based on the measured d i s t r ib u t io nc o e f f i c i e n t s .

f o r

One version of a f lowsheet for removing rare e a r t h s from MSBRf u e l s a l t us ing the metal t r an s f e r p r o ces s i s shown i n F ig. 1.t h i s method, uranium- and prota ctini um-fre e fu e l s a l t from theprotact in ium removal s te p i s f ed t o a series of con tac to r s tage sthraugh which bismuth co ntain ing dissol ved reduc tant i s c i r c u l a t e d .The b ismuth in each of these fue l - sa l t con tac to r s tage s a l s o c i r cu la t esthrough a correspond ing l i th ium ch l o r ide con tac to r s tag e wi th in aseries of c ont act ors through which a l i t h iu m ch lo r id e stream flows.T h i s l i t h iu m ch lo r id e stream, i n t u r n , c i r c u l a t e s t hr ou gh a s i n g l e

Using


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U, Pa-FREE SALTFROM Pa-REMOVAL STEP

ORNL DWG 76-685

I f YDROFL~8RlNATOR06TRIPPER\ BISMUTH -LITHIUMSTRIPPERSOLUTION4 / L /PROC4ZES;$EfALT . RECIRCULATING

RECONSTITUTIONSTEP,i ;SR$JTz

Fig. 1. Metal transfer process using multiple MTE-3--type contac tors.


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con tac to r , where t he l i th i um ch lo r ide i s contacted with a bismuth-l i t h iu m s t r i p p e r s o lu t i o n .

An advan tage of t h i s arrangement i s tha t the fue l s a l t - -b i smuthcontac tors and t he l i th iu m chlor ide--bismuth cont act ors can beconstruc ted contiguous t o one anoth er, and t he bismuth can be madet o f low between th e two by th e pumping ac ti on of th e ag it at o rs (describedi n expe riment s MTE-3 and MTE-3B i n Sect . 3 ) .need for external bismuth pumps i s eliminated. Another advantage i sth a t the b ismuth i s t h i s typ e of co ntactor would be a near-isothermal,cap tiv e phase t ha t would minimize th e occurrence of mass-transfercorros ion.

Thus i n t h i s method, th e

Although oth er va r i a t io ns can be synthes ized, th e removal ratesof neodymium measured i n ex pe riment MTE-3B a re discussed i n terms ofprocessing requirements for a 1000-MW(e) MSBR usi ng t h e f lo ws he etshown i n F ig. 1.

3. DESCRIPTION OF METAL TRANSFER EXPERIMENTS MTE-3 AND MTE-3B3.1 Process Vessels and Equipment

The ba si c equipment used i n t he experiments (shown diagra mmati callyi n F ig. 2 ) , cons i s ted o f th r ee ca rbon s t ee l vesse l s : (1 ) a 14-in.(0.36-m)-diam fluoride s a l t r e s e r v o i r co n t ain in g t h e f u e l car r ie rs a l t (72-16-12 mole % LiF-BeF2-ThF4), a 10-in. (0.25-m)diam sa l t -metal contactor , and a 6-in. (0.15-m)-diam rar e-e art h st ri p pe r. Aphotograph of the process equipment i s shown i n Fig. 3. The sal t -m e t a l con tac to r i s divided into two equal compartments by a carbons t ee l p a r t i t i o n t h a t s e p ar a t e s t h e f l u o r i d e and L i C l sa l t s . A 1/2-in.(13-mm)-high s l o t a t the bo ttom of the par t i t i on in te rconnec t sth e capt iv e pool of b ismuth-l ithium-thorium sol ut i on i n th e contacto r .Mechanical ag i t a t or s i n both compar tments of the contact or and i n th es t r i p p e r were used toimprovecontact between the s a l t and bismuthphase s. Four-bladed tu rb in es , 2-7/8-in. (73 mm) i n d iameter and havinga pi tc h of 45", were located i n each phase.a g i t a t o r s i s shown i n Fig. 4.w e r e s u ch t h a t t h e s a l t and bismuth flows were directed toward thei n t e r f a c e .metal t ransfer exper iments are l i s t ed i n Table 1.

A photograph of t h eThe blade mounting and shaft rotation

The engineer ing drawings used i n t he cons truc t ion of th e


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ORNL-DWG-71-147-RI

VENT

ARGONSUPPLY

LiF-BeFZ- ThFeFLUORIDE SALT- METAL RARE EARTHSALT CONTACTOR STRIPPERRESERVOIR

Flow diagram fo r metal tran sfer experiment MTE-3.

I4I


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Fig. 3 . Photograph of processing ve ss e l s f or metal tra nsf er experimentMTE-3B with heaters and thermocouples installed.


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Fig. 4. Photograph of a gi ta to rs used fo r promoting mass transferbetween the s a l t and bismuth solu tio ns i n metal tra nsferexperiments MTE-3 and MTE-3B.


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cTable 1. Engineering drawings used i n constru ctio n of th e m e t a l t r a n s f e rexperimentDrawing number De sc ri pt io nF-12172-CD-116EM-12172-CD-OZD

26D27E29E30E31D3 2E33D34D35E36D37D38D39D46D47D48E49c51D52E53c

M-12053-CD-83C

FlowsheetFluor ide s a l t tankDetai ls of pump nozzle, viewing port, s a l t funneland drainA g it a to r d e t a i l s of assemblyContactor vessel assemblyContactor vessel p lan viewContactor vessel sec t ionsContactor vessel d e t a i l s h e e t 1Contactor vessel sampler de ta i l sThermowell detailsAcceptor vessel assemblyAcceptor vessel sec t ions A-A, B-B, an d C-CAcceptor vessel d e t a i l sT rans fe r l i n e i s o l a t io n f lange assembly and de ta i l sD e t a i l s fo r brazing copper sheath t o steel pipeHeat t r a ns f e r l in e subassemblyAgi tato r -blades assembly and d e t a i l sVessel stan d and mounting de t a i l sSamplersDetails of s a l t t r a n s f e r l i n e p i pi ngF luor ide s a l t pump assembly and d e t a i l sSample la dl e body de t a i lS a l t and b ism uth f i l t e r


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The ou ts ide sur f aces o f the carbon s t e e l vessels were coated with'L 0.015-in. (0.4-mm)-thick chromium--nickel--6% aluminum ox id at io n-r e s i s t a n t materia l (METCO* No. P443-10) using a plasma sp ray gun. Thi sprevented a i r o x id a t io n of the carbon s t ee l vessels a t t h e o p e ra t in gtemperature of 'L 923 K.

Fuel s a l t w a s c i r c u la t e d b etween th e f l u o r i d e s a l t reservo i r andone sid e of th e co ntac tor by means of a special ly designed gas-operatedpump u t i l i z i n g molten bismuth check val ves .c i r cu la t ed b etween th e s t r ip p e r and th e o th e r s id e o f th e co n tac to r bya l t e r n a t e l y p re s s u ri z i n g a nd v e nt i ng t h e s t r i p p e r vessel . The bismuthp ha se i n t h e c o n t a c t or w a s circulated between the two compartments inthe con tac tor by the ac t ion of th e ag i ta to rs , and no d i re c t measurement o ft h i s f l ow ra te w a s made du ri ng ex per ime nts . However, measurements made i na mockup using a mercury-water system ind ic ate d th a t th e bismuth flowr a t e between t h e two compartments would be high enough t o c aus e t h e rare-ea r th co n cen t r a t io n s i n t h e compartment s to b e e s sen t i a l ly eq u al .The s a l t f low rates used were about 1% f those requ i red fo r p rocess ing thef u e l s a l t from a 1000-MW(e) MSBR.

Lithium chlor ide w a s

8

Approximate quanti t ies of s a l t and bismuth used i n t he experimentwere the fo l lowing: (1) 110 kg o f f l u o r i d e s a l t and 64 kg of bismuth-l i th ium-thorium (contai ning about 0 .0018 atom fr ac t i on l i th ium and0.0014 atom f r ac t i on thorium) i n the con tac tor , and (2) 1 0 kg of l i th iu mch lor ide and 44 kg of bismuth-lithium (containing 0.05 a tom f rac t ionl i t h i u m ) i n t h e s t r i p p e r .

3.2 Experimental ProceduresProcedures fo r th e makeup, p ur i f ic a t io n , and add i t ion of the

s a l t and b ismuth phases t o t he p rocess ves se l s were designed t o minimizecontamination of the se materials w i t h ' o x i d e ( a i r , water, and any oxidesp resen t i n th e ca rb on s t ee l process vessels). P r i o r t o t h e a d d i t i o n o ft h e s a l t s and b ismu th , t h e in t e r n a l su r f ace s of a l l vessels were t r e a t e dwith hydrogen a t 923 K t o r ed u ce r e s id u a l i r o n o x id es .oxid es had been removed by sa nd bla st ing during fa bri cat ion .)t h i s treatment, a purif ied argon atmosphere (Q 0.1 ppm of H20) wasmainta in ed i n th e vessels t o p r e cl u de f u r t h e r o x i da t i o n.

