ML19317F184

Unusual Event Rept 287/75-11:on 751008,Valve 3LPSW-78 Failed,Restricting Svc Water Flow.Caused by Improper Installation of Coupling Pin in Valve Operating Mechanism. Pin Reinstalled

ML19317F184
Person / Time
Site:	Oconee
Issue date:	11/10/1975
From:	DUKE POWER CO.
To:
Shared Package
ML19317F178	List: ML19317F177 ML19317F184
References
287-75-11, NUDOCS 8001080898
Download: ML19317F184 (1)

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d DUKE POWER COMPANY OCONEE UNIT 3

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Report No.: UE-287/75-11 ,

Rrpert Date: November 10, 1975 -

Ev nt Date: October 8,1975 Freility: Oconee Unit 3, Seneca, South Carolina Identification of Event: Valve failure resulting in restricted LPSW flow b 7,

Conditions Prior to Event: Unit in cold shutdown 4

D wcription of Event:

On October 8,1975 during an Oconee Unit 3 outage, difficulty was encountered.in main- l taining low pressure service water (LPSW) flow to the "3B" decay heat cooler above 18Q0 gpm. The "3A" decay heat cooler was placed into service to provide adequate heat re-moval. Subsequent investigation revealed that valve 3LPSW-78, LPSW outlet from the dscay heat cooler, had failed in the partially closed positiondrestricting,the service vster flow. ... (

D2eignation of Apparent Cause of Event:

This incident was apparently caused by improper installatio~n of k coupling pin in the valve operating mechanism. The function of the pin is to couple the valve operator sleeve to the valve shaft. Due to a misalignment of the guide holes, the pin was ap-parently improperly installed from the bottom rather than from the top of the sleeve.

Subsequently, the pin vibrated loose and fell out, allowing the throttle valve to close.

Analysis of Even::

This incident resulted in partial blocking of LPSW flow to one of two redundant decay htat coolers while the reactor was in a cold shutdown condition. Adequate decay heat rcmoval capability was provided throughout this incident. It is concluded that the health and safety of the public was not affected.

Corrective Action:

Tha tapered pin fastening the operator sleeve to the valve shaft has been properly in-etalled and the valve returned to service. This is the first of this type failure ex-parienced at Oconee end is considered to be an isolated incident.

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800108pp