ML17349A759

Special Rept:On 930225,4B EDG Failed.Caused by Intermittent Connection,Resulting in Voltage Spikes.Cold Solder Joint Repaired & EDG Voltage Regulator Cabinet Inspected

ML17349A759
Person / Time
Site:	Turkey Point
Issue date:	03/10/1993
From:	Plunkett T FLORIDA POWER & LIGHT CO.
To:	Ebneter S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
L-93-67, NUDOCS 9303220452
Download: ML17349A759 (8)

Text

ACCEI.ERA D DOCUMENT DIST 83UTION SYSTEM REGUL RY INFORMATION DISTRIBUTI SYSTEM (RIDS)

ACCESSION NBR:9303220452 DOC.DATE: 93/03/10'OTARIZED: NO DOCKET FACZL:50-251 Turkey Point Plant, Unit 4, Florida Power and Light C 05000251 AUTH. NAME AUTHOR AFFILIATION PLUNKETT,T.F. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION EBNETER,S.D. Region 2 (Post 820201)

SUBJECT:

Special rept:on 930225,4B EDG failed. Caused .by intermittent connection. Cold solder joint repaired & 4B EDG test started w/voltage regulator in automatic mode.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 RAGHAVAN,L 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFBHE 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRIL/RPEB 1 1 ,NRR/DRSS/PRPB 2 2 NRR/JDSSA SPLB 1 1 NRR/DSSA/SRXB 1 1 C-T~ 1 1 RES/DSIR/EIB 1 1 RGN- FILE 01 1 1 EXTERNAL: EGErG BRYCEiJ.H 2 2 L ST LOBBY WARD -1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POOREiW. 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACI THE DOCUMEN'I'ONTROL DNK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FIKOM DISmIDUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF 'COPIES REQUIRED: LTTR 30 ENCL 30

P.O. Box 029100. Miami, FL, 33102-9100 WR ~5 1993 L-93-67 10 CFR 50.36 Stewart D. Ebneter Regional Administrator, Region U. S. Nuclear Regulatory Commission II 101 Marietta St., N.W., Suite 2900 Atlanta, GA 30323 Nr. Stewart D. Ebneter:

Re: Turkey Point Unit 4 Docket No. 50-251 S ecial Re ort - Diesel Generator In accordance with Technical Specification 4.8.1.1.3, the attached Special Repoit details the 4B Emergency Diesel Generator failure of February 25, 1993..

Should there be any questions on this information please contact us.

Very truly yours,

~i~

T. F. Plunkett Vice President Turkey Point Nuclear TFP/JEK/jk Attachment cc: USNRC, Document Control Desk, Washington D.C.

Ross C. Butcher, Senior Resident Inspector, USNRC, Turkey Point Plant 220083""

9303220452 9303i0 PDR ADOCK 05000251

'S PDR an FPL Group company

ik

~l

SPECIAL REPORT 4B EMERGENCY DIESEL GENERATOR VOLTAGE REGULATOR FAILURE PURPOSE:

Technical Specification (TS) 4.8.1.1.3 requires the submission of a special report to the NRC in the event of a diesel generator failure. The Technical Specification requires the report to include the information recommended in Regulatory Position C.3.b of Regulatory Guide 1.108, Revision 1, August. 1977.

BACKGROUND:

Turkey Point Unit 4 has two Emergency Diesel Generators (EDGs) which were installed in 1991 during a dual unit outage for Units 3 and 4. The Unit 4 EDGs have not had 100 valid tests since being declared operable after installation. The failure in the 4B EDG voltage regulator circuit, causing spiking of the output voltage, occurred on February 25, 1993. The following discussion addresses each of the areas listed in Regulatory Position C.3.b of Regulatory .

Guide 1.108, Revision 1, August, 1977.

(1) Diesel Generator unit involved:

The 4B EDG was involved in the unit failure.

(2) Identif th failur as bein the n'" fail re in th last 10 valid tests:

25 valid tests have been completed since the 4B EDG was installed and declared operable. This is the second failure.

(3) Cause of failure:

A cold solder joint was identified during a visual inspection of the remote gate firing module of the voltage regulator.

The solder joint on the lug of a resistor could be moved around a ring terminal. The signal through this resistor controls the -firing of a silicone controlled rectifier (SCR-3). An intermittent connection at this resistor caused the voltage spikes observed by the operators prior to the shutdown of the 4B EDG.

(4) Corr ctive measures ak n:

The cold solder joint was repaired. Further inspections of the 4B EDG voltage regulator circuitry did not reveal any similar deficiencies. The 4B EDG was test started with the voltage regulator in the automatic mode. With the generator unloaded, the output voltage was varied plus or minus 5% of

0 J

nominal in both the manual and automatic mode of regulator operation. Smooth field voltage response was observed. A two hour loaded test with the voltage regulator in automatic was successful. An operability test was successfully completed in accordance with Operations Surveillance Procedure, 4-OSP-023.1, Diesel Generator Operability Test.

The 4A EDG voltage regulator cabinet was inspected for similar deficiencies. None were found. The Unit 3 EDG voltage regulators are different in design and have continued to operate as designed. No further inspections of the Unit 3 EDG voltage regulators for deficiencies of this type are necessary.

(5) L n th of time he diesel enerator was navailable:

The 4B EDG was unavailable for 12.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> while trouble shooting and corrective repairs were performed.

(6) Definition of current surveillance test interval:

Two failures have occurred in the past 20 valid demands. The current surveillance test interval is once every seven days.

The seven day test frequency will be maintained until seven consecutive failure-free demands have been performed and the number of failures in the past 20 valid demands has been reduced to one.

(7) Verification of test interval in conformance with Re ulato Position C.2.d:

The test interval is in conformance with Regulatory Position C.2.d. and Turkey Point Technical Specifications Table 4.8-1.

ik 0