05000269/LER-1983-004, Forwards LER 83-004/03L-0.Detailed Event Analysis Encl

Forwards LER 83-004/03L-0.Detailed Event Analysis Encl

ML20069B340
Person / Time
Site:	Oconee
Issue date:	03/04/1983
From:	Tucker H DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20069B342	List: 05000269/LER-1983-004, Forwards LER 83-004/03L-0.Detailed Event Analysis Encl 05000269/LER-1983-004-03, /03L-0:on 830202,70 Ampere Circuit Breaker Failed to Trip Causing 350 Ampere Circuit Breaker to Trip Resulting in Loss of Power to SY-1 Battery Charger.Caused by Procedure & Component Failure.Breaker Replaced
References
NUDOCS 8303160565
Download: ML20069B340 (2)

LER-1983-004, Forwards LER 83-004/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2691983004R00 - NRC Website

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DUKE POWER GOMPANY P.O. HOJC 33180 CHAMLOTTE. N.C. 28242 H AI. B. TI'CKEH TEI.EPHONE

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March 4, 1983 1:-

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Mr. James P. O'Reilly, Regional Administrator

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Atlanta, Georgia 30303 M.c Re: Oconee Nuclear Station Docket No. 50-269

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-269/83-04. This report is submitted pursuant to Oconee Nuclear Station Technical Specification 6.6.2.1.b(2) which concerns conditions leading to operation in a degraded mode permitted by a limiting condition of operation per Technical Specification 3.7.2(e)1., and describes an incident which is considered to be of no signifi-cance with respect to its effect on the health and safety of the public.

Very truly yours, fB.V A /9_Q/

Hal B. Tucker PFG/php Attachment cc: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. C. Bryant NRC Resident Inspector i

Oconee Nuclear Station INP0 Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 Mr. E. L. Conner, Jr.

Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555

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r-Duke Power Company Oconee Nuclear Station Report Number: RO-269/83-04 Report Date: March 4, 1983 Occurrence Date: February 2, 1983 Facility: Oconee Units 1, 2, 3, Seneca, South Carolina Identification of Occurrence: AC Power was lost to the 125V DC 230 KV Switching Station Power System SY-1 battery charger.

Conditions Prior to Occurrence: Oconee 1 100% Full Power Oconee 2 100% Full Power Oconee 3 100% Full Power Description of Occurrence: On February 2,1983 at 0920, while the yearly periodic being performed on Power Circuit Breaker (PCB) -15, a maintenance (PM) was screwdriver that was being used slipped off a piece of equipment and inadvertently short circuited one 480V phase to ground on the switchyard 480 VAC system. A 70 amp breaker at the Switchyard Power Panel Board (SPA) malfunctioned and did not trip as it should have, causing the 350 amp breaker, which feeds AC power to the SPA, to trip. When the 350 amp fuse tripped, AC power was lost to battery charger SY-1, SY-S and PCBs 7 through 16 as well. Loss of the SY-1 battery placed Units 1, 2, and 3 under a Limiting Condition for Operation (LCO) per Technical Specification 3.7.2(e)1.

Apparent Cause of Occurrence: The cause of this incident was component malfunction and procedure deficiency. Had the 70 amp breaker functioned properly and tripped as designed, it would have prevented the tripping of the 350 amp breaker. Thus, AC power would have been maintained to the SPA and AC power would not have been lost to the SY-1 battery charger. The PM work was performed per normal and acceptable operating practices, but because of the minor accident, two terminal strips were shorted. The procedure should have taken into account the possibility that this type of accident could occur, and also, the possible safety hazard of working in close proximity of exposed and energized terminal strips.

Analysis of Occurrence: When the 480V AC supply to battery chargers SY-1 and SY-S was lost, battery SY-1 kept the SY-1 DC bus energized. Had a fault developed resulting in a loss of power to the SY-1 DC bus, redundant relaying is provided by the SY-2 DC bus. The health and safety of the public were not compromised by this event.

Corrective Action

The immediate corrective action war to reset the 350 amp feeder breaker.

In less than one hour from the time AC power was lost, the Keowee underground power path was tested and was determined to be operable. The 70 amp breaker and the trip unit of the 350 amp breaker will be replaced. It is recommended that the Transmission Department evaluate the work which led up to the short circuit and change their procedures / operating practices, as necessary, to prevent personnel from contacting energized equipment.