ORNL-2719.txt

CONTENTS

SUMIMAIY . cvtenirneeieuientioes e enseetesssestanssescessssessssnatesentessersesssusssssasersonsensessensensnsessssssssssessesssssssenes ]
I P OAU CION. . ettt st eeteesiseesaee e sbe e saesassenessassasssestosaessnssseeatessasnssssasesnnssaessrants 1
Materials, Methods, and Apparatus .....cccceveiiiccesese et st s ss e 2
General Discussion of the System LiF-UF ,-ThF, and the

Limiting Binary Systems .c.eeeviveieeceiicttninnnese it scetessresssstsseseesrastessssessssessasssensestsssnense 2
The 20 Mole % LiF Join and the LiF.4UF ,-LiF-4ThF, (ss)

Fractionation Paths ...ttt eesseeceteessassssesseessessssessaessssaessseses 20

P At e e e b s sa e sa e s bt s e e a s e sars s b et et s aeseen savRaarabenarsaten 21
The 53.8 Mole % LiF Join and the 7LiF-6UF4—7LiF-6ThF4 (ss)

Fractiongtion Paths ...t scseeniste et e sresaensesssasseresessssssassenssasss nsenassos 21
The 75 Mole % LiF Join and the 3LiF-ThF, (ss) Fractionation Paths......cccoovenirnerncnnc. 21
Relations Between the Solid SolUtionS ... cuiieeeuinienrcctnice e e sve st esnaaes 31
ACKNOWIEAGMENTS ... .ottt rte e sttt e sieerbe e e sert e ses eraesbe s st esen sasbeesaensene 34
APPENAIX .cueerinriiieiiiciiriinierereeteeesitassreesresesaesstessasts s aes s sssassensaessasre seresssars senesenesatesessraeneeannrases 43
ORNL-2719
Chemistry-General
TID-4500 (14th ed.)

Contract No. W-7405-eng-26

REACTOR CHEMISTRY DIVISION

PHASE EQUILIBRIA IN THE SYSTEMS
UF —ThF , AND LiF-UF -ThF

C. F. Weaver
R. E. Thoma
H. Insley

H. A. Friedman

This document has been reviewed and is determined to be

DATE ISSUED

AUl L4 1959

OAK RIDGE NATIONAL LABORATORY
Ock Ridge, Tennessee
operated by
UNION CARBIDE CORPORATION
for the
U.S. ATOMIC ENERGY COMMISSION
PHASE EQUILIBRIA IN THE SYSTEMS UF ,~ThF ; AND LiF-UF ;-ThF

C. F. Weaver R. E. Thoma

SUMMARY

As part of a study of materials potentially
useful as fluid fuels for high-temperature reactors,
equilibrium diagrams for the condensed systems
UF,-ThF, and LiF-UF ,-ThF, have been de-
termined. Both thermal analysis and quenching
techniques were used, with phase identification
accomplished by petrographic and x-ray diffraction
analysis. A complete series of solid solutions
without maximum or minimum is formed by UF,
and ThF,. The system LiF-UF,-ThF, contains
no ternary compounds but does contain four
ternary solid solutions. The compounds LiF+-4ThF,
and LiF+-4UF, form a continuous series of solid
solutions, as do the compounds 7LiF <6 ThF, and
7LiF-6UF,. A series of solid solutions exists
having compositions at 33Y% mole % LiF between
LiF-2ThF, and 23 mole % UF,. Another series of
solid solutions exists having compositions at
75 mole % LiF between 3LiF+-ThF, and 15.5 mole
% UF ;. Seven primary-phase fields appear in the
system, those which are solid solutions being
indicated by (ss): LiF, 4LiF-UF4, 3LiF-Th(U)F,
(ss), 7LiF-6ThF ,~7LiF-6 UF, (ss), LiF-2Th(U)F
(ss), LiF+4ThF ,-LiF-4UF, (ss), and UF ,-ThF,
(ss). Phase relations were established trom the
liquidus to about 300°C. The three invariant
points which occur are the following: peritectic,
19 mole % UFA, 18 mole % ThF,, 609°C; peri-
tectic, 20.5 mole % UF4, 7 mole % ThF ,, 500°C;
and eutectic, 26 .5 mole % UF4, 1.5 mole % ThF4,
488°C.

The solid phases taking part in the invariant
reactions are the following: peritectic point at
609°C: LiF'4ThF4—LiF~4UF4 (ss) containing
28 mole % UF,, LiF:2Th(U)F, containing 23
mole % UF,, and 7LiF« ThF ,—7LiF.6UF, con-
taining 23 mole % UF ,; peritectic point at 500°C:
LiF, 7LiF«6ThF ~7LiF.6UF, (ss) containing
31 mole % UF,, and 3LiF-Th(U)F, (ss) containing
15.5 mole % UF,; eutectic point at 488°C:
4LiF-UF4, LiF, and 7LiF+6 ThF4—7LiF-6UF4 (ss)
containing 42.5 mole % UF .

The refractive indices of the ternary solid
solutions were determined as functions of compo-
sition and used for an optical analysis of the
solid solutions when they occurred with other
phases.  This information made possible the

H. Insley H. A. Friedman

construction of tie lines, fractionation paths, and
compatibility triangles for the three ternary
invariant points.

INTRODUCTION

Several years ago, R. C. Briant of the Oak
Ridge National Laboratory suggested the use of a
molten mixture of UF, and ThF, together with
fluorides of alkali metals and beryllium fluoride
or zirconium fluoride as a potential fuel for a
high-temperature, low-pressure nuclear reactor.!
A systematic study at ORNL during the past
several years has developed molten salt mixtures
whose chemical and physical properties seem to
suit them for use as fuels in U235 burner re-
actors,2 in plutonium burner reactors, and in
one-region U233 breeder reactors and as blankets
in two-region U233 breeder reactors. Nuclear
reactor designs have been proposed which would
utilize mixtures of Li’F, BeF,, ThF,, and UF,
as fuels.3-3

Little is known concerning the phase relation-
ships of the system LiF-Ber-UF4-ThF4 except
that solid solutions involving LiF, UF,, and
ThF, occur as primary and secondary phases at
low UF, and ThF, concentrations. Phase
diagrams of the limiting binary systems LiF-BeF
(ref 6), LiF-UF, (ref 7), and LiF-ThF, (ref 8)

YA, M. Weinberg and R. C. Briant, Nuclear Sci. and
Eng. 2, 797-803 (1957).

2E. S. Bettis et al., Nuclear Sci, and Eng. 2, 804-825
(1957).

3J. K. Davidson and W. L. Robb, A Molten Salt
Thorium Converter for Power Production, KAPL-M-
JKD-10 (1956).

4L. G. Alexander et al., ‘‘Conceptual Design of a

Power Reactor,”” chap 17 of Fluid Fuel Reactors,
Addison-Wesley, Reading, Mass., 1958,

5L. G. Alexander, ‘‘Nuclear Aspects of Molten-Salt

Reactors,’’ chap 14 of Fluid Fuel Reactors, Addison-
Wesley, Reading, Mass., 1958.

¢R. E. Thoma, Pbhase Diagrams of Nuclear Reactor
Materials, ORNL-2548,

7C. J. Barton et al., J]. Am, Ceram. Soc. 41(2), 63-69
(1958).

8R. E. Thoma et al., ‘‘Phase Equilibria in the Fused
Salt Systems LiF-Thl"'4 and NaF-ThF4," J. Pbys.
Chem. (in press).
have been published. The systems BeF,-UF,
(ref 9) and LiF-BeF,-UF, (ref 10) have been
investigated at the Mound Laboratory., Results of
phase equilibrium studies of the systems BeF,-
ThF, and LiF-BeF,-ThF, will soon be reported
by the authors. Preliminary diagrams of these
systems are in the literature.'1+12  The system
Bef ,-UF ,-ThF, has not, to our knowledge, been
investigated. The remaining systems, UF“-ThF4
and LiF-UF ,-ThF,, are the subject of this report.
Preliminary diagrams of these systems have been
reported by the authors.'2:13 As is to be expected
from the known similarities in the parameters of
the unit cells of ThF4 and UF4 (refs 14 and 15),
a salient characteristic of the condensed systems
UF,-ThF, and LiF-UF,-ThF, is the extensive

formation of solid solutions.

MATERIALS, METHODS, AND APPARATUS

The lithium fluoride used in this investigation
was reagent grade, obtained from Foote Mineral
Company and from Maywood Chemical Works. The
thorium tetrafluoride was obtained from lowa
State College and from National Lead Company.
The wuranium tetrafluoride was obtained from
Mallinkrodt Chemical Works. No appreciable
impurities were found in the uranium tetrafluoride
or thorium tetrafluoride by spectrographic, x-ray
diffraction, or microscopic analysis.

The phase equilibria data were obtained by
thermal analysis of slowly cooled melts and by
identifying the phases present in mixtures which
had been equilibrated and quenched. Because
uranium and thorium fluorides are easily converted

). F. Eichelberger, E. F. Joy, E. Orban, T. B.
Rhinehammer, and P. A. Tucker, unpublished work.

10, F, Eichelberger, D. E. Etter, C. R. Hudgens,
L. V. Jones, T. B. Rhinehammer, P. A, Tucker, and
L. J. Wittenberg, unpublished work.

1w, R. Grimes et al., '"Chemical Aspects of Molten-
Fluoride Reactor Fuels,’”’ chap 12 of Fluid Fuel Re-
actors, Addison-Wesley, Reading, Mass., 1958,

12”Sl.npplement to ‘Phase Diagrams for Ceramists’’’

(compiled by M. Levin and H. F. McMurdie),
American Ceramics Society, Inc., Easton, Pa. (in press).

]3R. E. Thoma et al., MSR Quar. Prog. Rep. Jan 31,
1958, ORNL.2474, p 81,

'I4W. H. Zachariasen, X-Ray Diffraction Studies of
qagzjg)ellaneous Uranium Compounds, MDDC-1152 (June

155, J. Katz and E, Rabinowitch, The Chemistry of
Uranium, NNES VIHI-5, McGraw-Hill, New York, 1951.

to oxides or oxyfluorides at elevated temperatures,
it was necessary to remove small amounts of
water and oxygen as completely as possible from
the starting materials. To facilitate the removal
of these substances, ammonium bifluoride was
added to the mixtures of lithium fluoride, thorium
fluoride, and uranium fluoride before initial
heating in the thermal analysis experiments,
While the mixtures were being heated the water
was evaporated from the system, The oxides
were converted by reaction with the ammonium
bifluoride to products which have not yet been
identified but which are likely to be ammonium
fluometallates.'6+17  Upon further heating, the
“ammonium fluometallates’® decomposed to form
the metal fluorides. These same mixtures were
later used in the quenching experiments,

The phases were identified by petrographic and
x-ray diffraction techniques. These methods for
characterizing phases, as well as a description
of the apparatus used for preparing and annealing
samples, were reported previously,”+8:18-21

GENERAL DISCUSSION OF THE SYSTEM
LiF-UF ,-ThF, AND THE LIMITING
BINARY SYSTEMS

The phase diagram of the condensed ternary
system LiF-UF4-ThF4 is shown in Fig. 1, and a
photograph of a three-dimensional model22 of the
system is shown in Fig. 2. The associated
binary systems are shown in Figs. 3-5.

One metastable compound (3LiFoUF4) and three
incongruently melting compounds (4LiF-UF4,
7LiF-6UF,, and LiF.4UF,) are formed in the
system LiF-UF ,. Optical properties, except those
of 3LiF-UF4, and x-ray diffraction data for these

;gmsza Quar. Prog. Rep. April 30, 1959, ORNL-2723,
p 93.

17, J. Sturm, Oak Ridge
personal communication.
8¢, J. Barton et al., J. Phys. Chem. 62, 665 (1958).

19R. E. Thoma et al.,, J. Am. Ceram. Soc. 42(1),
21-26 (1959).

20H. A. Friedman,
Techniques for Phase
Ceram. Soc. (in press).

21p, A. Tucker and E. F. Joy, Am. Ceram. Soc. Bull.
36(2), 52-54 (1957).

Model constructed by C. Johnson, summer participant

ot ORNL, 1958.

