ML20246C909

Special Rept SR-89-001-01:on 890206 & 0403,emergency Diesel Generator a Declared Inoperable.Caused by Fuse Not Being Secured in Fuse Holder & Oxidation of Speed Control Circuit Relay Contacts.Contacts Cleaned & Fuses & Holders Checked

ML20246C909
Person / Time
Site:	Waterford
Issue date:	05/03/1989
From:	Mcgaha J LOUISIANA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
SR-89-001-01, SR-89-1-1, W3A89-0130, W3A89-130, NUDOCS 8905100064
Download: ML20246C909 (5)

Text

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Ref:

10CFR50.36(c)(2)

Lo u i si nu a! WATERFORD 3 SES

• PO. BOX B + KILLONA, LA 70 POWE6 S LIGHT m==sm May 3, 1989 W3A89-0130 A4.05 QA U.S. Nuclear Regulatory Commission ATTENTION:

Document Control Desk Washington, D.C.

20555

SUBJECT:

Waterford 3 SES Docket No. 50-382 License No. NPF-38 Reporting of Special Report Attached is Special Report Number SR-89-001-01 for Waterford Steam Electric Station Unit 3.

This Special Report is submitted per 10CFR50.36(c)(2) and Technical Specifications 4.8.1.1.3 and 6.9.2.

Very truly yours, k

I

(

J.'R.

McGaha Plant Manager - Nuclear JRM/WMCark.

Attachment j

i cc:

R.D. Martin, NRC Resident Inspectors Office, INPO Records Center l

(J.T. Wheelock), E.L. Blake, W.M. Stevenson, D.L. Wigginton l

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i SPECIAL REPORT SR-89-001-01 Emergency Diesel Generator Secured Due To Failure Of The Manual Speed Control Circuitry INTRODUCTION At 2218 hours0.0257 days <br />0.616 hours <br />0.00367 weeks <br />8.43949e-4 months <br /> on February 6, 1989, Waterford Steam Electric Station Ur.it 3 was operating at 100% power when Emergency Diesel Generator (EDG) A was declared inoperable due to a failure of the electronic speed control circuit while the EDG was in manual operation. During subsequent troubleshooting the problem could not be duplicated but was determined to be in the manual speed control portion of the circuit. Becauue manual speed control is not in service in the emergency mode of operation the EDG was declared operable. The event was attributed to oxidation of the speed control circuit relay contacts.

Oxidation of these contacts has caused EDG intermittent speed control problems.

On March 6, 1989, the contacts were inspected, discovered to have a higher than normal resistance, and cleaned.

At 1126 hours0.013 days <br />0.313 hours <br />0.00186 weeks <br />4.28443e-4 months <br /> on April 3, 1989, while the plant was at 100% power, EDG A was again declared inoperable due to failure of the manual section of the electronic speed control. The cause of the failure could not be found or duplicated and the EDG was declared operable. Troubleshooting continued and on April 6, 1989, electricians discovered a fuse not secure in its fuse holder.

The loose fuse is considered to have contributed to both events described above. Fuses and fuse holders were checked on both EDGs.

A Condition Identification has been initiated to clean both EDG speed control relay contacts again before the refueling outage and a Station Modification Request to install a more reliable type of contacts has been approved. These events are classified as non-valid failures because manual speed control is bypassed in the EDG emergency mode of operation.

Therefore, there was never a threat to plant equipment or public safety.

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NARRATIVE i

At 2213 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.420465e-4 months <br /> on February 6,1989, Waterford Steam Electric Station Unit 3 was operating at 100% power when Emergency Diesel Generator (EDG) A was declared inoperable due to failure of the electronic speed control circuit while the EDG was in manaal operation. Operating Procedure OP-903-094, " Engineered Safeguard Features Actuation System Subgroup Relay Test - Operating", was being performed to satisfy requirements of Technical Specifications (TSs) 4.3.2.1 and 4.7.12.1.

As part of OP-903-094, EDG A was operated in the isochronous mode from 2113 to 2129 hours0.0246 days <br />0.591 hours <br />0.00352 weeks <br />8.100845e-4 months <br />.

Operations personnel noted that the EDG speed was within operational limits but lower than usual and slightly erratic during this part of the test.

Continuing with OP-903-094, EDG A was secured and cooled down.

At 2204 hours0.0255 days <br />0.612 hours <br />0.00364 weeks <br />8.38622e-4 months <br />, EDG A was restarted manually to perform a test trip of the EDG output breaker.

After a successful start without loading, Operations personnel discovered that EDG speed was controlling at 60 Hz but could not be adjusted at the manual electronic local or remote control station.

The EDG was secured and declared inoperable.

Troubleshooting of the EDG was performed and the only problem found was a blown fuse that did not affect EDG governor speed control circuitry.

