ML20206J633

Special Rept SR-86-004-00:on 860523,emergency Diesel Generator a Malfunctioned.Caused by Failure of Power Parallel Voltage Dropping Resistor in Electrical Governor Control Circuit.Power Resistors & Amplifier Replaced

ML20206J633
Person / Time
Site:	Waterford
Issue date:	06/20/1986
From:	Barkhurst R, Barkhurst R LOUISIANA POWER & LIGHT CO.
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
SR-86-004-00, SR-86-4, W3A86-0058, W3A86-58, NUDOCS 8606270223
Download: ML20206J633 (3)

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O LOUISIANA P O W E R & L I G H T! WATERFORD 3 SES = PO. BOX B + KILLONA. LA 70066-0751

$EUSl[SIYS June 20, 1986 W3A86-0058 A4.05 QA Mr. Robert D. Martin g%

Regional Administrator, Region IV U.S. Nuclear Regulatory Commission

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611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 JM23 9

Subject:

Waterford 3 SES U - -

Docket No. 50-382 License No. NPF-38 Reporting of Special Report

Dear Mr. Martin:

Attached is Special Report Number SR-86-004-00 for the Waterford Steam Electric Station Unit 3. This Special Report is submitted per Technical Specification 6.9.2.

Very truly yours, R.P. Barkhurst i Plant Manager - Nuclear l RPB/LWL/wp Attachment cc: NRC Document Control Desk 1 l

NRC, Director, Office of I&E C.W. Knighton, NRC-NRR J.H. Wilson, NRC-NRR NRC Resident Inspectors Office INPO Records Center (J.T. Wheelock)

B.W. Churchill i W.M. Stevenson l 8606270223 860620 PDR ADOCK 050003G2 g PDR 1

Q 6 -6% O s i

SPECIAL REPORT SR-86-004-00 Emergency Diesel Generator A Malfunction Due to Failure of Power Parallel Voltage Dropping Resistor INTRODUCTION At 0441 hours0.0051 days <br />0.123 hours <br />7.291667e-4 weeks <br />1.678005e-4 months <br /> on May 23, 1986 Waterford Steam Electric Station Unit 3 was operating at 100% reactor power when operations personnel started Emergency Diesel Generator A in accordance with procedure OP-903-094, " Emergency Safety Features Actuation Signal (ESFAS) Subgroup Relay Test-Operating." Due to the failure of a power parallel voltage dropping resistor in the electrical governor control circuit, the engine lost speed. At 0441 hours0.0051 days <br />0.123 hours <br />7.291667e-4 weeks <br />1.678005e-4 months <br /> the Reactor Auxiliary Building watch manually secured the EDG by actuating the overspeed trip.

Since the malfunction would have occurred in either the emergency or manual mode, this report is submitted pursuant to Technical Specification 4.8.1.1.3 and 6.9.2. This is the first valid failure of the EDG in the last 116 start attempts. Therefore, the surveillance frequency remains at least once per 31 days. The A EDG was returned to service at 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on May 25, 1986.

NARRATIVE At 0441 hours0.0051 days <br />0.123 hours <br />7.291667e-4 weeks <br />1.678005e-4 months <br /> on May 23, 1986 Waterford Steam Electric Station Unit 3 was operating at 100% reactor power when operations personnel started Emergency Diesel Generator A in accordance with procedure OP-903-094, " Emergency Safety Features Actuation Signal (ESFAS) Subgroup Relay Test-Operating." The Emergency Diesel Generator (EDG) achieved operating speed and voltage in approximately six (6) seconds, but did not maintain steady state conditions.

As the generator approached / achieved 600 RPM, speed began to decrease. When the speed decreased to approximately 280 RPM the " Incomplete Sequence" and

" Emergency Stop or Unit Shutdown" annunciators illuminated. Due to the presence of the Safety Injection Actuation Signal (SIAS) (as a result of the testing mentioned above), the engine started to crank again according to design. The engine speed increased to 600 RPM and began to slow again.

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This process repeated itself again. At approximately 0441 hours0.0051 days <br />0.123 hours <br />7.291667e-4 weeks <br />1.678005e-4 months <br /> the Reactor Auxiliary. Building operator manually secured'the EDG by actuating the overspeed trip. While troubleshooting, two start attempts were made in the manual remote made (0451 and 0501 hours0.0058 days <br />0.139 hours <br />8.28373e-4 weeks <br />1.906305e-4 months <br /> on May 23, 1986). In each case, similar results were observed. Operations personnel declared the A EDG inoperable at 0505 hours0.00584 days <br />0.14 hours <br />8.349868e-4 weeks <br />1.921525e-4 months <br /> and entered Technical Specification 3.8.1.la and c.

Troubleshooting on May 23, 24, and 25, 1986 revealed that the problem was due to the failure of a power parallel voltage dropping resistor in the electrical governor circuit. Since one of the resistors failed open, the higher voltage drop on the remaining resistor resulted in a lower reference voltage at the amplifier. Therefore, as the engine reached 600 RPM, the lower reference voltage precipitated a high (approximately 10v) amplifier output voltage which caused the fuel rack to move to the minimum fuel position.

As described in Condition Identifi:ation Work Authorization 27028, both power resistors, the frequency sensor board and amplifier were replaced. Following the successful test of EDG A on May 25, 1986, maintenance personnel, along with assistance of the vendor representative, made several additional adjustments to both the A and B EDC. They are as follows:

o The fuel rack linkage was balanced and adjusted.

o The compensation characteristics of the hydraulic actuator were adjusted.

o The speed control of the hydraulic actuator was set at 60.8 hertz. ,

o The electronic governor speed control was. set at 60 hertz.

o The electronic governor gain and reset was adjusted.

In accordance with Technical Specification 3.8.1.1 operations personnel verified that the B EDG, along with all required systems, subsystems, trains, components, and devices which depend on the B EDG as a source of emergency power, were operable. Therefore, the inability of the A EDG to satisfactorily complete the required surveillance did not pose a safety concern.

PLANT CONTACT T. Smith, Maintenance Superintendent, 504/464-3138 2

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