National Laboratory,

**Modifications of Quenching
Equilibrium Studies,”” J. Am.
ThE,

(AL UNCLASSIFIED
ORNL-LR-DWG 28245AR2

PRIMARY-PHASE AREAS

(@) UF,-ThE, (ss)

(b) LiF-4UF,-LiF-4ThF, (ss)
() LiF-2Th(UIF, (ss)

(d) 7LiF-6UF,-7LiF-6ThE, (ss)
(e) 3LiF-Th(U)F, (ss)

(f) LiF

TEMPERATURE IN °C
COMPOSITION IN mole %%

LiF- 4ThE,

LiF'2ThF4
P87 N

AN
7LiF-6ThF,
P 762 A

\ (b
P 597 Ay
£ 565 00
3LiF-ThF4
£ 568 A A

S

pAY

o) Q

P 609
@)\

3 0
AD\, B
RS 6o T NP 500
% 25 W\
T O \ o) \ \\ ,
VAR ARWNAN Y

845 aLiF-UF,” £500" '£490 P 610 PTT5 LiF-4UF
7LiF-6UF,

Fig. 1. The System LIF-UF4-TI1F4.
UNCLASSIFIED
PHOTO 32550

+
® TLiF-gu,

Lif +71k.
if 6'."‘ ]h’“‘“‘
+

LF-4uf, UF4UE, + u, (¢

LiF-4UF,

300

TLF-8UF,

Fig. 2. Three-Dimensional Model of the System LiF-UF,-ThF,.
TEMPERATURE (°C)

TEMPERATURE (-C)

UNCLASSIFIED

ORNL —LR-DWG 17457

1100

/

A

{000 /

200 v

:
/

700 \ /

600 \

/ u~
500 \/ 5 u
yod © <
4LiF UF4/ = W
~ -
400
LiF 10 20 30 40 50 60 70 80 90 UF,
UF, (mole %)
Fig. 3. The System LiF-UF ..
UNCLASSIFIED
ORNL-LR-DWG 26535A
el T T T T 1
& | i N ‘ 5 UNCLASSIFIED
ORNL~-LR-DWG 27913R
1050 ! R ! 1200 | :
950 ———-L—u—r-—--wa E | ! [L - o ‘ l
‘ 4 T T 1100 tremmme '~ LiQuID
1 | f 1 T & ‘"%, $ i |
850 ha——— : ; A“,k*l-__. U SUN— 2 \T 1 T /
\ { 51000 |- -~—*LIQUID + ThE, - UF, SOLID SOLUTION
: ui
750 ——1 /- —— o . ;
; \ ‘ / = 900 |-— — A-j«‘m-;,-ug, SOLID SOLUTION
; i | | . - |
N\ ! NN RS S I T . ! :
850 P\ g . soo L IS N N N
VY cun m iR 4_ T, 10 20 30 40 50 60 70 80 90 UF,
550 F—F = e RIS y
3LiF-ThE,—| 7LiF -6ThE,— LiF-2ThE, — E - | UFy {mole %)
i :
250 | I l

LiF 10 20 30 40 50 60 70 80 90 ThE‘
ThE, (mole %)

Fig. 4. The System LiF-ThF,

Fig. 5. The System ThF4-UF4.
compounds are shown in Tables 1 and 2, re- A complete series of solid solutions without

spectively. The compound 4LiF-UF, has a lower maximum or minimum is formed in the system
limit of stability at 470°C. The compositions and UF ,-ThF,. The optical properties of these solid
temperatures of the three peritectic invariant solutions are shown in Table 1 and Fig. 6. The .

points and the eutectic invariant point are
(1) peritectic: 26 mole % UF ,, 500°C; (2) eutectic: NeLASSFED
27 mole % UF,, 490°C; (3) peritectic: 40 mole % ' ORNL-LR—DWG 279145 -
UF,, 610°C; (4) peritectic: 57 mole % UF,, 775°C. | A |

One congruently melting compound (3LiF-ThF4)
and three incongruently melting compounds
(7LiF-6 ThF,, LiF2ThF,, ond LiF.4ThF,) are
formed in the system LiF-ThF ,. Optical properties
and x-ray diffraction data for these compounds are
shown in Tables 1 and 2, respectively. The
compositions and temperatures of the three peri-
tectic and two eutectic invariant points and one
congruent melting point are (1) eutectic: 23 mole | [
% ThF,, 565°C; (2) congruent melting point: 25 rag b | | x
mole % ThF,, 573°C; (3) eutectic: 29 mole % The 20 4%‘: (mo!e?)eo 80 U
ThF,, 568°C; (4) peritectic: 30.5 mole % ThF,, 4 7
597°C; (5) peritectic: 42 mole % ThF4, 762°C; Fig. 6. Indices of Refractlon vs Composition for ThF ;-
(6) peritectic: 58 mole % ThF,, 897°C, UF, (ss),

INDEX OF REFRACTION

Table 1. Optical Properties of LiF-UF4, LiF-ThF4, and UF4-ThF4 Solid Phases®

Compound Optical Character Sign Optic Angle N,or N, N, or N.y
4LiF.UF, Biaxial + 45° 1.460 1.472
7LiF-6UF4 Uniaxial - 1.554 1.551
LiF-4UF, Biaxial - 10° 1.584 1.600
3LiF~ThF46 Biaxial - 10° 1.480 1.488
7LiF-6ThF4 Uniaxial + - 1,502 1.508
LiF«2ThF, Uniaxial - 1.554 1.548
LiF«4ThF 4" Biaxial - 10° 1.528 1.538

UF4-ThF4 (ss€)

(70% UF ) Biaxial - 60° 1.536 1.586
(60% UF ) Biaxial - 60° 1.530 1.580
(50% UF ) Biaxial - 60° 1.516 1.566
(40% UF ;) Biaxial - 60° 1.510 1.560

% Data taken from R. E. Thoma et al., *Phase Equilibria in the Fused Salt Systems LiF-ThF4 and NaF-ThF4,"
J. Pbys, Chem, (in press); H. Insley et al., Optical Properties and X-Ray Diffraction Data for Some Inorganic Fluoride
and Chloride Compounds, ORNL-2192 (Oct. 23, 1956); and L. A. Harris, G. D. White, and R. E. Thoma, ** Analysis of
the Solid Phases in the System LiF-ThF4," J. Pbys., Chem. (in press). .

bThis routinely observed biaxiality appears to be produced by strain in the 3Li|=-'l'hl=4 and LiF-4ThF4 crystals,
inasmuch as the crystal type is tetragonal as determined by x-ray diffraction measurements,
©Solid solution.
Table 2. X-Ray Diffraction Patterns for the Solid Phases Occurring in the Systems LiF-ThF, ond LiF-UF ;*

3LiF-ThE, TLiF-6THF, LiF-2ThE, LiF 4ThF, ALiF-UF, ILiF-UF, TLiF-6UF, LiF-4UF,
&) 1, 4R v, AR) 1, 4R i, 4R) i, 4R 1”1, AR) 1, 4R) i,
6.42 00 607 15 7.97 5 8.4 3 567 0 49 0 66l 6 102 8
a.46 00 591 20 637 0 776 3 546 25 480 15 597 20 633 12
4.37 00 536 % 39 00 651 5 513 70 44 100 582 15 607 5
2.62 8 5.5 15 3.8 65 580 25 493 00 4.34 00 5.2 % 573 2
3.09 55 495 325 5 482 5 4ss VI X 15 515 0 a9 8
2.866 0 485 20 3 5 4m 70 444 00 39 8 465 0 470 2
2.788 0 475 00 297 0 3.8 00 42 7 340 80 437 13 425 %0
2.542 2% 400 85 282 25 240 0 382 0 340 10 395 55 3.88 2
2.327 0 392 15 2675 7 325 0 355 0 304 25 385 13 37 100
2,189 0 374 15 2528 0 292 25 203 0 207 50 368 0 352 %0
2,104 65 355 65 2338 5 282 2% 289 25 2.4 80 3.49 B 306 8
2,071 2% 344 o 2s 85 2,603 10 2866 3 27m 3 33 9 343 8
2,036 0 33 70 2053 0 2398 0 2747 0 259 B 3s 70 306 12
1.959 3.2 60 200 65 2137 25 2468 o 2169 15 3.07 0 284 40
1933 60 303 00 1787 7 205 35 2398 20 2.083 s 29 95 27l 55
1.877 25 284 35 L0 10 2000 0 2= @ 2085 s 27 0 2542 8
7 25 2747 25 1689 5 2018 0 216 5 194 50 2707 3 2.3% 10
1,743 % 257 20 1603 5 2005 B 2,074 0 1913 25 2542 25 2300 10
1.701 35 243 0 1509 5 9w 0 202 20 1860 0 2350 13 2.2 8
1.66) o 239 10 1.820 0 1872 0 L75 25 228 25 2.000 10
1.618 0 2302 20 1778 3 1.83% 25 1723 2% 2.264 13 2088 3
1.547 I/ 237 20 1.725 5 1.685 25 2184 o 206 &0
1.520 35 2008 5 1719 5 1.662 8 2097 B e 50
2.001 15 1.666 5 1.646 0 2,060 30 1.888 2
1.892 55 1.605 5 1.599 8 2.047 5 1819 8
1.859 15 1.595 5 1.993 B 1767 25
1.804 15 1.563 5 1972 2
1.680 15 1.947 25
1.653 20 1.924 15
1.600 20 1.909 30
1.854 a5
1.825 2
1773 2
1,757 2
1.709 15
1.680 15
1.625 15
1.579 25
1.562 8

*Dota taken from R, E. Thoma et al., *Phoso Equilibrium in the Fused Salt Systems LiF-ThF , and NoF-ThF " . Phys. Chem. (in pross); H. Insloy et al., Optical Properties and
X-Ray Diffraction Data for Some Inorganic Fluoride and Chloride Compounds, ORNL-2192 (Oct, 23, 1956); L. A. Harris, G. D. White, and R. E. Thoma, *‘Anclysis of the Solid Phoses in
the Systom LiF-ThF ' J. Pbys. Chem. (in press); and L. A. Harris, Crystal Structures of 7:6 Type Compounds of Alkali Fluorides with Uranium Tetrafluoride, ORNL CF.58.3.15

{March 6, 1958).

- equilibrium phase diagram is based on the thermal
analysis data shown in Table 3 and the results of
quenching studies shown in Table 4,

The system LiF-UF ,-ThF, contains no ternary
compounds but does contain four ternary solid
solutions. The compounds LiFotiTI*aF“--LiF-AUF4
form a continuous series of solid solutions, as do
the compounds 7LiF-6ThF4-7LiF-6UF4. A
series of solid solutions exists having compo-
sitions at 331/3 mole % LiF between LiF.2ThF,
and 23 mole % UF4. Another series of solid
solutions exists having compositions at 75% LiF

between 3LiF-ThF4 and 15.5 mole % UF4. The

joins containing these solid solutions are
described in detail in sections below.

Seven primary-phase fields appear in the system:
LiF, 4LiF.UF, 3LiF-ThF, (ss), 7LiF«6 ThF ,—
JLiF-6UF, (ss), LiF2ThF, (ss), LiF-4ThF ,-
LiF-4UF4 (ss), and ThF4-UF4 (ss). Phase re-
lations were established from the liquidus to
about 360°C. Three invariant points occur: peri-
tectic: 20.5 mole % UF4, 7 mole % ThF,, 500°C;
eutectic: 26.5 mole % UF4, 1.5 mole % ThF4,
488°C; peritectic: 19 mole % UF,, 18 mole %
ThF,, 609°C. The reactions which take place at
Table 3. Thermal Analysis Data for the Systems UF4-TI1 F4 and LiF-Th F4-UF4*
Interpretation Key
| = liquidus
a = boundary between UFA-Th F4 (ss) and LiF+4UF ,~LiF-4Th F4 (ss) primary-phase fields
b=4LiF.U Fq decomposition
¢ = boundary between LiF°2ThF4 (ss) and LiF°4UF4-LiF'4Th Fy (ss) primary-phase fields
d = ternary eutectic
e= LiF, 3Li|""°T|'1F4 (ss), 7LiF-6UF4-—7LiF'6Th F4 (ss) peritectic
f = boundary between 3LiF+*Th F4 (ss) and 7LiF°6UF4-7LiF°6Th Fy (ss) primary-phase fields
g = boundary between LiF and 7LiF'6UF4-7LiF°6Th F4 (ss) primary-phase fields
h = liquid disappearance at {
i= 3Li|'-'°ThF4 (ss) exsolution
k = liquid disappearance at m
m = boundary between LiF and 3LiF*Th F4 (ss) primary-phase fields
s = solidus

Composition Temperature Interpretation Composition Temperature Interpretation
(mole %) (°C) (mole %) (°c)
UF4-ThF4** LiF-Tl1F4-UF4
70-30 1025 20-10-70 747
1023 750
1005 20-20-60 965 1
985 951 |
60-40 1051 | 780 a
1045 | ' 785 a
1010 20-30-50 982 |
993 941 |
955 825 a
50-50 1085 | 817 a
1080 | 20-40-40 805 a
1050 | 795 a
1035 20-50-30 915
1017 837 a
1005 832 a
990 825 a
985 20-60-20 835 a
40-60 1040 | 832 a
1035 20.70-10 855 a
1022 860 a
1005 33)4-33)4-33), 859 o
990 846 a
960 830 a
815 a
LiF-ThF“-UF4 815 a
20-10-70 962 | 33),-46%-20 478 b
960 | 430

*In general, more than one thermal analysis was made for each nominal composition, All the thermal breaks are
listed, but it is not intended to imply that they all occurred on a single cooling curve, The variation in temperatures
associated with the same phenomenon is believed to be caused by supercooling effects.

**Each of these slowly cooled melts contained only one phase according to x-ray diffraction and petrographic
analysis, indicating that there is no miscibility gap in the system UFA-Th F4.

8
13

Table 3 (continued)

Composition Temperature . Composition Temperature .
(mole %) (°C) Interpretation (mole %) (°C) Interpretation
33)%-46%-20 320 40-30-30 823
300 470 b
33%-51%-15 890 a 458 b
870 a 40-40-20 902
852 a 902
33),-56%-10 91 | 861 l
961 | 860 1
875 a 590
875 a 588
665 c 467 b
663 c 423
960 | 40-50-10 865 ]
956 | 860 |
875 a 855 1
875 a 675 c
695 c 675 c
692 c 50-10-40 755 |
35-20-45 895 | 755 !
893 I 482 d
805 a 480 d
805 a 420
800 a 428
799 a 50-15-35 635
480 d 483 d
423 482 d
35-45-20 928 430
928 50-25-25 803 l
850 a 490 d
850 a 490 d
845 a 451
845 a 442
40-10-50 840 l 53.8-6.2-40 720 |
840 | 715 |
777 482 d
777 450
475 b 53.8-10-36.2 717 !
445 717 |
40-20-40 825 | 481 d
800 445
790 53.8-11.2-35 730 |
782 625
467 b 490 d
428 485 d
40-30-30 863 | 441
853 1 430
825 53,8-13.2-33 725 !

