ML20070N660

Special Rept SR-94-003:on 940404,EDG a Experienced Nonvalid Failure While Performing Valid Test.Probably Caused by Emergency Mode Master Run Relay 4EX1 de-energized During Run.Troubleshooting in Progress

ML20070N660
Person / Time
Site:	Waterford
Issue date:	05/04/1994
From:	Packer D ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
SR-94-003, SR-94-3, W3F1-94-0048, W3F1-94-48, NUDOCS 9405090061
Download: ML20070N660 (5)

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Entergy Operations, Inc.

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D.F. Packer p : i. n . . e ;. r

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W3F1-94-0048 A4.05 i PR May 4, 1994 l

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 l Reporting of Special Report  ;

Gentlemen: i Attached is Special Report Number SR-94-003-00 for Waterford Steam Electric Station Unit 3. This Special Report is submitted in accordance with Technical Specifications 4.8.1.1.3 and 6.9.2 and USNRC Regulatory Guide 1.108.

Very truly yours, yhf I

D.F. Packer General Manager - Plant Operations DFP/CJT/tjs Attachment cc: L.J. Callen, NRC Region IV G.L florreich J.T. Wheelock - INP0 Records Center R.B. McGehee N.S. Reynolds NRC Resident Inspectors Office g:

Administrator - LRPD /

05007n 9405090061 940504 PDR

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ADOCK 05000382 S PDR

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SPECIAL REPORT SR-94-003 4

REPORTABLE OCCURRENCE At 0023 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> on April 4, 1994, Emergency Diesel Generator (EDG) 'A' experienced a nonvalid failure while performing a valid test. At 1654 hours0.0191 days <br />0.459 hours <br />0.00273 weeks <br />6.29347e-4 months <br /> that same day, EDG 'A' experienced a second nonvalid failure while troubleshooting for the failure that occurred at 0023 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. Pursuant to Technical Specification (TS) 4.8.1.1.3, all diesel generator failures, valid or nonvalid, shall be reported in a Special Report to the Commission

. pursuant to Specification 6.9.2 within 30 days.

INITIAL CONDITIONS Plant Power: 0%

Plant Operating Mode: Mode 6; Refueling Procedures Being Performed Specific to this Event:

OP-009-002, " Emergency Diesel Generator" OP-903-115, " Train A Integrated Emergency Diesel Generator / Engineering Safety Features Test."

Technical Specification LCO's in Effect Specific to This Event: None Major Equipment Out of Service Specific to this Event:

Emergency Diesel Generator 'A' EVENT DESCRIPTION During the Refuel 6 Outage, EDG 'A' was inoperable for maintenance from 1120 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.2616e-4 months <br /> on March 24, 1994, to 2012 hours0.0233 days <br />0.559 hours <br />0.00333 weeks <br />7.65566e-4 months <br /> on April 9, 1994. During that time, EDG 'A' experienced two nonvalid failures.

The first nonvalid failure occurred during the performance of a valid test. At 2359 hours0.0273 days <br />0.655 hours <br />0.0039 weeks <br />8.975995e-4 months <br /> on Acril 3, 1994, EDG 'A' was automatically started and loaded to implement Section 7.5 of OP-903-115. Section 7.5, " Train A )

Safety Injection Actuation Test With Concu' rent loss of Off Site Power," I is performed at least cnce per 18 months while shutdown to demonstrate diesel operability in accordance with TS requirements.

During the test two conditions were noted. After depressing and holding the emergency stop push button, test personnel noticed that Fuel 011 l Solenoid 20F01 was not energized as expected. Also, prior to closing Safety Bus 3A3-S to 3A2 tie breaker 4KVEBKR3A 11, the diesel start light on the Control Room EDG Control Panel operating switch was not illuminated. This switch was illuminated during the initial start. l l

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After operating at load for approximately 17 minutes, EDG 'A' tripped at 0023 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> while paralleling to offsite power. There was no annunciation ,

at the time of the trip to indicate its cause. The trip occurred when the diesel transferred from the emergency operating mode to the test mode.

This transfer is concurrent with the closure of Safety Bus 3A3-S to 3A2

tie breaker 4KVEBKR3A 11. The OP-009-002 Start Evaluation Sheet generated for the event categorized the trip as a nonvalid failure pursuant to Position 2.e.(2) of Regulatory Guide 1.108, 4

A definite root cause of the failure could not be determined. However, l the most probable cause of the failure is that Emergency Mode Master Run Relay 4EX1 was de-energized at some point during the diesel run. This would explain de-energization of Fuel Oil Solenoid 20F01. The 20F01 solenoid would have de-energized immediately upon de-energization of 4EXI.

