ML20151F734

Special Rept:On 880307 & 08,diesel Generator 1A Experienced One Valid & Three Invalid Failures,Respectively.Caused by Loss of Generator Excitation Due to Shorted Rectifier Diode CR6.Circuit Replaced

ML20151F734
Person / Time
Site:	Catawba
Issue date:	04/06/1988
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
NUDOCS 8804180424
Download: ML20151F734 (2)

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DUKE POWER COMPANY P.O. BOX 13989 CHARLOTTE. N.C. 98949 HAL II. TUCKER Tatars.own swa r .. we (704)073 483:

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April 6, 1988 U. S. Nuclear Regulatory Comission 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 a Diesel Generator 1A valid failure on March 7, 1988, and three invalid failures on March 8, 1988.

Very truly yours,

/

JR IJ -

Hal B. Tucker JGT/10019/sbn Attacilment xc Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Comission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. P. K. Van Doorn hTC Resident Inspector Catawba Nuclear Station 8804180424 880406 PDR ADOCK 05000413 S ED ga

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SPECIAL REPORT CATAWBA NUCLEAR STATION, UNIT 1 .

DIESEL GENERATOR 1A INVALID FAILURE  !

ON MARCH 7, 1988 (

AND THREE INVALID FAILURFS I

ON MARCH 8, 1988 While performing the operability verification of Diesel Generator (D/G) 1A on March 7, 1988, the D/G failed to reach the required 441 RPM within 11 seconds during start number 623 at 1005 hours0.0116 days <br />0.279 hours <br />0.00166 weeks <br />3.824025e-4 months <br />. High differential pressure across the fuel oil pump strainers and oil filters prompted the issuance of Standing Work Requests 5402, 5404, 6921, and 9004. The strainers and filters for D/G 1A were ,

replaced by 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on that day. This is the third Valid Failure in the last r

- 100 Valid Starts on D/G 1A and the first in the last 20 Valid Starts. The surveillance interval remained at 31 days following this Valid Failure, which is  ;

in accordance with Technical Specifications Surveillance 4.8.1.1.2.

Invalid Test Start numbers 624, 625, and 626 were performed to troubleshoot Start l number 623.

l Invalid Failure Start number 627 was performed on March 7, 1988, at 1955 hours0.0226 days <br />0.543 hours <br />0.00323 weeks <br />7.438775e-4 months <br /> to I verify operability by loading the D/G. The D/G started properly and loaded to 5700 KW but tripped on overcurrent protection after exhibiting varying excitation voltage. Invalid Failure Start numbers 628 and 629 were performed to .

troubleshoot the overcurrent trip on Start number 627. The D/G started but would f not load due to loss of generator excitation. Work Request 27213 OPS was '

initiated and identified a shorted rectifier diode (CR6) in the excitation circuit which was subsequently replaced._  ;

I Valid Success Start number 630 was performed on March 8, 1988, at 1535 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.840675e-4 months <br /> following replacement of the rectifier diode. D/G 1A was unavailable for 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br />, 30 minutes as a result of these problems. Unit I was in Power Operation  :

during the period D/G 1A was unavailable. D/G 1B was verified operable as well l as offsite power as required by Technical Specifications. I I

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