(Most of theseA f t e r

*METCO, Inc. , 1101 Pr os pe ct Avenue, Westburg, Long I s la nd , N.Y.


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The s a l t and bismuth solutions were made up i n aux i l ia ry vessels ( a l s otreated with hydrogen) a t Q 923 K t o remove ox ide s). The bismuth w a shygrogen treated a t 'L 923 K, w hi le t h e f l u o r i d e s a l t and LiCl s a l twere contacted with bismuth containing thorium for oxide removal.makeup and purification, a l l s o lu t i o n s were f i l t e red by pas s ing th rough as in ter ed molybdenum f i l t e r ('L 30-p pore-diameter) duri ng tr an sf erf rom the auxi l iary vessels i n t o t h e p r o ces s vessels.vessels had been charged with the s a l t and bi smuth so lu t ion s , the en t i r esystem w a s maintained a t temperatures above the l iquidus temperature(1 90 K) of the so lu t ions .

Af te r

Af te r t he p rocess

The experimental procedure w a s e s s e n t i a l l y t h e same for each run.The rare ear th f o r which the mass t r an s f e r rate and overa l l mass t r a n s f e rc o e f f i c i e n t s w e r e t o be measured was added t o th e f luo r id e s a l t , t h ea g i t a t o r s were s t a r t e d and ad ju st ed t o t h e d e s i r ed s peed , c i r cu l a t i o nof t h e f l u o r i d e s a l t and L i C l w a s s t a r t e d , and the s a l t and bi smuth phaseswere per iod ica l ly sampled dur ing t he run per iod and analyzed fo r rare-ear th con ten t . I n each run , t race q u a n t i t i e s o f a r ad io ac t i v e i s o to p e

wereincluded i n the rare-ea r th addi t ion , and count ing of t he radio-ac t i v i ty of the samples w a s used to fo l low the t r ans fe r rate.

Samples of the s a l t and bismuth phases were taken us ing a small3

('L 0.4-cm ) s t a i n l e s s s t ee l sampling capsule with a s in t e r ed metalf i l t e r (Q 20-p pore-diameter) . A 1/16-in. (0.16-mm)-diam c a p i l l a r ytube a t tached to the capsu le w a s used f o r i n s e r t i n g i t i n t o t h e s o l u t i o nt o be sampled (see Fig . 5) . Dur ing ins er t ion , th e capsule w a scon t inuous ly purged wi th p ur i f i ed a rgon gas u n t i l i t w a s p o s it i o n ed i nth e s o lu t i o n .taken by applying a vacuum to the capsule.bismuth so lu ti on reached t he upper, co o l s ec t i o n o f t h e cap i l l a r y t u be , i ts o l i d i f i e d .allowed t o c ool under an argon atmosphere befo re removal.

The flow of purge g a s w a s then stopped, and a sample w a sWhen t h e molten s a l t o r

The sample w a s then withdrawn i n to th e sample po rt and

A l l ru ns i n th e second experi ment, MTE-3B, were made using the raree a r t h neodymium.were includ ed i n t he neodymiqm added t o th e experiment.concen t ra t ion i n each phase w a s determined by counting the 0.53-MeVgamma em it te d by t h e 147Nd i n t h e sample.neodymium co nt en ts of se le ct ed samples were determined by a n is oto picd i l u t i o n mass spectrometry technique.

I n these runs , t race amounts ( 5 0 t o 1 5 0 m C i ) of 147NdNeodymium

I n a dd it io n, t h e t o t a l .

This proved t o be a va lua ble means


19/71

-13-

PLASTIC TUBING -TO ARGON AN0 VACUUM

VENT

SUPPL IES

OF VESSEL

SALT LEVEL

-B1 LEVEL

ORNL DWC NO. 72-10406

1/16 in . STAINLESS STEELCAPILLARY TUBING - 40 in . LO NG

3/16 i n . O R I L L

1/4 i n . O l A MSTAINLESS STEEL R O O

POROUS METAL FILTER,20+ PORE S IZE ,34 7 STAINLESS STEEL

Fig. 5 . Schematic diagram of sample capsule and sample port used inexperiment MTE-3B.


20/71

-14-

of checking on th e t racer coun t ing re su l t s and w a s e s p e c i a l l y u s e f u lf o r those samples with very low neodymium concentrations (< 1ppm),where counting techniques were inadequate.

For runs i n th e i n i t i a l experiment MTE-3, i n which the rare e a r t h seuropium, lanthanum, and neodymium were use d, co un ti ng of t h e 1.28-MeVgamma e mit te d from t h e 154Eu t racer w a s u sed t o f o l l ow th e t r an s f e rrate, and the lanthanum concentration w a s determined by neutron act ivat ionand subsequent counting of the 14'La produced.

T h is r ep o r t p r im ar i l y d e s c r i b e s t h e r e s u l t s o b t a ined us ing t h e raree a r t h neodymium i n th e second m e t a l t r ans fe r exper iment , MTE-3B.f i r s t experiment , MTE-3, w a s conducted by o th er s and rep ort edprevious ly ;r e s u l t s .

The

r e s u l t s are summarized f o r comparison wit h MTE-3B

4. ANALYSIS OF DATAExperiment MTE-3B invo lved t h e su cc es si ve tr a n s f e r of rare e a r t h

from a f l u o r i d e s a l t t o a bismuth-lithium-thorium poo l, t o a l i t h iu mch lo r id e s a l t , and , u l t imate ly , to a bismuth-lithi um pool . The r a te a twhich the rare e a r t h w a s t r ans fe r red th rough the several con tac to r s tagesw a s governed by the equ i l ib r ium d i s t r i bu t i on coef f ic ien t o f the raree a r t h , t h e s a l t and bismuth flow rates , and th e mass-transfercoe f f ic ien t s . The de te rmina t ion o f these mass- t rans fe r coe f f i c i en t s w a sone of the major requirements f o r meeting the obj ect ive s of th e exper iment.

An idea l i zed ske tch o f the conta ctor ar rangement fo r t he experiment i sshown i n F ig. 6.

From a r a re -ear th material balance i n each of th e seven regionsin d i ca ted i n Fig . 6 , t h e foll owin g eq uat ion s governing t h e movement ofrare ea r t h through the reg ions were der ived:

V3 dtx3 = K A (X x3 - F 2 ( ~ 3 ~ 4 1 ,11 2 DA


21/71

F L U O R 1SALT

J

O R N L D W G 76-716

Fig.

eFi F3

x6

6 . Idea lize d diagram of t he metal tra nsf er experiment showingthe regions used fo r mass transfer calculations.

-Li - Bi


22/71

-16-

I IK3A3(X6-TI7 dt

wheret = time, sec ,x = molar concentration of rare e a r t h i n r eg io n i, i = 1,2,. . .7

3Vi= volume of f l u i d i n region i, i = 1 , 2 , * . . 7 , c m ,F1 = flow r a t e of f luor ide s a l t , g-moles/sec,F2 = flow r a t e of bismuth between contactor compartments, g-moles/sec,F3 = flow r a t e of l i th ium ch lo r ide be tween the s t r i pp er and th e

i

contactor, g-moles/sec,DA = e qu i li b ri u m d i s t r i b u t i o n c o e f f i c i e n t f o r t h e rare e a r t h

between fluoride s a l t and bism uth- lith ium- thori um, g-mole/g-mole,DB = e q ui li br iu m d i s t r i b u t i o n c o e f f i c i e n t f o r t h e rare ea r t h between

bismuth-lithium-thorium and li th iu m ch lo ri de , g-mole/g-mole,DC = e qu i li br iu m d i s t r i b u t i o n c o e f f i c i e n t f o r t h e rare earth betweenl i th ium chlo r ide and bismuth- li thium s t r i pp er so lut i on, g-mole/g-mole,

A1 = i n t e r f a c i a l area between f luor ide s a l t and bismuth-lithium-2thorium, cm ,

A2 = i n t e r f a c i a l area between bismuth-lithi um-thorium and L i c l ,2cm 9

A3 = i n t e r f a c i a l area between L i C l and bismuth-lithiums t r i p p e r a l l o y , c m2,

K1 = over a l l mass- t ransfe r coe f f ic ien t a t t h e f l u o r i d e salt--bismuth-li thium-thorium in te rf ac e (based on con cen tra tio n i nt h e f l u o r i d e s a l t phase) , cm/sec,

K2 = ove ra l l massL transfe r coef f i c ien t a t the bismuth-lithium-thorium-4 iC1 in t e r f ac e (based on concen t ra t ions i nthe bismuth phase), cm/sec,


23/71

-17-

Kg = over a l l mass - tr ans fer coef f ic ie n t a t theLiC1--bismuth-li thium in te rf ac e (based on concen tration s in th eli t hiu m chl ori de phase), cm/sec.

a/The ov er al l mass-t ransfer coe ff i c ie nts are dependent on the

indi vidu al mass-t ransfer coe ff i c ie nts f or each phase and the equi l ibr iumd i s t r i b u t i o n c o e f f i c ie n t s f o r t h e r a re ea rt h between the s a l t and bismuthsolutions. They are expressed as follows:

- = - + + -1 1

1 1 BK2 k4 kg

K1 k2 k3DA - = - + - ,

1+-,1K3 kg k7DC- = -where

k2..-k7 = i n d iv id u a l mass t r an s f e r c o e f f i c i en t s f o r e ach r eg ion i nthe con tac to r and s t r ip pe r vessels (subscr ip ts correspondt o th e numbers ass igned t o each phase i n Fig . 6).

