ORNL-TM-2596.txt

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.." RECEIVED BY DTIE JUL 231969

 

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OAK RIDGE NATIONAL LABORATORY
operated by

UNION CARBIDE CORPORATION w
NUCLEAR DIVISION

for the
U.S. ATOMIC ENERGY COMMISSION

ORNL- TM-259¢6

 

Copy No. - ~33

Date - July, 8, 1969

FRACTIONAL CRYSTALLIZATTON REACTIONS IN THE SYSTEM LiF-BeF,-ThF,

R. E. Thoma and J. E. Riccil

ABSTRACT

Equilibrium and non-equilibrium crystallization reactions in the system
LiF-BeF,-ThF, are analyzed in relation to their potential application to

molten salt reactor fuel reprocessing. Heterogeneous equilibria in the

temperature range from the liquidus at 590°C to the solidus at 350°0C are
described quantitatively and in detail by means of ten typical isothermal
sections and by three temperature-composition sections. The implications
of metastable fractionatiom-~in this temperature interval are discussed

as & possible feed control step in reductive extraction reprocessing of
molten salt breeder reactor fuels.

NOTICE This document contains information of a preliminary nature
and was prepared primarily for internal use at the Oak Ridge National
Laboratory. It is subject to revision or correction and therefore does
not represent a final report.

QEIRIBUTION 08 TS SOCTIAIR & IRTHITE
This report wos prepored as an account of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on beholf of the Commission:

A. Makes any warranty or representation, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contained in this report, or that the use of
any information, apparatys, method, or process disclosed in this report may not infringe
privotely owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any information, apparatus, method, or process disclosed in this report.

As used in the above, ‘‘person octing on behalf of the Commission’' includes any employee or

contractor of the Commission, or employee of such contractor, to the extent that such employee

or contractor of the Commission, or employse of such contractor prepares, disseminates, or
provides access to, any information pursuant to his employment or contract with the Commission,

or his employment with such contractor.

e e oo LEGAL NOTICE - om o o e oo e sy

 

-
CONTENTS

Abstract

P
Introduction v

. . .

Liguid-Soli
id Phase Reactions In The System L
m LiF-BeF,-ThF
4 - . a2

 
 
  
 

   
 

LEGAL NO TICE
This yeport WRE prepared a8 an account of Governtasnl aponaoud work. Neithel the United
States, nor e Commission, nor AnY parson Acling on Lebalf of the Commission:

A. Makes an¥ warranty oT represeuuuon, expressed of jraplied, with respect to the RCOU~
racy, completeness, oF usefulness of 1he information eonumed in this Teport, O that the use
of aay {nformatien, apparatus, method, ot process Alaclosed in thid report may oot infringe
privately owned rights; oF

B. Assumes any Javilities with reapoct to the use of, or for damages resulting from the
uge of any information, apparatus, method, or process discioped In this report.

As used in the above, ‘'perscen acting on bebaif of the Commission’ jnoludes eny €m=
pioyee of contractor of the Commliaszon: or smployee of such contractor, to the oxteut that
guch employse or coniractor of the Commission, oF employee of such contracior prepares,
d;uscmlnatei. or prqvlde. access 1o, any ipformation pur suant w0 nie emp&oyment or contract
with the Commigsiom oF nig employ ment with Buch contracior.

    
   
         
       
      
      
    
   
   
  
      

 
 

 
  

 

