ML20115E193

Special Rept 92-006:on 920915,EDG 11 Tripped While Preparing to Perform Function Test of EDG 11 Per Surveillance Procedure 06-OP-1P75-M-0001.Caused by Leaking Reset Air Tubing Connection.Technicians Trained

ML20115E193
Person / Time
Site:	Grand Gulf
Issue date:	10/15/1992
From:	Cottle W ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
92-006, 92-6, GNRO-92-00132, GNRO-92-132, NUDOCS 9210220043
Download: ML20115E193 (3)

Text

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W. T Cottle I

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U.S. Nuclear Regulatory Commission Mail Station P1-137 Washington,'D.C. 20555 Attention: Document Control Dnsk

Subject:

Grand Gulf Nuclecr Station Unit 1 i Docket No. 50-416-License'No. NPF-29

-Special Report'92-006 Invalid. Failure-of-Emergency Diesel Generator 11 Due to Loose Tubing Connection GNRO-92/00132 On September 15, 1992, Operations personnel. prepared to perform a-functional test of Emergency Diesel Generator: (EDG) . 11 in accordance with Surveillance Procedure 06-OP-1P75-M-0001.

The ' EDG was. started in accordance with the above procedura and

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achieved rated RPM. However approximately one minute following the start and prior to a load attempt, EDG 11 tripped. A trouble-shooting work order was initiated to' investigate the cause of the diesel failure.

The troubleshooting activities ~ included--inspection of the Group 2 trip devices and tubing. During the investigation, ~ nly o one' problem was . identified. A . leaking reset --air tubing connection was

. identified- at the crankcase pressure switch 1P75N1600. The leak-prevented pressurization of-the Group 2 trips which resulted in a diesel . trip. Several- simulated diesel runs were successfully performed. No other abnormal conditions-wereiobserved..

Following tho' investigation, a maintenance' run was performed-without occurrence. The diesel responded as. designed and . no abnormalities were observed.

It is believed that the tubing connection to the crankcase pressure switch was not properly installed--following tube disassembly during Refueling Outage Five (RFOS)..During RFOS, all tubing on the; front-(governor-end) - of EDG 11 was L removed to support the jacket water

. pump-gear replacemeW. The re-installation of some pieces of tubing

'l were difficult to align-because of. tubing deformation, i i

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.GNRC -92/0013 2 l Page 2 of 4 l

It is possible that the tubing connection was not properly aligned at installation. Plant personnel performing the installation may have felt that the connection was tight, however the sightly loose fitting . and normal operational induced vibration allowed the fitting's leakage to prevent pressurization of the Group 2 trips.

The location of the loose tubing connection could be an environmental factor that contributed to in dequate tubing installation and leak testing.

Recent EDG 11 Group 2 trips (as reported in SR 92-004 and SR 92-005, dated July 23, 1992 and September 15, 1992 .espectively) warrant follow-up actions to increase confidence thaf. other tubing connections do not result in recurrence, i and are receiving Currently, Instrument Control. Techniciant  ;

, training associated with tubing fittings. This training "I11-

refresh technicians' knowledge in proper installation of tubing fittings and aid them in recognizing when tubing and fitting replacement is required.

Periodic tests will be performed to verify the ability of the pneumatic' Group 2 trip system to maintain pressure. These tests will be performed until reasonable assurance exist that the system integrity is adequate, The occurrence was caused by operation of a Group-2 trip signal.

4 The.only Group 2 trip that is not bypassed during the emergency operating mode of the EDG is Low Pressure Lube Oil. The Low Pressure Lube Oil trip is pressurized through a different flow path during an emergency condition. Therefore, this condition would not have rendered the EDG incapable of performing its intended safety function. Therefore this occurrence is considered an invalid failure of the LDG unit.

Yours truly, w T'~~~ d m i

WTC/RR/

cc: (See Next Page)

a-1 J s' . l October 15, 1992

,GNR6-92/0013? ,

Page 3 of 4 cc: Mr. R. H.- Bernhard Mr. D. C.-Hintz Mr. R. B. McGehee ,

Mr.. N.:S. Reynolds Mr. H . - L. Thomas Mr. Stewart D. Ebneter Regional Administrator U.S. Nuclear Regulatory. Commission Region II.

'101 Marietta St., N.W., Suite 2900 i Atlanta, Georgia 30323 Mr. P. W. .O'Connor (w/2)

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

WashisOLon, D.C. 20555 l

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