ML20045G582

LER 93-003-00:on 930608,RPS MG a Tripped,Resulting in Successful ESF Actuations & Isolations Due to Defective Procedure.Voltage Adjust Potentiometer for MG a Voltage Regulator Replaced on 930617.W/930708 Ltr

ML20045G582
Person / Time
Site:	Brunswick
Issue date:	07/08/1993
From:	Jonathan Brown, Thearling G CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BSEP-93-0109, BSEP-93-109, LER-93-003-03, LER-93-3-3, NUDOCS 9307140153
Download: ML20045G582 (4)

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Carolina Power & Light Company ww w y s. . . ;-s . :. , : : .-

Brunswick Nuclear Plant P. O. Box 10429

.Southport, N.C. 28461-0429 JUL 081993 FILE: B09-13510C 10CFR50.73 SERIAL: BSEP-93-0109 l U.S. Nuclear Pegulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 1 l

BRUNSWICK STEAM ELECTRIC PLANT UNIT i )

DOCKET NO. 50-325 . ,

LICENSE NO. DRP-71 4 LICENSEE EVENT REPORT 1-93-003 l

Gentlemen:

In accordance with Title 10 of the Code of Federal Regulations, the enclosed' icensee Event Report is o'bmitted. This report fulfills the requirement for a written report within h tty (30) days of a reportable occurrence and is submitted in accordance with the format set forth in NUREG-1022, September 1983.

Very trulf yours,

/ W

! J. M.. Brown,-Plant Manager' Unit 1 trunswick Fuclear Plant-GMT/gmt Encicsure cc: Mr. S. D. Ebneter Mr. P. D. Milano Mr. R. L. Prevatte 4nn..

9307140153 930708 PDR ADDCK 05000325 "n -

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. I NRC FORM 366 U.S. feUCLEAR REGULATORV COMMISSION APPROVED OMB NO. 3150-0104  !

, (5/92) EXPIRES: 5/31/95

[ STIM A Tf D PUhD[N PEN RE SPONSE TO COMPLY WITH T HIS INF ORM ATION COLLf CTION REQUE ST: 50.0 HRS. F ORW AllD LICENSEE EVENT REPORT (LER) COMMtNTS m cARa,NG ,UnntN CST, Marc TO THe ,N,ORM.T,0N AND RECONDS M ANAC.f MENT EA ANCH (MNBB 77141, U.S. NUCL ' AR ftf GULATORY COMMIS$10N WASHINGTDN, DC205540001, AN!s TO THE PAPT RWORK MDUCTION PROJECT (3150 0104L OfflCE OF M ANAGEMENT AND BUDGET. WASHINGTON. DC 20503.  !

F ACILITY NAME (1) DOCF ET NUMBIM 121 F AGE (31 Brunswick Steam Electric Plant, Unit 1 05000325 1 of 3 i TITLE 14) l j

ENGINEERED SAFETY FEATURE ACTUATIONS OCCURRED DURING "A" REACTOR PROTECTION SYSTEM '

MOTOR-GENERATOR TRIPS.

EVENT DATE (5) LER NUMBER 16) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YFA% MONTH DAY YEAR NUMBER NUMFfR Q$QQQ 06 09 93 93 0 07 08 93 F ACILITY NAME DOct ET NUMPER 05000 OPERATING t l MODE (9)

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20 402!b) 20 405(c) X 50.73(aH2)hv) 73.71 tbl POMR 20 405(all1101 50 30kH1) 50. 73(aH2Hvl 73 71(c)

LEVEL (10) O 20 405f aH1Hi4 50.36kH 2) 50.73f aH2Hviin OTHER n 405taH1H6i) 50 73(aH2HO bO.73taH2HvinHA) 15peuf y in Abstract 20 405(ay1Havl 50,73(aH2Hn) 50.73(aH2HvmH01 and Text) 20.405(ay1)(v) 50.73taH2Hnd 50 73taH2Hul LICENSEE CONTACT FOR THIS LER (12)

NAME TfLEPHONF. NUMBE R Glen M. Thearling, Regulatory Compliance Specialist (919) 457-2038 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) cAust Sv sitM COMPO NE N T M A NUF At.T L riE 4 O P CAUSI SY S TEM COMPOivf NT M ANdF ACTURE R T  ;

SUPPLEMENTAL REPORT EXPECTED (141 h EXPECTED " N' " U^# "^^

SUsMiSSiON m ,,

^ l ,o uy wwm t ot cTt o wcMeoN o ATn DATE (15) l wr.-= : .

ABETR A C f H imit to 1400 rpaus. i e approximately fifteen single space typewntien knes) t i, At 2151 on June B, 1993, the " A" Reactor Protect icn System 'RPS) motor-generator (m-9) set tripped. The trip of the RFS channel " It " bus resulted in successful Engineered Safety Feature actuations and isolations. The isolaticn signals affected the inboard valves, many of which were already closed as the reactor was defueled. For the recovery, the "A" kPS bus was transferred to the alternate power source and the affected systems were realigned as lequired by current plant conditions.

At 1948 on June 11, 1993, a lightning strjke on the grid caused a voltage spike which resulted in a trip of the RPS channel "A" alternate supply and subsequent successful actuations and isolations. The "A" RPS channel was re-energized from the alternate power source and the systems were realigned as required by curreat plant conditions. The first trip occurred due to a dirty voltage adjust potentiometer (rheostat) for the "A" m-g set voltage regulator, which has been replaced. Cleaning of remaining RPS m-g set voltage adjust potentiometers will be performed, with a procedure revision submitted to incorporate cleaning as part of periodic preventive maintenance.