Overall mass - tr ans fer coef f ic i en t s fo r each run were ca lcu la te d bys e l ec t i n g v a lue s f o r K1 K2 , and K3 which resul ted i n the best agreementbetween calc ulat ed t ime-dependent conc ent rati ons fo r each region and t heexp erim ent all y measured time-dependent con cen tra tion s.

The appropr ia te known va lues fo r the i n i t i a l concen t ra t ion in eachregion, xi; the fluid volume of each region, V i; the area of each of th et h r ee i n t e r f ace s , AI, A2, and A3; and the th re e equ il ib r ium d i s t r ib u t io nco e f f i c i en t s , DA, DB, and DC were sub s t i tu t ed in t o Eqs. (6)- (12) .estimates of K1 K2, and K3 were a l s o s u b s t i t u t ed i n to t h e s e equ a ti o ns ,which w e r e then solved using a computer program.were subsequently compared with the measured r e s u l t s , new estimates f o rK1, K2 , and Kg were chosen, and these were s u b s t i t u t e d i n t o t h ed if fe re nt ia l Eqs. (6)-(12). This process w a s repeated us ing adjus te dv a lu e s f o r K1 K2, and K3 u n t i l t h e ca l cu l a t ed r e s u l t s r ep ro du ced sa t i s-fac tor y measured res ul ts .t h i s manner w e r e taken as th e experimenta lly p reva i l ing ove ra l l mass-t r a n s f e r c o e f f i c i e n ts .

I n i t i a l

The ca lcu la te d res u l t s

The values for K l , K 2 , and K3 determined i n


24/71

-18 -5. EXPERIMENTAL RESULTS

Four ru ns (Nd-1, -2, -3, and -4) us in g t h e rare e a r t h neodymium asa r ep r e s en t a t i v e f i s s i o n p ro du ct were completed i n metal t r a n s f e rexperiment MTE-3B. Neodymium w a s chosen as t h e r e p r e s e n t a t i v e rare-e a r t h f i s s i o n p ro du ct f o r t h e s t u d i e s i n MTE-3B f o r several reasons:

1. Neodymium is one o f the more impor tan t t r iv a l en t f i s s i onprodu cts t o be removed from a molten-sal t breeder re ac torf u e l s a l t .

2. The us e of 147Nd t racer with i t s r e l a t i v e l y s h o r t h a l f -l i f e (11days) would p reven t excess ive le ve l s o f r a d io ac t i v i ty i n theexperimen t (a dd it io na l neodymium, co nt ai ni ng 147Nd tracer, w a sadded dur ing the s tudies) .Results could be compared with those obtained using neodymiumi n t he f i r s t experiment, MTE-3.

3.

D a t a f r o m N d - - 1 , -3, and -4, w e r e analyzed, and ov er al l mass- t ransferc o e f f i c i e n t s a t t h e t h r e e salt-metal i n t e r f a c e s were determined. Mass-t r a n s f e r c o e f f i c i e n t s were not determined i n expe riment Nd-2 due t ounexpected entrainment of f luoride s a l t i n t o t h e L i C l i n t h e c o n ta c to r .Entrainment of f l uo ri de s a l t i n t o t h e L i C l a f f e c t s t h e e q ui li b ri u md i s t r i b u t i o n c o e f f i c i e n t s of t h e rare ea rt hs and thorium between th eL i C l and bismuth phases such that thorium is t r a n s f e r r e d i n t o t h e L i C 1 .Entrainmen t a l s o occu rred dur in g run Nd-1; however, th e amount of f l uo r i des a l t entrained w a s r e l a t i v e l y s m a l l (Q 1.3 wt % F i n t h e L i C l ) , and thed i s t r i b u t i o n co e f f i c i en t s m easured a t the end of run Nd-1 were n ea r t h eexpected va lu es . During ru n Nd-2, t h e cumu lati ve amountof f luor ide s a l t entrained (Q 3 wt %) became s i gn if ic an t . Thed i s t r i b u t i o n c o e f f i c i e n t s ( p a r t i c u l a r l y f o r t ho ri um a t the LiC1-bismuthi n t e r f a c e i n t h e c o n ta c to r) were reduced, and a s i g n i f i c a n t q u a n t it y o fthorium w a s t r a n sf e r r ed i n t o t h e L i C l and w a s subsequen t ly c i r c u la ted in toth e s t r i p p e r , where it r eac t ed w i th t h e l i t h iu m r ed u c t an t i n t he B i - L iso lu t ion . Th is r ea c t io n cont inued u n t i l most o f t he l i th ium reduc tan twas l o s t from the s t r i p p er and th e neodymium w a s no longer extractedi n t o t h e L i - B i i n t h e s t r ip p e r,about 50 hr of op er at io n of run Nd-2; th us no det erm ina tio n of mass-t r a ns f e r coe f f ic ien t s could be made.

11

Ext rac t ion of neodymium stop ped a f t e r


25/71

-19-

Because of t he entrainment of f l uo ri de s a l t i n t o t h e L i C l dur ing runsNd-1 and Nd-2, i t became nec essa ry t o remove both t he L i C l from thecont acto r and st r i pp e r and t he bismuth--5 a t . % L i f rom the s t r ipperafter run Nd-2.the system before s tarting run Nd-3.

Fresh L i C l and bismuth-lithium s ol ut io n were charged to

5.1 Overall Mass-Transfer Co ef fi ci en ts and Equilib riumDi st ri bu ti on C oe ffi cie nts fo r NeodymiumOpera ting c on di ti on s and system param eters f o r ru ns Nd-1 throug h Nd-4

i n metal t ransfer exper iment MTE-3B are shown i n Tab le 2.the de te rmina t ions o f ove ra l l mass- t ransfe r coe f f i c ie n t s fo r the rare e a r t hneodymium f o r run s Nd-1, -3, and -4 i n metal t r a n s f e r exp erimen t MTE-3Bare given i n Table 3. Values fo r t he equi l ib rium d i s t r ib u t io n

Resul ts of

c oe ff ic ie nt s f o r neodymium measured a t the completion of each run,during period s of no s a l t c i r cu l a t i o n , are shown i n Table 4.

Prev ious ly repor ted va lues fo r o ver a l l mass - tr ans fer coe f f i c ie n t s fo reuropium, lanth anium , and neodymium ob ta in ed i n t h e ex per ime nt, MTE-3,are shown i n Table 5 fo r r e fe rence .

Values f or ov er al l mass-t ransfer co ef f i c i en ts f or neodymium a t t h eth r ee s a lt -b is mu th i n t e r f ace s i n metal t r a n s f e r expe rimen t MTE-3B (Table 3)were obtained by selec t in g values fo r th e mass-t ransfer coe ff i c ie nts whichr e s u l t e d i n a "bes t f i t " between the exper imental ly obtained conce ntrat ionsdur ing each run and the calcul ated c oncentra t ions as d i scu ss ed i n S ec t . 4 .The exper imenta l ly measured va lues fo r th e equ i lib r ium d i s t r ib u t io n co ef f ic ien t sf o r neodymium between t h e s a l t and bismuth solutions w e r e used i n ca lcu la t ingthe "bes t f i t " case.

Resu l t s are shown i n F ig s. 8-18. In these f ig ures , the exper imenta ld a t a p o in t s are indicate d fo r each solu t ion , and the l i n e shown repr esen tsthe "bes t f i t " fo r th e ca lcu la t ed concen t ra t ions dur ing each run.agreement w a s o b ta ined f o r t h e f l u o r i d e s a l t solution and the bismuth--5a t . % l i t h iu m s o lu t i o n i n t h e s t r i p p e r f o r e ach r un .t h e da t a obt ai ne d by cou nt in g th e 0.53-MeV gamma em it te d by t h e 147Ndtracer (with r es u l t s expres sed i n d i s in tegr a t ion s per minu te per gram)were used.an al ys is f o r t o t a l neodymium i n the se two phases.by t o t a l neodymium a n al ys is (&g) are shown for the bismuth-thorium-l i t h iu m s o lu t i o n i n t h e co n t ac to r and t h e L i C l i n the con tac to r and s t r ip per .

