ORNL-1816 - the Molten Salt Energy Technologies Web Site

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ruthenium was apparently volatilized out of the
reactor entirely. Ruthenium and niobium plated
out heavily on the metal walls of the reactor. The
distribution ratio between metal wall and salt was
about 5 for ruthenium activity and less than 0.01
for niobium activity.
The behavior of plutonium in the fused salt
fluoride-volatil ity process is important in processing
fuel that has a high proportion of U238. The
results of many fluorination runs at 650°C show
that only about 0.01% of the plutonium is carried
over with the UF, product.
Further study was carried out on the absorption
of UF, in NaF-ZrF, (56-44 mole %) at 65OOC.
In one trial, 9 g of UF, was absorbed in 30 g of
NaF-ZrF, in 1 hr with no noticeable loss. However,
passage of helium through the fused salt,
either concurrently with or after the UF, addition,
erable fuming. A positive test for
fluorine with potassium iodide paper was obtained,
which indicated reduction of the adsorbed UF, to
the tetra- or pentavalent form of uranium. A
gravimetric test, based on the reaction of fluorine
with sodium chloride, showed that the breakdown
of UF, to F, and UF, amounts to 1 to 2% per hour
at 65OOC.
Engineering information is needed on two steps
in the fluoride-volatility process: fluorination and
,. UF, cold-trapping. Effective contacting of fluorine
with molten ARE fuel is desirable to minimize
fluorine consumption and gaseous waste and to
assure complete recovery of the uranium. The cold
trap should be operated in such a manner that all
the UF, will be condensed and collected on the
PERIOD ENDING DECEMBER 70,7954
properties of the liquid could not be demonstrated
by a simple correlation of friction factor with
Reynolds number, such as is found in ordinary
fluid flow through pipes. The acetylerie tetra-
bromide studies showed that vertical mixirig of the
liquid phase was induced by a gas rate of 9.5 cfm
in a 12-in.-dia column. Equipment is now being
assembled to verify these conclusions with molten
Na F-Z r F ,.
Cold traps to be used for a quantitative study
of the effect of temperature and gas flow rate on
the completeness of UF, removal are being con-
structed. The design of these traps is based on a
K-25 cold-trap design.
APPLICATIONS OF FUSED SALT-VOLATILITY
PROCESSES
A long-range study has been made to survey the
over-all feasibility of fused salt-voIatiIi,ty tech-
niques in the chemical processing of ARE-type
reactor fuels and certain types of heterogeneous
reactor fuel elements. The volumes of raclioactive
waste from such processes should be mulch lower
than those from the aqueous processes, and
processing costs should be low, even though a
means of disposing of excess fluorine will have
to be provided. Total chemical costs, ?which in
present aqueous processes represent approximately
10% of operating costs, have been estimated to be
20g per gram of U235. The operational procedure
is much simpler, and the equipment should be
inexpensive, even though nickel will be required
as the material of construction.
Results of recent work on fuel element dissolution
137