ORNL-2106 - the Molten Salt Energy Technologies Web Site

Although it appears that the solubilities ‘of the
rare earth fluorides in the NaF-ZrF,-UF, mixture
are sufficiently high to prevent precipitation upon
their formation as fission products during ART
operation, some studies of solubility of individual
rare earths and rare-earth mixtures are currently
under way. One possible development from such
a study might be the demonstration of a simple
means for removal of the rare-earth fluorides from
the fuel mixture if the magnitudes and temperature
dependences of the solubilities are adequate.
PERIOD ENDJNG JUNE IO, 1956
apparent in analysis of the filtrates obtained, these
data should be considered as preliminary. It is
anticipated that more reliable values will be
available within the next quarter,
CONCENTRATION CELLS AND TRANSFERENCE
NUMBERS IN FUSED SALTS
R. F. Newton
It is well known that transference numbers are
needed for correlating the electromotive forces of
concentration cells with activities or other thermodynamic
properties of the solutions involved. While
measurements have been and are being made of the
transfer of ions of fused salts across porous dia-
PRELIMINARY SOLUBILITY VALUES OF CcF3
IN NaF-ZrF4-UF4
C. hi. Blood
phragms, some investigators doubt that these data
can be properly interpreted as the “true” trans-
As a start of a systematic determination of soh- ference numbers of the ions, since the diaphragm
bilities of the rore-earth fluorides in ART-type
fuels, such as NaF-ZrF,-UF, (55-40-5 mole %),
itselfmay cause a flow of salt across the boundary,
It is of interest to note, however, that relative
one experiment was performed to determine the transference numbers, which are the values of
approximatesolubility of CeF, in a typical solvent. thermodynamic interest, can be measured in an
A previously purified mixture of the NaF-frF,-UF, ordinary Hittorf experiment.
solvent and approximately 2.5 mole % CeF, were It is well known that the transport of water as
enclosed in a nickel container and heated to 85OoC part of a hydrated ion in aqueous systems cannot
The mixture was continuously stirred by bubbling be determined without some rather questionable
hydrogen and helium, alternately, through a dip leg. assumptions, but standard transference numbers of
Two hours prior to filtration, the temperature of the aqueous ions are given relative to the water. For
solution was lowered to 80O0C Samples of liquid example, in a mixture of two salts, such as AgCI
were then withdrawn through a nickel filter tube at and NoCI, the transference number of Ag’ may be
800, 700, and 6OOOC. A second set of filtrates was defined relative to the NaCI. The fictions of the
obtained in the same manner at 700 and at 600OC ideal transference numbers, tia, tip, and ti, are
after the mixture had been given an additional useful in this analysis. In an ordinary Hittorf
hydrofluorination and hydrogenation treatment. The transference experiment in which silver electrodes
salts contains m moles
NaCI, N faradays of electricity
ssed, and the “idealized” anode comportles
of Ag’ by electrode reaction
f CI- by transfer and loses Nrio
oles of Ag by transfer.
as a gain of N moles of
0.59
of AgCI ad of
fer. The best that c
ver, is to compare the ASCI in a given quantity
aCI at the end with that in the same amount of
r example, the mode portion
the end of the experiment
NaCI, and the “idealized”
st Nri0 moles of NaCI,
this represents 1 + Ntia moles of NaCl at the
start. The AgCl at the start was m + mNtia, and
109