05000254/LER-1980-020-03, /03L-0:on 800831,during Electromatic Relief Valve Operability Surveillance Qos 201-1,electromatic Relief Valve 1-203-3B Failed to Close.Caused by Steam Cutting of Pilot Valve Allowing Steam to Leak Out Exhaust Port

/03L-0:on 800831,during Electromatic Relief Valve Operability Surveillance Qos 201-1,electromatic Relief Valve 1-203-3B Failed to Close.Caused by Steam Cutting of Pilot Valve Allowing Steam to Leak Out Exhaust Port

ML19338F009
Person / Time
Site:	Quad Cities
Issue date:	09/24/1980
From:	Dunesia Clark COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19338F007	List: 05000254/LER-1980-020, Forwards LER 80-020/03L-0 05000254/LER-1980-020-03, /03L-0:on 800831,during Electromatic Relief Valve Operability Surveillance Qos 201-1,electromatic Relief Valve 1-203-3B Failed to Close.Caused by Steam Cutting of Pilot Valve Allowing Steam to Leak Out Exhaust Port
References
LER-80-020-03L-05, LER-80-20-3L-5, NUDOCS 8010070367
Download: ML19338F009 (3)

LER-1980-020, /03L-0:on 800831,during Electromatic Relief Valve Operability Surveillance Qos 201-1,electromatic Relief Valve 1-203-3B Failed to Close.Caused by Steam Cutting of Pilot Valve Allowing Steam to Leak Out Exhaust Port

Event date:
Report date:
2541980020R03 - NRC Website

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60 61 DOCKET NUMBER 68 69 EV ENT DATE 74 75 REPORT DATE 80 i

EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h d

lo121l At 3:25 a.m., while performing the Electromatic Relief Valve Operability Surveillance l

(QOS 201-1) during normal unit shutdown, electromatic relief valve 1-203-3B failed to l

gl loi ;l close.

Probable consequences were minimal. The other three electromatic relief l

l o i s t I valves and the Target Rock Safety / Relief Valve were tested satisfactorily. The feed-4 1

i o le g l water system maintained normal reactor water level. At 3:27 a.m.,

the reactor was lol7; l manually scrammed. At 3:58 a.m., the relief valve closed with a reactor pressure of g

190 psig and suppression chamber temperature of 1060F.

Suppression chamber cooling had l a la l l been initiated before this event.

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40 41 42 43 44 47 CAusE DESCRIPTION AND CORRECTIVE ACTIONS h li l o ; ] The cause of the stuck open relief valve is steam cutting of the pilot valve which l

LLL'.J l allowed steam to leak out the exhaust port.

Thus, pressure could not equalize around I

i,121 I the relief valve disc to assist spring pressure in closing the valve. The relief L'.13.J l v lve will be rebuilt and shop tested for leaks and operability before replacement.

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l it will be tested for coerability at reactor oressure durino startuo from refuelino.

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abPOWER OTHER STATUS is O RY DISCOVERY DESCRIPTION I I ' 15 I I,,,Q_jh I O ! 0 l 5 lhl NA l

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NAME CF PREPANR PHONE.

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LER NUMBER:

LER/R0 80-20/03L-0 11.

LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill.

FACILITY NAM _F.

Unit One f

IV.

DOCKET NUMBER:

050-254 V.

EVENT DESCRIPTION

On August 31, 1980, Unit One was in the process of shutting down -for End-of-Cycle Five refueling outage.

During shutdown, the electromatic relief valve manual operability surveillance, procedure QOS 201-1, was performed.

At 0325 hours0.00376 days <br />0.0903 hours <br />5.373677e-4 weeks <br />1.236625e-4 months <br />, the 1-203-38 electromatic relief valve opened satisfactorily, but failed to close when the control switch was turned to the CLOSED position. The position indication light Indicated closed, but the acoustic monitor and the valve exhaust temperature indication indicated the valve was open.

Several attempts were made to close the valve with the control switch, but the valve remained open. At 0327 hours0.00378 days <br />0.0908 hours <br />5.406746e-4 weeks <br />1.244235e-4 months <br />, two minutes after the valve was opened, the reactor was manually scrammed f rom the Control Room.

The reactor pressure was a 918 PSIG and the suppression chamber temperattre was 90 F.

At 0358 hours0.00414 days <br />0.0994 hours <br />5.919312e-4 weeks <br />1.36219e-4 months <br />, the 3B relief valve closed, with the reactor pressure of 190 PSIG and a suppression chamber temperature of 1060F.

Following closure of the relief valve, a normal unit shutdown was resumed.

At 0410 hours0.00475 days <br />0.114 hours <br />6.779101e-4 weeks <br />1.56005e-4 months <br />, the Nuclear Regulatory Commission, Washington office, was notified of the transient condition.

The manual operation of the relief valves was performed in accordance with the surveillance requirements specified in Technical Specification 4.5.D.-

1.a.

The test is performed by opening a turbine bypass valve and verifying the bypass valve closes to maintain constant reactor pressure when the relief valve opens. The other three electromatic relief valves and the Target Rock Safety / Relief Valve were tested satisfactorily. At no time during the transient were the reactor pressure vessel thermal limitations exceeded.

VI.

PROBABLE CONSEQUENCES OF THE OCCURRENCE.

The probable consequences of the occurrence were minimal. The electromatic relief valves are designed to prevent overpressurization of the reactor pressure vessel in the event of a sudden reactor isolation and to auto-matically blowdown the reactor under accident conditions to allow the low pressure emergency core cooling systems to function. The reactor feed-water system was used to maintain normal reactor water level. The auto-blowdown system was always available and could have performed as designed to allow LPCI and core spray injection had it been necessary. Although the suppression chamber water temperature reached 1060F at the end of the event, the reactor was subcritical and cooling down, and the containment j

cooling mode of RHR was operating. Safe shutdown of the reactor was not affected as a result of this occurrence, j

1

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Vll. CAUSE:

The cause of this occurrence is attributed to excessive steam cutting on the pilot valve seat. This allowed steam to leak past the pilot valve and out the exhaust port so that steam pressure could not equalize around the electromatic relief valve disc to assist spring pressure in closing the valve. When the valve was removed from the steamline for inspection of the valve internals, there was no evidence of seizing between the disc and disc guide. The orifice in the retainer plug was free of foreign material as was the pilot valve assembly.

The electromatic relief valve is manufactured by Dresser Industries, Type 1525VX, serial number BK7072.

It was installed in the 3B position on February 10, 1979, af ter being overhauled.

Vill. CORRECTIVE ACTION:

The valve has been removed from the steamline and has been thoroughly inspected. Work Request Q07848 has been initiated to inspect the valve operator solenoids and mechanical actuator.

The relief valve will be rebuilt by the Mechanical Maintenance Department. The valve will be shop tested for leaks and operability.

It will also be tested at

.eactor pressure when the unit starts up following refueling.

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