Table 3 {continued)

10

Composition Temperature ] Composition Temperature ]
(mole %) ©C) Interpretation (mole %) (°C) Interpretation .
53.8-13.2-33 725 I 57-15-28 467 b
487 d 57-21.5-21.5 717 |
485 d 690
436 481 d
53.8-15-31.2 726 I 481 d
718 | 458
485 d 458
455 57-26-17 708 !
53.8-18.2.28 740 | 707 |
740 | 496 e
485 d 495 e
485 d 485 d
446 485 d
53.8-23.1-23.1 773 | 427
770 l 57-28-15 733 |
485 d 733 !
437 500 e
53.8-30-16.2 766 I 499 e
7351 ! 480 d
498 e 480 d
485 d 417
468 b 57-30-13 748 |
53.8.36.2-10 763 | 748
762 I 515 f
517 f 514 f
515 f 487 d
447 485 d
57-4-39 666 ! 422
663 | 57-32-11 750
550 750
535 687 1
493 g 686 |
493 g 521 f
488 d 521 f
480 d 58+22.20 725 |
57-10-33 688 ! 725 I
687 l 490 d
491 d 442
490 d 58-24.18 715 I
470 b 715 !
470 b 495 e
57-15-28 705 | 480 d
705 I 430
492 g 60-5-35 625 I ©
487 d 620 |
483 d 489 d

Table 3 (continued)

Composition Temperature ] Composition Temperature )
(mole %) °0) Interpretation (mole %) ©0) Interpretation
60-5.35 488 d 60-30-10 685 |
450 670
445 665
435 527 f
60-10-30 655 | 525 f
655 | 420
490 d 60-35-5 726 |
489 d 718 I
489 d 546 f
475 b 546 f
475 b 62-10.28 618 1
465 615 1
462 545
60-15-25 670 | 535
670 | 492 g
490 d 491 g9
489 d 485 d
458 470 b
451 62-20-18 650 |
445 650 !
60-20-20 678 I 497
678 | 495
495 g 495
495 9 485 d
490 d 485 d
490 d 440
465 b 62.28-10 687
465 b 685
458 675 I
445 665 |
445 587
60-22.18 685 | 525 f
685 | 410
550 t 62.33-5 704 I
495 703 |
492 545 f
485 d 543 f
485 d 64-24-12 652
467 b 625
60.25-15 710 533 f
657 525 f
657 525 f
508 e 523 f
483 d 64-31.5 673 |
470 b 669 |
60-30-10 690 | 544 t

1
Table 3 (continued)

Composition Temperature Interoretation Composition Temperature Int toti
(mole %) (°C) P (mole %) °C) nterpretation
64-31.5 543 f 69-27-4 540 f
525 69-29.2 612
66-24-10 622 611
620 558 f
567 | 557 f
528 f 70-10.20 495 f
523 h 495 f
517 h 487 d
6629-5 640 I 485 d
640 | 477 b
536 f 462 b
535 f 70.20-10 544 f
530 h 540 f
525 h 524 h
67-26-7 615 521 h
615 520 h
547 f 520 h
542 f 430
68-17-15 592 | 415
592 | 70.24.6 575 |
543 f 575 |
530 f 549 f
512 h 540 f
511 h 70.5-12,5-17 500 e
487 i 500 e
487 i 475 b
430 475 b
68-24-8 610 455
607 450
540 | 442
536 | 441
530 f 400
520 f 70.5-17-12.5 525 f
500 e 520 f
69-4.27 490 9 515 h
487 ] 511 h
480 d 511 h
478 d 475 b
472 b 471 b
467 b 442
445 439
425 71-1.28 507 |
420 489 d
69-27-4 604 | 475 b
600 | 545
549 f 71.2.27 484 d

12

Table 3 (continued)

Composition Temperature . Composition Temperature .
o Interpretation o Interpretation
(mole %) (°C) {mole %) ("C)
71.2.27 475 b 72-8-20 516 |
475 b 508 |
448 508 |
71.5.24 488 d 492 d
485 d 490 d
485 d 450
483 d 72-10-18 560
452 500 e
442 475 b
440 428
435 72-11.17 512 |
71.24.5 560 | 501 e
558 l 500 e
545 h 461 b
544 h 456
535 h 72-12-16 517 |
71.5-1-27.5 484 d 515 |
484 d 508 |
470 b 489 d
455 485 d
71.5-2.26.5 504 441
487 d 428
475 b 72.18-10 530 |
467 b 527 |
451 472 b
72-1.27 762 425
469 b 72,5-1.26.5 480 d
467 b 475 d
463 b 467 b
72.2.26 475 b 467 b
475 b 450
450 73-2-25 485 d
430 476 b
72.3.25 658 475 b
484 d 433
475 b 73-11-16 517 I
462 b 5N f
444 500 e
428 484 d
72-4.24 504 482 d
490 d 469 b
487 d 460 b
445 73-12.15 514 |
72-6-22 487 d 503 e
482 d 477
480 d 477

13
Table 3 (continued)

Composition Temperature . Composition Temperature
(mole %) (°c) Interpretation (mole %) (°C) Interpretation

73-12-15 460 75-15.10 535 |
439 525 m
415 525 m
412 75-20.5 555 |

73-15.12 517 | 555 |
515 | 550 |
510 f 75-23-2 803
507 f 563 |
505 e 532 s
390 77-15.8 645

74-20+6 535 f 546 |
535 f 545 |

74-24-2 555 f 540 k
553 f 538 k
465 i 77-19-4 575
460 i 575

75-5-20 535 550 |
528 | 550 i
526 | 538 k
489 d 80-10.10 755
487 d 748
445 493 i
431 490 i

75-10-15 535 | 428
527 | 80-15.5 625 |
512 k 625 |
507 k 541 k
442 541 k
432 430

75-12-13 524 I 420
521 [ 415

75-15.10 740

14

s
Table 4, Thermal-Gradient Quenching Results for the ThF4-UF4 Liquidus and the LiF-Th F4-U F4 Liquidus?

Compos ition Liquidus
(mole %) Tempoerafure Primary Phase
(°C)
UF ,-ThF,
40-60 1053 + 4 UF,-ThF, (ss?)
50-50 1062 £ 3 UF ,-ThF, (ss)
60.40 1053 £ 4 UF - ThF, (ss)
70.30 1053+ 4 UF,-ThF, (ss)
UF ,-ThF ,-LiF |
2.23.75 5723 3LiFsThF , (ss)
2-24.74 5623 3LiF*ThF, (ss)
2.2969 594 %3 TLiFs6ThF ,~TLiF+6UF , (ss)
4-19.77 567 £3 LiF
4-27-69 5986 TLiFs6 ThF ,~7 LiF*6UF , (ss)
5.15.80 615+3 LiF
5.19-76 5622 3LiF*ThF  (ss)
5.20.75 5623 3LiF*ThF, (ss)
5:24-71 56513 TLiF*6ThF ,~7LiF+6UF , (ss)
22-6.72 504 + 4 LiF
23.1.23.1-53.8 744 %3 LiFedThF ,~LiF*4UF  (ss)
24-4-72 495 2 LiF + 7LiFs6 ThF ,~7LiF*6UF , (ss)
25.2.73 49112 LiF + 7LiFs6 ThF ;~TLiF*6UF , (ss)
25-3.72 49512 LiF + 7LiFs6 ThF ,~7LiF+6UF , (ss)
25.25-50 806 13 LiF*4ThF ,~LiF*4UF  (ss)
26-2-72 496 12 LiF + 7LiF*6ThF ,~7LiF*6UF ; (s5)°
26,5-1-72,5 495 +2 4LiFeUF, + 7LiFs6ThF ~7LiF*6UF , (ss)
26.5-2-71.5 504 2 4LiF°UF , + 7LiF*6ThF ~7LiF+6UF  (ss)
27-1.72 49112 4LiFeUF , + TLiFs6 ThF ,~7LiF*6UF , (ss)
27.2.71 49512 LiF + 7LiF*6ThF ,~7LiF*6UF , (ss)
27.5.1-71.5 49512 4LiFsUF , + 7LiF*6 ThF ,~7LiF-6UF , (ss)
28.1.71 508 £ 2 TLiF+6ThF ,~7LiF*6UF, (ss)
28-10.62 615+3 LiFedUF ,~LiF*4ThF  (ss)
28-18.2.53.8 729 %3 LiF+4UF ,~LiF*4ThF (ss)
30.10-60 6332 LiF+4UF ,~LiF*dThF  (ss)
30-30-40 859 + 1 LiF+4UF ,~LiFe4ThF, (ss)

30-50-20 968 + 4 UF 4-Th Fq (ss)
Table 4 (continued)

1 ]

16

Composition Liquidus
(mole %) Tem%erafure Primary Phase
-G
UF4-ThF4-LiF

31.2-15-53.8 736 +3 LiFe4u F4-Li Fe4Th F4 (ss)

33-10.57 687 3 LiF+4U F4-LiF°4Th F4 (ss)

33-13.2.53.8 7233 LiF°4UF4-Li F*4Th F4 (ss)

5.26-69 581 12 7LiF+6Th F4-7Li F~6UF4

5:29-66 64513 LiFs2ThF , (ss)

5-31-64 66713 LiF+2Th F4 (ss)

5-33-62 70413 LiF2Th F4 (ss)

5-35-60 7143 LiFe2Th F4 (ss)

6-24-70 55512 7LiF*6Th F4—7LiF-6U F4 (ss)

72667 6125 7LiF+6Th F4--7LiF06UF4 (ss)

8-15-77 54813 LiF + 3LiF+Th F4 (ss)

10-10-80 649 3 LiF

10-15-75 547t 3 3LiF«Th F4 (ss)

10-16.74 55512 3LiFsTh F4 (ss)

10-18-72 54412 3LiF+Th Fgq (ss) + 7LiFe6Th F4-7Li F°6UF4 (ss)

10-20-70 57719 7LiFe6Th F“--7LiF'6UF4 (ss)

10-24.66 596+ 3 7LiF+6Th F4-7LiF-6UF4 (ss)

10-26-64 6003 7LiF6Th F4-7Li F-6UF4 (ss)

10-36.2-53.8 7701 3 LiFedThF ,~LiF+4UF , (ss)
772 £ 2 LiFe4Th F,~LiF-4U Fq (ss)

10.50.40 880 12 LiFe4Th F4-LiF'4U Fa {ss)

107020 101316 UF“-ThF4 (ss)

12-15.73 53313 3LiFTh F4 (ss)

12.5-17.70.5 56513 7LiF*6Th F4—7LiF~6U F4 (ss)

13-12.75 528 3 3LiFeTh Fgq (ss)

15-12.73 52312 LiF + 3LiFsTh F4 (ss)
5283 LiF+3LiF-ThF4 (ss)

151768 587 £ 2 7LiF*6Th F4-7LiF-6U F4 (ss)

16-11-73 519 £2 3LiF~ThF4 (ss)

161272 5283 7LiF+6Th F4-7LiF-6U Fq (ss)

16.2-30-63.8 777 13 LiF+4ThF ,~LiF+4UF ; (ss)

17-11.72 532+2 7LiF~6ThF4-7LiF-6UF4 (ss) + 3LiF'ThF4 (ss)

17-12,5.70.5 547 +3

7LiF+6Th F4-7Li F-tSUF4 (ss)

Table 4 (continued)

Composition Liquidus
(molo %) Tem;;erofure Primary Phase
(°C)
UF ,~ThF ,-LiF
18-10-72 511 12 3LiF+ThF, (ss)
18-18-64 61214 7LiF+6ThF ,~TLiF-6UF  (ss)
18-20-62 634 4 LiFe2ThF  (ss)°
18-22-60 680 1 3 LiFedThF ,~LiF*4UF , (ss)
20-8-72 508 +2 3LiFsThF, (ss)°
20-20-60 637 £2 LiFedThF ,—LiF+4UF , (ss)
20-40-40 862 3 LiF+4ThF ,~LiF+4UF , (ss)
20-45-35 892 +2 UF ,~ThF , (ss)
20-60-20 1011 £3 UF ,~ThF , (ss)
21.5-21.5.57 736 12 LiFed4 ThF ,~LiF+4UF , (ss)
35-5-60 630 £ 3 LiFs4UF ,~LiF*d4ThF , (ss)
35-11.2-53.8 72913 LiF*4UF ,~LiF+4ThF  (ss)
35-15.50 780 + 3 LiFedUF ,~LiF4ThF, (ss)
39.4.57 625 £2 LiF+4UF ,~LiF+-4ThF  (ss)
40-6.2-53.8 717 £3 LiFedUF ~LiF+4ThF  (ss)
40-10.50 76714 LiFedUF ,~LiF*4ThF, (ss)
40-20-40 82914 LiF*4UF ,~LiF+d4ThF , (ss)
40-40-20 972+ 3 UF ,-ThF, (ss)
50-10-40 808 * 3 LiFe4UF ,~LiF+4ThF , (ss)
50-30-20 968 * 4 UF ,~ThF , (ss)
60-20-20 960 1 2 UF 4~ThF, (ss)
70-10-20 963 +3 UF ,~ThF,, (ss)

%The uncertainty in temperatures in this table indicates the temperature differences between the quenched

samples.

bSolid solution,

“Most of the phases were identified by optical microscopy; in addition, this phase was identified by x-ray dif-

fraction.

these invariant points are the following:
The peritectic at 609°C -
LiF-4UF4-LiF-4ThF4 (ss) + liquid ==
7LiF.6 ThF ,~7LiF6UF , (ss) + LiF:2ThF , (ss)
The peritectic at 500°C
3LiF-ThF, (ss) + liquid ==
7LiF.6UF ,~7LiF«6ThF, (ss) + LiF

The eutectic at 488°C
Liquid = LiF + 3LiF-ThF4 (ss) +
+ 7LiF-6UF4--7LiF-6ThF4 (ss)

The equilibrium phase diagram in Fig. 1 is
based on the thermal analysis data shown in
Table 3 and the results of quenching studies
shown in Table 4 and in the appendix. The re-
sults of quenching experiments, excluding liquidus

17
temperature and compositions, which aid in
locating the invariant points and in describing
the invariant reactions are shown in Table 5.
The peritectic or eutectic nature of the invariant
reactions is further confirmed by the construction
of compatibility triangles and observing the
position of these triangles relative to their
invariant points.