Exce l len t

For these so lu t io ns ,

Equally good agreement w a s obta ined fo r th e da ta ob ta ined byThe resul ts obtained


26/71

-20-

T a b l e 2 . Operating condit ions f o r runs Nd-1 through_ _ Nd-4 i n m e t a l t r a n s f e r exper imen t MTE-3B

Run number 1 2

Run t i m e , hr 140a 138 165. 2a 165a. (l15.7>b (107. 8Ib (109.5IbAgi ta to r speed , rp s 5.0 5.0 4.17 1.67Fluor ide s a l t c i r c u l a t i o n 5.8 x 5.8 x 0 0

L i C l c i r c u l a t i o n rate, 2.0 2.0 2.0 2.0rate, m3/sec

m3/secAverage temperature, K 923 923 92 3

Qu ant iti es o f S a l t and Bismuth (g-moles)F lu o r id e fu e l s a l t i n

r e s e r v o i rF l u o r i d e f u e l s a l t i n

co n tac to rBi-Li-Th i n fl uo ri de s a l t

compartment of con-t a c t o r d

.Bi-Li-Th i n L i C l s a l tcompartment of con-t a c t o r

eL i C l i n c o n t a c t o rL i C l i n s t r i p pe rBi--5 a t . % Li i n s t r i p pe r

1535 1535 1535

161 161 161

132 132 129

161 161 156

101 101 101132 132 114190 190 190

923

1535

161

132

156

10111419 0

ab T i m e of f l u o r i d e s a l t and/or L i C l s a l t c i r c u l a t i o n .%ole w t = 63.2 g; p = 3.30 g/cm3; 1.1 = 0.0088 P a t 923 K. 13e 14Mole w t = 209 g; p = 9.66 g/cm3; 1.1 = 0.016 P a t 92 3 K.fMole w t = 199 g; p = 9.28 g/cm ;

To ta l t i m e o f f lu o r id e s a l t and/or L i C l s a l t c i r c u l a t i o n p l u s e q u i l ib r i umt i m e wi th ag i t a t io n bu t no s a l t c i r c u l a t i o n .%ole w t = 42.4 g; p = 1.48 g/cm3; 1.1 = 0.016 P a t 923 K. 12

3 = 0.0094 P a t 92 3 K.


27/71

-21-

Table 3. Overall mass-transfer co ef fic ie nt sa f o r neodymium i n metalt r a n s f e r expe rime nt MTE-3B

Ag it at or Run Ove ral l mass t r a n s f e rcoef i i e nts (ma/ec)bpeed t i m eunnumber ( r p s ) (hr) K1 K2 K3

Nd-1 5.0 116 0.006 0.20 0.06Nd-3 4.17 10 8 0.018 0.030 0.035Nd-4 1.67 110 0.0040 0.020 0.0055

aThe mass- t ransfer co ef f ic ie nt s K1 and K3 are based on t h e r a r e - ear t hco n cen t ra t i on i n t h e s a l t phase, and K2 i s based on the rare ear th con-cen t ra t ion i n t he b i smuth phase .

bDefined by Eqs. (13 )-( 15) .


28/71

~ . . . .. . . .. . . . . . -._. . . . .. . . . .-. . . . . . . . .

Table 4. Neodymium equilibrium distribution coefficientsayb

Run D* DB D,number Calculated Experimental Calculated Experimental Calculated Experimental>I lo3>I lo3

4=Nd-1' 0. 3e 0.027 1.67e 0.94 3.5 x 104gNd-3' 0.017f. 0.022 0.9qf 0.98 3.5 x 10

Nd-4' 0. 17f 0.027 0.9qf 1.0Eu-6, -7d 0.0088h 0.012 0.49 0.30

CoefficientsbDAY DBY DC =

neodymium in bismuth, m.f.neodymium in salt, m.f.re defined as follows:equilibrium-distribution coefficients between phases (A ) bismuth-thorium/fluoride salt,(B) bismuth-thorium/LiCl , (C) bismuth-5 at. % lithium/LiCl.

Experiment MT.E-3B.dExperiment MTE-3.eBased onfBased ongBased onhBased on

60 ppm of lithium in bismuth.50 ppm of lithium in bismuth.5 at. % lithium in bismuth.40 ppm of lithium in bismuth.

c c

Ir eh)I


29/71

Table 5. Overal l mass - trans fer coef f ic i en ts a fo r lanthanum,europiu m, and neodymium i n metal tr a ns fe r experime nt MTE-3

Runnumber

Agi t a torRare speedea r th ( rp s )

bOverall mass t r an s f er coe f f i c ie n t (mm/sec)K1 K2 Kg

La-1La- 2Eu-1

Eu-2, -3CEu-4, -5

Eu-6

Eu-7, -8

L aL aL aEuLaEu

L ar Nd

L a' Nd

2.503.331 . 6 7

3.33

3.333.33

5 O

15.215.414.3

15.0

12.264.6

15.4

0.00140.0020.00060.0010.0020.0030.0020.0020.0020.00260.0032

0.00110.00130.000390.0000150.00130.0000480.0200.0200.0650.0320.11

0.120.20.0620.011 I0.20 0330. 20.20.20.20.2

a

bSee foo tnot e (b) i n Table 3.The mass - t rans fer c oef f ic ien ts K 1 and KK2 i s based on the rare-e arth concentra&on i n the bismuth phase.are based on the rare-ear th concentra t ion in the s a l t phase, and

After argon sparg ing in the L i C l s i d e of conta cto r (bismuth-thorium/LiCl phases, K2).


30/71

00 -2

2.0

I .5

1.0

0 . 5

0

O R N L D W G 76 - 8 78I I I 1 I

t0 - R E S E R V O I RA - C O N T A C T O R

I I I I I I1 20 40 60 80 I00T I M E ( h r )

F i g . 7 . Neodymium concentration i n the fluo rid e s a lt in the re servo irand contactor during run Nd-1.

0

c


31/71

cO R N L O W 0 76-884

OO

I I I I I ISTOPPEDSTOPPEDL i C l IN THE CONTACTOR FLUORIDE

L i C l IN THE ST RIP PE R77 IRCULATION CIRCULATIONALT LiCl

et0

A 0 = CONTACTORA = STRIPPER

20 4 0 6 0 80 I0 0 120RUN T I M E (hr )F i g . 8. Neodymium concent ra tio n i n t he L i C l i n the contactor andstripper during run Nd-1.


32/71

~. . ." " - . .. ". . . .. . . ... ..

0.4QCI?4z0t-ep:I-w0z00

Q,

0.30-z 0.20

IEtc30w

- 0.10z

O,

O R N L O W 0 76 - 882I 1 I I I I

'I

a

S T O P P E DF L U O R I D E

I

1S T O P P E D I1

Aa

J IA @ = F L U O R I D E S AL T S I D E O F C O NT AC TO R

~ s L i C l ID E O F C O N T A C T O RI I I 1 I I I

2 0 40 60 8 0 I00 120R U N T I M E ( h t )Fig. 9. Neodymium conc en tra tio n in t he bismuth-thorium i n the

contactor during run Nd-1.

Ih)Q\I

c


33/71

-27-

ORNL O W 0 76-899

5.0

4.0

3.0

2.0

1.0

OO

I I I I I I I I I I I I I1

TIME ( h r )Fig. 10. Neodymium concentration i n the bismuth-5 a t. % lithium inthe s t r i pper during run Nd-1.


34/71

ORNL DWG 76-350 R25.0

4.0

3.0

2.0

I ,o

0 0

-STOPPED FLUORIDE-SALT CIRCULATION STOPPED Li ClCIRCULATION

TIME ( hr )Fig. 11. Neodymium concentration in the fluoride salt in thecontactor during run Nd-3, MTE-3B.

1


35/71

STOPPEDLiClCIRCULATION

ORNL DWG ?c)-8840.5 I 1 I I I I I I

0.2 STObPED lFL%l !YDECIRCULATION A

0.1 0- 0 . * FLUORIDE SALT SIDEor * LiCl SIDE

l

A

I I20 40 I60 I I I I I80 100 120 140 160RUN TIME (hr)Fig. 12. Neodymium concen tration in the bismuth-thorium solution inthe contactor during run Nd-3.


36/71

O R N L D W G 76-9112. 5

2.0

.5

.o

0.5

0

S TO P P E D F L U O R I D ES A L T C I R C U L A T I O NAI

a = C O N T A C T O RA = S T R I P P E R

A

1//i.

S T O P P E DL i C lC IRC U LA T IONII I I I I I t I A20 40 60 80 100 120 140 160 180R U N T I M E ( h r )

1W0I

Fig. 13 . Neodymium c onc en tra tio n i n t he LiCl in the contactor andstripper during run Nd-3.


