ORNL-1771 - Oak Ridge National Laboratory

4NP QUARTERLY PROGRESS REPORT
on d
3FeC12 = 2FeCI, + Fe , Fo = 0.35 V.
The NiCI, solutions, as far as is known, undergo
the same electrochemical reactions regardless of
concentration. Thus the changes in decomposition
potential with concentration may be assigned to
differences in NiC!, activity alone. With the aid
of the Nernst equation, the NiCI, activity at 33.3
mole % NiCI, may be coniputed to be 100 times that
in the 3.3 mole 76 solution and 300 times that in
the 1 mole % solution.
Solubility of Xenon in Molten Salts
R. F. Newton, Researcli Director's Department
D, G. Hill, Consultant
The use of molten salts as reactor fuels offers
the possibility of removing the gaseous fission-
product poisons, of which zmon is the rnost im-
portant, If, for example, the xenon concentration of
the SO-Mw CFRE can be held at 10% of its equi-
librium value (1.1 x mole of xenon per milli-
I iter of fuel), important perturbations in reactivity
can be avoided, In on aircraft reactor, however,
it will be nccessary to effect this removal nd xenon
with on absolute minimum of ouxiIiary equiprrient.
The available literature appears to contain no
measureinents of she solubility of gases in molten
salts. Accordingly, it has seemed desirable to
evaluate the solubility of xenon in molten fluorides
over the temperature range of interest. Preliminary
tests indicate that the following experimental tech-
nique is satisfactory.
The apparatus, which is constructed of nickc!
where it will be in contact with the fluoridc melt
and of glass elsewhere, consists of two sections
that can be isolated by freezing a plt~g of fluoride
in the U-tube connecting them, In one section of
the apparatus the melt is allowed to saturate with
xenon under predetermined conditions of ternpera-
ture and pressure. Melting of the fluoride plug
permits the saturated salt to flow into the other
section, whi!e the 1J-tube seal prevents entrance of
gaseous xenon into this section; refreezing of the
plug isolates the sections again. 117 the second
section, xenon is stripped from the salt by repeated
circulation of the hydrogen contained in the a p p
ratus through the salt and past a liquid-nitrogen-
cooled trap. After the stripping process is com-
plete, the hydrogen is removed, $he xenon is allowed
to come to room temperature, arid he amount col-
70
lected is ascertained by measurements in a modi-
fied Mcl_eod gage.
Preliminary experiments at 600'6 and essentially
1 atm of xenon indicate that the solubility in the
NaF-KF-LiF eutectic is not greater than loM7
mole of xenon per milliliter of salt. The method and
technique proved to be feasible, but minor experimental
difficulties necesFitatsd modification of
the nickel apparatus. More accurate data under
these and other conditions will be available in the
near fWtIJre.
Meanwhile, in order to gain familiarity with the
technique, the solubility of xenon in the KNO,-
NaNQ, eutectic (36 mole '36 NaNQ,) has been
measured in an apparatus constructed entirely of
glass. The solubility of xenon in this melt is
about 8.5 x mole/itil at 280°C and low7
mole/ml at 360°C. This liquid apparently shows
the positive temperature coefficient of solubility
expected for gases in molten salts.
%-Ray DiFfr~~fi~n Studies in Salt Systems
P. A. Agron M. A. Bredig
Chemistry Division
Cesium Halides. It has been suggested21t22 that
the increase in volume on melting of simple binary
salts is indicative ofstructural changes in the melt,
that is, of a decrease to a lower ionic coordination.
Volume increases up to 30% have been indicated for
the alkali halides. The x-ruy data23 on the thermal
expansion of solid CsBr and Csl gave volume
changes of approximately 26%, but an extrapolation
of about 50°C to their melting points WQS required
for the computation of these changes. It WQS there-
fore of interest to uscertain whether a solid-phase
transition analogous to the one known to exist in
CsCl occurs in the unexplored temperature interval.
This would replace the assumed structural change
in the melting process by one in the solid state.
High-purity CsBr and Csl were intimately mixed
with fine nickel powder to provide airs internal
stairdurd whose thermal expansion is know BCCU-
rate~y.,~ ~attice parameters as a function of tem-
perature were obtained on the hi yh-temperature
21J. W. Johnson, M. A. Bredig, and W. J. Smith, Gem.
Dzv. @LOT. ?Tog. Rep. Der. 31, 1952, ORNL-1482, p 32.
,P, A. Agron and M. A. Bredig, Ch~rn. Semzann. Prog.
Rep. June 20, 1954, ORML-1755 (in press).
24Ls Jo;dan and W. H. Swunger, J. Research Nnt. Bur.
xtandn7ds 5, 123 i ( 1930)-