 
INTRODUCTION

The ORNL Molten Salt Reactor Program is devoted to the development
of molten salt breeder reactors which employ mixtures of molten fluorides
as core fluids. Until recently, the most promising approach to the
development of molten salt breeder reactors appeared to be a two-
region reactor with fissile and fertile materials in separate fuel and
blanket streams. Thorium would be carried in the blanket salt, in a
salt stream which would consist of a 'LiF-BeF,-ThF, mixture. Advances
in chemical reprocessing have provided evidence recently that 233pg and
possibly the rare earth fission products can be separated from mixed
thorivm-uranium salt by reductive extraction methods employing liquid
bismuth. This development, along with other design developments, makes
possible a single-fluid breeder reactor, one which has greater simplicity
and reliability than the two-fluid reactor. The fuel for the single
fluid reactor would be composed of 7LiF, BeF,, Th¥,, and 233U’F4, and
might be expected to contain ~ 12 mole ¢ ThF,. Optimization of the 7LiF
and BeF, concentrations is not complete, because the trade-off values
of several significant factors have not yet been established. These
include selection limitations imposed by the equilibrium phase behavior
of the LiF-BeF,-ThF, system (°>3UF, concentration will be only 0.2 mole
%, and is therefore of little conseguence in this connection), physical
properties such as viscosity, vapor pressure, thermal conductivity, and
the relations of LiF-BeF,;-ThF, composition to the development of

chemical processes for removal of protactinium and the lanthanides.

Effective separation of the rare earth fission products from
fluoride salt streams which contain thorium fluoride is the keystone to
development of semi-continuous reprocessing in single-fluid molten salt
reactors. Several methods for reprocessing spent LiF-BeF,-ThF,-UF, fuels
are currently under investigation. The method which is regarded as most
tractable for engineering development involves the selective chemical re-
duction of the various components into liguid bismuth solutions. at about
6009¢, utilizing multistage countercurrent extraction operations. The
current status of engineering development of this process has been
described by Whatley et a1.2 The initigl steps remove uranium and.
protactinium by reductive extraction.3 A strong incentive then exists to
remove the rare-earth fission products from the remaining salt. The most

nearly feasible approach to this separation seems to be their extraction
into bismuth alloy,3 even though the recycle volumes of extractant are
marginally acceptable. The efficiency of this separation step would
be greatly enhanced if the concentration of the rare earths in the
salt mixture were increased by at least tenfold, and if the residual
salt solutions were of a much lower concentration of thorium fluoride.
That the LiF-BeF,-ThF, phase diagram4 shows the occurrence of low
melting mixtures of low thorium fluoride content which are producible
from MSBR single-core fluids by metastable crystallization has suggested
the possibility that non-equilibrium fractionation reactions might be
exploited as a feed control step in the reductive extraction process.
Because of its relative complexity, the unpublished version of the
LiF-BeF,-ThF, phase diagram may experience less frequent or less
effective application in molten salt reactor technoclogy than is
warranted by the developments cited above. We therefore describe in
thig report further detailed aspects of equilibrium and non-equilibrium

behavior in the system.

LIQUID-SOLID PHASE REACTIONS IN THE SYSTEM LiF-BeF,-Thl,

Methods for interpreting polythermal and isothermal phase diagrams
are described extensively in an earlier report5 where the phase relation-
ships in a number of fluoride systems were agnalyzed in detail. Interpre-
tation of the equilibrium behavior in the system LiF—Bng-ThF44 (Figure 1)
iy somevhat more complex than for the systems analyzed because of the
occurrence of an unusual solid solution which is produced as the compound
3LiF.ThF,; crystallizes from LiF-BeF,-ThF, melts. The crystal phase of
nominal composition, 3LiF.ThF,, precipitates as a ternary solid solution
which, at its maximum in composition variability (near the solidus),
is described by a composition triangle with apices at LiF-Th¥F, (75-25
mole %), LiF-BeF,-ThF, (58-16-26 mole %), and LiF-BeF,-ThF, (59-20-21
mole %). Two substitution models may provide an explanation for the
single phase solid solution area: (1) a substitution of one Be*" ion
for a Li+ ion with the simultaneous formation of a 'I‘h4+ vacancy for every
four Be2+ ions substituted for Li+ ions to provide electroneutrality and
(2) substitution of a single Bt ion for a Li® ion with the simultaneous