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ORNL DWG 76-351 R24.07 I I I I I I I I I I I I3.0 -

.STOPPED FLUORIDE- SALT CIRCULATION l

1 /

0 0 (

2.0 -

. -

0 f

0 STOPPED LiClCIRCULATION

I I I I I I I ! I I60 80 100 120 140 160TIME (hr)

Fig. 14. Neodymium concentration in the bismuth-5 at. % lithium inthe stripper during run Nd-3, MTE-3B.


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ORNL DWG 760352Rl5.0

4.0

3.0

2.0

I .o

I I I I I I I I I I I I I-

STOPPED FLUORIDE STOPPED Li Cl- SALT CIRCULATION CIRCULATION

-)--

I I I I I I I I I I I I I I I I20 40 60 80 100 120 140 160TIME (hr)

Fig. 15. Neodymium concentration in the fluoride salt in the contactorduring run Nd-4, MTE-3B.


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0.5b\D1Y

I I I I I I I I ISTOPPED FLUORIDE STOPPED LlClSAL7 CIRCULATION SALT CIRCULATION0 FLUORIDE SALT SIDE -A = Ll CI SIDE

0I2 0.4ao 0.3

gt-zW;t00

0.23sz0. I

0

A0Ae-

Iit A0 0

A

0 20 40 60 00 100 120 I40 160 180RU N TIME ( h r )

I

Fig. 16. Neodymium concentration in the bismuth-thorium in thecontactor during run Nd-4.


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ORNL O W 0 7 6 - 8 9 62.0

1.5at-zW02-o mu > 1.0I *3--f0Wzo 0. 5

0

S T O P P E D F L U O R I D ES A L T C I R C U L A T I O N= C O N T A C T O R

A = S T R I P P E R

S T O P P E D L i C lC IR CUL AT IONI/ /S T O P P E D L i C lC IR CUL AT ION/ I/-/-/ A

0A

0

A0

ee

I I I I I I A I I A2 0 4 0 6 0 80 100 120 140 160 180R U N T I M E ( h r )

Fig. 1 7 . Neodymium conce ntr ati on i n the L i C l in the contactor andstripper, run Nd-4.


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5.0

4.0

3.0

2.0

1.0

ORNL DWG 76-353RI

I I .I I I I I I I I I I I I I-

STOPPED FLUORIDE-SALT CIRCULATION STOPPED Li ClCIRCULATION

20 40 60 80 I00 120 140 160TIME (hr)

Fig.'18. Neodymium concentration in the bismuth-5 at. % lithium in thestripper during run Nd-4, MTE-3B.

--


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,-3 6-

More sc at te r and fewer poin ts appear i n thes e data .th at th e f ig ur es fo r th e t o t a l neodymium content more nea r ly repres ent th et r u e co n cen t ra t i o n i n t h e s e s o lu t i o n s s i n ce t h e r e s u l t s o b ta ined by t h ecount ing of samples f rom the se sol ut ion s were u n r e a l i s t i c a l l y h ig h ( by af ac t o r of 3 ) .a t th es e ver y low neodymium co nc en tr at io ns (< 1ppm).

However, i t i s f e l t

The di f f ic u l t y seemed t o be a b i a s i n t h e c ou nt in g d a t a

Tabulat ions of th e concentrat ions of 147Nd tr ac er and th e to t a lneodymium f o r a l l samp les removed dur in g ru ns Nd-1 th roug h Nd-4 are includedi n th e Appendix.

5.2 Entrainment Stu die s i n Experiment MTE-3BBased on previous s t ud ie s i n -awater-mercury system,15 it w a s

concluded t h a t entrainment of f lu or i de s a l t in to the bismuth and L i C l phasesi n the mechan ica l ly ag i t a te d con tac to r would occur i f the a g i ta to r s w e r eoperated a t speeds of 5 .0 rps o r h igher .transfer experiment, MTE-3, entrainment w a s not observed a t 5.0 r ps butw a s seen a t 6.7 rps.

However, i n t h e f i r s t metal16

S in ce f l u o r id e s a l t entrainment occurred a t an ag i ta to r speed o f 5.0r p s i n expe rime nt MTE-3B, a series of tes ts were made t o determine themaximum allow able a g i ta to r speed th a t could be used i n experiment MTE-3Bwithout entrainment.i n t h e c o n ta c to r a t s ev e r a ld i f f e r en t s p e ed s ( 3. 3, 4 .6 , and 5.0 r p s ) f o rtime periods ranging from 'L 50 to 'L 140 hr. During each t e s t a tcons tan t ag i ta to r speeds , s amples o f th e L i C l s a l t w e r e removed from thecon tac to r and ana lyzed fo r f lu or ide con ten t .conc entra t ion would ind ica te entrainment of f lu or id e s a l t i n t o t h e L i C 1 .Figure 19 shows th e f luo r ide ion Concent ra tion i n the L i C l as a func t ionof time f o r e ach ag i t a to r sp eed. The i n i t i a l co n cen t ra t i o n o f f l u o r id eion o f 'L 4 w t % rep rese nts the amount of entrainment th at occurred overa period of 'L 250 h r dur in g ru ns Nd-1 and Nd-2.speeds shown i n F ig .1 9re pres en ts the o rder i n which the t e s t s were run.An i n c r e a se i n t h e f l u o r i d e i o n c o n c en t ra t i on i s c l e a r l y i n d i ca t e d i n t h e'L 50-hr t e s t a t 5.0 r p s .entrainment (within exper imental l i mi ts ) appears t o have occurred over th e'L 200-hr combined tes t per iods a t these two speeds.

The tes ts were conduc ted by opera t ing the ag i ta to r s

An i n cr e as e i n f l u o r i d e i o n

The sequence of a gi ta t or

A t ag i t a t or speeds of 3 .3 and 4.6 rp s , no


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5

4

ORNL DWG 76-349Rl

.

+ 5.Orps-rcr - 3.3 rps -+p- 4.6rps w I

3 I I I I I I0 40 80 120 160 200 240 280TIME (hr)

Fig. .19. Results of tests to determine the entrainment rate of fluoridesalt into LiCl a s a function of agitator speed, MTE-3B.


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These res u l t s ind ica ted t ha t exper iments cau ld be c ar r i ed ou t a ta gi ta to r speeds up t o about 4.5 r p s without entrainment,and experimentsNd-3 and Nd-4 were conducted us ing agi ta tor speeds of 4.2 and 1.67 rps.I t w a s a l s o concluded th a t r ap id de te rminat ions o f f lu or i de ion concen t ra t ioni n t he L i C l duringexperimen:ts were needed to ve r i f y t ha t no entrainment w a soccurring. For t h i s pur pose , an O rio n Model 801A pH/mV meter* equipped withs p ec i f i c i o n ( f l u o r id e ) e l ec t r o d es w a s obta ined fo r r ap id ana lyses o f L i C lsamples.record th e emf between th e two bismuth phases i n t he con ta ct or ands t r i p p e r vessels th a t con tained d i f f e r en t concen t ra t ions o f l i th iumreduc tan t (0.0015 and 0.050 atom f r a c t i o n li thi um ).

The mV meter could a ls o be used t o continuously measure and

A change i n emf wouldi n d i c a t e a change i n t h e l i t h iu m co n cent r a t io n r a t i o i n t h e s e p h as es(Sect . 5.3) with a r e s u l t an t change i n t h e eq ui l ib r iu m d i s t r i b u t i o nco ef fi ci en t f o r neodymium and thorium between t he s a l t and bismuth phases.

5.3Weighed amounts of neodymium, as NdF3, c onta in ing 147Nd tracer w e r e

Neodymium and 147Nd In ve nt or y i n Exper iment MTE-3B

added t o t h e f l u o r i d e f u e l s a l t i n t he f u e l s a l t r e s e r v o i r o n t h r eeoccas ions dur ing operat ion of m e t a l t ransfer exper iment MTE-3B.and 147Nd tracer were prepared by th e Isoto pes Divis ion of ORNL.NdF3 containing the t racer w a s placed in a spe cia l ly des igned chargingcap sule used t o add th e neodymium t o t he f u e l s a l t (Fig. 20). Thecapsule w a s sealed by a spring-loaded d i s c which w a s so ldered to thecapsule. When ins ert ed in to th e molten f u e l s a l t (Q923 K ) , t h e s o l de rmelted and opened th e capsule , allowing th e NdF3 t o dis pe rs e in to th ef u e l s a l t . Capsules were insp ec te daf te r each add i t ion t o ensure tha ta l l of the neodymium had been tr an sf er re d i nt o th e fu e l s a l t .

The NdF3The

147Nd and t o t a l neodymium inv en tor y duri ng eac h run i n metalt r a n s f e r exp erimen t MTE-3B w a s followed by both counting and chemicalan al yse s of samples of th e s a l t and bismuth phases.147Nd w a s det erm ine d by cou nt in g t h e 0.53-MeV gamma em it te d, wh il e t h econcentrat ion of t h e t o t a l neodymium w a s de te rmined by an i so top ic d i lu t i onmass-spectrometry technique.

