ML20010G930

Forwards LER 81-140/03L-0.Detailed Event Analysis Encl

ML20010G930
Person / Time
Site:	McGuire
Issue date:	09/11/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20010G931	List: ML20010G930 ML20010G937
References
NUDOCS 8109220673
Download: ML20010G930 (3)

Text

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Mr. James P. O'Reilly, Director Eg U. S. Nuclear Regulatory Commission "8 g IO8/g Region II {/ Q ,.w, -

101 Marietta Street, Suite 3100  ?

Atlanta, Georgia 30303 1) d Re: McGuire Nuclear Station Unit 1 Docket No. 50-369

Dear Mr. O'Reilly:

Please find attached Repe.rtable Occurrence Report R0-369/81-140. This report concerns T.S. 3.3.1, "As a minimum, the reactor trip system instru-mentation channels and interlocks of Table 3.3-1 shall be operable..."

This incident was considered to be of no significance with respect to the health and safety of the public.

Very truly yours, William O. Parker, Jr.

PEP /php Attachment cc: Director Mr. Bill Lavallee Office of Management and Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Commission P. O. Box 10412 Washington, D. C. 20555 Palo Alto, California 94303 Ms. M. J. Graham Resident Inspector-NRC McGuire Nuclear Station

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. s McGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NUMBER: 81-140 REPORT DATE: September 11, 198.1 OCCURRENCE DATE: August 14, 19h1 FACILITY: McGuire Unit 1; Cornelius, N.C.

IDENTIFICATION OF 03 URRENCE: Channel 3 of Pressurizer Water Level indication was noted to be increasing above the level indications of the other (redundant) channels, which were in agreement.

CONDITION PRIOR TO OCCURRENCE: Mode 2, Start-up. Zero power physics testing prior to initial power level escalation was in progress.

DESCRIPTION OF OCCURRENCE: On August 14, 1981 Control Room monitors indicated that Pressurizer Level, Channel 3, had increased to approximately 30% above the levels of the other three channels. The affected channel was then tripped in compliance with the applicable Technical Specification 3.3.1. Action Statement.

The channel's behavior was recognized as characteristic of a leak in the high pressure (reference leg) side of the level detector sensing line, which was subsequently verified by inspection. In order to repair the leak it would be necessary to isolate the detector, thereby disabling two channels of Pressurizer Pressure (Protective System) instrumentation whose detectors share a common sensing line witF the level detector. Therefore, Reactor Shutdown was immedi-ately commenced to order to allow depressurization to below P-ll (1955 psi) which, in turn, would allow manual block of Safety Injection actuation by low pressurizer pressure signals.

The instrumentation line was soon repaired; however, recovery was delayed when it became necessary to replace the level detector manifold valve, recali-brate the detector, and correct difficulties experienced in venting the detector.

The instrumentation was not placed back in operation until August 18, 1981.

APPARENT CAUSE OF OCCURRENCE: The Leak was caused by an improperly seated tubing ferrule.

ANALYSIS OF OCCURRENCE: Sufficient evidence could not be obtained to determine whether the tubing connection had been improperly installed or the line had been physically disturbed as suspected. Nevertheless, the integrity of the tubing connection was broken.

SAFETY ANALYSIS: Failure of the single channel of Pressurizer Level instru-mentation did not prevent the functioning of the Reactor Protective System.

After the channel malfunctioned it was tripped, placing Pressurizer Level Reactor trip circuitry in a more conservative (1 out of 2) coincident logic scheme.

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Report Number 81-140 2

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! After the reactor was shut down and NC was depressurized to approximately 1900 psi,' the automatic Low Pressure actuation'of Safety Injection was manually overriden (blocked) to prevent unnecessary safety injection. This safety feature is automatically reactivated when pressure is raised back to 1955 psi.

j This incident caused no deterioration of Protective System functionability,

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therefore, neither the safe operation of the plant nor the health and safety of the public were affected.

CORRECTIVE ACTION: The affected channel was placed in the tripped condition, and the Pressurizer Level reference leg sensing line was repaired per procedure,

" Installation and Maintenance of Instrument Line Fittings and Tubing." The  ;

level transmitter was then calibrated using the procedure, " Pressurizer Level Protection Calibration."

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