+
formation of a Li vacaney. Model (1) would afford a solid solution
ORNL-LR-DWG 37420AR6

The, 1114

    
  
  
  
  

TEMPERATURE IN °C
COMPQSITION IN mole T

- LiF'4ThF4

LiF-ThF,

S LiF-2ThE,
3LiF-ThE, ss- 448 4

433 LiF -2ThF;

N

 

 

\/ A/
~
848 2LiF-BeF; 5001450 400 | 400 450 500
P as8 £ 360

Fig. 1. Polythermal Projection of the LiF-BeF,-ThF, Equilibrium Phase
Diggram.
limit in good agreement with the leg of the triangular area with the

lesser ThF, content wheregs model (2) would give a line extending from
3LiF.ThF, toward BeF,-ThF,; (60-40 mole ¢). This is a 1limiting line

vhich permits considerably higher ThF, content than that found experi-
mentally. Accordingly, it appears that both models are simultaneocusly
applicablé for the crystallization behavior of 3LiF-ThF, as it crystallizes
from LiF-BeF,-ThF, melts. Once the crystal structure of 3LiF.ThF, has

been established (a study of the structure is currently in progress6)

it will be possible to appraise the validity of these models.

Application of ternary phase diagrams to technology often requires
a knowledge of the identitiies and compositions of the various phases in
equilibrium at specific tempergtures. ©Such information is represented
by equilibrium phase diagrams. Typically, phase diagrams of ternary
systems are presented as projections of temperature-composition prisms
on their basal planes. When such schematic representation includes
liquidus temperatures, equilibrium crystallizafion and melting reactions
can be described in a quantitative manner. Here, the use of isothermal
sections is often valuable, particularly if the phase diagram is complex,.
The chief feature of the isothermal section is that it provides informa-

tion both about the identity and relative masses of coexisting phases.

The crystallization behavior of the 3LiF.ThF, ternary solid solution
determines the composition sequence as LiF-BeF,-ThF, melts are cooled.
A series of equilibrium isotherms is shown in Figs. 2 to 11, which
describe all the equilibrium reactions in the temperature interval from
590°C to 350°C, i.e., the liquidus-solidus interval of chief relevance
to the compositions which are likely to have application in molten salt
reactor technology, and in which all 3LiF.ThF, solid solution melting-
freezing reactions occur. Within this interval all the solid phases
of the system are involved. The equilibrium behavior of chief importance
to us is described further by the temperature-composition sections,
3LiF.ThF,-2LiF-BeF,, LiF.-ThF,-2LiF-BeF;, and LiF-2ThF,-2LiF-BeF,, shown

in Figs. 12-14 (schematic, not to scale).
ORNL-DWG 68-11676R

 

 

 

 

ThF, 111
. , TEMPERATURE IN °C
LiF+ 2ThFy LiF * 4ThE, COMPOSITION IN mole %
590°C
LiF - 2ThE,
2LiF-BeF,” LIF-ThE,
P 597
£ 568
3LiF - ThE,
£ 565
5
%0 550 £ 526
LiF BeF,
848 2|_iF-BeF2/5aof450 4001 400 450 500 555
P 458 £ 360

Fig. 2. Isothermal Section of the System LiF-BeF,-ThF, at 590°¢.
ORNL-DWG 68-11678R

 

 

 

 

Thig 1141
TEMPERATURE IN °C
COMPOSITION IN mole %
T=570°C
2L1F-BeF2 LiF - ThE,
£ 568
3LiF * Thi,
£ 565
S00
950 F 526
848 2LiF +BeFs 500?450 400 400 450 500 555
P 458 £ 360

Fig. 3. Isothermal Section of the System LiF-BeF,-ThF, at 570°C.
ORNL - DWG 68-{1679R

 

 

 

 

ThE, 111t
LiF+ 2ThF,
LiF - Thiy LiF - 4ThE,
3LiF * ThFy ss
TEMPERATURE IN °C
COMPOSITION IN mole %
LiF LiF +2Th,
562°C
LiF « Thi
3LiF  ThE,
950 E£526
848 oLiF -BeF, 500]450  400| 400 450 500 555
P 458 £ 360

Fig. 4. Isothermal Section of the System LiF-BeF,-ThF, at 562°C.

