ML20247K928

Special Rept:On 980428,letdown PCV Exhibited Slow Response When C RCP Was Started.Cause to Be Determined.Review of Operating Procedure Will Be Performed to Determine If Enhancements Are Necessary

ML20247K928
Person / Time
Site:	North Anna
Issue date:	05/15/1998
From:	Matthews W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
98-266, NUDOCS 9805220259
Download: ML20247K928 (2)

Text

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VIHOINIA ELucTurc Ann Poweit COMPANY Ricunoxu, Vino 1NIA 20261 May 15,1998 United States Nuclear Regulatory Commission Serial No.98-266 Attention: Document Control Desk NAPS: MPW Washington, D.C. 20555 Docket Nos. 50-339 License Nos. NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 2 PRESSURIZER PORV SPECIAL REPORT Pursuant to North Anna Technical Specification (TS) Section 6.9.2.f a Special Report is hereby submitted for a condition that resulted in a pressurizer (PZR) power operated relief valve (PORV) lifting to mitigate a reactor coolant system (RCS) low-temperature overpressure transient.

With Unit 2 in Mode 5, cold shutdown, the RCS loops were filled to solid water conditions using a loop vacuum fill method during start-up activities following a recent refueling outage. On April 28, 1998, with RCS temperature at approximately 127 degrees F and pressure at approximately 330 psig, the "C" reactor coolant pump (RCP) was started to facilitate heat-up of the RCS and sweep entrained air out of the loops.

Upon start of the RCP, an expected increase in RCS pressure was indicated and control room personnel initiated actions to control pressure. The letdown pressure control valve (PCV) potentiometer was adjusted to decrease pressure. The letdown PCV exhibited a slow response, and within 16 seconds of the RCP start, the PZR PORV (2-RC-PCV-2456) cycled open. The highest indicated pressure was 383 psig versus the PORV lift setpoint of 370 psig.

After the PORV opened, RCS pressure decreased rapidly. The letdown PCV potentiometer was adjusted to increase pressure. Once RCS pressure began to increase the potentiometer was adjusted to stabilize pressure. Letdown pressure control valve response was again sluggish and the PZR PORV cycled open a second time. Subsequently, pressure was stabilized below the PORV lift setpoint.

The sluggish operation of the letdown PCV is being evaluated to determine the cause.

A review of the operating procedure will be performed to determine if enhancements are necessary regarding RCP starts versus RCS temperatures and PZR PORV setpoints.

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9805220259 980515 PDR ADOCK 05000339 S PDR

. s The Station Nuclear Safety and Operating Committee has reviewed this report and it will be provided to the Management Safety Review Committee. Should you have any questions regarding this report, please contact us.

1 . .

l Very truly yours,

%WW W. R. Ma+ thews Site Vice President Commitments made in this letter: Evaluation of the letdown PCV operation and review of the l operating procedure regarding RCP starts versus RCS temperatures and PZR PORV

! setpoints.

cc: U. S. Nuclear Regulatory Commission Region ll l Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. M. J. Morgan NRC Senior Resident inspector l North Anna Power Station l

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