ML18113A563

LER 78-033/03L-0:on 780926,circulating Water Outlet Valve MOV-CW-200D Failed to Close When Operated Electronically. Actuator Cam for Shut Torque Switch Became Wedged.Switch Modified by Installing Holddown Screw Locking Hardware

ML18113A563
Person / Time
Site:	Surry
Issue date:	10/17/1978
From:	Baucom T VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18113A560	List: ML18113A559 ML18113A563
References
LER-78-033-03L, LER-78-33-3L, NUDOCS 7810200112
Download: ML18113A563 (2)

Text

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NRC U.S. NUCLEAR REGULATORY COMMISSION

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!During steady state power operation, circulating water outlet*valve MOV-CW-200D failed to* _close when operated electrically. This is reportable pursuant* to_* Technical

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS @

JThe actuator cam for the "shut" torque switch became wedged against a torque switch hold down screw. Corrective action was to modify the hold down screw locking ITTIJ hardware to increase clearance between the screw head and the actuator cam.

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~ Att?chment (Page 1 of~

Surry Power.Station, Unit 2 Docket No: 50-281 Report No: 78-033/03L-0 Event Date: 9-26-78 Failure of Circulating Water Outlet Valve MOV-CW-200D

1. Description of Event:

During steady state power operation, circulating water outlet valve HOV-CW-200D failed to operate electrically. This is reportable pursuant to Technical Specification 6.6.2.b.(2).

2. Probable Consequences and Status of Redundant Systems:

The corresponding inlet valve, MOV-CW-206D, was fully operable, providing full redundancy. In addition, MOV-C\v-200D was operable in the manual mode. The h~alth and safety of the general public were therefore not affected.

3. Cause:

Sometime prior to this event, MOV_-CW-200D was manually closed to assure leak tight closure. Manual closure of this valve causes the torque switch actuator cam to travel farther than when operated electrically. This additional cam travel caused the torque switch cam to wedge against the torque switch hold down screw. This situation did not interfere with the remote opening signal to the valve, but, remote closure circuit was interrupted because of the wedged position of the switch.

4. Immediate Corrective Action:

An operator was immediately assigned for .administrative control of MOV-CW-200D and it was closed manually.

5. Subsequent Corrective Action:

The torque switch hold down screw lock washer was removed to provide a clearance between the actual cam and the hold down screw, allowing full cam movement without interference. All other circulatinp, water valve operators were inspected and found to have adequate clearance.

6. Action Taken to Prevent Recurrence:

Action has* been taken to modify the hold down screw to provide adequate clearance.

7. Generic Implications:

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