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ANP PROJECT PROGRESS REPORT
PREPARATION OF SOLUTIONS OF LaF3,
BaF,, AND RbF IN NaF-ZrPpUF4
F. L. Daley
W. T. Ward
A special preparation containing La F,-Ba F,-RbF
(2.8-1.0-1.1 mole %) dissolved in a standard NaF-
ZrF,-UF, (50-46-4 mole %) mixture was requested
for use in determining whether the introduction of
the simulated fission products would produce sip
nificant viscosity changes. The usual methods of
purification and filtration were used, and the equip-
ment was modified so that small filtered samples
could be dispensed directly into the tubes used for
the viscosity measurements. The resulting prepara-
tion was studied to obtain some indication of the
solubilities of the fission products at 8WC in
this solvent. It is believed that the solubility of
LaF, may be typical of the solubilities of the rare-
earth fluorides, since LaF, presumably forms solid
solutions with other rare-earth fluorides.
Two filtered samples of the NaF-ZrF,-UF, mix-
ture without the additive were obtained, and two
more samples were obtained after the fission-
product mixture was added. A small portion of
solution -which remained unfiltered in the reactor
after withdrawal of all the samples was also re
covered for analysis. All filtrations were performed
No F-Zr F,-U F4
at approximately 800 f 10°C. During the course of
the viscosity measurements, the presence of a
finely divided solid material was detected in the
molten mixture, and a small sample of the solid
was obtained by decantation. The solid was
tentatively jdsntified by x-ray diffraction analysis
as free LaF,, with occluded solvent. The results
of chemical analyses of all the samples taken
are presented in Table 2.2.15.
The results indicate no greater concentration of
additives in the unfiltered portion (reactor heel)
than in the filtered samples, and consequently it
appears that the additives were completely dis-
solved at 800OC. From visual observations, how-
ever, the solution seemed to be essentially satu-
rated at this temperature. The saturating phase
appeared to be free LaF,, and the probable solu-
bility value for this compound at 800OC seems to
be about 2.5 wt %. During the preparation of this
material no particular effort was made to control
the filtration temperature at exactly 80O0C, and
visual observations could not be made conveniently
enough to fix a liquidus temperature; however, the
order of magnitude of the solubility of LaF, in
NaF-ZrF4-UF, (50-46-4 mole %) appears to be
about 2 mole 96 at 80OOC.
TABLE 2.2.15. CHEMICAL COMPOSITION OF NaF=ZrF4-UF4 SAMPLES BEFORE AND AFTER
INTRODUCTION OF La F3-BaF2-RbF TO SIMULATE FISSION PRODUCTS
Filtration temperature, 8OO0C
Maior Constituents (wt %) Impurities (ppm)
Na zr U Bo La Rb F Ni Cr Fe
Sample 1 10.7 38.8 8.8 0 0 0 41.9 90 50 65
Sample 2 10.3 38.8 8.7 0 0 0 42.5 35 40 45
Theoretical 10.41 37.98 8.62 0 0 0 42.99
NaF-ZrF4YF,, plus
La FB-Ba FZ-Rb F
Sample 3 9.2 35.7 8.0 1.23 2.62 0.86 41.7 80 50 90
Sample 4 9.5 34.6 7.7 1.16 2.56 1.00 41.8 100 65 160
Reactor heel 8.9 37.8 8.2 1.18 2.31 0.87 41.2 25 65 150
Theoretical 9.64 35.17 7.98 1.25 3.40 0.82 41.74
Solid detected during 18.1 0.62 26.6
108
viscosity measurements
.
W
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