05000397/LER-1998-002, :on 980311,reactor Scram & Plant Transient Occurred,Due to Failed Closed Main Steam Isolation Valve. Caused by Loss of Pneumatic Actuating Supply Pressure. Problem Evaluation Request Written for Failure of MS-V-22D

:on 980311,reactor Scram & Plant Transient Occurred,Due to Failed Closed Main Steam Isolation Valve. Caused by Loss of Pneumatic Actuating Supply Pressure. Problem Evaluation Request Written for Failure of MS-V-22D

ML17292B328
Person / Time
Site:	Columbia
Issue date:	04/09/1998
From:	Pfitzer B WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:
Shared Package
ML17292B326	List: 05000397/LER-1998-002, :on 980311,reactor Scram & Plant Transient Occurred,Due to Failed Closed Main Steam Isolation Valve. Caused by Loss of Pneumatic Actuating Supply Pressure. Problem Evaluation Request Written for Failure of MS-V-22D
References
LER-98-002, LER-98-2, NUDOCS 9804160338
Download: ML17292B328 (7)

LER-1998-002, on 980311,reactor Scram & Plant Transient Occurred,Due to Failed Closed Main Steam Isolation Valve. Caused by Loss of Pneumatic Actuating Supply Pressure. Problem Evaluation Request Written for Failure of MS-V-22D

Event date:
Report date:
3971998002R00 - NRC Website

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FACILITY NAME I I )

LICENSEE EVENT REPORT (LER TEXT CONTINUATION DOCKET NUHBER I2)

YEAR LER NUMBER I6)

SEQUENT1AL NUMBER AEVlSIOr NUMBER PAGE I3)

Washington Nuclear Plant - Unit 2 50-397 98 00 3

OF 5

TEXT(Ifmore space is required, use additional copies of NRC Form 366A) (17)

At approximately 40 minutes into the event, the initial.SCRAM was reset to minimize temperature stratification in the lower RPV head area.

Approximately 10 minutes later, during manual operation of MSRVs for RPV pressure control and manual operation of RCIC for level control, a second reactor SCRAM occurred due to RPV low level at +13 inches.

This second SCRAM is the subject of LER 98-003.

The second SCRAM was subsequently reset, emergency operating procedures were exited when entry parameters were restored to normal and conditions were stable, and the RPV was depressurized per normal plant operating procedures using main condenser turbine by-pass valves.

During.the activity of re-opening MSIVs to allow depressurization to the main condenser it was recognized by the operations crew that MS-V-22D would not re-open.

10CFR50.72 reports were made addressing the initial SCRAM and MSIVisolation, the Engineered Safety Feature (ESF) actuations that occurred due to low RPV level, the ESF actuations that occurred due to high drywell pressure, and the second RPV low level SCRAM.

mmedi e

rr tiv Ac ion A Problem Evaluation Request (PER) was written for the failure of MS-V-22D.

Plant Management initiated an investigation to determine the exact details of the event.

Additional PERs were initiated for the problems found.

Further Evaluation Although the cause of the SCRAM was not initiallyknown, investigation revealed the cause to be inadvertent closure of MS-V-22D due to a failed Containment Instrument Air(CIA)tLD] tube supplying actuating nitrogen to the valve actuator.

The ESF actuations that occurred due to low RPV level and high drywell

pressure, which are also reportable per 10CFR50.73, were a direct and expected result of the initial SCRAM.

A detailed review of the Final Safety Analysis Report (FSAR) and related documentation was performed to verify the observed. plant power level response, RPV pressure and level response, and containment pressure response were as predicted by analysis.

Given the differences in plant operations and the analysis assumptions, the plant response to the event was consistent with the analyses.

A scenario very similar to the actual event was run on the WNP-2 simulator.

With fullMSIVclosure, the RPV level decreased to approximately -27 inches during the simulation, versus approximately -50 inches experienced during the event.

Changes in simulator modeling of pressure-induced RPV level effects are planned and are further detailed in LER 98-003.

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