These events are of minimal safety significance as the Unit was defueled and primary and secondary containment were not required.

The cause classifications for these events per the criteria of NUREG-3022 are " defective procedure" for first event and "other" for the second.

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NRC FORM 366A U. S, NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 (5/92) EXPmES: 5/31/95 E STIM ATf D BURDEN Pt R RESPONSE TO COMPLY WITH THIS INF ORM ATION COLLECTICN REQUEST: 50.0 HR$. FORW ARD LICENSEE EVENT REPORT (LER) COMMcN,,RecARo BuRnrN esnMAT, TO mt iu,ORMA1,0N AND TEXT CONTINUATION Recoms MANAarMENT BRANCH IMNBR 7714), U.S. NUCLE AR PEGULATORY COMMISSION, WASHINGTON, DC 20555-0001. AND TO T HE FAPERWORK Rf DUCTION PROJE CT (3150 01041, OFFICE OF M ANAGEMENT AND BUDGCT. WASHINGTON. DC 20503.

FACitiTY NAME (1) DOCEET NUMBER (2) LER NUMBER 16) PAGE (3)

SE QUE NYlAL RE VISION Brunswick Steam Electric Plant """"'" * * '"

05000325 2 of 3 Unit 1 93 O t

TE KT ut more space is required. use ariditional N!tC form 366A 's) (17)

TITLE ENGINEERED SAFETY FEATURE ACTUATIONS OCCURRED DURING "A" REACTOR PROTECTION SYSTEM MOTOR-GENERATOR TRIPS.

INITIAL CONDITIONS The Unit i reactor was defueled.

EVENT NARRATIVE At 2151 on June 8, 1993, the "A" Reactor Protection System (RPS) motor-generator set tripped. This de-energized the RPS channel "A" bus and resulted in successful Engineered Safety Feature actuations and isolations. The isolation signals affected the inboard valves many of which were already closed due to plant conditions. The following occurred:

1. Standby Gas Treatment Trains initiated

2. Reactor Building Ventilation isolated

3. Group 1 (Main Steam Line Drain Valve) isolated (Reactor Recirculation Sample Valve) isolated

4. Group 2 (Drywell Floor and Equipment Drains) isolated (Transverse Incore Probe) received an isolation signal (Residual Heat Removal sample valves received an isolation signal

5. Group 3 (Reactor Water Cleanup) isolated

6. Group 6 (Containment Atmosphere Control Valves) isolated

7. Group 8 (Shutdown Cooling) received an isolation signal The "A" RPS bus was transf erred to the alternate power source and the af fected systems were realigned as required by current plant conditions. Prior to completing the investigation as to the cause of the trip, a second loss of the "A" RPS bus occurred.

At 1948 on June 11, 1993, a lightning strike on the grid caused a voltage spike on Emergency Buses E-1, E-2, E-3, and E-4. Unit 1 Reactor Protection System Bus "A" was powered from its alternate power source, Bus E-1, with its motor-generator still out of service for maintenance. The voltage spike resulted in a trip of the "A" RPS Channel and subsequent actuations and isolations, The isolation signals affected the same' inboard valves listed above. The "A" RPS channel was re-energized from the alternate power source and the systems were realigned as required by current plant conditions.

CAUSE OF EVENT The first trip occurred due to a dirty voltage adjust potentiometer (rheostat) for the "A" RPS motor-generator set voltage regulator.

A lightning strike on the grid while the RPS "A" Channel was aligned to the alternate power source caused the second trip.

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NRC FORM 360A U. S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 (S/92) EnPIRES: 5/31/95 E STIM ATED fiURDEN PER h[ $ PONE.E TO COMPLY WITH THlb e INFORM ATION COLLICTION REQUEST: 50 0 HRS, FORWARD

-. LICENSEE EVENT REPORT (LER) cOMMcN1Sst u no,No ,Unoru,$T,u uiTOTm iNro m A1,0 NANO TEXT CONTINUATION HE CO@S M A NAGE ME NT B6ANCH WNBB W 4L U.S NUCLE AR NfGULATORY COMMIS$10N. WASHINGTON, DC 20566-000*. AND TO THE PAPf RWORK REDUCTION PMOJECT (3150 0104), CIFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

F ACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER 161 PAGE (3)

SE QUE NTIAL RE VISION Bn2nswick Steam Electric Plant """""

05000325 3 of 3 Unit 1 93 0 TEKT (if enore space os required, use additwnalMtC form 3fSA 's) (17l CORRECTIVE ACTTONS The voltage adjust potentiometer f or the Unit 1 "A" motor-generator set voltage regulator was replaced on June 17, 1993 (WR/JO 92-ASBMI).-

The voltage adjust potentiometer for the Unit 2 "B" motor-generator set voltage regulator was replaced on January 25, 1993 (WR/JO 92-BCAL1). Work Request / Job Orders (93-AUJIl &

93-AUJK1) will support cleaning / replacement of the two remaining RPS m-g set voltage adjust potentiometers with the next performance of 1/2MST-RPS21SA, RPS Electrical Protection Assembly Channel Calibration.

The preventive maintenance program will be revised to include periodic cleaning of the RPS m-g set voltage adjust potentiometers, SAFETY ASSESSME[JI These events are of minimal saf ety significance as the Unit was defueled and the'resulting actuations and isolations were successful.

PREVIOUS SIMILAR EVENTS <

LER 1-92-022 EIIS CnMPONENT IDENTIFICATION System /comnonent EIIS Code Reactor Protection System / Regulator / Rheostat JE / RG / 70 Primary Containment Isolation System JM

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