ML20154C235

Special Rept:On 880412,19 & 25,diesel Generator 1a Failed to Start.Caused by Faulty Pneumatic Logic Components.Blowdown Frequency for All Generator Starting Sys Air Compressors Increased from Once to Twice Per Shift

ML20154C235
Person / Time
Site:	Catawba
Issue date:	05/12/1988
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
TAC-66403, TAC-66404, NUDOCS 8805180084
Download: ML20154C235 (3)

Text

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DuxE POWEn COMPANY l v.o. nox amas l CHA MLOTTF.,N.C. 98949 HAL H. TUCKEN tr.L*Posome vue passment (704)073 4834 ,

ensaanre<=mu m .

l May 12, 1988 i

Document Control Desk U. S. Nuclear Regulatory Conunission Wsshington, D. C.- 20555

Subject:

Catawba Nuclear Station, Unit 1 i Docket No. 50-413  !

Special Report l l

Gentlement  !

l Pursuant to Technical Specification 4.8.1.1.3, please find attached a Special t Report concerning a Diesel Generator 1A failure to start due to faulty pneumatic  !

logic components which took place on April 12, 1988.

Very truly yours, t

/

g i r l

Hal B. Tucker  ;

i JGT/19/sbn i

Attachment l

xc Dr. J. Nelson Grace Regional Administrator I U. S. Nuclear Regulatory Conunission Region II

. \ Marietta Street, NW, Suite 2900 At ;anta, Georgia 30323 Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station

~8805180084 880512 4'

J PDR ADOCK 05000413 S ED \\

SPECIAL REPORT CATAWRA NUCLEAR STATION, UNIT 1 DIESEL GENERATOR 1A FAILURE TO START DUE TO FAULTY PNEUMATIC LOGIC COMPONENTS On April 12, 1988, a Valid Failure occurred while performing Diesel Generator (D/G) 1A Operability Periodic Test. D/G 1A tripped during a start attempt (start no. 652) at 0352 hours0.00407 days <br />0.0978 hours <br />5.820106e-4 weeks <br />1.33936e-4 months <br />. This was the fourth Valid Failure in the last 100 Valid Starts, and the third within the last 20. Work Request 27513 OPS was written by i Operations for Instrumentation and Electrical (IAE) to troubleshoot D/G 1A and the D/G was declared inoperable at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />. Investigation by IAE revealed that one of the three low low lube oil pressure pneumatic trip valves was faulty.

It would periodically fail to close as oil pressure was applied to the valve.

This caused the D/G to trip, and apparently caused the previous trip on March 23, 1988, as the symptoms were identical. The other two trip valves were disassembled and showed signs of corrosion. All three of these trip valves were replaced.

Three subsequent D/G 1A start attempts were successful and the D/G was declared operable at 0025 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> on April 13, 1988. The D/G was inoperable for 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />, l 25 minutes.

The D/G remains on the seven day testing interval in accordance with Technical l Specification Surveillance 4.8.1.1.2.

l On April 19, 1988 and April 25, 1983, additional Valid Failures on D/G 1A during periodic testing occurred. The cause for these failures also appears to be l failures of the D/G Pneumatic Control System.

In order to minimize the potential for recurrence, Operations personnel have increased the blowdown frequency of all D/G Starting Air System (VG) air compressor aftercoolers from once to twice per shift. This is intended to reduce the amount of carry-over moisture entering the air dryers, which is the suspected cause of the valve corrosion problem. Operations personnel have requested the Maintenance group to double the frequency of performing Preventive Maintenance (PM) on the VG air dryers, from semi-annually to quarterly.

Operations personnel will initiate work requests to inspect the internals of all pneumatic trip valves on all remaining Unit 1 and Unit 2 D/Gs during scheduled maintenance periods over the next six months.

l l Performance personnel are planning to increase their frequency of testing Dew Point of the air in all VG receivers from semi-annually to monthly, l

Long term solutions to the D/G pneumatic trip problems are currently being investigated by Operations. Projects, and IAE personnel.

Operations personnel are pursuing modifications to install additional desiccant fi1*ers in each main instrument air line to the D/Gs. They are also pursuing the installation of automatic drains on the D/G Air Compressor aftercoolers.

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Special R; port May 12, 1988 Page Two IAE and Operations personnel are continuing to investigate the cause for -

corrosion of the low low lube oil pressure trip valves.

Projects and General Office personnel are evaluating alternative electric D/G trip systems for the Emergency Mode trips.

Operations personnel are to submit a Station Problem Report which will further evaluate the replacement of the non-emergency mode trips with an electronic system.

Offsite power and the alternate train D/G were verified to be operable during these periods of D/G 1A inoperability, as required by Technical Specifications, i

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