Because this system contains several series of
extensive ternary solid solutions, it cannot be
completely described without knowledge of the
composition of the crystalline phase or phases at
equilibrium at any temperature and composition.
(The phrase ‘‘ternary solid solution’’ as used in
this report implies that the solid solution compo-
sition lies within the system LiF-UF,.-ThF .

Table 5. Invariant-Point Data? for the System LiF-ThF ,-UF,

Quench
Composition Temperature?
(mole %) ':OC) Phases® Above Temperature Phases® Below Temperature
Tl'nF4 UF4
6 22 495 2 Liquid + LiF Liquid+LiF+7LiF-6UF4—
7LiF°6ThF4 (ss)
492 2 Liquid + LiF + 7LiF-6UF ,~ LiF? + 7LiF-6U|':4-7LiF°6T|'|F4 (ss)d
7LiF~6ThF4 (ss)
8 20 502 £ 2 Liquid + 3LiF°ThF4 (ss)d Liquid + 3LiF-T|'|F4 (ss)+ 7LiF-6UF4-
7LiF°6'|'|'|F4 (ss)
498 +2 Liquid-i-:?oLiFoThF4 (ss)+7LiF-6UF4— LiF +3LiFoThF4 (ss)+7LiF°6UF4—
7LiF°6ThF4 (ss) 7LiF+-6ThF , (ss)
10 18 502 +2 Liquid + 3LiF'ThF4 (ss) LiF + 3LiF-ThF4 (ss) + 7LiF-6UF ,~
7LiF-6'|'|'|F4 (ss)
489 +2 Liquid + 3LiF+ThF , (ss) + 7LiF+6UF ,~ LiF+3LiF-ThF4 (ss) + 7LiF+6UF ,—
7LiF-6ThF4 (ss) 7LiF-6ThF , (ss)
1 16 510 £2 Liquid + 3LiF:ThF (ss) Liquid+3LiF-ThF4 (ss) + 7LiF-6UF ,—
7LiF-6ThF4 (ss)
506 +2 Liquid + 3LiF-ThF, (ss)+7LiF-6UF4- Liquid -*-3LiF-ThF4 (ss) + 7LiF+6UF ,~
7LiF-6T|'|F4 (ss) 7LiF-6ThF, (ss) + LiF [inclusions in
3LiF-ThF , (ss)]
496 +3 Liquid + 3LiF-T|'1F4 (ss) + 7LiF-6UF4— Liquid + fBLiF-ThF4 (ss) + 7LiF-6UF4—
TLiF-6ThF, (ss) + LiF [inclusions in TLiF«6ThF  (ss) + LiF
3LiF-ThF, (ss)]
492 +2 Liquid + 3Lii"'-T|-|F4 (ss) + 7LiF-6UF ,— 3LiF°ThF4 (ss) + 7LiF+6UF ,—
7LiF-6ThF4 (ss) + LiF 7LiF°6ThF4 (ss) + LiF
11 17 501 3 Liquid + 7LiF-6UF4-7LiF°6ThF4 (ss)+ Liquid + 7LiF-6Ul"'4—7LiF~6ThF4 (ss) +
3Lil=-Thi"'4 (ss) 3LiF°ThF4 (ss) + LiF
497 13 Liquid + 7LiF-6UF4—7LiF-6ThF4 (ss) + 7Lil'-'°6UF4-7LiF°6ThF4 (ss) +
3LiF-ThF4 (ss) + LiF 3LiF'ThF4 (ss) + LiF
12 15 511 3 Liquid + 3LiF-'l'hF4 (ss) Liquid + 7LiF-6UF4—7LiF-6ThF4 (ss) +
3LiF~ThF4 (ss)
502 £3 Liquid + 7LiF-6U F“—7LiF-6ThF4 (ss) + 7LiF°6UF4—7Li|':-6ThF4 (ss) +

18

3LiF-ThF , (ss)

3LiF"|'|1F4 {(ss) + LiF
;;

1%

Table 5 (continued)

Quench
Composition T b
emperature Phases® Above Temperature Phases® Below Temperature
(mole %) ©Q)
ThF, UF,
12 16 523 £2 Liquid + 7LiF°6UF4--7LiF-6ThF4 (ss) Liquid + 7LiF-6UF ,~7LiF+-6ThF , (ss) +

LiF-ThF, (ss)

504 £3 Liquid + JLiF+-6UF ,~7LiF-6ThF , (ss) + JLiF-6UF ,~7LiF-6ThF , (ss) + LiF

3LiF-ThF,, (ss)
1 26.5 490 £ 3
7Li F'6ThF4 {ss)

12 487 £2
TLiF-6ThF 4 (ss)

1 27.5 485 +3
(ss)
1 28 490 £ 3

485+3  TLiF+6UF ,~TLiF-6ThF , (ss) +
ALiF-UF , + LiF(?) + liquid(?)

Liquid + LiF+4UF ,~LiF+-4ThF , (ss)?
615 + 4 Liquid + LiF-2ThF  (ss)?
Liquid + LiF-4UF ,~LiF-4ThF, (ss)?

24 18 640 +3

22 20 615 14

Liquid + 4LiF-UF, + 7LiF-6UF4_
Liquid + 4l.iF~UF4 + 7LiF.6UF4_
4LiF-UF , + 7LiF-6UF4-7LiF-6ThF4

Liquid + 7LiF.6U F4'—-7LiF~6ThF4 (ss)

4LiF-UF4 + 7LiF~6UF4—7LiF'6ThF4
(ss) + LiF

4LiF-UF4 + 7LiF-6UF4--7LiF'6ThF4
(ss) + LiF

4LiF',UF4 + 7LiF°6UF4—7Li F-6ThF4
(ss) + LiF

4LiF-UF , + 7LiF-6UF4-7LiF'6ThF4
(ss) + LiF(?) + liquid(?)

7LiF-6UF4«7LiF-6ThF4 (ss) +
4LiF.UF, + LiF

Liquid + LiF-2ThF, (ss)?
Liquid + 7LiF+6UF (~7LiF-6ThF , (ss)?
Liquid + 7LiF-6UF ;~7LiF+6ThF , (ss)?

2For liquidus data near invariant points see Table 4.

bThe uncertainty in temperatures indicates the temperature differences between the quenched samples.

©Only phases found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples for which the observed

phase is indicated as *‘liquid."”’

dMost of the phases were identified by optical microscopy. In addition, this phase was identified by x-ray dif-

fraction.

Each of the solid solutions in this system, how-
ever, may be formed from mixtures of two end
members and in this sense form a binary series.)
In general, in any series of complete solid
solution the physical properties (e.g., density,
optical properties, x-ray diffraction patterns, etc.)
of the individual members show a continuous
change between those of the end members. Hence
a determination of refractive indices of a number
of samples of known compositions in the solid
solution series provides a method of establishing
in the ternary system tie lines between the compo-
sition of crystals in this solid solution series

with the liquid with which it is in equilibrium.
In the case of the system LiF-ThF,-UF, the
determination of refractive indices of the members
of each of the four ternary solid solution series
present provides a particularly good method of
establishing tie lines, because the refractive
indices of the end members of each series are so
different that a good degree of precision can be
obtained.

Once the tie lines are established for a primary-
phase areaq, the fractionation paths may be drawn.
Fractionation paths in four of the primary-phase
areas of system LiF-UF,-ThF, are shown in

19
Fig. 7. The compounds LiF and 4LiF.UF, do not
form solid solutions. Consequently, the tie
lines, equilibrium paths, and fractionation paths
for their primary-phase areas can be drawn
directly from Fig. 1, and the case is trivial. The
fractionation paths for the UF 4~ ThF  (ss) primary-
phase area cannot be drawn from Fig. 1. From
Fig. 6 it can be seen that the indices of
refraction for UF ,-ThF , (ss) do not always change
rapidly enough with respect to composition to
allow a high degree of precision in tie-line de-
terminations. Consequently, no attempt was made
to determine the fractionation paths in this
primary-phase area.

ThF,

LiF- 4ThF,

LiF-2ThF,

=4

7LiF-6ThFq
P

g

THE 20 MOLE % LiF JOIN AND THE
LIF°4UF4-LIF°4TI1F4 (ss)
FRACTIONATION PATHS

A diagram of the 20 mole % LiF join is shown in
Fig. 8 and is based on the thermal analysis data
in Table 3 and the results of quenching studies in
Tables 4, 6, and 7. The join contains the
LiF04U|:4--L|'F-4ThF4 (ss) series, whose members
are green, are biaxial negative, and have optic
angles of approximately 10° The indices of
refraction of these solid solutions shown in
Fig. 9 and Table 8 vary almest linearly with UF,
concentration,

UNCLASSIFIED
ORNL-LR-DWG 35505R

LiF

3 AV UF,

VRV % = NV VIRLVIIRY.

7LiF-6UFR, P LiF - QUF,

Flg. 7. Fractionation Paths.

20

— e — e -

UNCLASSIFIED
ORNL-LR-DWG 27915AR

o THERMAL BREAKS | | |
© QUENCH DATA SEPARATING REGIONS (a@)(4}(c) AND (d)
1100 | THE SYMBOLS BELOW INDICATE CHANGES WITH
DECREASING TEMPERATURE
o (a) TO {5)
© (5 TO (o)
e (c) TO (0}
e (8) TO (&) (@)
-
1000 L\?\ )
T ———
\J\J»\:i
g '\JN} 4
w I3
3 ()
g LIQUID + UF, — ThF, ss
g, 900 T
=
o ~ I|.|ouu)+ UFy~ThF, ss +LiF-4UF, —=LiF -4 ThF, 55
\t‘\i!\: &
Z) I3 “
800 - ——
{d) E e,
Lif - 4UF, —LiF - 4ThF, ss
700
) 10 20 30 40 50 60 70 80
UF, (mole %)
Fig. 8. The Join LiF-4UF4-LiF'4ThF4.
UNCLASSIFIED
ORNL-LR-DWG 27916R
.62
1.60
g
£ 158 =
a” y INDEX OF L~
o REFRACTION\S/‘// )/fl
= 1.56 ' ;
° o~ INDEX OF
i REFRACTION
o ,54l e
z V/
1.2
1,50
(o] 10 20 30 40 50 €0 70 80
UF, (mole %)
Fig. 9. Indices of Refraction vs Composition for

LiF-4UF4—LiF-4TI-|F'4 (ss).

The fractionation paths for the LiF-4UF,-
LiF-4ThF, (ss) primary-phase area shown in
Fig. 7 are based on the tie-line data in Table 7.
They tend to parallel the system LiF-ThF, over
most of the LiF.4UF ,~LiF.4ThF, (ss) primary-
phase area, and they change from this pattern
only at the higher UF , concentrations.

THE 33)% MOLE % LiF JOIN AND THE
LiF-2Th(U)F, (ss) FRACTIONATION PATHS

A diagram of the 33, mole % LiF join is shown
in Fig. 10 and is based on the thermal analysis
data in Table 3 and the results of quenching
studies in Tables 4, 9, and 10. The join contains
the LiF.2Th(U)F , (ss) series, whose members are
green and are uniaxial negative. The indices of
refraction of these solid solutions shown in Fig. 11
and Table 11 vary linearly with UF, concen-
tration. The maximum extent of LiF2Th(U)F
(ss) at the solidus is 23 mole % UF4.

The fractionation paths for LiFoZTh(U)F4 (ss)
primary-phase area shown in Fig. 7 are based on
the tie-line data in Table 10. The fractionation
paths tend to parallel the system LiF-ThF, over
the entire primary-phase area.

THE 53.8 MOLE % LiF JOIN AND THE
TLiF<6UF4~7LiF-6ThF , (ss)
FRACTIONATION PATHS

A diagram of the 53.8 mole % LiF join is shown
in Fig. 12 and is based on thermal analysis data
in Table 3 and the results of quenching studies in
Tables 4, 12, and 13. The join contains the
7LiF-6UF4-7LiF-6ThF4 (ss) series, whose
members are green and are uniaxial. Their indices
of refraction, shown in Fig. 13 and Table 14,
vary linearly with UF, concentration.  There
should be one composition which is practically
isotropic, since the ordinary and extraordinary
indices of refraction cross. Actually there is
a range of compositions in the midportion of the
series which have a birefringence too low to be
observed. . :

The fractionation paths for the 7LiF-6ThF4-
7LiF~6UF4 primary-phase area shown in Fig. 7
are based on the tie-line data in Table 13. They
parallel the system LiF-ThF, over most of the
7LiF-6UF4-—7LiF-6ThF4 primary-phase area and
change from this pattern only at the higher UF4
concentrations.

