ML19322E855

LER 80-005/03L-0:on 800224,while Performing Misv Closure Timing,Valve AD 1-203-1B Failed to Close When Control Switch Was Operated.Caused by Blockage of Exhaust Restrictor on on Pilot Valve.Exhaust Restrictor Cleaned

ML19322E855
Person / Time
Site:	Quad Cities
Issue date:	03/20/1980
From:	Soden R COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19322E846	List: ML19322E855
References
LER-80-005-03L-01, LER-80-5-3L-1, NUDOCS 8004020357
Download: ML19322E855 (2)

Text

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EQl While performing MISV Closure Timing, surveillance procedure QOS 250-4, valve A0 l goi,; l l-203-1B failed to close when the control switch was operated. The redundant in-linel p;7q l A0 1-203-2B valve was placed in the closed position, according to Technical Spec- l

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CAUSE DEseniPTION AND COnHECTIVE ACTtONS

[' i o i L. The cause of the failure was due to a blockage of the exhaust restrictor on the l

[rji j l pilot valve. Blockaqe of the exhaust from the pilot valve resulted in a pneumatic I m] lock on the pilot valve, preventing main valve operation. The exhaust restrictor wasl p7ql cleaned and MSIV A0 1-203-lB was satisfactorily operated from the control switch. l li l41 I l 7 8 9 80 STA S  % POWE R OTHER STATUS 15C RV OISCOVERY DESCHiPTION s

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1. LER NUMBER: 80-05/03L-0

11. LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station 111. FACILITY NAME: Un8 t i IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

On February 24, at 9:05 AM, while performing MSIV closure

, timing, surveillance procedure QOS 250-4, valve A0 1-203-1B failed to close when the control switch was operated.

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At the time of the occurrence Unit One was operating at a reduced load of 318 MWe to perform an on-line control rod sequence exchange.

The redundant MSIV (A0 1-203-28) was closed and the drywell was de-Inerted so an entry could be made to determine the problem.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

The consequences of this occurrence were minimal because valve A0 1-203-2B, which is in-line with valve A0 1-203-1B, would have provided the necessary isolation in the event of a Group One isolation signal.

Vll. CAUSE:

The cause of the failure was a blockage of the exhaust restrictor on the pilot valve. Blockage of the exhaust from the pilot

valve resulted in a pneumatic lock on the pilot valve which prevented main valve operation.

Vill. CORRECTIVE ACTION:

Work request Q 3722 was written to investigate and correct r.ne problem. The solenoid assembly and pilot valve assembly wece replaced wi thout correcting the problem. The exhaust restrictor was cleaned and valve A0 1-203-18 operated correctly from the control switch. The remaining Unit One MSIV's were satisfactorily cycled and closure timed..

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