ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
- 5
4900
v) 4800
w
a
I- 3
d t700
W
0
B
I- 4600
W
m
I- 3
-I
I-
T3
0
4500
1400
n
z
a
5 4300
5
K
0
9
K
4200
4100
1000
-
ORNL-LR-DWG 3946
404 100 96 92 88 84 80 76 72 68 64 60 56 52 48 44 40 36 32 28 24 20 16 12 8 4 0
TIME (min)
in about 8 min. However, by this time the reactor
mean temperature was 138OoF, and it was there-
fore decreased (to 1350°F) by inserting the shim
rods. The reactor was again brought from low
power to high power in 2 min, and after 8 min at
high power the shim rods were withdrawn to in-
crease the mean temperature. It is most sig-
nificant that during the 2-min interval required to
bring the reactor from a nominal power of 100 kw
to 2.5 Mw the shortest recorded pile period was
only 14 sec. Furthermore, when at high power,
group withdrawal of the shim rods (0.02% Ak/sec)
resulted in a pile period of only 10 sec. These
two limiting periods were consistently repro-
ducible.
Additional insight into the behavior of the
negative temperature coefficient is also afforded
by Fig. 1.3. By time 84 min, the blower was off
and the reactor power was reduced to about
100 kw. The shim rods were then inserted to
make the reactor subcritical. At 86 min, the fuel
helium blower was turned on. The higher density
14
Fig. 1.3. Power Excursions.
cooled fuel made the reactor critical, and in 2 min
a AT of about 200°F was obtained. At this time,
however, the blower speed was automatically
reduced by a low-temperature signal. The blowers
were subsequently shut off and the shims inserted.
Although the reactor power level had been cali-
'.
brated against the activity count of a fuel sample,
the actual reactor power remained in doubt through-
out the experiment, not only because of uncertainty
regarding the retention of fission products by the
fuel but also because of discrepancies in heat
balances in the process systems, that is, heat
removed from fuel and sodium vs heat picked up
in their water heat dumps. While the causes of
these discrepancies are now being analyzed in 1 -
detail, the most reliable estimate of the reactor F
power is believed to be that obtained from the
temperature differences and flows in the fuel and
sodium systems. During one typical period of
power operation, the fuel AT of 370°F at 45 gpm
accounted for more than 1.9 Mw in the fuel, while
the sodium AT of 115°F at 150 gpm accounted
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0