0T
ORNL-DWG 68-11677R2

 

 

 

 

 

 

 

ThF; 1144
LiF * 2ThF,
, TEMPERATURE IN °C
LiF - 4Thf, COMPOSITION IN mole %
~490°C
LiF +2ThF,
2LiF *BeF,
LiF * Thi,

3LiF - Th,
L.iF e BeFa
848 2LiF°BeF2/ 1450 400| 400 450 555

P 458 £ 360

Fig. 5. Isothermal Section of the System LiF-BeF,-ThF, at 490°C.

1T
ORNL - DWG 68-11680R2

 

 

 

 

ThE, 1111
LiF « 4Thi,
TEMPERATURE IN °C
COMPOSITION IN mole %
Lif *2ThR, )
457°C
LiF « ThE;
3LiF + ThE,
LiF . - J BeF,
848 2LiF - BeF; 400] 400 450 555
£ 360

Fig. 6. Isothermal Section of the System LiF-BeF,-ThF, at 457°¢.,

¢t
ORNL-DWG 68-11675R

ThE, #H

    
     
 
   

TEMPERATURE IN °C
COMPOSITION IN mole %

447°C

LiF « 4ThE, &

LiF - 2ThF, £

LiF - Thi,

///'

// N

\/ — /> \/ : _
2LiF - BeF; 55

 

 
 

 

LiF
848

Fig. 7. Isothermal Section of the System LiF-BeF,-ThF, at 447°C.

£T
ORNL -DWG 69 ~5297

They 11

    
  
       
 
  
   

TEMPERATURE IN °C
COMPOSITION IN mole %

440°C

LiF - 4ThF, &

LiF « 2ThE,

/N

\J

LiF - ThE,

3LiF - ThE; l;'//

 

  

. ; 7 \/ B\ . L -
LiF & =
848 2LiF - BeF; 55

Fig. 8. Isothermal Section of the System LiF-BeF,-ThF, at 440°0C.

1
ORNL-DWG 68-11674

ThE, 1119

    
    
 
  

TEMPERATURE IN °C
COMPOSITION IN mole %

430°C

LiF + 4ThE,

LiF «2ThF,

LiF - Thiy

848 2LiF - BeF2 555

 

 

 

 

 

Fig. 9. Isothermal Section of the System LiF-BeF,-ThF, at 430°C.

T
ORNL-DWG 68-11673

Thi 1111

    
    
  
   

TEMPERATURE IN °C
COMPOSITION IN mole %

358°C

LiF < 4ThF,

LiF * 2ThF,

LiF- an-;,,

/’7 Y

848 2L|F BeFy— 500 555

 

     

 

 

 

Fig. 10. Isothermal Section of the System LiF-BeF,-ThF, at 430°C.

91
ORNL-DWG 68-11672
ThF, 1111

 
 
 
  

TEMPERATURE IN °C
COMPOSITION IN mole %

350°C
LiF: 4ThF,

LiF - 2ThF,

  
   
 

LiF+ Thi

3LiF-ThF,

/
/

- BeFa
848 2LiF-BeFy 555

 

   

   

Fig. 11. Isothermal Section of the System LiF-BeF,-ThF, at 350°C.

LT
18

The isothermal sections included in Figs. 2 to 11 are drawn to scale
and represent the experimental results which were the basis of the
previously published phase diza.g;f,rz_a,:n.‘4 Composition-temperature relations
in the LiF-BeF,-ThF, system for LiF concentrations greater than 50 mole

% are shown in detail in Fig. 15.

