ML20113E450

Special Rept SR-96-001-00:on 960603,output Breaker for EDG B Failed to Close.Caused by Intermittent Malfunction of Contacts on Synchronizing Switch.Performed Troubleshooting & Replaced EDG B Synchronizing Switch

ML20113E450
Person / Time
Site:	Waterford
Issue date:	07/03/1996
From:	Keuter D ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
SR-96-001-00, SR-96-1, W3F1-96-0101, W3F1-96-101, NUDOCS 9607080006
Download: ML20113E450 (5)

Text

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. W ENTERGY lM P*" '"*-

Killona, LA 70066 Tef 504 464 3120 D. R. Keuter S?$CE Waterford 3 W3F1-96-0101 A4.05 PR July 3,1996 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Subject:

Waterford 3 SES Docket No. 50-382 License No. NPF-38 Reporting of Special Report Gentlemen:

Attached is Special Report Number SR-96-001-00 for Waterford Steam Electric Station Unit 3. This report outlines the results of the investigation into the failure of the output breaker for Emergency Diesel Generator (EDG) B to close during Surveillance Testing on June 3,1996. The most probable cause of the output breaker not closing has been determined to be an intermittent malfunction of contacts on the synchronizing switch for the EDG. This Special Report is submitted in accordance with Technical Specifications 4.8.1.1.3 and 6.9.2 and USNRC Regulatory GuHe 1.108.

j Veiy truly yours,

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D.R. Keuter General Manager Plant Operations DRK/RTK/tjs Attachment

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Reporting of Special Report (SR-96-001-00) l W3F1-96-0101 Page 2 July 3,1999 -

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L.J. Callan, NRC Region IV C.P. Patel, NRC-NRR l

- D.F. Packer J.T. Wheelock - INPO Records Center R.B. McGehee N.S. Reynolds l

NRC Resident Inspectors Office Administrator - LRPD I

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SPECIAL REPORT SR-96-001-00 i

REPORTABLE OCCURRENCE l

On June 3,1996, Emergency Diesel Generator (EDG) B was started for the i

performance of Surveillance Procedure OP-M3-068 "EDG and Subgroup Relay Operability Verification". When Operations Personnel attempted to close the output breaker associated with the EDG, the breaker did not close. This event is classified as a nonvalid failure during a valid test in accordance with Regulatory Guide 1.108 and is being reported in accordance with Technical Specifications (TS) i 4.8.1.1.3 " Reports" and 6.9.2 "Special Reports". EDG B has experienced no valid failures in the last 20 valid tests and one valid failure in the last 100 valid tests. In l

accordance with the Waterford 3 Technical Specifications, the currently required surveillance test interval for EDG B is at least once per 31 days.

EVENT DESCRIPTION At 1011 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.846855e-4 months <br /> on June 3,1996, EDG B was started for the performance of Surveillanco Procedure OP-903-068 "EDG and Subgroup Relay Operability Verification" Operations Personnel placed the synchronizing switch in the GEN MAN position in preparation for closing the generator output breaker. Using the i

t generator output breaker manual close switch, Operations Personnel made several unsuccessful attempts to manually close the output breaker. Realizing that the breaker would not close, the Operator placed the synchronizing switch to the OFF position and then attempted to remove the key from the switch. It was noticed that the switch had been difficult to manipulate end the key was difficult to remove. The EDG was declared inoperable at 1032 hours0.0119 days <br />0.287 hours <br />0.00171 weeks <br />3.92676e-4 months <br /> due to the problems encountered in closing the output breaker. Technical Specification (TS) 3.8.1.1 "A.C. Sources" Action Statements b and d were entered. EDG B continued to run unloaded until 1056 hours0.0122 days <br />0.293 hours <br />0.00175 weeks <br />4.01808e-4 months <br /> when the EDG was secured. Troubleshooting was subsequently performed by Plant Maintenance - Electrical Personnel and Systems Engineering Personnel. At 1225 hours0.0142 days <br />0.34 hours <br />0.00203 weeks <br />4.661125e-4 months <br /> on June 3,1996, the EDG was started for a second time to perform Surveillance Procedure OP-903-068. The output breaker was successfully closed at 1241 hours0.0144 days <br />0.345 hours <br />0.00205 weeks <br />4.722005e-4 months <br /> and loading of the EDG was commenced.

