ML20154L105

Special Rept:On 880419,diesel Generator 1A Seventh Failure Occurred Due to Pneumatic Control Sys Problem.Caused by Leak in Orifice Check Valve.Check Valve & Shuttle Valve Replaced. Further Investigation Indicated Design Deficiency in Sys

ML20154L105
Person / Time
Site:	Catawba
Issue date:	05/19/1988
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
NUDOCS 8805310159
Download: ML20154L105 (2)

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. DUKE POWER GOMPAhT P.O. BOX 33180 CHARLOTTE, N.C. 28242 HAL B. TUCKER TELEPHONE nui rnaaman (704) 3 MF4W31 miza.sas paootw ios May 19, 1988 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555

Subject:

Catawba Nuclear Station, Unit 1 Docket No. 50-413 Special Report Gentlemen:

Pursuant to Technical Specification 3/4.8.1.1.3, please find attached a Special Report concerning the Diesel Generator (D/G) 1A 7th valid failure in the last 100 Unit i valid tests which took place on April 19, 1988.

Pursuant to Regulatory Guide 1.108 and Technical Specification 3/4.8.1.1.3, supplemental information regarding this failure will be provided prior to June 1, 1988, in a future special report regarding the 8th and 9th D/G 1A valid failures which occurred on April 25, 1988 and May 5, 1988, respectively.

Very truly yours, Hal B. Tucker JGT/23/sbn Attachment xc: Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station v

8805310159 880519 i g PDR ADOCK 05000413 S DCD c

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• DUKE POWER COMPANY CATAWBA NUCLEAR STATION SPECIAL REPORT REGARDING DIESEL GENT.ATOR 1A VALID FAILURE ON APRIL 19, 1988 DUE TO PNEUMATIC CONTROL SYSTEM PROBLEMS While performing the operability verification of Diesel Generator (D/G) 1A on April 19, 1988, the lJ/L tripped during start //662 at approximately 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br />.

This was the fifth Ve.11d Failure in the last 20 Valid Starts on D/G 1A and the sixth in the last 100 Talid Starts. The surveillance interval was at overy 7 days following the Val d Failure, which is in accordance with Technical Specification Surveill ocs 4.8.1.1.2. This is the seventh Valid Failure in the last 100 Valid Starts ca Unit 1 D/Gs.

At 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br />, Work Request 27635 OPS was initiated to investigate and repair the cause of the D/G trip. Two starts did not identify any abnormal parameters associated with Group II switchover and non emergency trips. Instrumentation sensors associated with-Lube Oil pressure, Crankcase pressure, and Pneumatic logic were inspected and proper calibration was verified. None the less, the sensors were replaced.

Troubleshooting continued on April 20, 1988. The proper calibration of-Jacket Water temperature and Lube Oil temperature instrumentation was verified. The D/G was started and did not trip, but the trip sensors did not come up to pressute until a few seconds before Group II switchover. Instrument tubings associated with Lube Oil pressure, Lube Oil temperature, Bearing temperature, Jacket Water ,

temperature, Crankcase pressure, and Vibration were pressurized to identify any leaks.

An orifice check valve, .004 orifice, was found to be leaking through its seat, causing depressurization of the pneumatic trip circuitry. The .004 orifice check valve was replaced, and also the P-3 shuttle valve was replaced although no problem was found. Three successful starts were performed on the D/G with all indications remaining normal.

On April 21, monitoring was continued while 3 engine starts were performed. All indications were found to be normal.

Duke Power Instrumentation and Electrical (IAE) personnel were not fully satisfied that the leaking check valve was significant enough to have caused the D/G trip, although no additional problems were identified at the time. An investigation of a subsequent failure of the D/G identified a potential generic design deficiency in the pneumatic control system. IAE personnel suspect that the deficiency

- likely contributed to the April 19, 1988 failure as well. The additional findings will be discussed in a future Special Report.

D/G 1A was unavailable for approximately 58 hours6.712963e-4 days <br />0.0161 hours <br />9.589947e-5 weeks <br />2.2069e-5 months <br /> as a result of this problem.

Unit I was in Mode 1, Power Operation, during this time. The availability of offsite power and D/G 1B's operability were verified as required by Technical Specifications.

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