ML20198M357

Special Rept:On 981210,operators Declared Number 11 Inoperable,Due to Failure of CR Chart Recorder.Caused by Inverter Board in Power Supply Circuitry of Recorder Due to Component Aging.Maint Personnel Replaced Failed Inverter

ML20198M357
Person / Time
Site:	Nine Mile Point
Issue date:	12/23/1998
From:	Rich Smith NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NMP1L-1392, NUDOCS 9901050318
Download: ML20198M357 (2)

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NiagarahMohawk'

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l December 23, 1998 NMPIL 1392 U. S. Nuclear Regulatory Commission l Attn: Document Control Desk j Washington, DC 20555  ;

RE: Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Subject:

Special Report I

Gentlemen: l

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l In accordance with Nine Mile Point Unit 1 (NMPI) Technical Specification (TS) Table i 3.6.11-2, " Accident Monitoring Instrumentation," Action Statement 4.b.2, Niagara Mohawk Power Corporation (NMPC) is submitting the following Special Report concerning the g inoperability of both #11 and #12 Containment Hydrogen Monitoring Systems (HMS). 1 (j Desedntion af Event On December 10,1998, at approximately 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, with the reactor mode switch e the "RUN" position during normal operation, NMP1 operators declared the #11 HMS inoperable .

- b9 due to the failure of the control room chart recorder. At the time, #12 HMS remained out of l service as described in a Special Report (NMPIL 1368) dated October 12,1998. On December 11,1998, operators returned #12 HMS after successful post-maintenance testing.

On December 17,1998, operators returned #11 HMS to service following successful post-maintenance testing.

1 i ram of Event Maintenance personnel determined the cause of the #11 HMS recorder failure to be a failed inverter board in the power supply circuitry of the recorder due to component aging.

9901050318 981225~ 0 DR ADOCK.0 Lycoming. New York 13093-0063

• 315.343.2110

• www.nimo.com

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Page 2 Corrwelive Arrinns Maintenance personnel replaced the failed inverter board, successfully tested the recorder, and returned it to service. I In accordance with TS Table 3.6.11-2 Action 4b, chemistry personnel obtained grab samples during the period when both #11 HMS and #12 HMS were out of service.

l Very truly yours, l Ah Robert G. Smith Plant Manager - NMPl RGS/KLidkap xc: Mr. H. J. Miller, Regional Administrator, Region I  !

Mr. G. K. Hunegs, Senior Resident Inspector Records Management 1

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