ORNL-1816 - the Molten Salt Energy Technologies Web Site

quarter. The various compositions and the amount
of each processed are listed below:
Composition
Amount
Processed (kg)
NoF-ZrF4-UF4 (50-46-4 mole %) 456.4
NaF-ZrF, (50-50 mole %) 339.4
NaF-ZrF4-UF4 (50-43.56.5 mole %) 323.8
11 19.6
received 682.4 kg of NaF-ZrF,-UF, (50-46-4
mole %) and 163.2 kg of NaF-ZrF, (50-50 mole %). f
3 Battelle Memorial Institute received 23.2 kg of 1
\ NaF-ZrF,-UF, (50-46-4 mole %), and the Naval f
\
'
Research Laboratory received 11.3 kg of NaF- \
f ZrF,-UF, (50-43.5-6.5 mole %). The remaining 1
material was distributed to various requesters in.1
the ANP program. *>,.qq
a+.- ~ ~ ~ ' ~ - r c n r - ~ ~ ~ ~ ~ ~ " ~ . - ~ ~
While processing fluorides for general distri-
bution, an attempt has been made to convert to an
electrolytic purification process for removal of
metallic impurities from fluoride melts. The first
trial of electrolysis was made on a non-uranium-
bearing mixture NaF-ZrF, (50-50 mole %) and
proved to be very successful. A 250-lb reactor
vessel was modified so that it could contain a
carbon cathode and a nickel anode, After a 250-lb
batch had been subjected to the usual preliminary
hydrofluorination, electrolysis of the melt was
carried out. For the electrolysis, a current of
40 amp at 3 v, a melt temperature of 1525OF, and
a helium atmosphere were used, and the melt was
aqitated. The melt reached the acceptable out-gas
PERIOD ENDING DECEMBER 10, 1954
Under ideal conditions, the use of hydrogen
stripping to remove metallic impurities requires
12 to 16 hr. With normal production, that is, reactor
vessels containing metallic impurity holdiJp from
previous batches, hydrogen stripping may take as
long as 50 hr. Therefore it is apparent that elec-
trol ytic purification of non-u ran ium-bear ing com-
positions is the better process, and it i!; to be
used as soon as permanent facilities can be in-
s tal led.
The electrolysis of uranium-bearing compositions
is still being investigated. Two batches of NaF-
ZrF,-UF, (50-43.5-6.5 mole %) have been subiected
to electrolytic purification. The first batch was
given 12 hr of electrolysis, and it was found that
the HF out-gas concentration appeared to level
off at 1.6 x lo', mole of HF per liter of effluent
hydrogen. Consequently, electrolysis was dis-
continued and the batch purification was iinished
by hydrogen stripping. Analysis of a filtered
sample from this batch yielded 225 ppm Fe, 20 ppm
Cr, and 40 ppm Ni. A second batch of the same
composition was electrolyzed until the desired HF
out-gas concentration was reached, after ;!7 hr of
purification, during which period 19 hr of elec-
trolysis was employed. Analysis of a filtered
sample from this batch showed 90 ppm Fe, 55 ppm
Cr, and 40 ppm Ni.
The large increase in electrolysis time required
for the uranium-bearing composition has led to a
more detailed study of the effect of uranium on the
electrolytic purification process. Also, the de-
sirabilityof obtaining a large stockpile of processed
fluorides by the first of the year and the present
uncertainties in the electrolytic purification of
sitions have led to the
of this method of removing
C. R. Croft
filtered sample from this batch yielded 40 ppm the highly corrosive character of alkali-metal
Fe, 60 ppm Cr, and 355 ppm Ni. fluorides which have been saturated with HF.
3
'V 7 e1
s i c ,
69