ML19316A404

RO 269/78-06:on 780310,field Flashing Breaker Failed to Close During Startup of Keowee Hydro Unit 2.Breakers & Associated Relays Checked.Circuits Checked.Cause of Breaker Malfunction Unknown.Search for Possible Causes Continues

ML19316A404
Person / Time
Site:	Oconee
Issue date:	04/07/1978
From:	DUKE POWER CO.
To:
Shared Package
ML19316A401	List: ML19316A400 ML19316A404 ML19316A409
References
RO-269-78-06, RO-269-78-6, NUDOCS 7912110663
Download: ML19316A404 (2)

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DUKE POWER COMPANY

, OCONEE UNIT 2 Report Number: R0-269/78-6 Report Date: April 7, 1978 Occurrence Date: March 10, 1978 Facility: Oconee Nuclear Station, Seneca, South Carolina Identification of occurrence: Keowee Unit 2, Field Flashing Breaker Inoperable Conditions Prior to Occurrence: Unit i 100% FP Unit 2 100% FP Unit 3 100% FP Description of Occurrence:

At 0701 on March 10, 1978 when an attempt was made to start Keowee Hydro Unit 2, the unit's field flashing breaker failed to close. The unit was thereby made inoperable, contrary to the requirements of Oconee Nuclear Station Technical Specifications 3.7.1. Keowee Unit I was verified operable at 0713. Unit 2 was returned to service at 1534 af ter a complete investigation of the breaker abnormality. The unit was left inoperable for slightly longer than normal to leave it in its failed mode during investigatiou by a Westinghouse representa-tive.

This type of incident has occurred on three previous occasions, which were reported in Reportable Occurrence Reports R0-269/77-29, R0-269/78-1 and R0-269/78-3, transmitted by my letters of January 18, February 3, and March 23, 1978, respectively.

Apparent Cause of Occurrence:

A breaker maintenance crew and a Westinghouse representative checked the field flashing, field and supply breakers as well as associated relays withcut noting any abnormalities. Control and closing circuits were also checked without any resulting failures. Therefore, the exact cause of the breaker malfunctions are still unknown. Further investigation is proceeding to identify a possible cause.

Analysis of Occurrence:

The failure of the breaker to close caused Keowee Unit 2 to become temporarily inoperable. Throughout this period, the second Keowee Hydro unit was fully operable and available to supply emergency power to the station if required.

The health and safety of the public were not endangered.

l 7912110 h a

Corrective Action:

A determination of proper corrective action will be made when the cause is established. Until that time, extensive investigation and monitoring will continue.

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