ML19263C750

Informs of Failure of Nuclear Instrumentation Channel 6.Old DC Amplifier Module Bench Tested & Found to Have Bad Integrated Circuit Chip,Which Was Replaced

ML19263C750
Person / Time
Site:	University of Missouri-Columbia
Issue date:	02/21/1979
From:	Alger D, Mckibben J MISSOURI, UNIV. OF, ROLLA, MO
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 7903010279
Download: ML19263C750 (2)

Text

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Research Reactor Facility UNIVERSITY OF MISSOURI Research Park Columbia. Missouri 65201 February 21, 1979 Telephone (314) 882-4211

. Director of Nuclear Reactor Regulations U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Reference:

Docket 50-186 University of Missouri License R-103

Subject:

Failure of Nuclear Instrumentation Channel 6 Description On January 28, 1979, while operating at a steady state power of 10 MW, channel 6, one of three Nuclear Instrumentation (N.I.) Power Range Channels, changed in indication from 101.5% to 82% in one step with no change in the other channels. Each power range channel is required to provide a rod run-in at 115% of full power and a reactor scram at 125% of full power. With channel 6 indicating 82% with the reactor operating at 10 MW, the rod run-in and reactor scram trips from channel 6 would not have tripped if re-actor power level had increased to 125% of full power, which is a deviation from Technical Specifications 3.3.a and 3.4.c.

Analysis At 0530 on January 28, 1979, while operating the reactor at a steady state power of 10 MW, an operator observed the indication on N.I. channel 6 decrease from 101.5% to 82% in one step. N.I. Power Range Channels 4 and 5 were in agreement with the heat balance, but channel 6 was not; therefore, the reactor was shut down at 0544 to comply with Technical Specifications 3.3.a and 3.4.c.

A ' ont panel check of the instrument showed that it indicated low which proved it was a circuitry problem, not a problem with the detector.

The O.C. Amplifier, AR-15, was replaced with a spare board and .3 second front panel check was made verifying the instrument circuitry was oper-ating properly.

COLUMBIA KANSAS CITY RCLLA ST. LOUIS an eaual opportunity institution

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Director of Nuclear Reactor Regulations February 21, 1979 Page 2 There was no failure of the safety system, since N.I. Power Range Channels 4 and 5 were operational and would have provided the required rod run-in or scram protection.

Corrective Actig As stated in the analysis, the reactor was shut down and the problem corrected. The old D.C. Amplifier module was bench tested and found to have a bad integrated circuit chip, which was replaced.

Sincerely, J. C. McKibben Reactor Manager CN s Don M. Alger Associate Director JCMK:vs cc: Directorate of Regulatory Operations, Region III Reactor Advisory Committee Reactor Safety Subcommittee