ML19332E612

Special Rept:On 891030,test Failure of Div II Diesel Generator Occurred.Caused by Cam/Spring Holding Fallen Screw in Console Section of Panel.Holding Screw Reinstalled in Switch.Control Switch Will Be Inspected in Upcoming Outage

ML19332E612
Person / Time
Site:	Clinton
Issue date:	11/29/1989
From:	Holtzscher D ILLINOIS POWER CO.
To:	Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
U-601562, NUDOCS 8912080069
Download: ML19332E612 (2)

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I PJIE iREQs Docket No. 50 461 Nr. A. B. Davis

. Regional Administrator Region III-U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinofa 60137

Subject:

Special Report: Test Failure of Division II Diesel Generator at Clinton Power Station (CPS)

Dear Mr. Davis:

CPS Technical Specification 4.8.1.1.3 requires all diesel generator failures, valid-or non valid, to be reported to the NRC pursuant to-Specification 6.9.2, SPECIAL REPORTS. Due to a failure of

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the Division II Diesel Generator (DG1B) during surveillance testing on October 30, 1989, this SPECIAL REPORT.is being submitted in accordance with the CPS Technical Specifications to provide the information required by Regulatory Guide 1.108, Revision 1, ' Periodic Testing of Diesel Generator Units Used as Onsite Electric T>wer Systems at Nuclear Power Plants," Regulatory Position C.3.b.

Dererfetion of Event On October 30, 1989; D01B was started and loaded to 3875 KW in

. parallel with offsite power in accordance with CPS Procedure 9080.01,

" Diesel Generator 1A (1B) Operability Manual," to satisfy Technical

' Specification Surveillance Requirement 4.8.1.1.2.a.5 (1-hour full load run). Approximately 15 minutes into the test, the main control room operator attempted to adjust the DG1B voltage in order to reduce the reactive load (KVAR) by using the voltage regulator control switch, 1HS.

DG830. This switch is a General Electric Model CR2940 raise neutral-lower switch that will spring return to the neutral position after movement in either direction (raise, lower). Raising and lowering DG1B voltage is_ accomplished by momentarily moving the voltage-control switch knob to the raise / lower position and releasing the knob to allow it to spring return to the neutral position. After the main control room operator lowered DG1B voltage and released the voltage control switch knob, he noticed that the indicated reactive load continued to decrease without further switch movement. Attempts to raise the DG1B voltage had G912080069 891129 PDR ADOCK 05000461 ki

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no effect. When repeating the attempt to raise the DG1B voltage, the main control room operator felt a lack of resistance to switch movement giving him the impression that the knob had loosened from the switch l mechanism. The main control room operator shut down DC1B using the i emergency stop pushbutton rather than allowing DG1B to run in a condition with a large negative reactive load. DG1B was declared inoperable and the appropriate Technical Specification ACTION was taken.

Cause of Event Investigation into the cause of the switch failure revealed that the cam / spring holding screw had worked free and fallen into the console section of panel H13.P870. Without the holding screw, the switch

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contacts remained in the " lower voltage" position even though the switch knob returned to the neutral position.

Corrective Action The holding screw was re'.nstalled in the switch uning a thread-locking material to prevent future loosening. DG1B was started at 1415 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.384075e-4 months <br /> on October 30, 1989, and the voltage regulator switch was exercised to demonstrate proper correction of the problem. Upon successful co.apletion of the maintenance, DG1B was started at 1506 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.73033e-4 months <br /> on October 30, 1989, to demonstrate OPERABILITY in accordance with the

. Technical Specifications. DG1B was restored to OPERABLE status at.1729 hours0.02 days <br />0.48 hours <br />0.00286 weeks <br />6.578845e-4 months <br /> on October 30, 1989.

This was the first failure of a voltage regulator control switch at CPS. The voltage regulator control switch on the main control room panel for DG1C was inspected and was found to be satisfactory. The control switch for DG1A will be inspected in an upcoming outage for DG1A currently scheduled for the week of December 18, 1989 (MWR D14100).

Additional Information This event is the first valid failure in the last 20 valid tests and the third valid failure in the past 100 valid tests. Therefore, the surveillance frequency for DC1B remains at once per 31 days in accordance with Technical Specification Table 4.8.1.1.2 1.

Sincerely yours,

%7i D. L. Holtzscher Acting Manager -

Licensing and Safety RFP/krm cc: NRC Clinton Licensing Project Manager NRC Resident Office NRC Document Control Desk Illinois Department of Nuclear Safety