THE 75 MOLE % LIiF JOIN AND THE
3LiIF<ThF, (ss) FRACTIONATION PATHS

A diagram of the 75 mole % LiF join is shown
in Fig. 14 and is based on the thermal analysis
data in Table 3 and the results of quenching

21
Table 6. Thermal-Gradient Quenching Data for 20 Mole % LiF Join®

UF b
4 Content Temp:rature Phases® Above Temperature Phases® Below Temperature
(mole %) o)
20 849 £3  Liquid+ UF 2 ThF (ss)? Liquid + LiFs4UF ,—LiFe4ThF  (ss)? +
UF ;- ThF,, (ss)?
30 827 + 3 Liquid + UF 2 ThF  (ss) Liquid + LiF+dUF ,~LiFe4ThF , (ss) +
UF ,-ThF  (ss)
816 £ 6 Liquid + UF - ThF  (ss) + LiF+dUF ;~LiFedThF (ss)
LiFe4UF ,~LiFs4ThF , (ss)
40 830 + 3 Liquid + UF - ThF , (ss) Liguid + LiFsdUF ~LiFe4ThF (ss) +
UF - ThF, (ss)
820 3 Liquid+LiF04UF4--LiFo4ThF4 (ss) + LiF'4UF4—LiF'4ThF4 (ss)
UF - ThF , (ss)
809 £ 5 Liquid + UF“-ThF4 (ss) Liquid + UF4-TI1F4 (ss) +
LiFedUF ,~LiFs4ThF, (ss)
800+5  Liquid + UF~ThF, (ss)? + LiFe4UF (—LiFe4ThF, (ss)?
LiF+dUF —LiFe4ThF, (ss)?
50 800 * 4 Liquid + UF 2 ThF (ss)? Liquid + UF ;- ThF, (ss) +
LiFedUF ,~LiF+4ThF , (ss)
60 811 + 4 Liquid + UF - ThF  (ss) Liquid + UF - ThF  (ss) +
LiFidUF ,~LiFedThF, (ss)
805 + 4 Liquid + UF ;- ThF , (ss) + LiFs4UF ,—LiF*4ThF (ss)?
LiFedUF (~LiFe4ThF , (ss)
70 782 + 2

Liquid + UF4-ThF4 (ss)

LiFs4UF ,—LiF+dThF , (ss)

%See Table 4 for liquidus values.

bThe uncertainty in temperatures in this table indicates the temperature differences between the quenched

samples.

COnly phases found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples for which the observed

phase is indicated as *‘liquid.”

dMosf of the phases were identified by optical microscopy; this phase was also identified by x-ray diffraction.

22

v
Table 7. Tie-Line Data for L|F°4UF4—L|F°4T|\F4 (ss) Primary-Phase Area

Quench
Composition Temperature Index of Solid Solution
(mole %) Range Refraction, Composition
- (°C) N (mole % UF4)
UF, ThF, 4
5 61% 729-801 1.541 5
10 36.2 695-765 1.548 13
10 50 753-879 1.544 8
10 56% 708801 1.546 10
13 30 690-700 1.550 15.5
15 28 683-700 1.550 15.5
15 51% 670—735 1.548 13
16.2 30 648—651 1.556 24.5
646-763 1.554 21.5
17 26 663—700 1.552 18.5
18 24 643-658 1.554 21.5
20 20 635 1.558 28
20 22 619-658 1.556 24.5
20 40 860 1.548 13
741 1.552 18
20 45 877 1.550 15.5
734 1.554 20
20 46% 635-735 1,552 18
21.5 21.5 613-736 1.559 29
23.1 23.1 614 1.562 34
620—641 1.562 34
646 1.560 31
686-742 1.558 28
621-661 1.560 31
25 15 708 1.564 38
656 1.566 41
613 1.568 44
651 1.564 38
618 1.566 41
617-635 1.564 38
25 25 804 1.558 28
693 1.560 31
28 10 613 1.568 44
28 18.2 707 1.562 34
700 1.562 34
610 1.565 40
30 10 613-629 1.570 47
30 30 843 1.552 18
31.2 15 611-641 1,569 45.5
678 1.569 45.5
734 1.565 40
607 1.571 48
33 10 607684 1.574 53
Table 7 (continued)

Quench
Composition Temperature Index of Solid Solution
(mole %) Range Refraction, Composition
UF, e (°C) N, (mole % UF ;)
4
33 13.2 720 1.574 53
610 1.572 50
33l sk 792860 1.560 31
35 5 623-629 1.582 63
612-623 1.582 63
35 11.2 726 1.574 53
610 1.576 55
35 15 763-777 1.568 44
756 1.570 47
693-731 1.572 50
36.2 10 641 1.575 54
608 1.578 58
626-674 1.578 58
39 4 614-623 1.590 71
40 6.2 714 1.580 60
610 1.584 65
40 10 731 1.576 55
693 1.579 59
40 20 846 1.568 44
741 1.570 47
45 20 855 1.572 50
734 1.574 53
50 10 781-805 1.578 58

24

Table 8. Refractive Indices for
LIF-‘4UF4-LIF-4T|'0F4 (ss)

UF4 Content Refractive Indices

(mole %) Na. N'y
20 1.544 1.553
30 1.550 1.560
40 1.554 1.565
50 1.560 1.574
60 1.567 1.580
70 1.574 1.590

1

¢

TEMPERATURE (°C)

1100

1000

900

800

700

600

500

(@)
(b)
(c)
(d)
(e)
(F)
(g)
(h)

UNCLASSIFIED

ORNL-LR-DWG 35506R

UF4 — ThFs ss + LIQUID

LiF - 4UF, = LiF - 4ThF, + LIQUID

UF,—=ThF, ss + LIQUID + LiF - 4UF, = LiF - 4ThF, ss

LiF - 2ThF, ss + LIQUID + LiF- 4UF, — LiF - 4ThF, ss

LiF - 4UF, —LiF- 4ThF, ss + LIQUID + 7LiF- 6 UF, — 7LiF- 6ThF,; ss

LiF- 2ThF, ss

LiF- QUF,— LiF - 4ThFs ss + 7 LiF- 6 UF4— 7LiF - 6ThFs ss

LiF - 4UF, —LiF-4ThF, ss + 7LiF - 6UF, = 7LiF - 6 ThF, ss +LiF - 2ThF, ss

|

A THERMAL BREAKS
® QUENCH RESULTS
O TIE LINE INTERSECTION

(d) . S @)
LIQUID (6) |

\ —
A
‘ \
\%
(b)
] ] Y H '\
(F) \';-1/ (€)
l(/?)I
|| (9)
|
L 1
10 20 30 40 50 60 662,

UF, {mole %)

Fig. 10. The 33) Mole % LiF Section.

25
Table 9. Quench Data for LIF-ZThF4 (ss)

UF, Content Temperature® Phases Above® Phases Below? .
(mole %) (°C) Temperature Temperature
5 723 + 4 Liquid + LiF-4UF ,—LiF-4ThF, (ss)€ LiF-2ThF, (ss)© e
10 700 + 4 Liquid + LiF+4UF —LiF-4ThF, (ss)° LiF-2ThF, (ss)€
15 667 * 4 Liquid + LiF-4UF ,~LiF-4ThF, (ss)° LiF-2ThF, (ss)=¢
20 632 % 4 Liquid + LiF-4UF —LiF-4ThF, (ss)° LiF-2ThF, (ss)57

“The uncertainty in temperatures indicates the temperature differences between the quenched samples.

bOnly phoses found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples for which the observed
phase is indicated as *‘liquid.”’

®Most of the phases were identified by optical microscopy; this phase was also identified by x-ray diffraction.
4This continues down to at least 578°C.

Table 10. Tie-Line Data for LiF:2Th F4 (ss) Primary-Phase Area

Quench
Composition Temperature Index of Solid Solution
(mole %) Range Refraction, Composition .
OF ThE (°C) N, (mole % UF4)
4 4
5 29 618 1.556 5
5 31 644 1.556 5
5 33 658670 1.556 5
5 35 698 1.556 5
10 36.2 611-665 1.560 15
633-695 1.560 15
" 32 615-700 1.557 7.5
13 30 615-687 1.560 15
15 25 619-658 1.559 12.5
15 28 620678 1.561 17.5
17 28 620-657 1.560 15
18 20 616630 1.563 23
618634 1.563 23
18 22 618-624 1.564 23 )
618-630 1.564 23
18 24 619-637 1.562 20 "

26
INDEX OF REFRACTION

1.57

1.56

1.55

1.54

1.53

UNCLASSIFIED

ORNL-LR—-DWG 35507R

N,,=ORDINARY INDEX OF REFRACTION/

G

/

o —

N =EXTRAORDINARY INDEX OF REFRACTION

PROBABLE LIMIT
OF EXISTENCE

I
l
}
|
I
|
| FOR LiF- 2ThF, ss
I
I
|
|
I
I

15

UFg (mole %)

20

25

Fig. 11. Indices of Refraction vs Composition for LiF-2Th(U)F4 (ss).

Table 11. Refractive Index Data for LiF-2ThF, (ss)

UF4 Content
(mole %)

Refractive Indices

Ny N¢
5 1.554
10 1.558
15 1.561 1.554
20 1.562 1.555

30

27
TEMPERATURE (°C)

28

850

800

750

700

650

600

550

()
(&)
(¢}
()
{e)
(N

LiF - 4UF, - LiF - 4ThF4 ss + LIQUID

LiF - 2ThF, ss + Lif - 4UF, —LiF - 4ThF, ss + LIQUID
LiF - 2ThF, ss + LIQUID

LiF - 2ThF, ss + 7LIiF - 6UF, — 7LiF - 6ThF, ss + LIQUID
7LiF - 6UF, — 7LiF - 6ThF, ss + LIQUID

7LiF - 6UF,— 7LiF - 6ThF, ss

UNCLASSIFIED
ORNL-LR-DOWG 27917AR

A THERMAL BREAKS
® QUENCH RESULTS

© TIE LINE INTERSECTION

—]

W

; e I\ LIQUID
A \

N

°
\*\\\b\:|
{a) o A A

/| )
/

(2)

(&)

e

(n

10 15 20 25 30 35
UF, (mole %)

Fig. 12. The Join 7LiF-6ThF4-7LlF»60F4.

40

45 46.2

)
Table 12. Thermal-Gradient Quenching Data for the 53.8 Mole % LiF Join?

b
UF4 Content  Temperature Phases® Above Temperature Phases® Below Temperature
(mole %) °c)
10 695 +5 Liquid + LiF-4UF ,~LiF-4ThF, (ss) Liquid + LIF-2ThF, (ss)
608 t3 Liquid + LiF:2ThF, (ss) 7LiF-6UF 4=7LiF-6ThF, (ss)
16.2 646 +2 Liquid + LiF-4UF ,~LIF-4ThF, (ss)?  Liquid + LiF-2ThF  (ss)
642 + 4 Liquid + LiF-4UF ,~LiF-4ThF , (ss) Liquid + LIF-2ThF, (ss)
61213 Liquid + LIF-2ThF , (ss) 7LiF-6UF ,~7LiF-6ThF, (ss)?
611 14 Liquid + LiF-2ThF4 (ss) Liquid + LiF‘ZThF4 (ss) +
7LiF-6UF ;~7LiF-6ThF , (ss)
23.1 61213 Liquid + LiF-4UF ;~LiF-4ThF , (ss) Liquid + LiF-4UF ,~LIF-4ThF, (ss) +
7LiF-6UF ,~7LiF-6ThF (ss)
611 £3 Liquid + LiF-4UF ,~LiF-4ThF, (ss)+  7LiF-6UF ~7LiF-6ThF  (ss)
TLiF-6UF ,~7LiF-6ThF, (ss)
607 +2 Liquid + LiF-4UF ;~LiF-4ThF, (ss)+  7LiF-:6UF,~7LIF+-6ThF , (ss)
7LiF-6UF ,~7LiF-6ThF, (ss)
31.2 6113 Liquid + LiF+4UF ;~LiF-4ThF  (ss) 7LiF-6UF ,~7LiF-6ThF, (ss)
36.2 642 t 4 Liquid + LiF-tiUF“—LiF-4ThF4 (ss) Liquid + l.iF'ZTI'oF4 (ss)

9See Table 4 for liquidus values.

bThe uncertainty in temperatures indicates the temperature differences between the quenched samples.

©Only phases found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples for which the observed

phase is indicated as “‘liquid.”’

dMost of the phases were identified by optical microscopy; this phase was also identified by x-ray diffraction.

