ORNL-2106 - the Molten Salt Energy Technologies Web Site

THE SYSTEM MgF2-CaF2
L. M. Bratcher
In the course of an investigation of the system
NaF-MgF2-CaF,, thermal data were obtained with
two MgF,-CaF, mixtures which indicated that the
literature value forthe melting point of the eutectic
mixture in this system might be too 10w.l~ There-
fore six additional mixtures were prepared which
covered the composition range 37.5 to 50 mole %
CaF,. Cooling curves obtained with these
mixtures showed that the eutectic mixture con-
tained approximately 48.5 mole % CaF, and melted
at 985 f 5'C, as compared with the literature value
of 940OC.
THE SYSTEM RbF-CaF2
L. M. Bratcher
Preliminary thermal analysis data indicate that
there is a eutectic between RbF and a binary
compound (probably RbFCaF,) that contains less
than 10 mole % CaF, and has a melting point of
765OC. Cooling curves with mixtures containing
10 to 45 mole % CaF, did not show reproducible
liquidus thermal effects, but the thermal effect at
765OC became less marked with increasing CaF,
concentration in this range. Petrographic exami-
nation of samples containing 10 to 20% CaF,
showed increasing amounts of a cubic compound
having a refractive index of approximately 1.410.
A 1:l compound (molar ratio) has been reported19
to be present in the similar system KF-CaF,.
THE SYSTEM LIF-NIF,
L. M. Bratcher
Data obtained with three mixtures in the LiF-
NiF, system covering the composition range 10 to
30 mole % NiF, were given in the previous
report.20 The compound found in this system was
tentatively assigned the formula 3LiF*NiF,,
mainly on the basis of petrographic and x-ray
diffraction studies of slowly cooled melts. The
thermal analysis data obtained to date are
difficult to interpret, but it appears likely that
the compound melts incongruently to NiF, and
liquid at a temperature only slightly above the
18E, Beck, Metallurgic 5, 504 (1 908).
"Pa Silber and Ma Ishaque, Cornpt. rend. 232, 1485
(1951).
"La M. Bratcher, ANP Quar. Prog. Rep. March 10,
1956, ORNL-2061, P 78.
PERIOD ENDING JUNE 10. 1956
minimum I iquidus temperature. We Il-crystal I ized
NiF, was found in slowly cooled mixtures con-
taining 30 mole % NiF, or more. The first attempt
to determine the melting point of NiF, was
unsuccessful, but the melting point was evidently
below 1200°C, the maximum temperature to which
the material was heated.
THE SYSTEM UF4-U02
R. J. Sheil
Preliminary thermal analysis data and the
results of studies of a few slowly cooled mixtures
in the UF4-UO, system were reported previou~ly.~~
Thermal analysis data obtained during this quarter
were not very satisfactory because of the previ-
ously mentioned undercooling difficulty and a
container problem. The use of graphite con-
tainers for the UF,-UO mixtures was abandoned
when it was discovered that mixtures containing
4 wt % UO, or more penetrated both ordinary
(C-18) and high-density graphite when heated to
a maximum temperature of llOO°C. Mixtures
containing 2 wt % UO, or less did not penetrate
ordinary graphite to a noticeable extent when
heated to the same temperature. Surface tension
measurements of UF,-UO, mixtures will be made
in an effort to account for this interesting
phenomenon. The recent thermal analysis studies
were conducted in sealed nickel capsules to
minimize changes in oxide content of the mixtures
while the thermal analysis data were being
obtained. This closed apparatus does not permit
the use of seeding, which apparently will be
required in order to obtain reliable liquidus values
in this system. Heating curves and some cooling
curves obtained with mixtures containing 4, 6,
8, and 10 wt 95 UO, show evidence of a eutectic
which melts at approximately 91OoC. Extrapolation
of available liquidus temperature data for these
mixtures involves considerable uncertainty, but
it appears that the eutectic probably contains
9 to 11 % UO, (10.3 to 12.6 mole % UO,).
THE SYSTEM ZnF,-ZnO
L. M. Bratcher H. A. Friedman
During the course of earlier investigations of
alkali fluoride-ZnF, systems,22 a variation in
21Ra J, Sheit, ANP Quar. Prog. Rep. March 10, 1956,
ORNL-2061, P 71.
M. Bratcher, R. E. Traber, Jr., and C. J. Barton,
ANP Quar. Prog. Rep. June 10, 1952, ORNL-1294, p 94.
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