05000281/LER-1981-056-03, /03L-0:on 810902,RCS Cold Leg Sample Valve Opened W/O Operator Action & Would Not Stay Closed.Caused by Failure of seal-in Limit Switch in Valve Operator.Lock Nuts Became Loose Due to Vibration & Valve Usage

/03L-0:on 810902,RCS Cold Leg Sample Valve Opened W/O Operator Action & Would Not Stay Closed.Caused by Failure of seal-in Limit Switch in Valve Operator.Lock Nuts Became Loose Due to Vibration & Valve Usage

ML20011A394
Person / Time
Site:	Surry
Issue date:	10/01/1981
From:	Joshua Wilson VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20011A385	List: 05000281/LER-1981-056, Forwards LER 81-056/03L-0 05000281/LER-1981-056-03, /03L-0:on 810902,RCS Cold Leg Sample Valve Opened W/O Operator Action & Would Not Stay Closed.Caused by Failure of seal-in Limit Switch in Valve Operator.Lock Nuts Became Loose Due to Vibration & Valve Usage
References
LER-81-056-03L-02, LER-81-56-3L-2, NUDOCS 8110090386
Download: ML20011A394 (2)

LER-1981-056, /03L-0:on 810902,RCS Cold Leg Sample Valve Opened W/O Operator Action & Would Not Stay Closed.Caused by Failure of seal-in Limit Switch in Valve Operator.Lock Nuts Became Loose Due to Vibration & Valve Usage

Event date:
Report date:
2811981056R03 - NRC Website

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Cat.SE DESCRIFT1on AND CORRECTIVE ACTI NS h B i The f:tilure of TV-SS-202B was due to the failure of a seal-in limit switch in the i

g i valve operator. The lock nuts holding the actuating arm for the switch became loose r

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ATTACHMENT 1 SURRY POWER-JTATION,' UNIT 2 DOCKET NO:.

50-281 REPORT NO:

81-056/03L-O s

. EVENT DATE:

09-02-81 TV-SS-202B FAILED OPEN.

1.

DESCRIFFION QF EVENT:

With the unit at steady state full power it was observed that TV-SS-202B (Cold leg Sample valve) opened without operator action, and would not stay (2).

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closed. This is contra'ry to T.S.-3.8.A.1 and is reportable per T.S.6.6.2.b 2.

PROBABLE CONSEQUENCES AND STATUS OF REDUNDA!TT EQUIPMENT:

. Trip valve TV-SS-202B is one of ' two series trip valves which are opened to obtain an RCS Cold Leg Sample. They are normally closed to maintain-containment integrity. The redundant valve, TV-SS-202A, remained closed during this event and the manual isolation valve for TV-SS-202B was closed when the problem was identified; therefore, the health and safety of the public were not affected.

3.

CAUSE

The failure of TV-SS-202B was due to the failure of a seal-in-limit switch in the valve operator. The contacts of this seal-in switch close when the valve opens to seal-in the open signal. When these contacts close, the valve will open. The actuating arm for the switch is mounted on a cam in the' valve

- operator and held in place by two lock nuts. Through usage and vibration, one of these lock nuts became loosened allowing the actuating cam to move such that the actuating lever ' contacted the seal-in switch, initiating anppen signal without operator action.

4.

IMMEDIATE CORRECTIVE ACTION

The immediate corrective actions were to verify that the redundant, isola-tion valve was closed and then close the manual isolation valve.

5.

SUBSEQUENT CORRECTIVE ACTION:

The seal-in switen was readjusted, and the lock nuts tightened. The valve j

was then cycled to verify proper operation.

6.

ACTION,TO PREVENT RECURRENCE:

l This event is a random event, therefore, further corre6Sve action is not deemed necessary at this time.

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GENERIC IMPLICATIONS:

None.

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