ORNL-4191 - the Molten Salt Energy Technologies Web Site

Sample No. M Wil 1
FP-9-4
FP-10-25
FP-11-5
FP-11-13
FP-11-32
FP-11-38
FP-I 1-49
FP-12-6
FP-12-11
FP-12-21
10,978
16,450
17,743
20,386
25,510
27,065
30,000
32,450
33,095
35.649
168
Table 14.2, Concentration of U3+ in MSRE Fuel Salt
4u3+ Rumup
Oxidation
(equivalents)
~~~
1.87
0.93
0.40
0.26
0.88
0.26
0.50
0.40
a. 10
0.50
If the induction period for the radiolytic generation
of fluorine were shortened due to the increased
activity level of the sample, the fluorine evolved
during the loading of the sample could react with
the inner walls of the Monel hydrogenation vessel.
The copper and nickel fluorides formed would be
subsequently reduced during the hydrogemation
steps to produce HF.
The above hypothesis appears to be supported
by the results of the following experiment. One
of the samples which produced the high HF yields
was allowed to stand in the hydrogenator at room
temperature for about a week. The sample was
then subjected to additional hydrogenation steps,
and ISF was produced in quantities comparable
with that obtained in the original runs. After
standing several iiiore days at room temperature,
the sample was removed from the hydrogenator.
Smaller but significant quantities of HF were
obtained when the empty hydrogenator was
subjected to the high-temperature hydrogenation
procedure.
The last three samples, FP-12-6, FP-12-11, and
FP-12-21, wexe all taken after a relatively brief
period of reactor operation following a lengthy
reactor shutdown period. None of these analyses
produced the excessively high I-IF yields which
were observed for the previous two samples. This
appears to be further confirmation that the excessive
HF yields resulted from a buildup in sample
activity with extended reactor operation.
Since the first addition of beryllium to the fuel,
not obviously affected
all the determinations of U +
Be
Added
(equivalents)
~~~
3.61
2.59
1.86
3.95
1.14
3+
U ”total’
Ca lcii 1 at ed
(70)
- ~~
~
0.31
0.58
0.54
0.77
0.69
0.66
0.80
0.76
1.14
1.54
3+
U /Utotal, Analysis (%)
Step 111
0
0.35
0.37
0.37
0.33
0.42
0.38
0.39
Step IV
~~ ~
0.1
0.45
0.37
0.42
0.34
0.37
1.2
0.50
by radioactivity have fallen in the 0.33 to 0.50%
range (the one result of sample FP-12-11 could be
explained by a leaky valve) and do not reflect the
beryllium additions in the periods between the
samplings. This could be accounted for by the
evolution of fluorine in much smaller quantities
than appeared to be the case in samples FP-11-38
and FP-11-39. If this is the case, the only permanent
solution would be to maintain the samples
at 20OOC during the lime of transfer to the hot
cell for analysis. However, an apparatus is now
being designed which will pertiiit the hydrogenation
of synthetic fuel samples under carefully controlled
conditions. It is felt that this experiment will
provide a check of the validity of the transpiration
method and will give further evidence as to whether
or not the fluorine evolution is a real problem.
Experimental work is also being carried out to
develop a method for the remote measurement of
ppm concentrations of HF in helium or hydrogen
gas streams. The technique is primarily for application
to the U3 i~ transpiration experiment but, if
successful, should also be applicable to the determination
of HF in the MSRE off-gas. The method
is based on the collection of HF on a small NaF
trap which is held at 70°C to prevent the adsorption
of water. ‘This is followed by a desorption at
a higher temperature to give a concentrated pulse
of HF that can be measured by thermal conductivity
techniques.
A cornponents testing facility has been set up
which includes a dilution system to produce I~IF
“standards” as low as 20 ppm, a therrnostatted