PERIOD ENDING SEPTEMBER 70, 7954 o r nearly pure, UF,. Recent studies of LiF-UF, mixtures have confirmed the b e l i e f " that no compounds form and that these materials comprise a A partial phase diagram simple eutectic system. for t h i s simple system i s shown as Fig. 5.3. T h e NaF-UF, system has been studied more thoroughly than any other binary alkali-metal fluoride-UF3 system. The best thermal a n a l y s i s data obtained for t h i s system (data obtained with those mixtures which showed the least evidence of contamination o f the melt by tetravalent uranium) obare shown i n Fig, 5.4. The earlier data, tained by mixing N a F w i t h previously synthesized
UF, in sealed capsules, are shown by open circles.
The more recent data, shown by s o l i d circles, were
I2L. M. Bratcher et ul., ANP Quur. Prog. Rep. J u n e 10, 1954, ORNL-1729, p 43. l 3 V . s. C o l e m a n a n d w. c. Whitley, ANP Qum. f r o g . R e p . Sept. 10, 1952, ORNL-1375, p 79. 14W. C. Whitley, V. S. C o l e m a n , and C. J. Barton, ANP Qum. Prog. Rep. D e c . 10, 19S2, ORNL-1439, p 109.
Ir.
OANL-LA-OWG
obtained by reducing NaF-UF,
mixtures with ex-
cess uranium i n open crucibles protected by an atmosphere of helium. Some data, also obtained during the past quarter, were obtained by a method which represents a compromise between the t w o previously mentioned methods. Mixtures were prepared i n open stirrer-equipped crucibles by combinUF,: These i n g dry N a F with freshly prepared" data are indicuted i n Fig.5.4 by the solid triangles.
T h e agreement between the data obtained by the various methods i s considered to be gratifying, in v i e w of the d i f f i c u l t i e s associated with the ease of
oxidation o f U3+to U4'. The identification of the compound i s based chiefly upon the results of petrographic examination of slowly cooled melts. The p o s s i b i l i t y that the compound might be Na,UF, rather than Na,U,F, and the p o s s i b i l i t y that appreciable quantities o f UF, may be "hidden" in these materials have not been completely ruled out by these studies. Very few compositions containi n g more than 50 mole % UF, have been prepared, and the data i n t h i s part of the system are probably of l i t t l e value.
*
29;
ORhL-LR-DWG
PREPARED
5
0
IO
$5
20
25
2924
:N O p t 3
30
35
40
45
50
UF3 (mole %I
Fig. 5.4. Tentative NaF-UF, System.
P a r t i a l Phase Diagramof
the
KF-UF, and far advanced. It
Phase equilibrium studies of the
RbF-UF,
0
Fig. 5.3.
10
20
30
40
UF, (mole Z )
50
60
7C
Tentative P a r t i a l Phase Diagram of
the LiF-UF, System.
systems are not so appears that the most probable compositions for the compounds observed are K3UF,, K,U,F, and
Rb,UF, about
md 720째C
"Prepared
that the KF-K,UF, at approximately
by
W. C.
15
eutectic melts a t mole % UF,. It
Whitley, July 1954.
59