29
Table 13. Tie-Line Data for 7LiF~6UF4-7LIF-6ThF4 (ss) Primary-Phase Area

Quench
Composition Temperature Index of Solid Solution
(mole %) Range Refraction, Composition >
UF4 ThF4 (*C) N, (mole % UF4)
2 29 586-591 1.508 5.5
4 27 558-592 1.510 7
5 24 558-563 1.510 7
5 29 557-605 1.512 9
5 31 599 1.512 9
5 33 584-599 1.512 9
5 35 601 1.512 9
6 24 553 1.512 9
7 26 550607 1,510 7
10 20 546-568 1.516 12.5
10 24 576-593 1.516 12,5
10 26 597 1.515 12
12.5 17 536-562 1.524 19.5
13 30 578-610 1.518 14.5
15 17 585 1.520 16
15 25 532-606 1.519 15 .
15 28 578-610 1.520 16
16 12 525 1.524 19.5
17 12.5 521-547 1.525 20.5 .
17 26 578-610 1,522 18
18 18 554-608 1.520 16
18 20 601-612 1.522 18
554-608 1.522 18
18 22 521 1.524 19.5
607 1.522 18
608 1.522 18
18 24 532-612 1.522 18
20 20 520-620 1.526 21.5
20 22 612 1.524 19.5
532 1.526 21.5
21.5 21.5 596-607 1.526 21.5
25 15 528-609 1.532 26.5
601 1.534 28.5
510-612 1.532 26.5
26.5 2 497 1.548 41
27 2 493 1.550 42.5
28 1 497 1.550 42.5
28 10 608 1.534 28.5
544 1.536 30
30 10 609 1.536 30 ’
528 1.538 32
33 10 596-601 1.540 34 .
35 5 528-604 1.544 37.5
606 1.544 37.5
510 1.546 39
39 4 553-609 1.547 40

30
Table 14. Optical Properties for
7LiF-6UF ,~7LIF-6ThF, (ss)

Index of
UF4 Content Refraction, Birefringence
(mole %) N
w
10 1.514 0.003
16.2 1.522 Low
23.1 1.528 Very low
1.529 Very low
1.530 Very low
3]02 10538 Very low
36.2 1.540 Low
1.542 Low

UNCLASSIFIED
ORNL-LR-DWG 27918R2

1.62
» 160
S
o
Q 1.58
< -
@ N, =ORDINARY INDEX OF REFRACTION
v N, =EXTRAORDINARY INDEX OF REFRACTION\\
T 456
w -
5 P
>
W 1.54
= ’-,-/
- —-’//f’

1/
1.50 &=
] 5 10 {5 20 25 30 35 40 45

UF4 (mole o/o)

Fig. 13. Indices of Refraction vs Composition for
7|..iF-6ThF4—7LiF~6UI"'4 (ss).

studies in Tables 4, 15, and 16. The join con-
tains the 3LiF:ThF, (ss) series, whose members
are green, biaxial negative, and have optic angles
of approximately 10° The indices of refraction
of these solid solutions shown in Fig. 15 and
Table 17 vary linearly with UF, concentration.
The maximum extent of 3LiF-Th(U)F4 (ss) is
15.5 mole % UF .

The fractionation paths for 3LiF-Th(U)F4 (ss)
primary-phase area shown in Fig. 7 are based on
the tie-line data in Table 16.

RELATIONS BETWEEN THE SOLID SOLUTIONS
Compatibility Triangles

Since the composition of each of the phases in
equilibrium at each of the invariant points has
been determined, this information can be used to
construct the compatibility triangles associated
with the invariant points. Figure 16 shows these
triangles and is based on the tie-line data in
Table 18.

The position of the invariant-point compositions
relative to their compatibility triangles indicates
that the invariant points at 609, 500, and 488°C
are peritectic, peritectic, and eutectic, re-
spectively. These conclusions are in agreement
with those in the section ‘‘General Discussion of
the System LiF-UF ,-ThF, and the Limiting
Binary Systems,’’ this report.

The direction of decreasing temperature along
the boundary line between the primary-phase areas
of 7LiF-6Ul":4—7LiF-6ThF4 (ss) and LiF.4UF -
LiF-tlThF4 (ss) is difficult to determine because
the temperature variation along this boundary line
is less than 5°C. The relative directions of the
tie lines from the 609°C invariant point to the
corners of the associated compatibility triangle
(Fig. 16) indicate, however, that this boundary
temperature decreases in the direction of the
ternary invariant composition,

Subsolidus TwoePhase Regions

For a point representing a specified composition
in any two-phase subsolidus region in the system
LiF-UF -ThF ,, the tie line connecting the compo-
sitions of the two phases in equilibrium at that
point must be a straight line passing through the
point, This fact provides a method for checking
the accuracy of the refractive index curves
(Figs. 8, 11, 13, and 15) of the ternary solid
solutions, Tie-line data are given in Table 19
for the following regions:

LiF + 3LiF-Th(U)F, (ss)
LiF + 7LiF6ThF ,—7LiF-6UF , (ss)
3LiF-Th(U)F, (ss) + 7LiF-6ThF ,~7LiF -6UF, (ss)

The ends of these tie lines and the corresponding
points of nominal composition are shown (Fig. 17)
to be nearly colinear.

31
32

TEMPERATURE (°C)

575

550

525

500

475

450

(a)
(6)
(c)
{(d)
(e)
()

UNCLASSIFIED
ORNL-LR-DWG 35503R

LIQUID + 3LiF - ThF, ss

LiF + LIQUID

LiF + 3LiF - ThF, ss +LIQUID

LiF + 7LiF - 6 ThE, — 7LiF - 6UF, ss + LIQUID
4LiF-UF, + LIQUID + LiF

4LiF-UF, + LIQUID

(g) 4LiF-UR + 7LiF-6ThF, ~7LiF -6UF, ss + LIQUID
(A) 3LiF-ThF, ss
(/) 3LiF - ThF, ss + 7LiF - 6ThF, — 7LiF - 6 UF; ss + LiF
(/) LiF + 7LiF - 6 ThF,— 7LiF - 6 UF, ss
(k) LiF + 4LiF +UF, + 7LiF -6 ThF, — 7LiF - 6 UF, ss
(/) 4LiF-UF,+ 7LiF-6ThF,— 7LiF - 6 UF, ss
o
A THERMAL DATA
® QUENCH DATA
O TIE LINE DATA
LIQUID
(2)
‘-‘-.___J___—_————_?
NG
(e)
¢ @ T

(4)

() () Lo [~
/ IR
\ !\(/)

10 15 20 25
UF, (mole %)

Fig. 14. The 75 Mole % LiF Section,

(U

Table 15. Thermal-Gradient Quenching Data for the 75 Mole % LiF Join?

U F4 Content Temperofureb

(molo %) °c) Phases® Above Temperature Phases® Below Temperature
2 5544 Liquid + 3LiFsThF , (ss) 3LiFThF , (ss)
5 533 +3 Liquid + 3LiF*ThF , (ss) 3LiFThF , (ss)
460 + 29 3LiFeThF (ss)° LiFeThF ,° + 7Li F6UF ,~
7LiF6ThF, (ss)?
10 51510 Liquid + 3LiFTh F4 (ss) 3LiF°ThF4 (ss)
49315 3LiF+ThF, (ss)€ 3LiF+ThF, (ss)€ + LiF + 7LiF+6UF 4~
TLiF6ThF, (ss)
13 506 * 3 Liquid + 3LiFsThF  (ss) 3LiFeThF , (ss)
49113 3LiF*ThF, (ss)f 3LiF+ThF, (ss)® + LiF +
7LiF6UF ;~7LiF*6ThF, (ss)
15 5003 Liquid (traces) + LiF (traces) + LiF + 3LiF*Th F4 (ss)+ 7Li F'6UF4-—
3LiF6ThF, (ss)? 7LiF*6ThF  (ss)
480 +2 LiF + 3LiF-ThF , (ss)€+ 7LiF«6UF,—  LiF + 7LiFs6UF ;~7LiF*6ThF, (ss)®
TLiF6ThF, (ss)€
20 5035 Liquid + LiF Liquid + LiF + 7LiF6UF .~
7LiF*6ThF, (ss)€
491 %2 Liquid + LiF + 7LiF-6UF ,~ LiF + 7LiF*6UF ,~7LiF*6 ThF, (s5)°

7LiF<6Th F4 (ss)

4506 Table 4 for liquidus values.
The uncertainty in temperatures indicates the temperature differences between the quenched samples.

cOnly phases found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples &r which the observed
phase is indicated as *‘liquid."’

This exsolution was observed by using xeray diffraction technique only.
®Most of the phases were identified by optical microscopy; this phase was also identified by x-ray diffraction,

33
Table 16. Tie-Line Data for 3LIF-ThF, (ss) Primary-Phase Area

Quench
Composition Temperature Index of Solid Solution
(mole %) Range Refraction, Composition
UF, T, (°C) N., (mole % UF )
2 24 559 1.490 2.0
5 19 560 1.490 2
10 16 535 1.496 6.5
12 15 530 1.495 6.0
15 12 514-.525 1.500 10.0
16 1n 513 1.500 10.0
18 10 504-510 1.500 10.0
20 8 504 1.503 12.5

UNCLASSIFIED
ORNL-LR-DWG 31217R2

1.540 £
1.530 — e

|

P4
2 1.520 MAXIMUM EXTENT OF — =
o 3LiFThF,
= SOLID SOLUTION
@ :
j
W 1.510 T
4.6 L 4
g 1.500 FRQCT\O Y

\ )
w _——_-'_'—-‘"_'——-L'-f_

2
<)

UF, CONTENT {mole %)

Fig. 15. Indices of Refraction vs Composition for
3LIF°TI1F4 (ss).

Isothermal Sections

The equilibrium-phase behavior of a ternary
system involving solid solutions can be clearly
and unambiguously described only by an extensive
series of isothermal sections, An abbreviated
series of such sections for the system LiF-UF -
ThF , is presented in Figs. 18 through 21. These

34

Table 17. Refractive Indices for 3LiF-ThF, (ss)

UF4 Content Refractive Indices

(mole %) N, N'y
2 1.482 1.490
S 1.486 1.494
10 1.492 1.498
13 1.496 1.503
15 1.498 1.507

show the polyphase equilibria for all compositions
at the temperatures specified.

ACKNOWLEDGMENTS

It is a pleasure to acknowledge the assistance
of T. N. McVay, who was responsible for all the
refractive index measurements in the system
UF ,-ThF, and a portion of the petrographic phase
identification in the system LiF-UF,-ThF,. In
addition we are especially grateful to R, F.
Newton, F. F. Blankenship, and J. E. Ricci for
helpful advice concerning many phases of the
investigation.

'y

{e

1Y

[ 3

UNCLASSIFIED
ORNL-LR~-DWG 35504

ThF,

LiF - 2ThF,

7LiF - 6ThF,

~—609°C

3LiF - ThF4 (c)

LiF 4LiF - UF,, 7LIF - 6UF, LiF - 4UF, UF,

Fig. 16. Compatibility Triangles in the System LiF-UF4-ThF4.

35
Table 18. Compatibility Triangle Data

Quench

Composition

Phases Present*

Refractive Indices
of Solid Solution

Composition

(mole %) of Solid Solution
(mole % UF))

UF, ThF, Ne N., T4

27 1 7LiFo6UF4—7LiFo6ThF4 (ss) 1.550 42,5
4LiF-UF4
LiF

28 1 7Lti6UF4-—7LiF-6ThF4 (ss) 1.550 42.5
4LiF-UF4
LiF

26,5 1 7LiF-6UF4--7LiF-6ThF4 (ss) 1.550 42,5
4LiF-UF‘4
LiF

27 2 7LiF‘6Ul':4—7LiF-6TI'|F4 (ss) 1.550 42,5
4LiF-UF4
LiF

15 10 7LiFo6UF4--7Li!’-6Thl’=4 (ss)** 1.538 1.506 32
Z!Lil"'-'l'hF4 (ss)** 1.506 15
LiF

17 LA 7LiF-6UF4—7LiF~6ThF4 (ss) 1.536 30
3LiF-ThF4 (ss) 1.504 13.5
LiF

20 8 7LiF06UF4—7LiF-6ThF4 (ss)** 1.537 31
3LiF-T|'|F4 (ss)** 1.504 13.5
LiF

18 10 7LiF‘6UF4-7LiF-6ThF4 (ss) 1.536 30
3LiF-ThF4 (ss) 1.504 13.5
LiF

18 22 LiF-4UF4-LiF-4ThF4 (ss) 1.558 28
LiF-2ThF4 (ss)** 1.564 23
7LiF-6UF4-7LiF-6ThF4 (ss)** 1.524 23

*Only phases found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples for which the observed

phase is indicated as **liquid.”’

**Most of the phases were identified by optical microscopy; this phase was also identified by x-ray diffraction.

36

[
Taoble 19, Subsolidus Two-Phase Reglons

Quench . .
Com‘:’os‘:fion Refruct.we Indl.ces Composition
Phases Present* of Solid Solution of Solid Solution
{mole %)
N N (mole % UF4)
UF, ThF, Y @
4 19 LiF
:‘SLiF-ThF4 (ss)** 1.493 4
5 15 LiF
3LiF-ThF4 (ss)** 1.495 6.5
8 15 LiF
3LiF-ThF4 {ss)** 1.498 9
10 10 LiF
7LiF-6UF4,-7LiF-6ThF4 (ss)** 1.528 22
15 10 LiF
7LiF°6U|"'4—7Li|=°6T|'\|:4 (ss) 1.524 28
20 5 LiF**
7LiF.:6UF ,~7LiF-6ThF, (ss)** 1.542 36
22 6 LiF=**
7LiFo6UF4—7LiF'6ThF4 {ss)** 1.542 35.5
24 4 LiF**
7LiF°6UF4—7LiF-6ThF4 (ss)** 1.546 39.5
25 3 LiF
7LiF-6UF4—7LiF-6ThF4 (ss) 1.548 41
26.5 2 LiF
7LiF-6UF4-7LiF-6ThF4 (ss) 1,548 41
4 27 3LiFoThF4 (ss)** 1.490 2
7LiF-6UF4--7LiF-6ThF4 (ss)** 1.510 7
5 24 3LiF°ThF4 (ss) 1.492 3
7LiF-6UF4--7LiF-6ThF4 (ss) 1.512 9
5 29 3LiFoThF4 (ss) 1.490 2
7LiF-6UF4.-7LiF-6ThF4 (ss) 1.512 9
10 16 :*!LiF-ThF4 (ss) 1.498 8
7LiF-6UF4--7LiF-6Th|"'4 {(ss) 1.528 23.5
é 24 I*!LiF-ThF4 (ss) 1.494 5
7LiF-6UF4—7LiF'6ThF4 (ss) 1.514 10
10 18 3Li|="l'h|=4 (ss) 1,498 8
7LiF-6UF4—7LiF-6ThF4 (ss) 1.526 21.5
10 20 3LiF-ThF4 {ss) 1.496 6.5
7LiF'6UF4—7LiF-6ThF4 (ss) 1.522 18
12 15 3LiF-ThF4 (ss) 1.500 10
7LiF-6UF4—7LiF-6ThF4 {ss) 1.530 25
12.5 17 3LiF.ThF4 (ss) 1.496 6.5
7LiF~6UF4--7LiF-6ThF4 (ss) 1.528 23,5
17 12.5 3LiF-ThF4 (ss) 1.504 13
7LiF-6UF4—7LiF'é'l'hl"'4 {ss) 1.532 26.5

*Only phases found in major quontity are given. Minor quantities of other phases resulting from lack of complete reaction
between solids or from trace amounts of oxide impurities are not noted. Glasses or pocrly formed crystals assumed to have been
produced during rapid cooling of liquid were found in those samples for which the observed phose is indicoted as ““liquid.”’

