ML17223B168

Special Rept:On 910320,1B Emergency Diesel Generator (DG) Nonvalid Failure Occurred Due to Circuitry Failure of DG Synchronizing Circuitry.Relay Exhibiting Binding Calibr & Will Be Replaced

ML17223B168
Person / Time
Site:	Saint Lucie
Issue date:	04/17/1991
From:	Sager D FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-122, NUDOCS 9104240135
Download: ML17223B168 (3)

Text

ACCELERATED DIS UTION DEMONSTRATION SYSTEM t

r REGULATORY INFORMATXON DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR: 9104240135 DOC. DATE: 91/04/17 NOTARIZED: NO DOCKET FACIL:50-335 St. Lucie Plant, Unit. 1, Florida Power 6 Light Co. 05000335 AUTH. NAME AUTHOR AFFILIATXON SAGER,D.A. Florida Power S Light Co.

RECIP.NAME RECIPIENT AFFXLIATION Document Control Branch (Document Control Desk) R

SUBJECT:

Special rept:on 910320,1B emergency diesel generator non-valid during surveillance testing.Sys protection tested relay electriclly 6 found operable & plams available to replace engineering dedication.W/910417 ltr. D DISTRIBUTION CODE: ROOID COPIES RECEIVED:LTR )

ENCL I SIZE:

TITLE: OR Submittal: General Distribution NOTES:

A RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D PD2-2 LA 1 1 PD2-2 PD 1 1 NORRIS,J 2 2 D XNTERNAL: ACRS 6 6 NRR/DET/ECMB 9H 1 1 NRR/DET/ESGB 1 1 NRR/DOEA/OTSB1 1 1 1 NRR/DST SE2 1 1 NRR/DST/SELB SD 1 1 NRR/DST/SICB 7E 1 1 NRR/DST/SRXB 8E 1 1 NUDOCS-ABSTRACT 1 1 OC 1 0 OGC/HDS3 1 0 KE FXLE Ol 1 1 RES/DSXR/EIB 1 1 EXTERNAL: NRC PDR 1 1 NSIC 1 1 R

D D

D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM P 1-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 24 ENCL 22

P.O. Box, Ft. Pierce, FL 34954-0128 April 17, 1991 L-91-122 10CFR50.36 U. S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Gentlemen:

Re: St. Lucie Unit 1 Docket No. 50-335 Special Report Date of Event: March 20, 1991 Emer enc Diesel Generator Failure The attached Special Report is being transmitted pursuant to the requirements of St. Lucie Unit 1 Technical Specifications 4.8.1.1.3 and 6.9.2. The report provides notification of a 1B Emergency Diesel Generator non-valid failure during surveillance testing.

Should there be any questions on this information, please contact use Very truly yours, D. A. ger Vice sident St. Lucie Plant DAS:GRM:kw DAS/PSL 5416 Attachment cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant 9104240135 910417 PDR ADOCK 05000335 S PDR P,$ ~, g ~9 Qn FPL Group company

NRC SPECIAL REPORT DIESEL GENERATOR NON-VALID FAILURE At 0904 on March 20, 1991, the St. Lucie Unit One 1B Emergency Diesel Generator was started for its monthly surveillance run. Several attempts were made to synchronize the diesel generator onto the grid; however, the D/G output breaker would not close. Electrical Maintenance was called in to troubleshoot the synchronizing circuitry, and the 1B diesel generator was shut down and declared out of service at 0947.

Corrective Actions: Electrical Maintenance Personnel determined that the D/G synchronizing relay was malfunctioning. System Protection personnel tested the relay electrically and found it to be operable. However, mechanical manipulation of the contact arms caused binding. A calibration of the relay was performed and it was noted that the relay exhibited intermittent binding of the contacts. No replacement relays were available at the time of this failure. Plans are in place to replace the relay following an engineering dedication of a replacement, and PC/M package. The 1B diesel generator was restarted at 1248 and the output breaker was closed at 1255. The surveillance was successfully completed at 1407 and the diesel was declared back in service. The diesel was declared out of service for a total of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and 20 minutes.

The problem was evaluated to be a non-valid failure per Regulatory Guide 1 108 C.2.e.2, in that the affected circuitry was the D/G synchronizing

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circuitry. This circuitry is used for surveillance purposes only, when the diesel must be tied onto the live bus. During a Loss of Offsite Power event, this circuitry is bypassed and the D/G will automatically pick up the plant safety bus. At no time during this event was the diesel generator unable to perform its intended safety function.

Failure Summary: With the recent incorporation of amendments to Technical Specification 3.8.1.1 (July 1990), there have been no recorded valid failures of the 1B Emergency Diesel Generator and nine (9) successful starts. The surveillance frequency remains once per 31 days as per Tech Spec 3.8.1.1.