ML20202G917

Operations Monthly Summary for Univ of Mo Research Reactor for Nov 1998

ML20202G917
Person / Time
Site:	University of Missouri-Columbia
Issue date:	11/30/1998
From:	MISSOURI, UNIV. OF, COLUMBIA, MO
To:
References
NUDOCS 9902050340
Download: ML20202G917 (3)

Text

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FILE klo UNIVERSITY OF MISSOURI RESEARCH REACTOR OPERATIONS MONTHLY

SUMMARY

November 1998 Prepared by:

Operations Staff 9902050340 981130 f"I PDR ** C Oc:*

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November 1998 The reactor operated continuously in November with the following exceptions:

five shutdowns for scheduled maintenance and refueling; two unscheduled shutdowns.

On November 10, a reactor scram occurred due to a loss of site electrical power during a thunderstorm. The emergency generator operated satisfactorily for one hour and ten minutes until electrical power was restored. The reactor was then returned to normal operation.

On November 23, a nuclear instrument channel #5 high power scram occurred while an operator was handling the B-6 silicon irradiation position holder. The channel #5 drywell has recently been repositioned to a temporary location in order to make room for the installation of new gamma metrics nuclear instruments.

When handling this B-6 holder, it is possible to pass it between the drywell/ detector and the reactor. Should this occur, which we believe to have been the case, it is possible to effectively shadow this detector. The effect of this would be to create a void by replacing an amount of the water that normally exists between the detector and the core with the (approximately) 7 inch holder-plus-silicon. This would cause the detector to " detect" more neutrons and thus increase its iridication. The indication for channel #5 subsequently rose to 119%, where the scram occurred.

The scram setpoint is 119% and was tested approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> prior to this event. The reactor physicist has since verified, by computer model, that this " void" would cause a concomitant neutron flux change as seen by the channel #5. The computer model predicted a flux increase by a factor of 3.5 to 4.0 at channel #5 detector position when a 7" diameter silicon is introduced between the graphite 7

reflector and the detector. The reactor was subsequently returned to normal operation. Operators have since been explicitly instructed to avoid placing any material between this detector and the reactor core. When the new gamma metrics instruments become operable, this detector and drywell will no longer be in use and this particular problem should not recur.

i Major maintenance items for the month included: installing, and subsequently replacing, the detector for the second gamma metrics nuclear instrunient; O j rebuilding the south back-up door solenoids; installing and testing the new I' secondary acid addition valves.

5 ' ,L UNSCHEDULED SHUTDOWNS

. D.p_te No. Type Cause l

11/10/98 1091 Seram Loss of site electrical i power.

11/23/98 1092 Scram Detector shadowing OPERATIONS

SUMMARY

HOURS OPERATED THIS PERIOD 650 TOTAL HOURS OPERATED 215,934 HOURS AT FULL POWER THIS PERIOD 648 TOTAL HOURS AT FULL POWER 212,819 INTEGRATED POWER THIS PERIOD 270 MWD TOTAL INTEGRATED POWER 82,827 MWD i

i MAINTENANCE ACTIVITIES 11/02/98 Refueled - removed core 98-52, loaded core 98-53, 11/09/98 Refueled - removed core 98-53, loaded core 98-54.

Installed new detector for second gamma metrics instrument.

Rebuilt south back-up door solenoids.

11/16/98 Refueled - removed core 98-54, loaded core 98-55.

Installed new secondary acid addition valves.

Replaced the most recently installed gamma metrics detector.

11/23/98 Refueled - removed core 98-55, loaded core 98-56.

11/30/98 Refueled - removed core 98-56, loaded core 98-56.

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