**Most of the phases were identified by optical microscopy; this phase was also identified by x-ray diffraction.
38

UNCLASSIFIED

ORNL—LR—DWG 35740R
3

50% ThF,

7LiF-6ThF,

® PHASE COMPOSITION
A QUENCH COMPOSITION

3LiF - ThF,

-—
-—
——
e

-
-

- -

— ——

=3

——

-

— UF, 7 LiF - UF,

Fig. 17. Subsolidus Tle Lines.

1)

Q)
»

UNCLASSIFIED
ORNL—LR—DWG 35742

4
(@) CONTAINS:
1) LiF-4 ThFy— LiF-4UFfF,ss
2) LiF-2ThF,ss
3) 7LiF- 6 ThF, — 7 LiF-6UF,ss
4) LIQuUID
LiF - 4ThF4 — —)
'y
.
.
%o,
LiF -2ThE », e
q 5 . <
o <. e <
[ ] “ 9\ . v
.o ® x < .. P/\ /d\
e A ‘(} ® 'é(\ fa)l
o. 'éf\ > * P\P\G
(’,&\ LS c’“ .o <.
_‘\’ . p‘%‘ P /4}9%
N ¢ A g 7 e »
66)( Za “ 77 % %\
/c) P% ..// .. %
r 7 e
V4 o.
/7
2oy %
Y4 ¢ °
/ 7 r-} <, .
Ay ,/ // < > *
/7 e 3 ‘
/7 A= .
/ A %P\ %
/// ® S?\ . [}
/I/ "\.o P “ ..
x = .. <. © [
A A% .
LIQUID C s Tx% & s %
/ AN C'“ 4 .
Lif < o - .
N P‘p N\ 0. ‘5&‘ ..
»
° .
LIQUID < '.
Lif \/ \ \/ VALV V \V4 LV UF,
7LiF-6UF4 LiF-4UF4

Fig. 18. 609°C Isothermal Section.

39
UNCLASSIFIED
ORNL—LR—DWG 35744

TLiF +6ThFq g < (@) CONTAINS:
" s 1) 7LiF- 6UF, — 7LiF- 6 ThF,ss
° % 2) 3LiF- Thi,ss
-.’\A 3) LiF
®
°, “a 4) LIQUID
.o '0"
e
o (b) CONTAINS:
®
“ 'x 1) TLIF- 6UF, ~7LiF-6ThF, ss
% <. 2) LiF- 4UFy ~LiF-4ThF,ss
. ‘5@ 3) LiF-2 ThF,ss
e A
0. 5‘\
.. ?%
, 3LiF-ThFss + '..(b),/
SLIF-ThGy A 7LiF- 6UF, —TLiF- 6UF, ss "
o. ° (’2\
[ ‘. -
®
. % <
® .o "\
.. .. ‘?
.. ”/¢. 6‘/;
. ”’ -~ [}
LiIF + ‘. e % o
[ ] o [
3LiF- ThF, ss . P o %
. 4” // ¢
. PR ®
- (@) PR % p(,
- _ e
-~ - LIQUID + “ %
P O\ TLiF- 6UF, — o
=7 ==""  LiF+LIQUID ¢\ 7LiF-6ThFyss 2
- -
7LiF- 6UF,

Fig. 19. 500°C Isothermal Section.

«

UNCLASSIFIED
ORNL—LR—DWG 35738

ThE,
73 (o) CONTAINS:
. 1) TLiF- 6UF, — 7LiF: 6 ThF,ss
* & :
‘ AN 3) LiF
e <. 4) LIQUID
e
® 0
‘.. %) (b) CONTAINS:
<\
* ® o 1) 7LiF-6UF, —7LiF-6ThF, ss
[
. %4\ 2) LiF - 4UF, —LiF- 4 ThF, ss
[
'.. /%“ 3) LiF- 2ThF, ss
¢ v
3LiF-ThR, ss + o %
7LiF- 6UF, —7 LiF- 6ThF, ss % (5)
o 1IN
: v
3LIF -ThR, 4 ./A
. s <.
. o <
[ ]
.’. .o 6&’(\
[ ] e
;" e \
L] b -
: . o C.
LiF + ° =% =
. ™ e o — L ashas™
SLIF-ThRyss % =TT N
s~ - % %
i P *®y
// 3LiF- ThF,s55 + - o ¥
7 4 . e X
o7 TLIF-6UF, — _ - %
,7 TLiF -6 ThEF, s5 LiF + =
-’ .= e C
7T HLF T TLiF-B8UR, — 7LiF-6ThF, ss . ;\\
P - * <
- - e 1
///,/’// —————— — ::_.:_-:.—:-". ¥
//’/ ——————————— -— "'"'-.-.---- .. 6’(\
,/ —————————— - - - >
Lip &2l o= = = TN V@) e \/ \/ \/ VAP
4 Lif - UF,

Fig. 20. 488°C Isothermal Section.

41
UNCLASSIFIED
ORNL—LR—DWG 35739

ThF,
(o) CONTAINS:
1) LiF- 4UF, —LiF - 4ThF, ss
2) 7 LiF-BUF, — 7TLiF- 6 ThF, ss
3) LiF- 2 ThF,
LiF - 4 ThE, #—
FraThg A (5) CONTAINS:
<. % 1) 7LiF- 6UF, ~ 7 LiF+ 6 ThF, ss
<\ o .
‘> % 2) 3L1F‘ThF455
X %\0. 3) LiF
LiF-2Thf RN A
R N E)
o 3 % >\ (c) CONTAINS:
. [}
A S %% %G 1) 3LiF-ThF,ss
. o % 6‘\0 ] . 4
A ‘(\ /\.. > .. d:p 2) LlF
C ok S e X
ST % 7% 23
= @A?\m .o /,// .° .
7 LiF -6ThE, X / 2
9 Py ’;“ 0// / .. 64\
o.. I /(a)// x (o. )?\
/ A °
.. / // <. “ .. (’K\
" 7 DA =,
/
3LiF- ThF, ss® ‘1, % %
_ 4% e ’, =\ e P
+7LiF-6UFR=% 4 VS o
3LIF-ThE ¢ 7LIF-6ThFgss _:./’ C ol
.o _________ Pl ) C} .o
{cypr L ° ‘5’/\ < ®
/ ’ .. ‘5Pd‘ ¢
)y -7 . 7%
// /// .. '{‘p .O
7/ i L .
/ P LiF + i *
Y -7 TLiF-6UF, —7LiF-6ThFss ¢ .
e ° .
/7 7 0. [
-~ ®
LiF &~ AV vV \V, VARV V V */ \Y/ UF,
7 LiF - BUF, LiF -4UF,

42

Fig. 21. 450°C Isothermal Section.

»

[

Appendix

MISCELLANEOUS THERMAL-GRADIENT QUENCHING RESULTS FOR THE SYSTEM LiF-UF-ThF,

Composition

7LiF-6T|1F4 (ss)

Temperature?
(mole %) ©c) Phases® Above Temperature Phases® Below Temperature
UF, ThF4
2 24 522 + 4 Liquid + 3LiF- ThF4 (ss) Liquid + 3LiF-ThF4 (ss) + 7LiF°6UF4—
7LiF'6ThF4 (ss)
2 29 563 £3 Liquid + 7LiF'6UF4—7LiF*6T|‘|F4 (ss) Liquid + 7LiF-6UF4-—7LiF°6ThF4 (ss) +
3LiF-Th|"'4 (ss)
3 19 561 3 Liquid + LiF Liquid + LiF + 3LiF-T|'|F4 (ss)
4 19 53217 Liquid + LiF + 3LiF°ThF4 (ss) LiF + 7LiF°6UF4—7Li|':-6ThF4 (ss)¢
4 27 555 4 Liquid + 7LiF-¢$UF4—7LiF°6ThF4 (ss) LiF + 3LiF~ThF4 (ss) + 7LiF°6UF4-
7LiF-6'|'h|"'4 (ss)
548 +4 Liquid + 7Lil=-6UF=4—7LiF-6T|'|F4 (ss) + 7LiF~6UF4-7LiF-6ThF4 (ss) +
3LiF°T|1F4 (ss) 3LiF'ThF4 (ss)
5 15 556 4 Liquid + LiF Liquid+LiF+3LiF-ThF4 (ss)
540 £3 Lic;uid+LiF+3LiF°ThF4 (ss) LiF+3LiF°ThF4 (ss)€
462 +3 LiF + 3LiF'T|'\F4 (ss) LiF + 3LiF°ThF4 (ss) + 7LiF°6UF4-
7LiF°6ThF4 (ss)
5 19 558 +2 Liquid + 3LiF-ThF4 (ss) Liquid + 3LiF-ThF4 (ss) + LiF
5 24 555 +3 Liquid + 7LiF°6UF4--7LiF-6ThF4 (ss) Liquid + 3LiF-ThF4 (ss) + 7LiF°6UF4—
7LiF-6ThF4 (ss)
549 +3 Liquid + 3LiF-T|'|F4 (ss) + 7LiF-6UF4- 7LiF'6UF4-7LiF-6ThF4 (ss) +
7Li|='6ThF4 {ss) 3LiF°T|1F4 (ss)
5 26 558 +2 Liquid + 7LiF°6UF4—7LiF~6ThF4 (ss) Liquid + 3LiF°ThF4 (ss) + 7LiF'6UF4-
7LiF-6ThF4 (ss)
546 +2 Liquid + 7LiF'6UF4--7LiF-6ThF4 (ss) + 7LiF-6UF4—7LiF'6ThF4 (ss) +
3Lif"'-ThF4 (ss) 3LiF-'I'|'|F4 (ss)
5 29 615 t3 Liquid + LiF°2ThF4 (ss) Liquid + LiF'2ThF4 (ss) + 7LiF+-6UF ,—
7LiF-6ThF4 (ss)
605 +3 Liquid + LiF-2ThF4 (ss) + 7LiF+6UF ,— Liquid + 7LiF'6UF4--7LiF-6ThF4 (ss)
7LiF-6ThF4 (ss)
557 £3 Liquid + 7LiF°6UF4-—7LiF-6ThF4 (ss) Liquid + 7Li|"'°6UF4—7LiF-6ThF4 (ss) +
3Li|"'°'|'hF4 (ss)
547 £ 3 Liquid + 7LiF-6U F4-7LiF-6ThF4 (ss) + 7LiF°6UF4—7LiF-6ThF4 (ss) +
3LiF-ThF4 (ss) 3LiF-ThF4 (ss)
5 31 609 4 Liquid + LiF'2ThI'-'4 (ss) Liquid + LiF+2ThF , (ss) + 7LiF-6UF4-
7LiF'6ThF4 (ss)
602 +3 Liquid + LiF'ZThF4 (ss) + 7LiF+6UF ,— Liquid + 7LiF«6U F4—7Lil'-'-6'|'hF4 (ss)

