ML19317F061

Unusual Event 287/74-03:on 741005,containment Isolation Valve 3CS-5 Failed to Close When Engineered Safeguards Test Was Initiated.Caused by Loose Wire Termination or Dirty Contact.Preventive Maint Program Being Established

ML19317F061
Person / Time
Site:	Oconee
Issue date:	11/08/1974
From:	DUKE POWER CO.
To:
Shared Package
ML19317F057	List: ML19317F056 ML19317F061 ML19317F064 ML19317F068
References
RO-287-74-03, RO-287-74-3, NUDOCS 8001080753
Download: ML19317F061 (1)

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s DUKE POWER COMPANY OCONEE UNIT 3 Report No.: UE-287/74-3 Report Date: November 8, 1974 Event Date: October 5, 1974 Facility: Oconec Unit 3, Seneca, South Carolina Identification of Event: Failure of Valve 3CS-5 Conditions Prior to Event: Unit in Cold Shutdown Description of Event:

On October 5, 1974, containment isolation valve 3CS-5, which allows re-circulation of the quench tank, was tested following =aintenance action several days before. The valve failed to close when the test was initiated from the Engineered Safeguards Panel (RZ module) which simulates an Engineered Safeguards signal. ,

. Designation of Apparent Cause of Event: ,

3: ., .t. ... -

A maintenance technician checked wire terminations at valve 3CS-5 and the motor control center. All connections were tightened and relay contacts cleaned. The valve was successfully operated 10 times following this maintenance action. The apparent cause of the failure of 3CS-5 to'close is assumed to have been a loose wire termination or dirty contact.

Analysis of Event:

Since the reactor was in a cold shutdown condition during this time period, containment integrity was not required. Valve 3CS-5 is a normally closed valve which is opened to allow recirculation of quench tank water through the quench tank cooler. Redundant-containment isolation valve 3CS-6 was operable during this time and would have maintained containment integrity in the unlikely event it had been necessary. The failure of this valve occurred while performing a requalification' test on the valve following '

maintenance action. The requalification test operates the valve 10 times initially and once a day for 10 additional days to restore confidence in a .

valve following maintenance action. .This incident did not affect the y health and safety of the public. ~ ' ,' ' ~~

Corrective Action:

A preventative maintenance program is being established for the Engineered

. Safeguards System which will prevent future occurrences of this nature.

Wire terminations will be tightened and electrical contacts cleaned on a periodic basis. Due to the scope of this program, an estimate of the completion date of this maintenance program has not been established.

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