The con cen trat ion of

*Orion Research, I nc ., Cambridge, Mass.

t

L


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O R N L D W G 76-874

- . D. x 0.028 WALL 316STAINLESS STEEL TUBINGWELD TUBE TO CAP

ALL DIMENSIONSIN INCHES STAINLESS STEEL SINTEREDMETAL FILTER

STAINLESS S TEE L SPRINGIN COMPRESSION

'-THICK CARBON STEEL DISC.ELD SPRING TO TUBE SOLDER TO TUBE USINGS O - 5 0 LEAD-TIN SOFT SOLDERWALL AND D ISC 2

Fig. 20. Capsule used to add neodymium containing 147Nd tracerto the fuel salt in experiment MTE-3B.


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-4 0-

Table 6 compares t h e neodymium and 147Nd in ven to ry i n metalt ra n s fe r experime nt MTE-3B based on t h e amounts added t o t h e system andthose ca lcu la ted from the concen t ra t ions i n a l l phases determined bysampling.determine d by samp ling was'in good agreement wi th t h e amounts added,varying between 8 4 and 100% fo r each of th e f our runs .

As see n i n Table 6 , t h e i nv en to ry of neodymium and 147Nd t racer

These r e s u l t s ind ic at e th at (1) t he l oss es of neodymium werei n s i g n i f i c a n t , (2) th e neodymium remained di sp er se d i n t h e s a l t and bismuthso lu tio ns , and (3) th e sampling procedures provided samples th a t adequatelyrepre sente d th e con cen tra tio ns of neodymium in t h e s a l t and bismuths o lu t i o n s .

5.4 Li th ium Reductant i n the Bismuth Solut i ons i n theContactor and Str ipper

The equi l ibr ium dis t r ib ut io n co ef f i c i en ts f or neodymium (and ot he rrare e a r t h s ) between t h e s a l t and b ismuth s o lu t ion s i n th e m e t a l t r a n s f e rprocess are dependent on th e l i th ium reduc tan t concen t ra t ions i n th ebismuth solut ion s (Sect . 2). Therefore , mass - t rans fe r co ef f ic i en t s fo rt h e rare e a r t h s are dependen t on these equ i l ib r ium d is t r ibu t ionc o e f f i c i e n t s .

During th e runs i n experiment MTE-3B, th e con ce nt ra ti on s of li th iu mr ed u c t ant i n t h e b ism uth s o lu t i o n s were known i n i t i a l l y . T h e re la t iveco n cen t ra t i o n s o f l i t h iu m i n t h e b is mu th i n t h e co n t ac tor (Q 0.0015 m.f.)and i n t h e s t r i p p e r (Q 0.05 m.f.) were determined during t he experimentsby measuring th e emf between the se two bismuth so lu ti on s. The co nt ac to rand s t r i p p e r v e s s e l s are e l e c t r i c a l l y i s o l a t e d f rom each o th e r by ane l e c t r i c a l l y in s u l a te d " i s o l a t i o n f la n g e I ' and th e bismuth solu t i on sare connected by t h e molten L i C l t h a t circulates between the contactorand s t r i pp er . The re la t ive concen t ra t ions of l i th ium i n the b i smuthso lu ti on s can be calc ula ted from th e emf measurement by t he follow ingequation : 7

emf = -RT/nF I n C1/C2, (16)where

emf = emf deve loped between t h e two so lu ti on s, V ,n = valence,R = gas cons tan t = 1.987 cal/mole*K,F = Faraday = 23,050 c a l f1 g-equiv) -1,


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Table 6. Neodymium and 147Nd i nv ent ory and mass balance i n metal t r a n s f e r exp erim ent MTE-3B

Nd by sampling,e",~~~~~~Nd added to system Nd determined by sampling Nd addedNd Nd-147 T ot al Nd (21- Nd-147 (mci) To ta l Nd Nd-14 1

Start End S t a r t md St ar t Fnd

1 2.24 71.4 2.10 2.11 63. 1 59.9 93.7 94.2 88.4 83.92 4.61 83.5 4.10a -- 73.0a -- 88.9 -- 87.4 --3 5.91 148.9 4.98 5.03 144.1 144.1 84.3 85.1 96.8 96.84 5.91 148.9 5.12 5.32 150.9 131.5 86.6 90.0 100.3 88.3

IPI

%rial inventory not determined due to f luor ide s a l t entrainment.


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C1, C2 = concentrat ion 's of l i th ium i n th e two bismuth solut ions .For th e concentra t ions of l i th ium redu ctant i n the bismuth phasesi n ex per ime nts conducted i n MTE-3B, t h e expe cted emf w a s 'L 275 mV.

Measurements of emf t ak en in t e r m i t t e n t l y du ri ng run s Nd-1 and Nd-2gradually decreased from 'L 300 mV t o 'L 25 mV near the end of run Nd-2,i n d i ca t i n g l o s s of l i t h iu m red uc t ant i n t h e s t r i p p e r (see Table 7).( Th is l o s s of l i t h iu m i n t h e s t r i p p e r w a s caused by th e entrain ment off l u o r i d e f u e l s a l t i n t o t h e L i C l and by subsequent re ac ti on of th etho rium i n t h e f u e l s a l t w i th t h e l i t h ium . I t r e s ul t e d i n no f u r t h e re x tr ac t io n of neodymium as w a s observed.)

I n t h e f i n a l two exp eri men ts, Nd-3 and Nd-4, t h e emf between t h econ tac to r and s t r ip per w a s followed continuously by using a recordingmillivo lt-met er. No entrainment of f l uo ri de f u e l s a l t occurred duringth ese runs,and th e emf between the bismuth so lu ti on s remained es se nt ia ll ycons tant a t 'L 250 mV, ind ica t ing no s ig n i f ic an t change in t h econcen t ra t ions o f l i th ium reduc tan t .

5.5 System PerformanceI n s t a l l a t i o n o f metal t ransfer exper iment MTE-3B w a s e s s e n t i a l l y

During March 1975, the process vessels w e r eomplete i n February 1975.p res sure t es te d (both a t room temperature and a t an operat ing temperatureof 'L 923 K ); and the in te r na l s u r faces of the p rocess vessels andcharging vessels w e r e hydrogen treated a t 'L 923 K t o remove re s i du aloxides. Aft er th e hydrogen treatm ent, a l l v e s s e l s w e r e maintained underp u r i f i ed a r go n (Q 0.1 ppm of H20) t o prevent oxid atio n. The add i t ion o fa l l s a l t and b i smuth so lu t ions to theprocess vessels w a s completed duringMay 1975 w it h t h e syst em a t the operat ing temperature of Q 923 K.

The i n i t i a l exper iment s (Nd-1 and Nd-2) were c a r r i e d o u t i n Ju ne1975, and, a f t e r removal of t h e L i C l from the contactor and s t r ip pe rand the removal of t h e bismuth--5 a t . % l i th ium from the s t r i ppe r , f r e shL i C l and bismuth--5 a t . % l i t h iu m were added t o the system. The f i n a ltwo ex pe rime nt s (Nd-3 and Nd-4) w e r e conducted during January 1976.The system was not coo led t o room temperatu re u n t i l the f i r s t week ofApri l 1976; thus the sys tem w a s maintained a t th e opera t ing tempera tu reof 'L 923 K f o r ab o ut l lm o n th s . The t h r ee ag i t a t o r s i n t h e co n t acto rand s t r i p p e r v e s s e l s were operated f o r about 700 h r a t speeds ranging


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-43-

Table 7. Measurements of emf between th e bismuth s ol ut io ns i n th econ tac tor and s tr ip pe r ve ss el s during runs Nd-1 and Nd-2i n metal t r a n s f e r exp erim ent MTE-3B

Calcu la ted l i th ium concen tra t ionL i - B i i n s t r ip p er b(atom fract ion)

06.8184971

108

011.530.848.163.678 .1100.1

Run Nd-130020020019 5195

225

RUG Nd-216 516 515 512 410 08825

0.0520.0200.0150.0150.0140.014

0.00950.00950.00840.00570.00420.00360.0016

aRun t i m e = t i m e f r o m s t ar t of f l u o r i d e s a l t c i r c u l a t i o n .bBased on the assumption tha t th e i n i t i a l concen t ra t ion of l i th ium

(0.0012 a t . %) i n t he b ismuth- thor ium phase i n t he con tac torremained co ns ta nt thro ugho ut r un s Nd-1 and Nd-2.concen t ra t ion of l i t h iu m i n th e b i smuth- li th iu m a l lo y i n th es t r i p p e r w a s Q 0.050 a t . X .