The straight lines appearing in Figs. 2 to 1l are tie-lines (or
"eonodes") connecting two phases which are in equilibrium. In Fig. 16,
point P, as a point on such a tie-line joining points b and z, represents
a mixture of the phases (or compositions) b and z with the mole fraction

of b equal to the ratio of line lengths zP/zb.

In the case of a mixture of three phases, such as the points a, b, ¢
making up the total composition at point P (Fig. 16), the relative
amounts of the phases a, b, ¢ making up P may be determined as follows,
with the three fractions defined as x of a, y of b, 1l-x-y of ¢. Then:

(1) Graphically: extend the line bP to fix the point z on the
line ac. Then y = zP/zb, and x = (zc/ac) (1-y).

(2) Analytically: 1let the fractions of the components A and B
at each of the four points (a, b, ¢, P) be

Aa Ab Ac AP’
Ba Bb BC Bp.
Then by similar triangles, we hagve

B

-B B -B
a z = "a ¢

= O

 

 

 

o

NU‘J
o

td

Z Ab_Ap
Then BZ = Bb - fiAb + BAZ Ba - Qfla + aAZ

Hence A = (Ba - Bb) tBAy - ah
B-.

2 7By < By + B
Then y =B - B
P2z

% " B

 

R

td
I
19

ORNL -DWG 69 - 5294

 

 
    

 

 

 

 

 

573
L,B= 2 LiF - BeF,
LsT = 3LiF. ThF,
565
!
P - 458°
" P."444°
LiF UQ+LW+LZB//
LyT :
3'ss Lyl +LIF+L B
3 LiF- ThF, | 2 LiF - BeF,
(LoT) (L,8)

Fig. 12. The Section 3LiF:ThF,-2LiF-BeF,
20

ORNL-DWG 69-5295

 

    
    
 
 

 
  
     

 

 

  
     
     

 

 

 

 

 

LT =Lif - ThF‘
LT, = LiF - 2ThF,
LT, = LiF - 4ThF,
LzB = 2LiF - BGFZ
LIQ + LT,
p-762°
LiQ
LIQ +LT, +LT,
LIQ+LT,
P-597°
LIQ+LT +LT,
LIQ+LT
LIQ+LT +L,7,, LIQ+L4T, +LiF /LlQ-H_iF
P-458°
~=— L1Q +LiF +L,B
P-444°
LT +L 5T, L10+LaTu ¥t 28 P-433°
L3T“”k<\\ L3T33+LZB
LiF - ThF, 2LiF - BeF,
(L) (L,B)

Fig. 13. The Section LiF.ThF,-2LiF.BeF,
21

ORNL—- DWG 69~ 5296

 

 

 

 

 

 

 

\ LIQ+ThF, LT =LiF - ThF,
/ LT, = Lif - 2ThF,
p_897o ' LT"—' LiF- 4ThF4
LIQ+ThF,+LT,
LIQ
LIQ+ LT4
P—T762°
LIQ+LTeLT,
Lch-LTz
/LIQ+ LiF
P-458°
LIQ+LiF+L.B
LIQ+ LT 2
LIQ+LT,#LT ““~4JQ+LZB
P-448° , - - = -
LIQ+LT,+L LA LaTu s LT LIQ +L4T,,
2 31;3 LIQ+L.T +L28
38 P-433°
LiF-2ThF, 2LiF-BeF,
(LT,) (L,8)

Fig. 14. The Section LiF.2ThF,-2LiF-BeF,
22

ORNL-DWG 68-942A

   
  

TEMPERATURES IN °C LiF « ThF, A&
COMPOSITION IN mole %

    

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AVAVA\AV‘VAVAVAVA\.\"VA"VA VA 87

       
   
    
 
   

  
 

  

  

    
 

    
    

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AN/ NG A N T PR A AR TR SO N N N DA
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AVAVAVAVA YAVAVAYA "\, if#“mmwwwwpuflmmmwv4w
Amwunmmmmmmanmmmn*A N VN
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NSNS

