ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
Fig. 1.8.
Weld Crack.
Cross Section Through Thermocouple
below criticality or at very low power levels.
Samples were withdrawn by pressurizing the pump
bowl sufficiently to cause flow through a heated
lnconel tube into a sampling device, which was
constructed to allow line flushing before col-
lection of the sample.
Analyses of the samples were carried out by
the ANP Analytical Chemistry Group and are
shown in Table 1.1. As may be seen, the
chromium content of the fuel was essentially
constant at 100 ppm after 155 hr of circulation
of the fuel carrier through the reactor. If corrosion
of the lnconel is assumed to have been uniform
over the surface of the system - and since it was
operating isothermally during this period, such
an assumption is reasonable - the chromium con-
centration of 100 ppm would represent about 0.5
20
TABLE 1.1. ARE FUEL SAMPLE ANALYSES
Hours After
Filling with
Barren Carrier
19
60
110
1 55
157
178
182
205
242
24 6
268
286
3 07
Uranium Chromium
(wt X) (PPm)
1.84
3.45
5.43
9.54
12.21
12.27
12.54
12.59
13.59
81
90
102
100
150
190
2 00
205
300
320
37 8
420
445
mil of attack on the Inconel.
As was anticipated, the chromium content of
the melt was found to increase a few hours after
each addition of fuel concentrate (Na,UF,). By
the time the final sample was taken, after 307 hr
of molten fluoride circulation, the chromium content
was found to be 445 ppm. Again, if a uniform
rate of attack of the lnconel is assumed and if
the removal of circulated material from the system
during this time (to maintain desired pump liquid
level) is taken into account, this chromium content
would represent about 5 mils of attack on the
lnconel system. If the data in Table 1.1 are
plotted as chromium content vs time, it is seen
that the chromium content had begun to level off
by the time the final sample was taken. A projection
of the slope of the chromium curve indicates
a maximum chromium concentration of about
600 ppm after several hundred hours of operation.
There is no doubt that mass transfer of chromium
metal began soon after power operation started,
since there were then large temperature differentials
across portions of the system. Sampling
was not possible at this time and could not, of
course, have given information on mass transfer.
Heat transfer characteristics of the ARE did not
appear to have changed during its 150 Mwhr of
operation, and so whatever mass transfer occurred
was unimportant. Details of mass transfer will
be studied when sectioning of the equipment
becomes possible.