Surveillance Procedure OP-903-068 was successfully completed at 1751 hours0.0203 days <br />0.486 hours <br />0.0029 weeks <br />6.662555e-4 months <br /> on June 3,1996. The EDG was declared operable at 1856 hours0.0215 days <br />0.516 hours <br />0.00307 weeks <br />7.06208e-4 months <br /> on June 3,1996, and TS 3.3.1 1 Action Statements b and d were exited.

CAUSAL FACTORS Entergy believes that the most probac!e cause of the EDG B output breaker not closing is an intermittent malfunction of contacts associated with the synchronizing switch. This is based on the Operator noticing the difficulty in manipulating the j

synchronizing switch and the subsequent difficulty in removing the key from this

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switch. In addition, a similcr failure was experienced on EDG A in 1994 (reference Special Report 94-001-01) in that the synchronizing switch for EDG A had

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l intermittent contact failures that were not repeatable during the troubleshooting j

process. Past experiences with the EDG A synchronizing switch indicate that had.

the Operator made another attempt to place the synchronizing switch in the GEN MAN position and attempted to close the EDG B output breaker, the breaker most probably would have closed.

CORRECTIVE MEASURES l

Concilion Report (CR) 96-0864 was generated in accordance with Waterford 3 l

Administrative Procedure UNT-006-011, " Condition Report", to provide a means to l

implement the Waterford 3 Corrective Action Program. As an immediate corrective l

action, troubleshooting was performed by Waterford 3 Plant Maintenance -

l Electrical Personnel and Systems fingineering Personnel. Several closing I

prmissives for the output breaker associated with EDG B were checked for proper operation. No abnormal indications were detected.

A Condition identification (Cl) has been generated to replace the synchronizing switch for EDG B. Replacement of the synchronizing switch will require lifting leads in a highly congested area which could potentially cause inadvertent actuations of other devices. Therefore, this synchronizing switch is currently scheduled to be replaced during the Waterford 3 Refuel 8 outage. As an interim corrective measure, a Caution Tag has been placed on this switch to alert Operations Personnel as to the condition of this switch.

l SAFETY SIGNIFICANCE l

.The synchronizing switch contacts which are believed to be intermittently malfunctioning are not used when the EDG operates in the emergency mode.

These contacts would not have prevented the EDG from performing its safety function. Throughout the event descnoed above, EDG B was available to perform the safety function because at no time during the event was the emergency mode of operation affected.

j The A train EDG was operable throughout the time period that EDG B was inoperable (but available). Safety analysis assumes that a single failure disables or,e protection train. However, a single EDG, safety bus, and essociated Engineered Safety Features equipment are adequate to protect the reactor during 7

i the worst case postulated accident.

l' The TS require an inoperable EDG to be restored to operable status within 72 j

hours. EDG B was inoperable (but available) for approximately 8.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

j Therefore, the TS requirements were satisfied.

j Based on the above information, this event did not compromise the health and L

safety of the public or plant personnel.

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SIMILAR EVENTS A review of the Licensing Research System database identified one Special Report (SR-94-001-01) that documents an EDG A trip on reverse power that occurred at Waterford 3 due to a malfunctior. # mntacts on the synchronizing switch. This Special Report states that the it....mation available to date indicates that the EDG A reverse power trip that is described in Special Report 94-003-00 was also caused by contacts on the synchronizing switch. The synchronizing switch for EDG A was replaced during the Refuel 7 outage and no further malfunctions attributable to this switch have been encountered.

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