 

  
 
     
    

SO KA vm*..'«.nuv
NN SN INANT N NN "" TAVAVAVAVAVAY s "AVAVA AVA 5 "A'A
AT OR PP OREIRRRE S SIF AR IR A AR A A A ; A

AN/ NN NN v"“h\' A/ Y \'Av NN 'AVAVAVA\'\VA'\VAVAVAVAVAV VA 'AVA A Av VA\'
o0 LTRSS QOORX XK AL

    
  

X mwum“ummmmmwummA
nuuuumuummgmmwuwmu';mmmuwmmmmmunflflmmw A
d@mmmmwmmmunmmsnmm' N AN NSO AN N SRS mh Aamm
X vwmwwmmmmmmwmwhnu.ummmmmmrmmnwwnnnm'mflmmummmmu
n&'ywk fl§mgmvmnnw1mmruflkwmmm»wmmmmmm;wmmmMfimmmw
év e \\AVAVA\'WA\\VA\ QN S\ B IR LN NN AN I NN NN SN,
AVAVAVAVAYA' e"’ V VA\'CVAVAVAVAV e N \V AN XY N S TS TN NI "-VAVAVAVAVAVAWVA'AVAVA
*unne S SO ¢ dhmn.‘fwmune LIRS IR
JAVAVAVAVAY -numn # AN Q PO “WE'AWWNMN‘“WNNMNNMWWNm.
muummmwmm@wu nmmmm' nmwummm»wrmmvmmummmgmmmw
VAVAVAVAVAVAVAVAN.\WAVAVAVAVAV,A VAVAV IR A R

I\ N N i
2LiF*BefF; T P-458 40

  

 
   
  

 
    
    
     

A 0

   

7\VAVAVAVAVAY)” AVAVAN
50E-360

   

Fig. 15. Phase Diagram of the LiF-BeF,-ThF, System for Compositions
50 - 100 mole % LiF.
23

B , ORNL DWG. 69-7559

 

A C
Fig. 16. Schematic Drawing for Use in Calculating Relative Fractions
of Coexisting Phases at Point P.
24

POTENTTAL APPLICATION OF FRACTIONAL CRYSTALLIZATION

IN CHEMICAL REPROCESSING

Under equilibrium conditions, the crystallization end-point in
three component systems such as in the LiF-BeF,-ThF, system, depends
on the "compatibility" or three solid phase triangles of the equilibrium
diagram. As an example, compositions in the triangle LiF - 3LiF-ThF,-
2LiF+BeF, have their crystallization end-point at the 444°C peritectic
reaction point. As noted previously,7 dynamic crystallization of
LiF-BeF,-ThF, mixtures does not follow the equilibrium crystallization
diagram exactly; instead, non-equilibrium crystallization proceeds
characteristically by sub-cooling (i.e., delayed crystallization under
dynamic cooling), and by incomplete recombination of liquid and solid
phases at the peritectic reaction points. Thus, liquids are produced
from mixtures which are of interest to us, primarily those containing
high concentrations of LiF, which are richer in BeF,; than their
equilibrium counterparts, and which crystallize as described by the
lower melting areas of the phase diagram. The consequence of non-
equilibrium fractionation is thus to produce liquid residues which are

lower in ThF, content than at equilibrium.

Let us examine the difference between equilibrium and non-equilibrium
crystallization behavior of a liquid composition that would partially
typify the reactions of MSBR salts. Suppose the composition ¢, LiF-
BeF,-ThF, (63-32-5 mole %), undergoes equilibrium crystallization.

On complete solidification, the frozen salt will consist of the three
crystalline phases, 3LiF¥-ThF,; ss, 2LiF-BeF,; and Li¥F.2ThF, in proportions
given by the position of point ¢ in the correSpénding triangle of Figs.

9, 10, and 11.

