ML19261A837

LER 78-033/03L-0 on 781219:during Automatic Isolation of Ventilation Sys,Inlet Isolation Dampers 1-5741 a & B Failed to Close.Pilot Solenoid on Air Operator of Damper Valves Stuck & Failed to Supply Air Signal Needed to Close Valve

ML19261A837
Person / Time
Site:	Quad Cities
Issue date:	01/17/1979
From:	Schnitzmeyer J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19261A832	List: ML19261A829 ML19261A837
References
LER-78-033-03L, LER-78-33-3L, NUDOCS 7902080220
Download: ML19261A837 (2)

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[ o 14 l l damper closed, thus providing inlet isolation. The consequences of this occurrence l o s were minimized by the fan discharge louvers closing and preventing reverse air i o s l flow. This, in conjunction with the starting of the Standby Gas Trains, prevented l O 7 l any leakage of the reacto'r building atmosphere to the environs. l l

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[T J O ] l The pilot solenoid on the air operator of each damper va lve had stuck and failed to l i i l supply the appropriate air signal needed to close the valve. The defective sniennia I

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1. LER NUMBER: R0 78-33/03L-0 ll. LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station 111. FACILITY NAME: Unit One IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

On December 19, 1978, gases created by repetitive backwashing the Unit Two Cleanup Demineralizers, caused the Reactor Building Ventilation System to auto isolate. During this isolation it was discovered that the inlet isolation dampers 1-5741 A & B failed to close. The reactor building supply and exhaust fans tripped and the outlet isolation dampers 1-5742 A & B did close as designed. The solenoid for inlet damper 1-5741A was tarped, and the damper shut, thus providing isolation on the ir.iet vent duct.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

The consequences of this occurrence were minical because each fan has louvers which close with the tripping of the fan, thus preventing any reverse air flow. Subsequently, even though inlet dampers 1-5741 A & B failed to close there was redundancy in these louvers. This, in conjunction with the auto starting of the standby gas trains, allowed no leakage of the reactor building atmosphere to the environs.

Vll. CAUSE:

The cause ofthis occurrence is attributed to equipment failure.

The pilot solenoid on the air operator of each damper valve had failed to supply the appropriate air signal to close the valve. An inspection of the pilot valves revealed that an accumulation of dirt in the casing had caused the piston, which controls air flow, to stick. The pilot valves are made by the Versa Company and are model number VGS-4522.

Vill. CORRECTIVE ACTION:

The defective solenoid pilot valves were replaced and the dampers operated prope. ly. Procedure changes have been initiated to verify that the dampers close during the Standby Gas Auto Initiation and Reactor Building Ventilation Auto isolation Surveillance Test (Q0S 7500-4) which is performed once per operating cycle. Also a procedure change has been i n i t i..ted to the Rx Vent Isolation / Fuel Pool Radiation Monitor Outage Report (QOS 1700-01) to verify proper damper operability.