T h e i n i t i a l


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between 100 and 300 rpm (1.67 t o 5.0 rp s) duri ng t h i s period .f l u o r i d e s a l t pump w a s i n o p e r a ti o n f o r % 295 hr,and L i C l c i r c u l a t i o n w a smaintained for % 475 hr . With th e exception of one of th e ag it at or sea lswhich developed a le ak and allowed inleakage of argon buffe r gas i nt o thesys tem sh o r t ly a f t e r t e rmin a t io n o f th e l a s t run (Nd-4), a l l equipmentfunctioned wi thout inc iden t throughout the l i f e of the exper iment .Sp ec i f i ca l ly , no heater, thermocouple 3 or con t ro l system malfunct ionsoccurred.observed.inspec ted af t e r shutdown t o de termine the e f fec t iven ess o f the ox ida t ion-r e s i s t a n t spr ay coat ing (METCO No. P443-10) i n p ro t ec t in g the se sur fac esag a in s t o x id a t io n a t th e opera t ing tempera ture .were found t o b e i n ex ce l l en t co n d i t io n , w i th o n ly a small amount ofoxide present .

The

Also, no leak age of s a l t or bismuth from the system w a sThe out sid e surf ace s of the carbon s t e e l process vessels were

The ou ts ide sur faces

During the f o u r runs conducted i n m e t a l transfer experiment MTE-3B,807 samples of t h e sa l t and bismuth solutions were t ak en fo r an a ly ses.As discuss ed above, th e sampling procedures adequately obtainedrepre sen t a t ive samples o f t he p rocess so lu t ions .

6. DISCUSSION OF RESULTSThe objectives of metal t ra n s f e r pro ces s exper iments MTE-3 and

WE-3B were to measure the ra te of removal of repr ese nta t iv e rare -ear thf i s s io n p ro d uc t s f ro m a mo l ten - sa lt b r eede r r eac t o r f u e l s a l t and t oe v a l ua t e t h e s u i t a b i l i t y o f m e ch an ic al ly a g i t a t e d c o n t a c t o r s f o r t h emetal t r an s f e r p ro cess .mass- t ran s fe r co e f f i c i e n t s f o r rare e a r t h s a t t h e th r ee sa l t - b i smu thi n t e r f a c e s i n t h e s y st em a nd t o s t ud y t h e e f f e c t of a g i t a t i o n on t h et r a n s f e r c o e f f i c i e n t s i n s t i r r e d c o nt a ct o rs .

Thus it w a s n ecessary t o d e termin e th e o v e r a l l

I n metal tr a ns fe r p roc es s experi ments MTE-3 and MTE-3BY o n ly th eo v e ra l l mass- t ran sf e r co e f f i c i e n t s were measured, as d i scussed i n Sec t. 4.R e s u l ts of i n d i v i d u a l m a ss -t ra ns fe r c o e f f i c i e n t s i n s t i r r e d c o n t a c to r s i nwhich the phases are not dispersed have been reported.thes e s tu d ie s , mass- t ransfer co ef f i c i en ts i n organ ic-water , mercury-water ,and LIF-BeF2-ThF4 sa lt -b is mu th sy st em s were determined, and correlat ionswere developed which re la te t h e in d iv id u a l mass- t ran sf e r co e f f i c i e n t s f o r

5, 18-20 In

b


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J

,

each phase to th e prope r t ie s of th e sol ut ion s and system parameters suchas th e s iz e and speed of t h e s t i r re r .mass- t ransfer co eff ic i en t on the agi ta to r speed var ied widely .

The re po rt ed dependence of th e

The ov er al l mass-transfer co ef fi ci en ts obtained f or neodymiuma t t h e t h r ee s a l t- b is mu th i n t e r f ac e s i n t h e f i v e ru n s i n exp er im en tsMTE-3 and MTE-3B a t a g i t a t o r ( s t i r r e r ) speeds ranging from 1 .67 r p s t o 5.0r p s are show inlog-log pl o ts i n Figs . 21-23.ef fe ct of a gi ta to r speed on mass- t ransfer co ef f i c i en ts cannot be madebecause oth er system parameters - p a r t i cu l a r l y t h e eq u i l i b r i u mdis tr ibut ion coeff ic ients for neodymium -were not the same f o r a l l runs.Also, s ince the ove ra l l mass- t ransfe r coe f f ic ien t s w e r e determined bys imultaneous so l u t i on of s even d i f f e r en t i a l equa t ions to de te rmine massb a lance , p r ec i s e v a lu e s f o r t h e t h r ee co e f f i c i en t s c a l cu l at ed f o r e achrun are not poss ib le .

D i r ec t co r r e l a t i o n of t h e

Although there i s a g r ea t d ea l o f scat ter i n the d a ta shown i n F igs .21-23, th e ove ra l l mass- t rans fe r coe f f ic ien t s genera l ly increase wi thin c r eas in g ag i t a t o r s peed as pred ic ted .va lues from those runs i n which on ly t he a g i ta to r speed w a s changed(e.g. , runs 3 and 4) c l ea r l y shows an i n c r ea s e i n t h e o v e r a l lm a s s -

Dir ect comparison of sele cte d

t r an s f e r co e f f i c i en t s when t h e ag i t a to r s peed w a s eleva ted from 1.67 t o4.17 rps.pre vio us exper iment MTE-3) shows an in cr ea se when th e a g i t a t o r speed w a sele vat ed from 3.33 t o 5.0 r p s .t h e s e f i g u r e s for reference purposes only .i n t h e c i t e d r e f er en ces i n d i ca t e t h a t m ass -t ran sf e r co e f f i c i en t s arep r o p o rt i o n a l t o ag i t a t o r sp eed r a i s ed t o a power between 0.9 and 1.65.

The ov era l l mass- t rans fe r co ef f ic i en t s fo r rare e a r t h s a c r o s s t h e

S imi la r ly , a comparison of runs 6 and 7 (conducted i n a

A dashed l i n e o f s lo p e 1 i s included onVarious cor re la t io ns developed

s a l t and bismuth phases determined i n experiments MTE-3 and MTE-3B wereonly about 1 o 50%of those th at would be predi cted by curre nt lyav a i l ab l e co r r e l a t i o n s , w i th t h e l a r g e s t d i s cr ep ancy o ccur r in g a t t h el i th ium chlor ide--bismuth in te r fa ce s .o r d e r t o o b t a in co r r e l a t i o n s t h a t would r e l i a b ly p r e d i c t h e o v e r a l l mass-t r a n s f e r c o e f f i c i e n t s f o r s t i r r e d c o n t a ct o r s i f t h i s t y p e of c o n t a ct o r i st o be used i n a fu l l - s ca le p rocessing p la n t to remove the ra re -ear thf i s s i o n p r od u ct s.p h y s i ca l p r o p e r t i e s o f t h e s ev e r a l s o lu t i o n s ,to l a rg er p rocess ing equ ipment r equ i re s fu r the r i nves t ig a t ion .

F u r th e r s t u d i e s are r eq u i red i n

I n add i t io n to t he in f luence of a g i ta to r speed andthe e f fe c t o f s ca le -up


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4

O R N L D W G 76-883

I I I I I I

JJaaW>0

100 150 200 250 300I I I 1 I I

/0/I I

Fig. 21. overall mass-transfer coefficients for neodymium at thefluoride salt-bismuth interface at agitator speeds of100-300 rpm.The datrhed line of slope = 1 shown for reference purposesonly.

Numbers in parentheses refer to run numbers.


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d

aWLLv)z(LI-a

:O?2-tJaaW>0

to-;

-4 -

O R N L D W G 1 6 - 8 7 9A G I T A T O R S P E E D ( r p m )100 150 200 250 300

I I I I I I

( 1 )E

I(4)E (31E

I I I I I I2.1 2.2 2.3 2.4 2.5o L O G A G I T A T O R S P E E D ( r P m )Fig. 2 2 . Overall mass-transfer coefficients for neodymium at the

Numbers i n parentheseslithium chloride-bismuth inter face i n the contactor atagitator speeds of 100-300 rpm.re fe r to run numbers. The dashed l i n e of slo pe = 1 i sshown for reference purposes only. *


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-48-

O R N L DWG 76-81?

C\GITATOR SPEED ( r p m l .100 150 200 2 5 0 300I I I I Io-

Fig.

-YnuE- 10-I-tW-0LLLLw0VUWILv)2

+v)v)

aaaI-JaW>0

-J lo-,a

/I I (3)

I I I I I I1.9 2.0 2.1 2.2 2.3 2.4 2.50-L O G A G I T A T O R S P E E D ( r p m )

23. Overall mass-transfer coefficients for neodymium at thelithi um chloride/bismuth--5 a t . % l i thium i n the stripperat ag ita tor speeds of 100-300 rpm.refer to run numbers.shown for reference purposes only.

