ML17292B111

LER 97-011-00:on 971010,HPCS Battery Charger Failed.Caused by Failure of a Phase Firing Control Circuit Board Due to Aging During 7 Yrs of Use.Hpcs Sys Was Immediately Declared inoperable.W/971110 Ltr

ML17292B111
Person / Time
Site:	Columbia
Issue date:	11/10/1997
From:	Bemis P, Tamara Powell WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-97-206, LER-97-011, LER-97-11, NUDOCS 9711190086
Download: ML17292B111 (7)

Text

~m J:~QO GULATORY INFORMATION DIST DIST IBUTION SYSTEM (RIDS)ACCESSION NBR:9711190086 DOC.DAT//o AUTH.NANg uc ear Project, Unit 2, Washin AUTHOR AFFILIATION ELL,T.J.Washin ton g on Public Power Suppl S Washington Public Pow p y ystem RECXP.NAME RECIPX ENT AFFXLIATXON ic Power Supply System DOCK 0500

SUBJECT:

LER 97-011-00:on

'l of"A" h f'l W/971110 lt DXSTRXBUTION CODE: XE22T COPIES RECEIVED:LTR ENC Lz.censee Event Report (L ER), Incident Rpt, etc.NOTES'.RECIPXENT ID CODE/NAME PD4-2 PD INTERNAL: ACRS AEOD/SPD/RRAB NRR/DE/ECGB NRR/DE/EMEB NRR/DRCH/HICB NRR/DRCH/HQMB NRR/DSSA/SPLB RES/DET/EIB EXTERNAL: L ST LOBBY WARD NOAC POORE,W.NRC PDR COPIES LTTR ENCL 1 1 , AEOD/SPD/RAB NRR/DRCH/HHFB NRR/DRCH/HOLB NRR/DRPM/PECB NRR/DSSA/SRXB RGN4 FILE 01 1 1 1 1 1 1 LITCO BRYCE,J H NOAC QUEENER,DS NUDOCS FULL TXT RECXPIENT ID CODE/NAME COLBURN,T 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 COPIES LTTR ENCL 1 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1.1 1 1 NOTE TO ALL"RXDS" RECX PLEASE HELP US TO R OR REDUC TO REDUCE WASTE.TO'HAVE Y CE T UM OF COPIES DESK (DCD}ON EX~~%SION 415-2083 RGANXZATXON, CONTACT T ON REMOVED FROM DISTRIBUTI ON LIS'.ACT THE DOCUMENT CONTR<TOTAL NUMB E FULL TEXT CONVERSION REQUXRED BER OF COPIES REQUXRED~LTTR 25 ENCL 25

~~'ASI'II~GTOi I L'lll.lc I 0th'I:I<SUI I LV SYS'I'I&I i'.O.Ik>x 965~l(i<hliuiil.ltiki%i@;lors

~)9352-Oi>6 November 10, 1997 G02-97-206 Docket No.50-397 U.S.Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Gentlemen:

Subject:

WNP-2, OPERATING LICENSE NPF-21 LICENSEE EVENT REPORT NO.97-011-00 Transmitted herewith is Licensee Event Report No.97-011-00 for WNP-2.This report is submitted pur'suant to 10 CFR 50.73 and discusses the items of reportability, corrective action taken, and action to preclude recurrence Should you have any questions or desire additional information pertaining to this letter, please ca 11 me or Mr.P.J.Inserra at (509)377-4147 s ectfully, P.Bemis Vice President, Nuclear Operations Mail Drop PE23 Attachment CC: EW Merschoff-NRC MV KE Perkins, Jr.-NRC RIV, WCFO TG Colburn-NRR INPO Records Center-Atlanta, GA NRC Senior Resident Inspector-MD927N (2)DL Williams-BPA, MD399 PD Robinson-Winston 2 Strawn 97iii90086 97iii0 PDR ADOCK 050003'P7 S PDR LICENSEE EVENT M".PORT (LKR)FACILITY NAME (I)Washin ton Nuclear Plant-Unit 2 DOCKET NUHBER (2)50-397 PAGE{3)1 OF 3 TITLE (4)HIGH PRESSURE CORE SPRAY (HPCS)BATTERY CHARGER FAILURE RESULTING IN HPCS SYSTEM INOPERABILITY EVENT DATE (51 OAY LER NUHBER{61 SEQVENRAL NUMBER REV.NUMBER REPORT DATE{71 OTiiER)ACILITIES INVOLVED IB)DOCKET NUMBER OAY YEAR FACIUIY NAME 10 10 97 97 011 00 11 10 97 FACILITY N AM E N/A DOCKET NUMBER 05000 OPERATING MODE{9)THIs REpoRT Is svBHITTED pvRSUAMT To THE REOUIREHEIITs of'0 cfR 5:{check one or more)(111 POWER LEVEL (1o1 81 20.402(b)20.405(a)(1)