43
Appendix (continued)

Composition

Temperature®
(mole %) (°C) Phasesb Above Temperature Phasesb Below Temperature
UF, ThF4
5 33 605 £3 Liquid + LiF+2ThF ; (ss) Liquid + LiF-2ThF4 (ss) + 7LiF'6UF4-—
7Lil""6Tl'||"'4 (ss)
599 +3 Liquid + LiF-2ThF4 (ss) + 7LiF°6UF4— Liquid + 7LiF-6UF4--7LiF-6ThF4 (ss)
7Li|:°6'|'h!'-'4 (ss)
S 35 605 +4 Liquid + LiF-IZThF4 {ss) Liquid + 7LiF'6UF4—7LiF°6'|'hF4 (ss)
6 24 551 £3 Liquid + 7LiF-6UF4—7LiF-6ThF4 (ss) Liquid + 3LiF:ThF , (ss) + 7LiF-6U F4—
7LiF°6ThF4 (ss)
541 3 Liquid+3LiF-ThF4 (ss) + 7LiF+6UF ,~ 3LiF-ThF4 (ss) + 7LiF-6UF -
7LiF-6ThF4 (ss) 7LiF-6ThF4 (ss)
7 26 547 3 Liquid + 7LiF-6UF4-7LiF°6ThF4 (ss) Liquid + 3LiF'ThF4 (ss) + 7LiF-6UF4-
7LiF'6ThF4 (ss)
8 15 517 £3 Liquid-i-LiF=1-3Li|:~'l'hl'-'4 (ss) LiF+3LiF-ThF4 (ss)
480 2 LiF + 3LiF-ThF4 (ss)€ LiF + 3LiF-ThF4 (ss) + 7LiF+6UF ,~—
7LiF-6ThF4 (ss)
10 10 528 =3 LiF + liquid Liquid-&-Li[""+3Li|"'-'l'hF4 (ss)
488 +3 Liquid + LiF +3LiF-ThF4 (ss) 7LiF°6UF4---7LiF-6T|'\F4 (ss)€ + LiFS +
3LiF-'|'|'\F4 (ss)©
464 £3 LiF€ + 3LiF-ThF, (ss) + 7LiF+-6UF ,—  LiF€ + 7LiF-6UF ,~7LiF-6ThF  (ss)®
7LiF~6T|'|F4 (ss)€
10 16 533 2 Liquid + 3LiF-T|'|F4 (ss) Liquid + ?»LiF-ThF4 (ss) + 7LiF°6UF4—-
7LiF-6ThF4 (ss)
10 18 5132 Liquid + 3LiF-ThF , (ss) + 7LiF-6UF4— 7LiF'6UF4—7LiF-6ThF4 (ss) +
7LiF-6ThF4 (ss) 3LiF-ThF4 (ss)
10 20 543 +3 Liquid + 7LiF'6UF4—7LiF‘6ThF4 (ss) Liquid + 3LiF°ThF4 (ss) + 7LiF-6UF ,~
7|..iF°6ThF4 (ss)
538 £ 2 Liquid + 7LiF°6UF4—7LiF-6ThF4 (ss) + 7LiF°6UF4—7LiF~6ThF4 (ss) +
f.*lLiF-ThF4 (ss) 3LiF-ThF4 (ss)
10 70 889 4 Liquid + UI""‘—ThF4 (ss) LiF°4UF4—LiF'4ThF4 (ss)
11 32 612 3 Liquid + LiF'2T|'\F4 (ss)® Liquid+LiF°2ThF4 (ss)c+7LiF-6UF4—
7LiF°6ThF’4 (ss)®
607 £3 Liquid + LiF°2ThF4 (ss) + 7LiF+-6UF ,~ Liquid + 7LiF-6UF4—7LiF'6ThF4 (ss)
7LiF‘6ThF4 (ss)
12 15 525 2 Liquid + 3Li|:"°'|'|'\|:4 {ss) Liquid + 3LiF°ThF4 {ss) + 7LiF°6UF4-
7LiF-6ThF4 (ss)
505 £2 Liquid + 7Li|=°6UF4-7LiF-6T|1F4 (ss) + 7LiF-6UF4-7LiF-6ThF4 (ss) +
3LiF-ThF , (ss) 3LiF-ThF , (ss)
12.5 17 532 +4 Liquid + 7LiF'6UF4-7LiF-6ThF4 (ss) Liquid + 3LiF-ThF, (ss) + 7LiF-6UF ,-

44

7LiF~6'|'hF4 (ss)

(13
Appendix (continued)

Composition

Temperature?
(mole %) (°C) Phases? Above Temperature Phases? Below Temperature
UF4 ThF,
12.5 17 514 3 Liquid + 7LiF<6U F4-7LiF~6ThF4 (ss) + 7Lii:-6UF4-7LiF'6T|'|F4 (ss) +
3LiF-ThF4 (ss) 3LiF-ThF4 (ss)
13 30 688 +2 Liquid + LiF-4UF ,~LiF-4ThF (ss)€ Liquid + LiF-2ThF (ss)©
612 £3 Liquid + LiF'2ThF4 (ss)€ Liquid + 7LiF-6UF4—-7LiF-6ThF4 (ss)€
15 12 511 £3 Liquid-}-3LiF'ThF4 (ss) Liquid+3LiF°ThF4 (ss)+7LiF~6UF4—
7LiF-6ThF4 (ss)
15 25 612 4 Liquid + Lil:-2ThF4 (ss) Liquid + 7LiF°6UF4—7LiF-6ThF4 (ss)
529 +4 Liquid + 7LiF-6UF4—7LiF-6ThF4 (ss) Liquid + 3LiF-T|'\F4 (ss) + 7LiF°6UF4—
7LiF-6ThF4 (ss)
15 28 680 +3 Liquid + LiF°4UF4—LiF-4ThF4 (ss) Liquid + LiF-2ThF4 (ss)
617 £3 Liquid + LiF-2ThF4 (ss) Liquid + LiF~2ThF4 (ss) + 7LiF'6UF4—
7Lil"'~6ThF4 (ss)
612 +3 Liquid + LiF-2ThF4 (ss) + 7LiF-6UF4- Liquid + 7LiF°6UF4—7Lil"'-6'l'hl=4 (ss)€
7LiF-6ThF4 (ss)
16 11 510 £2 Liquid + 3LiF-ThF , (ss) Liquid + 3Lil"'°"|"hF4 (ss) + 7LiF'6UF4—
7LiF-6ThF4 (ss)
501 t8 Liquid + 3Lil".ThF4 (ss) + 7LiF°6UF4— Liquid + 3LiF-T|'|F‘1 (ss) + 7LiF°6UF4—
7LiF°6'l'hF4 (ss) 7LiF-6ThF4 (ss) + LiF
492 +2 Liquid + 3LiF"ThF4 (ss) + JLiF-6UF ,— 3LiF-ThF4 (ss) + 7LiF-6UF ;-
7LiF°t€"|"hF'4 (ss) + LiF 7LiF°6ThF4 (ss) + LiF
16 12 523 £2 Liquid + 7LiF°6UF4-7LiF°6ThF4 (ss) Liquid + 3LiF°ThF4 (ss) + 7LiF'6UF4—
7LiF°6ThF4 (ss)
17 11 499 5 Liquid-i-7LiF~6UF4—7LiF-6ThF4 (ss)+ LiF +3Lil='T|'||':4 (ss)+7LiF-6UF4—
3LiF"l'hF4 (ss) 7LiF°6ThF4 (ss)
17 12.5 519 3 Liquid + 7Lii"'-6UF4—7LiF°6ThF4 (ss) Liquid + :?«LiF-ThF4 (ss) + 7LiF°6UF4-—
7LiF’6ThF4 (ss)
507 +3 Liquid + 7LiF-6UF4-7LiF°6ThF4 (ss) + 7LiF-6U|"'4—7Lil'-'-6'|'hF4 (ss) +
3Li|:-ThF4 (ss) 3LiF-ThF4 (ss)
490 +3 7LiF-6U F4—7LiF-6ThF4 (ss) + 3LiF+ThF, (ss) + 7LiF-6UF ,~
3LiF-ThF‘1 (ss) 7LiF°6ThF4 (ss) + LiF
17 26 660 £3 Liquid + Lil'=-4UF4—LiF-4T|1F4 (ss) Liquid + LiF'2'l'hF4 (ss)€
617 =3 Liquid + LiF:2ThF, (ss) Liquid + LiF°2ThI'-"4 (ss)€ +
TLiF+6UF ,~7LiF-6ThF  (ss)°
612 4 Liquid + LiF'2ThF4 (ss) + Liquid + 7LiF-6UF4--7LiF-6ThF4 (ss)
7LiF'6U|"'4—7LiF°6ThF4 (ss)¢
18 10 502 2 Liquid + 3LiF:ThF , (ss) Liquid + 3LiF°ThF4 (ss) + 7LiF°6UF4-

7LiF'6ThF4 (ss)€

45
Appendix (continued)

Composition

Temperature?
(mole %) (°C) Phases? Above Temperature Phases? Below Temperature
UF4 ThF4
18 10 489 2 Liquid + 3LiF'-ThF4 (ss) + 7LiF°6UF4— 7LiF-6UF4-7LiF-6ThF4 (ss) +
7LiF-6T|'1F4 (ss) 3LiF-TI1F4 (ss) + LiF
18 20 637 13 Liquid + LiF-4UF4—LiF-4ThF4 (ss)€ Liquid + LiF-2ThF‘1 (ss)
615 +4 Liquid + LiF-2ThF4 (ss)® Liquid + 7LiF~6U|:4~-7LiF-6ThF4 (ss)
612 4 Liquid + LiF-2ThF4 (ss) Liquid + 7LiF-6UF4—7LiF-6ThF4 (ss)
18 22 634 4 Liquid + LiF°4U|':4-LiF-llThF4 (ss) Liquid + Lil"'-2T|'|l'-'4 (ss)
626 £3 Liquid + LiF-4UF4-LiF°4ThF4 (ss) Liquid + LiF-2ThF"4 (ss)©
612 £3 Liquid + LiF-2ThF  (ss)® Liquid + 7LiF+6UF ,~7LiF-6ThF, (ss)®
612 +4 Liquid + LiF-2ThF , (ss)© Liquid + 7LiF<6UF ,~7LiF+6ThF (ss)€
20 8 502 +2 Liquid + 3LiF-ThF4 (ss) Liquid + 3LiF-ThF4 (ss) + 7LiF+-6UF ,—
7LiF~6ThF4 (ss)
498 +2 Liquid + 3LiF-ThF4 (ss) + 7LiF-6UF4- LiF + 3LiF.ThF , (ss) + 7LiF-6UF ,~
7LiF-6ThF4 (ss) 7LiF-6ThF4 (ss) e
20 20 620 £3 Liquid + LiF'4UF4—LiF-4ThF4 (ss) Liquid + 7LiF-6UF4--7LiF°6T|'|F4 (ss)®
517 £2 Liquid + 7LiF-6UF4—7LiF'6ThF4 (ss) Liquid + 3LiF-ThF4 (ss) + 7LiF+6UF ,— .
7LiF-6ThF4 (ss) v
20 45 883 +2 Liquid + UFA-ThFA (ss) Liquid + LiF-4UF4—LiF-4ThF4 (ss)
21.5 21.5 610 £3 Liquid + LiF-4UF4-LiF~4ThF4 (ss) Liquid + 7LiF°6UF4-7LiF-6ThF4 (ss)©
22 6 495 12 LiF + liquid LiF + liquid + 7LiF+6UF ,—
7LiF-6ThF4 (ss)
487 £2 LiF+|iquid+7LiF-6UF4-— 7LiF'6UF4—7LiF-6T|1F4 (ss)€ + LiF¢
TLiF-6ThF  (ss)©
24 4 488 +2 7LiF«6U l""‘--7LiF-6ThF4 (ss) + LiF + 7LiF-6UF4—7LiF’-6ThF4 (ss)
LiF + liquid
25 2 487 £ 2 Liquid + LiF + 7LiF-6UF ,— LiF + 7LiF°6UF4-—7LiF-6ThF4 (ss)
7LiF-6Th F4 (ss)
25 3 491 3 Liquid + LiF + 7LiF'6UF4- LiF + 7LiF-6UF4-7LiF-6ThF4 (ss)
7Lii'-'-6ThF4 (ss)
25 15 615 +3 Liquid + LiF-AUF“—LiF-ciThF4 (ss) Liquid + 7LiF-6UF4--7LiF~6ThF4 (ss)
613 +2 Liquid + LiF-4UF4—LiF-4ThF4 (ss) Liquid + 7LiF°6UF4—7LiF-6ThF4 (ss)
607 6 Liquid + LiF°4UF4—LiF-4Th F4 (ss) Liquid + 7LiF°6UF4-7LiF-6ThF4 (ss)
26 2 489 12 Liquid + LiF + 7LiF-6UF4— LiF + 7LiF'6UF4—7LiF-6ThF4 (ss)©
7Li|"'°6'|'hF4 (ss)€
26.5 2 495 £2 Liquid + 7LiF+-6U F4—7LiF-6ThF4 (ss) Liquid + LiF + 7LiF+-6UF ,—
JLiF<6ThF ; (ss)
490 +3 Liquid+LiF+7LiF'6UF4-— LiF+7LiF-6UF4--7LiF-6'|'hl"4 (ss)

46

7LiF«6Th F4 (ss)
Appendix (continued)

Composition

a
(mole %) Temperature

©C) Phases? Above Temperature Phases? Below Temperature

UF, ThF,

28 10 610 £3 Liquid + LiF'4UF'4-—LiF-dThF4 (ss) Liquid + 7LiF'6UF4-7LiF-6ThF4 (ss)
30 10 611 £2 Liquid + LiF-4UF ,~LiF+4ThF  (ss) Liquid + 7LiF-6UF ,~7LiF-6ThF , (ss)
30 50 827 5 Liquid + UF ,-ThF, (ss) Liquid + UF ,-ThF, (ss) + LiF-4UF ;-

LiF-4ThF , (ss)

33 10 604 +3 Liquid + LiF-4UF ,~LiF-4ThF , (ss) Liquid + 7LiF+6UF ,~7LiF:6ThF, (ss)
33), 33%  862%2  Liquid + UF-ThF  (ss) Liquid + LiF+4UF ,—LiF-4ThF, (ss)
39 4 612 3 Liquid + LiF-4UF ,~LiF+4ThF , (ss) Liquid + 7LiF+6UF ;~7LiF+-6ThF , (ss)
45 20 859 +3 Liquid + UF ,-ThF , (ss) Liquid + LiF-4UF ,~LiF+-4ThF , (ss)

%The uncertainty in temperatures indicates the temperature differences between the quenched samples.

bOnIy phases found in major quantity are given. Minor quantities of other phases resulting from lack of complete
reaction between solids or from trace amounts of oxide impurities are not noted. Glasses or poorly formed crystals
assumed to have been produced during rapid cooling of liquid were found in those samples for which the observed
phase is indicated as ‘‘liquid.”

“Most of the phases were identified by optical microscopy; in addition, this phase was identified by x-ray diffrac-
tion.

47
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ORNL-2719
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H. Insley

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(19

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