ML20101N068

Special rept:96/001 on 960229,EDG Failed.Cause by Failed Shuttle Valve.C/A:Valve Replaced

ML20101N068
Person / Time
Site:	Grand Gulf
Issue date:	04/01/1996
From:	Hutchinson C ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
96-001, 96-1, NUDOCS 9604080220
Download: ML20101N068 (2)

Text

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'd C01437 2600 C. R. Hutchinson April 1, 1996 J2 mom

"" 1 U.S. Nuclear Regulatory Commission Mail Station P1-37 Washington, D.C. 20555 Attention: Document Control Desk

Subject:

Grand Gulf Nuclear Station Docket No. 50-416 License No. NPF-29 Valid Failure of Emergency Diesel Generator 12 Due to a Failed Shuttle Valve (Special Report 96/001)

GNRO-96/00032 Gentlemen:

On February 29,1996, Emergency Diesel Generator (EDG) 12 tripped following a start for a monthly surveillance run. The start for the monthly surveillance run followed an EDG maintenance outage in which the pneumatic control board was taken out of service for maintenance. During this maintenance, air is removed from the control board.

In accordance with GGNS procedure, a simulated run is conducted before declaring the EDG  ;

operable following removal of air from the control board. During the simulated run, certain trips are verified and the control board is checked for air leaks prior to restoring the EDG to operable status. After initial difficulty, the simulated run was completed. The EDG was retumed to operable status and prepared for a start.

With all engine starts, a 60 second timer is initiated. This timer allows the engine time to build adequate oil pressure. If after 60 seconds adequate oil pressure is present, the engine continues to run and control board shuttle valves shift position. Failure of the shuttle valves to properly reposition, vents sir from portions of the pneumatic control board, causing the engine to trip. During the February 29 event, performance of the simulated run failed to detect the sticking shuttle valve. This valve vented air from the pneumatic control board, causing EDG 12 to trip.

The shuttle valve was replaced, the EDG was restarted, and the surveillance run successfully completed. The simulated run procedure (07-S-23-P75-3) will be reviewed by System Engineering to determine if additional measures can be implemented during the simulated run that would indicate a sticking shuttle valve failure. Also, shuttle valve performance will be discussed with the other owners of TDI EDGs in nuclear service to determine whether suitable hardware exist to enhance shuttle valve performance.

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April 1, 1996 l GNRO-96/00032 Page 2 of 3 l Given the fact that the above sequence is not bypassed on an emergency start, this event was i classified as a valid failure. This failure of EDG 12 brings its reliability numbers to 1 failure in the last l 25 valid test, and 1 failure in the last 100 valid test. EDG 12 remains on a monthly test hequency. l EDG 12 was unavailable 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and 22 minutes due to the trip and shuttle val 3 replacement. This l 15 hour1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and 22 minute interval does not include the time the engine was out of service for the routine '

maintenance. There were no other failures associated with this event.

i Yours truly, ,

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cc: Mr. J. E. Tedrow (w/a)

Mr. R. B. McGehee (w/a) 1 Mr. N. S. Reynolds (w/a)

Mr. J. W. Yelverton (w/a)

Mr. Leonard J. Callan (w/a)

Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Mr. J. N. Donahew, Project Manager (w/2)

Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 13H3 >

Washington, D.C. 20555 i

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