For non-equilibrium crystgllization this triangle has no signifi-
cance. The non-equilibrium process consists of four consecutive steps,

seen on the basis of the following diggram:
25

LiF:2ThF, (=D)

 

LiF

 

2LiF.BeF, (= H)

Step (1): freezing starts at ~ 446°C for composition c¢, and the
liguid travels on the solid solution liquidus surface to reach curve
P; - P3 at some point g (at ~ 440°C), while precipitating some solid
solution of composition between a and b, say a' as average.

Step (2): 1liquid travels on curve P;-Pi, to reach P; (4339C),
vhile precipitating a mixture of solid solution (of composition between
b and s, say b' as average) and 2LiF:.BeF,.

Step (3): 1liquid travels on curve P;-E, to reach E(356°) while
precipitating mixture of LiF.2ThF, + 2LiF-BeF,.

Step (4): 1liquid at E(356°) freezes to mixture of LiF:2ThF, +
2LiF.BeF, + BeF,.

Quantities involved for 1 mole of starting composition c:
26

Step (1): draw straight line a'c and extend it to curve P;-P,,

to fix point g:

Moles of liquid reaching £ = a'c = m;
a'g

Moles of ThF, precipitated (in step 1, or between 446 and 440°)
=X, (1-m) = pa,
in which X 1 = mole fraction of ThF, at a', etc.
Step (2): draw straight line b'-H, and extend straight line gP;

back to fix peoint y on line b'-H:

 

2LiF‘BeF, (=H)
27

- ¥4

Moles of liquid reaching P3 = YPs (m) = my;
Moles of ThF, precipitated (in step 2, or between 440° and 433°)
= X %?H (my-mp) = ps.
Step (3): draw straight line DH and extend straight line P4E
back to fix point z on the line DH:

   

Z P 3 |
E

&

 

LiF
2LiF-BeF, (=H)

Moles of liquid reaching E = %%1 (mz) = m3;

Moles ThF, precipitated (in step 3, or between 4330 and 3569)

=2 (zH
3 (gfi) (m2-m3) = p3,
since xp = 2/3.
Step (4): moles ThF, precipitated in this step (at 356°)
=x, - (P + P2 + p3).
Thus, given the original composition ¢ on the phase diagram as we
have it, one can meke estimates regarding what happens in steps (1) and

(2), and these estimates fix what happens in steps (3) and (4), for the
28

limit of non-equilibrium behavior. This means a process in which there
is never any interaction between precipitated solid and solution. Actusl
behavior will of course be somewhere between this and the equilibrium

process.

Since non-equilibrium fractionation of LiF-BeF,-ThF, melts
produces final liquids which are low in thorium, and since the
concentrations of rare earths in the solutions are expected to be about
20 ppm at the time when fuel processing is economically mandatory, one
might anticipate that a semi-zone refining step might well produce
and transport liquids of low thorium concentration and containing a
relatively high concentration of rare earths (the solubility of the
lanthanide trifiluorides in any of the melts one might encounter is
almost certainly to be at least 200 ppm at the low temperatures which
would be present in this part of the feeder apparatus), The efficiency
of this concentration step could possibly be impaired seriously if the
rare earth trifluorides either formed intermediate compounds (such
compounds are formed only for the lanthanides of 2 63) which interacted
with the crystallizing phases or otherwise formed solid solutions with
any ‘of the crystallizing phases. The structure of 2LiF-BeF28 and
LiF-ThF49 are known and believed to be incapable of serving as solid
state hosts for the rare earth fluorides. The 3LiF-.ThF, sclid solution
is an unknown factor in this consideration and could conceivably act as
a solvent for lanthanide ions. This possibility as well as the
possibility that LiF:2ThF, might also serve as a solid state solvent
for lanthanide ions could be examined easily through a small scale

laboratory program.
8.

29

Consultant, Department of Chemistry, New York University, University
Heights, New York.

