ORNL-1816 - the Molten Salt Energy Technologies Web Site

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reactor fuels. Uranium metal is determined by
converting it to UH, with hydrogen at 250°C, then
increasing the temperature in an atmosphere of
carbon dioxide to 400'C to decompose the hydride,
and finally measuring the volume of gas liberated
as a consequence of thermal decomposition. Under
these conditions, CO, was reduced to CO by uranium
metal and also by UF,. A trap of I,O, was
incorporated to oxidize CO and thus remove this
source of error.
Asolution of methylene blue was found to oxidize
trivalent uranium quantitatively to the tetravalent
state without liberation of hydrogen. A procedure
in which methylene blue is used as the oxidant was
developed for the determination of trivalent uranium
in a variety of materials. The method appears to
be applicable to routine analysis.
Two other reagents, cupric chloride and titanium
tetrachloride, wi I I, under selected conditions,
oxidize trivalent uranium to the quadrivalent state
only. The latter reagent can probably be adapted
to an automatic coulometric titration procedure for
this purpose.
Calibration of the apparatub for the determination
of oxygen as oxide in fluoride reactor fuels was
completed for quantities of oxygen up to 235
mg/liter. In this range the relationship log
k/c = A 6
+ B is valid; k is the specific conduc-
tivity of water in HF, c is the concentration, and
A and B are constants.
A colorimetric method was adapted for the determination
of sulfur as sulfate or sulfide in fluoride
salts. The sulfur is used to form methylene blue,
an intensely colored dye, for which the absorbancy
is readily measured. The method was also applied
to the determination of sulfur in sodium. A semiquantit
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in off-aas streams was set UD that is based on the
PERIOD ENDING DECEMBER 10,1954
11. Recovery and Reprocessing of Reactor Fuel
A plant for recovering (in seven batches) the
uranium from the ARE fuel and rinse by the
fluoride-volatil ity process is being designed, and
construction is scheduled for completion by
December 31, 1955. It is estimated that the amount
of material to be processed will be 12.4 ft3 of
NaF-ZrF,-UF, containing 65 kg of uranium, This
plant will demonstrate, on a pilot-plant scale, the
feasibility of the fluoride-volatility process as
applied to the processing of a circulating-fuel
aircraft reactor, The feasibility of the process has
been established on a laboratory scale, The basic
equipment, as now envisioned, will consist of a
fluorinator, an absorption column packed with NaF,
a cold-trap system, and a fluorine disposal unit.
This method of recovery and decontamination can
also be used for processing heterogeneous reactor
fuel elements of the type that c:an be dissolved in
fused fluoride salt by means of hydrogen fluoride.
Compactness of plant, operation at atmospheric
pressure, and economical waste disposal are some
of the advantages of this type of process.
PART Ill. SHIELDING RESEARCH
12. Shielding Anciiysis
Calculations made by the Monte Carlo method
with the use of the ORACLE were completed for
the attenuation of gamma rays in the sides of Q
a two-component crew shield and the heating by
gamma rays in the beryllium slabs adjacent to the
gamma-ray slab source. The results of the gamma-
ray heating study are of interest for calculations of
thermal stresses and consequent cooling require-
region of the circulating-
fuel. reflector-moderated reactor. AttemDts were
termina ti ons. to explain some of the values of scattered flux
r
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