ML20238C680

Special Rept Spr 87-009:on 871105,Fire Detection Zone F Declared Inoperable Due to Sporadic Integrated Fire Sys Computer Alarms.Caused by Signal Noise in Computer Loop Remote Cabinet.Repairs Reduced Frequency of Problem

ML20238C680
Person / Time
Site:	Summer
Issue date:	12/18/1987
From:	Nauman D SOUTH CAROLINA ELECTRIC & GAS CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
SPR-87-009, SPR-87-9, NUDOCS 8712310149
Download: ML20238C680 (1)

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So tb Carolins Electnc & Gas Company n A. N uen Columbia, SC 29218 Nuclear Operations (803) 748-3513 SCE&G December 18, 1987 n 3 *. b 3 (3"{ M.C D, Dr. J. Nelson Grace Regional Administrator U. S. Nuclear Regulatory Commission Region II, Suite 2900 101 Marietta Street, N. W.

ttlanta, Georgia 30323

Subject:

Virgil C. Summer Nuclear Station Docket No. 50/395 ,

Operating License No. NPF-12 Special Report (SPR 87-009)

Dear Dr. Grace:

Attached is a Special Report for the Virgil C. Summer Nuclear Station. This report is submitted in accordance with the requirements of Action Statement (b) of Technical Specifications Section 3.3.3.7, " Fire Detection Instrumentation."

Should there be any questions, please call at your convenience.

'ery truly yours, l .f.

D. A. Nauman 3

CJM/ DAN:jez t Attachment c- 0. W. Dixon, Jr.fr. C. Nichcis, Jr. R. L. Prevatte E. C. Roberts J. B. Knotts, Jr.

O. S. Bradham Marsh & McLennan

[:. R. Moore I&E Washington W. A. Williams, Jr. Document Management Branch Group Managers INP0 Records Center W. R. Baehr ANI Library C. L. Ligon (NSRC) Surveillance Systems R. M. Campbell, Jr. RTS K. E. Nodland NPCF J. C. Snelson File G. O. Percival 8712310149 871218 PDR ADOCK 05000395 S PDR I

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'.' ~ Attachment to Dr. J. Nelson Grace Letter December 17, 1987 Page 1 of 1 EVENT DESCRIPTION Fire detection Zone F on the 463'-0" elevation of the Control Building'was declared inoperable on November 5.-1987 due to sporadic Integrated Fire Systems computer alarms. The zone was removed from service for maintenance troubleshooting into the cause of the alarms. A fire watch patrol was established in accordance with the requirements of Action Statement (a) of Technical Specifications section 3.3.3.7, " Fire Detection Instrumentation,"

and remained in effect until the zone was returned to service on November 25, 1987.

Fire detection equipment for this zone consists of ionization smoke detectors which actuate a preaction sprinkler system and the Control Room computer alarm. Maintenance investigation into the problem determined that the alarm was caused by signal noise in the Fire System computer loop remote cabinet for this zone and did not affect the operation of the smoke detectors and associated preaction sprinkler system.

ACTION TAKEN Maintenance installed test equipment on the system and determined that the alarms were being generated from noise in the computer portion (loop remote cabinet) of the circuitry. The smoke detectors and preaction sprinkler system operation were unaffected by the invalid alarm.

Extensive troubleshooting by maintenance personnel isolated and replaced varicus system subcomponents which were contributing to the noise. The 7one was tested after the repairs and shown to be fully operational pricr to oeing returned to service on McVember 25, 1987. Computer tlarms observed since the system v!as returned to service indicate tht;t the repa!rs reiscco the frequency of the occurrence but did not totally resolve the protflem.

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The Licensee will cuntinue to monitor and evaluate the perfennance cf tne f computer system in an attempt to identify the source of the invalid alarms.

As previously stated, the noise does not affect the operability of the systerr as defined in the Technical Specifications.

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