ML19263C750
| 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
~
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