PNO-II-90-049, on 900911,unit Lost Shutdown Cooling to Reactor for 5 Minutes.Caused by Hotleg Suction Valve to RHR Sys Closing Possibly Due to Mod Work Performed in Auxiliary Instrument Room.Operators Opened Valve & Cooling Restored

PNO-II-90-049:on 900911,unit Lost Shutdown Cooling to Reactor for 5 Minutes.Caused by Hotleg Suction Valve to RHR Sys Closing Possibly Due to Mod Work Performed in Auxiliary Instrument Room.Operators Opened Valve & Cooling Restored

ML20059J005
Person / Time
Site:	Sequoyah
Issue date:	09/11/1990
From:	Wilson B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-90-049, PNO-II-90-49, NUDOCS 9009190129
Download: ML20059J005 (2)

//

r- [, September 11, 1990 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-III-90-49 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The it. formation is as initially . received without verification or evaluation, and is basically all that is known by the Region 11 staff on this date.

FACILITY: Tennessee Valley Authority Licensee Emergency Classification-Sequoyah Unit 2 Notification of Unusual Event Docket No. 50-328 x Alert Soddy Daisy, Tennessee Site Area _ Emergency-General Emergency

'Not Applicable

SUBJECT:

LOSS OF SHUTDOWN COOLING On September 11, 1990, at 1:33 p.m., Unit 2 lost . shutdown cooling to the reactor for - 5 minutes. This was the result of the hotleg suction valve 7 to i the Residual Heat Removal System, 2-FCV-74-1, going closed. This valve- i provides a suction path from the Reactor Coolant System to the RHR . System i for shutdown cooling. Operators were alerted to this problem at 1:32 p.m.  ;

when an RHR high pressure ' alarm was received.. .0perators were inable- to  !

Operators turned- off

• the RHR pumps, open the valve from the control room.

pra- eded to the local instrument panel, _and selected a different ' pressure-channel to monitor. The hotleg suction valve then -opened. Operators started the RHR pumps and shutdown cooling was restored. - Reactor Coolant 3' temperature increased 5 degrees to 132 degrees during the period of time that shutdown cooling was lost. The : licensee declared the . alert at 2:07 p.m.

and terminated the alert at the same time. The licensee-' believes that modification work being performed in the Auxiliary Instrument -Room may have caused the high pressure signal. Although the 28 disel ' generator was running for a surveillance test at the time of the event, it and' all other accident mitigation systems required in the shutdown mode were opereble.

The unit had shutdown on September 7, '1990 to begin the cycle 4 refueling-outage.

NRC staff continues to review the actions of TVA on this issue. l Media attention is expected.

The state of Tennessee has been informed.

i' This information is current as of 4:00 p.m. on September 11, 1990.

1 CONTACT: B. A. Wilson FTS: 841-5526 .

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