ML19340A230

RO 287/76-05:on 760504,isolation Valve 3CS-5 Inoperable During Surveillance Testing.Caused by Torque Switch Failure. Valve 3CS-5 to Be Repaired Next Unit Outage.Temporary Operation of Valve from Breaker Cabinet Approved

ML19340A230
Person / Time
Site:	Oconee
Issue date:	06/02/1976
From:	DUKE POWER CO.
To:
Shared Package
ML19340A228	List: ML19340A227 ML19340A230
References
RO-287-76-05, RO-287-76-5, NUDOCS 8001140845
Download: ML19340A230 (1)

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DUKE POWER COMPANY OCOMEE UNIT 3 Report No.: R0-287/76-5 Report Date: June 2, 1976 Occurrence Date: May 4, 1976 Facility: Oconee Unit 3, Seneca, South Carolina Identification _o* Occurrence: ES valve determined inoperable during surveillance testing De cription of Occurrence:

On May 4,1976, during the performance of surveillance testing, the quench tat k reactor building isolation valve 3CS-5 could not be cycled from the open to the closed position. This valve is an Engineered Safeguards valve and is required to close upon receiving an ES actuation signal in order to assure containment integrity. Within approximately one hour from tae time the determination of inoperability was made, the redundant containment isolation valve was locked closed. Oconee Technical Specification 3.6.4 (b)(2) states that a containment isolation valve may be inoperable provided the affected penetration is isolated within four hours by the use of a deactivated automatic valve secured and locked in the isolated position.

Apparent Cause of Occurrence:

Investigation revealed that valve 3CS-5 would not close electrically from the Control Room due to an inoperable torque limit switch; however, the valve was operable locally at the breaker by overriding the torque limit switch. The specific cause of torque switch failure has not been determined due to inaccessibility of the valve during power operation.

Analysis of Occurrence:

Valve 3CS-5 was properly isolated in compliance with Oconee Technical Specification 3.6.4(b)(2) by securing the redundant valve, 3CS-6, in the closed position. In the event that containment integrity had been required, the redundant isolation valve would have closed upon an ES actuation.

Con tainment integrity was not affected by this incident, and it is therefore concluded that the health and safety of the public were not affected.

Corrective Action:

Valve 3CS-5 will be repaired during the next unit outage. In the interim, a temporary procedure has been prepared and approved to operate the valve when needed from the breaker cabinet where the torque limit switch may be electrically overridden.

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