ORNL-1816 - the Molten Salt Energy Technologies Web Site

Therefore, the ARE supplied evidence that the
rare gases escape readily from the fluoride fuels
under dynamic conditions. Since the amount of
xenon present in a circulating-fuel reactor is probably
more than the amount produced in one complete
fuel cycle (50 sec in the ARE), the amount remaining
in the fuel will be measured by using an ARE
fuel sample for radiochemical comparison of the
concentration of the fission products (Sr89, Cs137,
and Ce’,’) which come through rare-gas precursors
with those ( CS’~~ and Zr95) which do not,
The gamma-ray scintillation spectrometer to be
used for the experiments has been calibrated with
Cs137, Na2*, and Hg203, and the equipment has
been tested with radioactive noble gases taken
from samples of off-gas from the iodine dissolver
used by the Radioisotopes Department of the
Operations Division. The gases used were primarily
Xe133 and Xe135. In order to prevent the
ma rays from other short-lived nuclides from
competing unfavorably with those from Xe135 and
thus making resolution of the Xe’35 isotope difficult,
a charcoal adsorption column (0.190 in. in
diameter and 0.5 in. long) for delaying isotopes
such as those of krypton was tested at room temperature
by using KrE5 and the gamma-ray spectrometer,
It was found that the charcoal trap would delay
krypton isotopes for about 10 min (at a flow rate
of about 15 cm3/min) and xenon isotopes for about
200 min. Thus spectrometer would measure
only long-lived is
Fission products may be lost from ARE-type fuel
by volatility of the fission product or of one of its
precursors; by interaction of the fission product or
es such as ~ e ~ ~ ~ .
by any of these means, since it will be “carried”
by the large quantity (50 mole %) of ordinary ZrF,
PERIOD ENDING DECEMBER 70,1954
in the fuel and since it has no known rare-gas
precursor (if Kr95 exists, it probably has a very
short half life, say 1 or 2 sec). This isotope will
be used therefore as the basis for normaliiring the
yields of the other radioisotopes to be studied.
Volatility of the rare gases will be examined by
studying the yields of Sr89 and of CS~~’‘ which
come through 2.6-min Kr89 and 3.0-min Xe137,
respectively, Low yields for these two isotopes
would indicate high volatilities for their parents,
Kr89 and Xe137. A further check of the experiments
will be made by using Ce141, a descendant of
3-sec Xe141, which should be retained in the fuel,
and Cs136, a shielded nuclide formed directly in
fission. Comparison of Zr9’ with Cs136 anti Ce141
will give a measure of the loss of the important
alkali and rare-earth elements through adsorption
on metal surfaces, since C S ’ ~ and ~ rare-earth
elements will be present only in trace quantities
but chemical zirconium will be present in very
large quantities, as mentioned above.
The data obtained from the ARE fuel sample will
be compared with similar data to be obtained from an
irradiated sampleof NaF-ZrF,-UF, (50-46-4 mole %)
that will be maintained solid to retain all the fission
products, The cooling period for the irradiated
sample will be the same as that for the ARE fuel
sample.
LIT R HO Rl ZO NTAL- B E AM-HO L E
FL UORlD E-FU EL LOOP
0. Sisman J. G. Morgan
W. E. Brundage M. T. Morgan
C. D. Baumann A. S. Olson
R. M. Carroll W. W. Parkinson
and Physical Properties” (this report). The curve
obtained for pressure of air vs heat removcil gives
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