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1.2 REACTlVlTY BALANCE
J. R. Engel
The extended periods of full-power reactor
operation in runs 11 and 12 have provided the
most severe tests to date of the on-line reactivity
balance calculation. Runs 11 and 12 increased
the integrated power by 16,200 and 7650 Mwhr,
respectively, to a total of 40,307 Mwhr. In addition
to the usual calculations of power- and timedependent
factors, calculations were required in
each of these runs to compensate for 235U additions
that were made with the reactor at full
power. The overall performance of the calculation
was highly satisfactory, and no anomalous
reactor behavior was indicated at any time. However,
some additional calculation modifications
were required to eliminate errors that developed.
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Fig. 1.5. Residual Reactivity During MSRE Run 11.
Balances at Power
Figures 1.5 and 1.6 summarize the results of
the on-line calculations during this report period.
These results are reproduced exactly as they
were generated, with no corrections for computer-
induced errors. For legibility, only about 2% of
the data points are shown, but each plotted point
is the result of an individual calculation. Thus
the scatter in the plotted points is an indication
of the precision of the calculation. The points
at which changes were made to correct errors are
indicated by notes.
Except for one negative excursion caused by
circulating voids immediately after a power shut-
down in run 11 (Fig. l.S), all the calculated values
of residual reactivity were between -0.03 and
t 0.10% 8k/k. An apparent gradual decline in