This fuse is bypassed in the EDG emergency mode of operation.

In the emergency mode of operation the EDG runs in the isochronous mode and manual speed control is bypassed. The EDG was started in both the isochronous and manual modes and it operated normally without problems. Therefore, Operating Procedure OP-903-068, "EDG Operability Verification", was successfully completed and EDG A was declared operable at 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br /> on February 7, 1989.

There have been previous intermittent speed control problems due to oxidation of the relay contacts in the governor mai 40 electronic speed control circuitry.

Oxidation of the contacts changes their resistance and affects speed control, requiring the contacts to be cleaned. Therefore, a condition identification (CI) was issued to check the speed control contacts the next time EDG A would be secured for maintenance.

On March 6, 1989, the contacts were checked and a higher than normal resistance was measured across them. The contacts were cleaned and a normal resistance was measured. A successful EDG operability check was then performed per OP-903-068. The event that occurred on February 6, 1989, was therefore attributed to oxidation of the electronic speed control relay contacts.

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4 At 1126 hours0.013 days <br />0.313 hours <br />0.00186 weeks <br />4.28443e-4 months <br /> on April 3, 1989, while the plant was operating at 100% power, EDG A was again declared inoperable due to failure of the electronic speed control circuit during manual operation.

OP-903-094 was being performed and EDG A was run satisfactorily in the isochronous mode from 1050 to 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />.

Continuing with OP-903-094, at 1104 hours0.0128 days <br />0.307 hours <br />0.00183 weeks <br />4.20072e-4 months <br /> EDG A was successfully restarted manually without loading.

EDG A speed was controlling at 60 Hz but could not be adjusted manually at the electronic remote control station. Local manual electronic speed control was not attempted so as not to change any conditions in the speed control circuit before maintenance personnel could check the circuit. The EDG was secured and declared inoperable.

Maintenance personnel tested the speed control circuitry without starting the EDG.

The remote electronic speed control was checked and it did not raise or lower speed. When speed control was shifted to local operation, speed control returned. Troubleshooting could not duplicate the problem. Because the problem i

in this event was limited to the manual speed control circuit, which is bypassed W

in the emergency operating mode, EDG A was declared operable at 2152 hours0.0249 days <br />0.598 hours <br />0.00356 weeks <br />8.18836e-4 months <br /> after OP-903-068 was completed satisfactorily.

To ensure there was not a hidden probicm, troubleshooting continued over the next three days.

On April 6, 1989, an intermittent problem was discovered.

An electrician measuring voltage across the fuse through which power is supplied to the motor operated potentiometer (MOP) found only 10 volts instead of the required 134 volts.

The function of the MOP is to change EDG speed when the MOP receives a raise or lower signal from the electronic speed control circuit. When the electrician moved the voltmeter probes against the fuse, voltage across the fuse returned to 134 volts. The fuse was not held securely by the clip in the fuse holder.

This caused intermittent power interruptions to the MOP resulting in intermittent loss of manual speed control. The fuse holder clip was adjusted to hold the fuse firmly.

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The first event is now attributed to two problems with two causes:

the oxidation of the relay contacts by the discovery of their high resistance and the behavior of the EDG in the isochronous mode; and the interruption of power to the M0P by the loose fuse. When the contacts were cleaned following the first event the situation was assumed to be resolved.

However, when the second' event occurred, plant personnel realized there had to be another problem with the speed control circuit. The root cause of the second event was that the fuse clip in the fuse holder did not hold the fuse securely. Other fuses and fuse holders were checked on both EDGs.

l The Maintenance Department has initiated CI 261885 to clean the EDG A governor speed control contacts in June 1989 and the EDG B governor speed control l

contacts in May 1989.

Station Modification Request (SMR) EG-004 has been approved to replace the contacts with more reliable mercury wetted contacts.

This SMR is planned to be implemented in refueling outage 3 in November, 1989.

There is a long (40 week) procurement time required for the new contacts.

If the new contacts are nct ready for installation by refueling outage 3, the installed contacts will be cleaned periodically until the new contacts are installed.

Both of these events have been classed as non-valid diesel generator failures by the criteria of Regulatory Guide 1.108 C.2.e. (2) due to malfunctioning of equipment not operative in the emergency operating mode.

Therefore, this report is submitted pursuant to TSs 4.8.1.1.3 and 6.9.2.

There has only been one failure during a valid test of EDG A since the operating license was issued.

The surveillance test interval required by TS Table 4.8-1 has always been "at least once per 31 days" since issuance of the operating license. Because the speed control circuit is bypassed in the emergency mode of operation and would not affect the EDG's ability to perform its safety function, neither event presented a threat to plant equipment or public safety.

PLANT CONTACT T.H. Smith, Plant Engineering Superintendent, 504/464-3127.

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