05000269/LER-1981-003, Forwards LER 81-003/03L-0.Detailed Event Analysis Encl

Forwards LER 81-003/03L-0.Detailed Event Analysis Encl

ML20005A799
Person / Time
Site:	Oconee
Issue date:	02/24/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20005A800	List: 05000269/LER-1981-003, Forwards LER 81-003/03L-0.Detailed Event Analysis Encl 05000269/LER-1981-003-03, /03L-0:on 810125,dc Input Fuse in 1DID Vital Inverter Blew,Causing Inverter to Lose Power source.1DIB Inverter Tripped When Ac Output Breaker Apparently Opened. 1DID Trip Caused by Blown Fuse.Cause of 1DIB Trip Unknown
References
NUDOCS 8107010279
Download: ML20005A799 (3)

LER-1981-003, Forwards LER 81-003/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2691981003R00 - NRC Website

text

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Tebruary 24, 1981 2's..: e 2 e

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c u n. 4 Mr. James P. O'Reilly, Director U. S. Nuclear Regulatory Commission

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Atlanta, Georgia 30303

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Re: Oconee Nuclear Station

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9 Doekat No. 50-269

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-269/81-3 This report is submitted pursuant to Oconee Nuclear Station Technical Specification 6.6.2.1.b(2),

which concerns operation in a degraded mode permitted by a limiting condition for operation, and describes an incident which is considered to be of no signi-ficance with respect to its effect on the health and safety of the public.

Ver truly yours,,'

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' William O. Parker, Jr.

JLJ:pw Attachment Mr. Bill Lava 11ee cc: Director Office of Management & Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Cocsission P. O. Box 10412 Washington, D. C.

20555 Palo Alto, California 94303 i

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DUKE POWER COMPANY OCONEE UNIT 1 Report Number: R0-269/81-3 Reoort Date:

February 24, 1981 Occurrence Date: January 25, 1981 Facility: Oconee Unit 1, Seneca, South Carolina Ideniification of Occurrence:

1DID Inverter D. C. Input Fuse Blown Copditions Prior to Occurrence:

85%

Description of Occurrence: At 1209 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.600245e-4 months <br /> on January 25, 1981, the D. C. input fuse in the 1DID vital inverter blew, causing the inverter to lose its power source. This inverter supplies power for the loads on the A. C. Vital In-strumentation Power Panelboard 1KVID.

These loads were manually transferred to the A. C. regulated bus approximately three to four minutes after the 1DID Inverter tripped, and the RPS Channel D loads were reset by 1217 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.630685e-4 months <br />. While investigating the problem on the 1DID inverter, personnel re-elved a call from the Control Room informing them that they had lost the 1DI3.averter and the associated A. C. Vital Instrumentation Power Panelboard 1KVIB. At approxi-

.mately 1450 hodrs, the A. C. output breaker c a the 1DIB inverter was discovered open. The inverter was put back on line and RPS Channel 3 was reset at 1503 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.718915e-4 months <br />.

E.S. Even Digital Channels and E.S. Analog Channel B were reset at 1517 hours0.0176 days <br />0.421 hours <br />0.00251 weeks <br />5.772185e-4 months <br />.

It is not known how the A. C. output breaker on the 1DIB inverter was opened.

At 1526 hours0.0177 days <br />0.424 hours <br />0.00252 weeks <br />5.80643e-4 months <br />, the 1DID inverter's A. C. output breaker was mistakenly turned off. This de-energized the panelboard 1RVID.

The 1DID inverter was immediately returned to service, and RPS Channel D was reset at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />.

This incident constitutes operation in a degraded mode per Technical Specification 3.7.2.d(3) and is thus reportable pursuant to Technical Specification 6.6.2.1.b(2).

_ Apparent Cause of Occurrence: The first trip of the 1DID inverter was caused by

>1own D. C. input fuse and a blown logic fuse. The blown fuses were possibly caused by poorly made connections in the logic cards' " edge connectors" and/or intermittent component problems on the logic cards. The resulting high D. C.

input current to the inverter also tripped the inverter D. C. input breaker and feeder breaker.

The trip of the 1DIB inverter occurred when the A. C. output breaker was apparently opened while personnel were working on the 1DID inverter. The breaker was not in the " trip" position so it must have been opened manually.

It is possible that the breaker was leaned up against and inadvertently opened since 1 DIS is very close to 1DID. None of the personnel remembers accidently leaning against 1DIB, and, in fact, were not aware that 1 DIS had tripped until notified by the Control Roem.

Thus it is not known how the A. C. output breaker on the 1DI3 l

inverter was opened.

After the first trip of the 1DID inverter, a non-Q.A. D. C. input fuse was used to bring IDID back up.

This is common practice since there has been trouble with this particular fuse before.

When it was decided to put 1DID back on line, a Q.A. fuse had to be_ installed. When personnel de-energized 1DID, the A. C. output breaker was mistakenly opened.

These breakers are proper *4 marked.

Analvais of Occurrence: Although both the 1KVTB and the 1KVID power panel-boards were de-energized, they were not de-energized simultaneously. Thus, the requirements of Technical Specification 3.5.1 were met. Therefore this incident was of no significance with respect to safe operation and the health and safety of the public were not affected.

Corrective Action

For the first trip of the IDID inverter, the loads for the

.panalboard 1KVID were manually transferred to the A. C. regu ated bus, and RPS l

Channel D was reset. The blown fuses were replaced.

The logic cards and their edge connectors on' the 1DID inverter will be thoroughly inspected.

Th., 1DID inverter loads will remain on the A. C. reg,ulated bus until the logic cards and edge connectors are inspected.

For the trip of the 1DIB inverter, the tiverter was put back on line, and RPS Channel B was reset. The E.S. Even Digital Channels and E.S. Analog Channel B were reset. The 1DIB inverter is currently operating satisf actorily.

For the second trip of the 1DID inverter, the A. C. output breaker was immediately returned to service, and the RPS channel was reset.

" Guards" will be installed on all inverter D. C. input and A. C. output breakers to prevent accidental operation.

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