Numbers i n parenthesesThe dashed l i n e of slo pe = 1 i s


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An impor tant fea tu re of the metal t r an s f e r p r ocess i s t h e select ivesep ara tio n of thorium from the rare e a r t h s a t th e bismuth--lithiumc h l o r i d e i n t e r f a c e . Rare earth- thorium sep arat ion fact or s , def ined as

RE-Th DThDRE (17)have been determined t o be i n t he range of l o 4 t o lo8 f o r t h e t r i v a l e n t andd i v a l e n t rare earth^.^ Thus neg l ig ibl e lo ss of thor ium from the f ue l

,

s a l t occurs i n the process . Because of entrainment of t he f lu or i de s a l ti n t o t h e L I C l i n experiment MTE-3B, i t w a s not poss ib le t o determine thesepara t ion fac to r . However, during s tud ies i n the f i r s t experimentMTE-3, i n which th e rare e a r t h s europium, lan thanum, and neodymium wereused, th e sep arat ion fa ct or s were es t imated based on the t o t a l amount ofthorium (< 10 w t ppm) found i n the bismuth--5 a t . % l i t hi u m a l l o y i n t h es t r i p p e r a f t e r a bo ut 400 hr of operat ion. Separat ion fa ct or sDTh/DRE f o r t h e se rare ea r th s i n t h e o rd e r of 1 0

Carter21 a t ORNL, have been made t o es tim ate th e cont actor s i z e andoperat in g condi t ions th at would be required i n order t o remove t hera re -ear th f i s s io n p roducts a t t h e d e sig n rate22 from t h e r ef er enc e MSBR.For these ca lc u la t ions , the rare earth neodymium w a s chosen as arepresentat ive example,moles (L 174 g) per day f o r a breeding r a t i o of 1.06. (Note: Reducingthe rare-ear t h removal r a t e would not have a p r o h i b i t i v e d e le t e r i o u s e f f e c ton the breeding r a t io - a thre efo ld reducti on would lower t he breedingra t io by abou t 0.01.)23 I n t h e s e ca l cu l a t i o n s , t h e e f f e c t s of s ev e r a lparameter s (mass -t rans fe r coef f ic ie n t s , in te r f ac ia l area, s a l t andbismuth flow r a t es , and number of ex tr ac ti on sta ge s) on th e removal r a t eof neodymium were evaluated, and a combination of parame ters t h a t wouldbe required to meet the design removal ra te w a s determined.

R es u lt s of t h e s e ca l cu l a t i o n s are summarized i n Table 8 . The

L

4 6t o 1 0 w e r e ind ica ted .P re l iminary ca lcu la t io ns , us ing a computer code developed by W. L.

The design removal rate of neodymium i s L 1 . 2 g-

cases shown were s e l ec t e d t o i n d i c a t e t h e e f f e c t o f several v a r i a t i o n s onneodymium removal rates. The fu el -sa l t f low ra te of 0.9 gpm (5.7 x l oh5m /see) w a s he ld cons tan t fo r a l l cases s in ce it i s t h e d e s ign f u e l - s a l tf low ra te fo r the r e fe rence p rocess ing p lan t .were used for a l l but one case s inc e t h i s seemed to be a reasonable compromisebased on prel iminary calculat ions .

8 .3Three contactor s tages

For case 1, t h e v a lu es of o v e r a l l m a s s -


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ir a n s f e r c o e f f i c i e n t s a t t h e t h r ee s a lt -b i sm u th i n t e r f ac e s (K1, K2, K3)are r eprese n ta t iv e of those ob ta ined i n our exper imental s tudies .area of 1 t 2 (0.093 m2) per s ta ge, th e bismuth f low rate of 3 gpm(1.9 x l om 4m3/sec), and the L i C l f low r a t e of 30 gpm (1.9 xm /see) were chosen as a b as i s f o r f u r t h e r ex t r ap ol a t i o n .Case 1, the neodymium removal r a t e of 0.003 g-mole/day is about afa cto r of 400 below th e des ign value of 1 . 2 g-moles/day.o v e r a l l m as s- tr ans fe r co e f f i c i en t s a t th e LiC1-bismuth i nt er fa ce si n t h e co n t ac to r and s t r i p p e r by a f ac t o r of 5 (case 2) increased th eremoval ra te by about a fa cto r of 4.i n t e r f a c i a l c o n t a c t areas t o 1 0 and 20 f t 2 (0.94 and 1 .9 m2) is s een i ncases 3 and 4, and the e f f ec t of in creas in g th e number of s t age sfrom 3 t o 6 is seen by comparing 4 and 5.the bismuth and L i C l f low ra tes t o 6 gpm (3.8 x m3/sec) and60 gpm (3.8 x m 3 / s e c ) is seen i n cases 7 and 9. In case 8 ,t h e o v e r a l l mas s- tr ans fe r co e f f i c i en t , K, a t the f lu or i de sa l t- -b i smuth

The

3 As s een i n

Increas ing

The e f fe c t o f increas ing the

The r e s u l t s from incre as ing

i n t e r f a c e is increased by a f ac to r o f 10.F ina l ly , th e des i red removal r a t e i s reached by use of th e parameters

shown i n ca se 11. For t h e choic es made, a neodymium removal rate of 1.37g-moles/day i s indicated for the fol lowing sys tem:

2s a l t and b ismuth in te r f ac ia l a reas / s tage = 20 f t 2 (1.86 m ) ,f l u o r i d e s a l t flow ra t e = 0.9 gpm (5.7 xbismuth flow r a t e = 18 gpm (1.1xL i C l f low r a t e = 60 gpm (3 .8 xK1 = 0.16 mm/sec, Kg = 1.0 mm/sec, and K3 = 4.0 mm/sec.

m2/sec),m2/sec),

m2/sec),

The values for K1 and K2 a t th e f lu or i de fu e l s a lt --b ismuth and LiC1--b is mu th i n t e r f ace s i n t h e co n t ac to r (case 11) are about a f a c t o r of10 higher than those observed i n m e t a l t r a ns f e r exper iments .from s tud ies i n the wate r-mercury con tac to r s ind i ca t e t ha t an inc reaseof about a f a c t o r o f 10 i n t h e m ass -t r an sf e r co e f f i c i en t m ig ht b eexpec ted wi th increased ag i ta to r tu r b ine d iameter over those used i n themetal t ransfer exper iments (1 .4 m v s 0.073 m).24 The va lu e f o r K3 a tt he in te rf ac e between th e LiC1--bismuth and t he 5 a t . % l i th i um i n t h es t r i p p e r (case 11) is about a fa ct or of 100 higher than t ha t observed i nmetal t r a ns f e r exper iments . Th is l a rge increase would l i ke ly requ i r e

R es u l t s

b


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in c rea sed ag i t a t i o n t o t h e p o in t of some degree of d isp ers i on of t hes a l t and bismuth i n th e s t r i pp er ; however, t h i s would probably beaccept able s inc e the l ike l ihood of b ismuth entrainment back in to thef u e l s a l t i s minimal i n the s t r ip pe r vessel.

Other combinations of th e var io us parameters could be used to ach iev eth e required removal ra te of neodymium. Cal cul ate d r e s u l t s , shown i nTable 8 , are in tended t o ind ica t e the e f fe c t o f s eve ra l parameters onth e removal r a te i n a f u l l - s i z ed m u l t i s t ag e metal t r an s f e r p r o ces s f o r t h eremoval of rare-e ar th f i ss io n products (using neodymium as an example)from a 1000-MW(e) MSBR.

7 . CONCLUSIONS

The obj ect i ves of them etal t r an sf er process experiments were (1)t o s tu d y t h e v a r io u s s t ep s i n t h e p r ocess , (2) t o measure th e r a t e ofremoval of rar e-ea r th f i ss io n products f rom th e molten-sal t rea cto r f u e l ,and (3) t o e v al u at e t h e s u i t a b i l i t y of a mechanical ly agi ta ted contactorf o r u se i n th e p rocess .

Conc lusions re la t i ng to these ob jec t i ves are as follows:1. During 15 exper iments i n engineering-scale process

equipment , repre sent at iv e rare-ea r th f i ss io n products(europium, lanthanum, and neodymium) were extr act ed frommol ten-sa l t b reeder r eac to r fu e l s a l t (72-16-12 mole XLiF-BeF2-ThF4) and tr an sf er re d i n t o bismuth-lithium a ll o y i nt h e s t r i p p e r vessel .

2. In thoseexp er iments in which en tra inment o f f lu or i de s a l t i n t ot h e L i C l s a l t did no t occur, the rare e a r t h s w e r e s e l e c t i v e l ytran sfer red (with resp ect t o thor ium) in to th e bismuth- l ith iumal loy . Separat ion fa c t o r s of about 10 t o 10 es t imated i nthe se experiments compare favo rably with pre dict ed va lue s ofabout 10 t o 1 0 f o r t r i v a l e n t and d i v a l e n t rare earths. Thus

metal transfer process for extraction of re

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