Because the 4EX1 relay was not operating at the time the emergency stop push button was depressed, Unit Master Run Relays 4X1, 4X2 and 4X3 (relays not required in Emergency Mode) would have de-energized. Consequently, the Control Room EDG Start /Stop control switch start lamp and Engine Shut Down Solenoid 20SD would have de-energized. Solenoid 20SD remains by-passed in Emergency Mode by two Emergency Mode Master Run Relays --

4EX2 and 4EX5. However, as a result of Solenoid 20SD being de-energized, EDG 'A' would have tripped when it transferred to the test mode with no indication of why the trip occurred.

Immediately after the trip, pertinent circuits were checked for loose connections. No loose connections were identified. A Work Authorization (WA) was prepared to troubleshoot Fuel Oil Solenoid 20F01 and those components that may have caused the nonvalid failure. Troubleshooting was conducted during a simulated start (i.e., Overspeed Trip, Field Flash Breaker, and Starting Air isolated) and an Engineered Safety Features Actuation Signal (ESFAS) Test Module start. Pertinent relays and solenoid coils were monitored during that time and verified to be functioning satisfactorily. No problems were identified with the Control Room EDG Control Panel operating switch, nor with the 20F01 and 20F02 Fuel Oil Solenoids.

Subsequent to the ESFAS start, it was decided to continue troubleshooting by paralleling to offsite power. While attempting to parallel to offsite power, EDG 'A' tripped in the test mode at 1654 hours0.0191 days <br />0.459 hours <br />0.00273 weeks <br />6.29347e-4 months <br />. The EDG Local Annunciator Panel gave indication of a reverse power trip. Also, the reverse power relay was verified tripped. The OP-009-002 Start Evaluation Sheet generated for the event categorized the trip as a nonvalid failure pursuant to Position 2.e.(7) of Regulatory Guide 1.108, 2 e

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l CORRECTIVE MEASURES In addition to troubleshooting, Section 7.6 of OP-903-115, "24-Hour EDG A Run And Subsequent Loss of Offsite Power Test," wr ruccessfully completed on April 5, 1994 at approximately 2052 hours0.0238 days <br />0.57 hours <br />0.00339 weeks <br />7.80786e-4 months <br />. If the conditions that i

caused the first nonvalid failure had existed during this test, then a l similar failure would have occurred. This is due to the fact that EDG 'A' 2 was paralleled to offsite power in the same manner as was done while implementing Section 7.5 of that procedure. Although the 4EX1 relay was

! operating satisfactorily during the troubleshooting, a Condition l

Identification has been initiated to replace this relay during the next

scheduled EDG 'A' maintenance outage.

1 Additional troubleshooting will be conducted to investigate the cause of

the reverse power trip. A Condition Identification has been written to i connect recorders and monitur EDG 'A' parameters during future ESFAS Test j Module starts. This corrective measure is being conducted as part of an i investigation into an earlier reverse power trip. Special Report SR j 001-00 reported an event that occurred on March 2, 1994, when EDG 'A' i tripped on reverse power while paralleling to offsite power. The investigation into that event will continue and corrective measures will

be taken as appropriate.

1 SAFETY SIGNIFICANCE The first nonvalid failure occurred when the diesel transferred from the

emergency operating mode to the test mode. This transfer is concurrent with the closure of Safety Bus 3A3-S to 3A2 tie breaker 4KVEBKR3A 11. The

components that would cause this type of failure are bypassed in the emergency operating mode.

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) The second nonvalid failure also occurred in the test mode. Reverse power i trips have no impact on the emergency mode of operation. In the emergency mode, the diesel is energizing an isolated safety bus. Reverse power trip 1 will be locked out of the diesel shutdown circuitry for the duration of an f emergency event and will not be enabled until normal offsite power is restored to the safety bus.

Neither of the nonvalid failures would have affected emergency mode operation. As a result, these events did not compromise the health :nd j safety of the public. Furthermore, EDG 'B' was operable throughout the

time EDG ' A' was unavailable.

• In accordance with Regul&tcry Guide 1.108, the current surveillance test interval for EDG ' A' is 31 days. This test interval is in accordance with j

the schedule of Regulatory Position C.2.d.

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SIMILAR EVENTS No previous events similar to the first nonvalid failure were identified.

However, as stated previously, Special Report SR-94-001-00 reported an event similar to the second nonvalid failure in that EDG 'A' tripped on reverse power while paralleling to offsite power. This event occurred on i March 2, 1994.

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