M. E. Whatley et al., Nuclear Applications, fin press).
J. H. Shaffer and D. M. Moulton, Reductive Extraction Processing
of MSBR Fuels, in Reactor Chemistry Division Annual Report for

Period Ending February 28, 1968, ORNL-4396.

R. E. Thoma, H. Insley, H. A. Friedman, and C. F. Weaver, J. Phys.
Chem. 64, 865 (1960).

J. E. Ricci, Guide to the Phase Diagrams of the Fluoride Systems,
ORNL-2396, 1958.

G. D. Brunton, ORNL, Unpublished work, 1969.

C. F. Weaver, R. E. Thoma, H. Insley, and H. A. Friedman, Phase
Equilibria in Molten Salt Breeder Reactor Fuels, I. The System
LiF-BeF, -[]F'4--ThF4 3 ORNL-2896 s, December, 1960.

J. H. Burns and E. K. Gordon, Acta Cryst. 20, 135 (1966).

G. D. Brunton, 21, 814 (1964).
Coo-JowumddwoH

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. Baes
Baker
Ball
Bamberger
Barton
Bauman

. Beall

. Beatty

. Bell

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. Bettis
Bettis
Billington
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. Blankenship
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Blumberg

G. Bohlmann
J. Borkowski
E. Boyd
Braunstein

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B. Briggs

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D. Brunton
A. Canonico
Cantor

W. Cardwell
L. Carter
I. Cathers
E. Caton
B. Cavin
M. Chandler
H. Clark
R. Cobb

k. Cochran
W. Collins
L. Compere
V. Cook

H. Cook

W. Cooke
T. Corbin
Cox
L.

Crowley

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Davis
DeBakker
DeVan
Ditto
Dworkin
Dudley
Eatherly
Engel
Epler
Ferguson
Ferris
Fraas

. Franzreb
Friedman
Fry

Frye, Jr.
Furlong
Gabbard
Gallsher
Gehlbach
Gibbons
Gilpatrick
Grimes
Grindell
Gunkel

. Guymon

. Hammond
Hannaford
Harley
Harman
Harms
Harrill
Haubenreich
Hebert
Helms
Herndon
Hess

. Hightower
. Hill
Hoffman
Holmes
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. Horton

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Kedl
Kelley
Kelley
Kennedy
Kerlin
Kerr
Keyes
Kiplinger
Kirslis
Koger

. Korsmeyer
Krakoviak
Kress
Krewson

. Lamb

Lane
Lawrence
Lin
Lindguer
Litman

. Long
Lotts

. Lundin

. Lyon

. Macklin

. MacPherson
. MacPherson
Mailen

. Manning

. Martin

. Martin

. Mateer
Matthews
Mauney
MeClung
McCoy
McElroy
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McHargue
McLain
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. McWherter
. Metz

. Meyer

. Moore

. Moulton

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DISTRIBUTION

148.
149.
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207.

. Mueller
. Nichol
. Nichols
Nicholson
Oakes
atriarcs
Perry
Pickel
Piper
Prince
Ragan
Redford
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Robbins
Robertson
Robinson
Romberger
Rosenthal
. Ross
. Savage
. Schaffer
. Schilling
ap Scott
Scott
Seagren
Sessions
Shaffer
Sides
Skinner
Slaughter
Smith
Smith
Smith
Smith
. Smith
piewak
Steffy
Stone
. Strehlow
Tallackson
. Taylor
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. Thoma
Thomason
Toth
Trauger
Unger
Watson
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226=227.
228-230.
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239-253.

33

DISTRIBUTION

Watts

Weaver

Wehster

Weinberg

Weir

Werner

West

Whatley

White

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Wilson
Young
C. Young

J. P. Young
E. L. Youngbhlood
F. C. Zapp

Central Research Library
Document Reference Section
Laboratory Records
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EXTERNAL DISTRIBUTION

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