ML20210K716

Special Rept 1-SR-86-016:on 860402,diesel Generator a Tripped on Overspeed & Declared Inoperable.Caused by Misaligned Overspeed Combustion Air Indication Switch.Slots Cut Into Switch Mounting Bracket & Switch Aligned

ML20210K716
Person / Time
Site:	Palo Verde
Issue date:	04/18/1986
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
1-SR-86-016, 1-SR-86-16, ANPP-36293-EEVB, NUDOCS 8604290024
Download: ML20210K716 (2)

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A  ?.5 caved unc Arizona Nuclear Power Project ggg gpR 2l FM I: 36 P.O. BOX 52034 e PHOENIX, ARIZONA 85072-2034 April 18,1986 r:;mn q. r ANPP-36293-EEVB PGN 98.05 Mr. John B. Martin, Regional Administrator Office of Inspection and Enforcement U.S. Nuclear Regulatory . Commission Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 1

- Docket No. STN 50-528 (License NPF-41)

Special Report - Nonvalid Diesel Generator Failure File: 86-020-404

Dear Mr. Martin:

Attached please find a Special Report (1-SR-86-016) prepared and submitted pursuant to Technical Specifications 4.8.1.1.3 and 6.9.2. 'Ihis report discusses a nonvalid diesel generator failure due to misalignment of an overspeed combustion air indication switch.

If you have any questions, please contact me.

Very truly yours, M 4*4 E. E. Van Brunt , Jr.

Executive Vice President Project Director EEVB/PGN/ dim .

Attachment ec: R. P. Zimmerman (all w/a)

A. L. Hon E. A. Licitra A. C. Gehr INPO Records Center 8604290024 DR 860418 ADOCK 05000528 PDR

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At,tichment to ANPP-36293 PALO VERDE NUCLEAR GENERATING STATION UNIT 1 Special Report 1-SR-86-016 Nonvalid Diesel Generator Failure Due to Misalignment of Overspeed Combustion Air Indication Switch Docket No. STN 50-528 License No. NPF-41 This Special Report is required by Technical Specifications 4.8.1.1.3 and 6.9.2 - for a nonvalid diesel generator failure. his report is written in accordance with Regulatory Position C.3.b of Regulatory Guide 1.108, Revision

'1, August 1977.

During the performance of the Emergency Diesel Generator "A" Start and Ioad surveillance test (41ST-1DG01) at 0238 on April 2,1986, with Palo Verde Unit 1 in Mode 5 (COLD SHUTDOWN), Diesel Generator "A" tripped on averspeed.

Diesel Generator "A" was declared INOPERABLE at 0341 on April 2,1986.

During troubleshooting, it was determined that the Overspeed Combustion Air Indication Switch was out of alignment such that the actuating arm did not fully depress the switch lever. Normal operating vibrations of the actuating arm during operation of the diesel generator were large enough to allow the switch to open and consequently cause the overspeed trip. Slots were cut into the switch mounting bracket so that the switch could be moved toward the actuator arm for proper alignment. When properly aligned, the switch lever is fully depressed. Diesel Generator "B" and the two diesel generators in Unit 2 have been inspected to ensure that all switches were properly aligned.

When the Overspeed Combustion Air Indication Switch opened, the fiber optics associated.with the 12EX relay was de-energized and an overspeed condition was sensed. This resulted in an overspeed trip on Diesel Generator "A". We fiber optics - associated with - the 12EX relay are bypassed in the emergency mode. Both overspeed switches must be opened for an overspeed trip to occur in the emergency mode. Since - both switches did not open and an actual overspeed condition did not exist, this is considered a nonvalid diesel generator failure.

There have been three valid failures, in the last 100 valid tests, for Palo Verde Unit 1 diesel generators. A test interval of not more than 7 days is being implemented in accordance with the schedule in Regulatory Position C.2.d of Regulatory Guide 1.108, Revicion 1, August 1977.

-At 1846 on April 3, 1986, Diesel Generator "A" was declared OPERABLE after a valid test was successfully completed. Diese] Generator "A" was unavailable for 1 day 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and 5 minutes.

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