ORNL-4191 - the Molten Salt Energy Technologies Web Site

14.1 DETERMINAT1ON OF OXIDE
IN MSRE SALTS
R. F. Apple J. M. Dale
A. S. Meyer
During the last week of December the moisture-
monitor cell in the oxide apparatus became inop-
erative. Because of other experiments being
performed in the same hot cell, the moisture-
monitor cell was not replaced until March. The
insensitive cell showed sortie superficial evidence
of radiation damage in that the potting compound
(an KTV preparation which is used to seal the tube
containing the spiral electrodes in a stainless
steel housing) had shrunk and cracked. Flow
checks revealed that substantially all the flow was
still passing through the electrolysis tube, so that
the damage to the potting compound could not have
been responsible for the cell failure. Resistance
measurements indicated that the failure was
caused by either removal of or some alteration to
the P,05 electrolyte film.
The analyses of oxide in radioactive salt samples
from the MSRE for this period are summarized in
Table 14.1.
Two samples of radioactive fuel (IPSL-19 and
IPSL-24), submitted from the In-Pile Salt Loop 2,
were found to contain 265 and 240 ppm of oxide
respectively. Sample IPSL-24 was stored under
helium at 200°C for a period of about six mont.hs
from the time of sampling until the analysis was
made.
14.2 DETERMINATION OF U3'
IN RADIOACTlVE FUEL BY A HYDROGEN
REDUCTION METHOD
J. RI. Dale R. F. Apple
A. S. Meyer
A transpiration method is currently being used
to determine thc + 0 concentration in molten
radioactive MSRE fuel. The molten fuel is sparged
with hydrogen to reduce oxidized species according
to fie reaction
MFrl + --
n in
- H, -+ MF, + (n - RZ)IIF ,
2
167
Table 14.1. Oxide Concentrations of MSRE Salt Somples
Sample
Dattt Received Oxide Concentration
(PPd
FP-11-28 (fuel) 3-2 1-67 58
FP-12-4 (flush) 6-17-57 11
FP-12-18 (fuel) 7-1 1-67 57
The rate of production of HF is a function of the
ratio of oxidized to reduced species in the melt.
The theory of the method has been described pre-
viously.
The computer program which was under develop-
ment has been completed and permits the calcula-
tion of expected IIF yields for any preselected
reduction steps on any melt composition. Using
the present fuel composition and the experimental
conditions of the transpirat ion experiment as input
data to the program, €IF yields were calculated for
varying initial concentrations of 1J3 '. Sample
concentrations of U3' were determined from the
comparison of the experimental and calculated WF
yields. Table 14.2 shows the U3+ results obtained
from the [IF' yields of the third and fourth reduction
steps of the analyses and compares them with ex-
pected values calculated by W. R. Grimes.
The calculated results assume that 0.16% of the
uranium in the fuel was origiiially present as U3 ',
that the chromium concentration increase from 38
to 65 ppm which occurred before the first sample
was taken resulted in the reduction of U4' to
U3 ', that each fission event results in the oxida-
tion of 0.8 atom of U3', and that there have been no
other losses of u3 '.
It will be noted that no analysis results are
listed for samples FP-11-38 and FP-11-49. Although
these samples were run in the normal manner, a
total of over 2000 micromoles of HF was evolved
for the four hydrogen reduction steps fox each
sample as compared with about SS micromoles for
the previous runs. Since this increased HF yield
coincided with an increase in activity in the traps
used to collect the HF, it appeared likely that the
buildup in sample activity during the extended
period of reactor operation might be responsible.
which 'J. M. Dale, K. 17. Apple, and A. S. Meyer, MSR
"n may be UF,, NiF2' FeF2' CrF2y
Proprarn Sernrmn. Pro&. Rrpf. f'cb. 28, 1967, C>&jL-
UF4 in order of their observed reduction potentials. 4119, p. 158,