Q 20.405(s)(1)(ii)20.405(a)(1)(iii) 20.405{a){1)(iv)20.405(s)(l)(v) 20.405(c)50.36(c)(1) 50.36(c)(2)50.73(s){2)())50.73(a)(2)(ii) 50.73(s){2)(iii)50.73(a)(2)(iv) 50,73(a)(2)(viii)(B) 50.73{a){2)(x) 50.73(a)(2)(v) 50.73(a)(2)(vii) 50.73(a)(2)(viii)(A) 73.71(b)73.71(c)OTHER LICENSEE CONTACT FOR THIS LER{12)NAME T.J.Powell, Licensing Technical Specialist TELEPHONE NUMBER ({nc{ude Area Code)(509)377-4161 CQHPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)CAUSE COMPONENT BG BYC C173 REPORTABLE TO NPRDS CAUSE ave)LM COMPONENT MANUFACTURER REPORTABLE TO NPRDS SUPPLEHENTAL REPORT EXPECTED{14)YES gf yea, con)ptciod EXPECTED SUBMISSION DATE).NO EXPECTED MONTH , DAY ABSTRACT: On October 10, 1997 at 2057 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.826885e-4 months <br /> with the plant in Mode 1, the High Pressure Core Spray (HPCS)Battery Charger (HPCS-C1-1),failed resulting in degraded 125 VDC bus voltage.The HPCS System was immediately declared inoperable.

Concurrent with the HPCS failure, the Reactor Core Isolation Cooling (RCIC)System was inoperable due to system testing.With both HPCS and RCIC inoperable, Technical Specification LCO 3.5.1 Action D.1 (be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />)was entered.The RCIC System was declared operable approximately 17 minutes later and LCO 3.5~1 Action D.1 was exited.The HPCS Battery Charger tested satisfactorily following installation of new control circuit boards and was declared operable on October 15, 1997 at 0150.The root cause of this event was failure of the"A" phase firing control circuit board due to component degradation (aging)after seven (7)years of reliable operation.

At all times, adequate core cooling was assured by the operability of the redundant and diverse low pressure Emergency Core Cooling System (ECCS)injection/spray in conjunction with the Automatic Depressurization System (ADS);therefore, this event had no safety significance.

t LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACILITY t(AHE (I)DOCKET Nut(BER (2)LER Nut(BER (6)SEQVEttTIAL ttuMBER R6V)S)ON NtNBCA PAGE (3)Washington Nuclear Plant-Unit 2 50-397 97 011 00 2 oF 3 TEXT (If more space is required, use additional copies o(NRC Form 366A)((7)Event De cri i n On October 10, 1997 at 2057 hours0.0238 days <br />0.571 hours <br />0.0034 weeks <br />7.826885e-4 months <br /> with the plant in Mode 1, the HPCS[BG]Battery Charger (HPCS-Cl-1) failed resulting in degra'ded 125 VDC bus voltage and Technical Specification LCO 3.8.4 Action B.1 was entered.The HPCS System was immediately declared inoperable.

Concurrent with the HPCS failure, the RCIC[BN]System was inoperable due to system testing.With both HPCS and RCIC inoperable, Technical Specification LCO 3.5.1 Action D.1 (be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />)was entered.RCIC System testing was completed and the system was declared operable at 2114 hours0.0245 days <br />0.587 hours <br />0.0035 weeks <br />8.04377e-4 months <br />, approximately 17 minutes after the HPCS Battery Charger initially failed, and Technical Specification LCO 3.5.1 Action D.1 was exited.Shortly after the HPCS Battery Charger failed, the 125 VDC bus voltage stabilized at 118 VDC with the HPCS Battery supplying the load.The HPCS Battery Charger shut itself down due to a high DC output voltage.The High Voltage Shut Down (HVSD)relay was found to be in a tripped condition.

In accordance with an approved trouble shooting plan, the high voltage relay was reset.On October 11, 1997 at 0349 hours0.00404 days <br />0.0969 hours <br />5.770503e-4 weeks <br />1.327945e-4 months <br />, the HPCS Battery Charger was re-energized and the HPCS 125 VDC bus voltage returned to 130 VDC with the HPCS Battery Charger supplying the load.The HPCS Battery Charger was functioning at this time but further troubleshooting was required to determine the cause of the original failure prior to its.return to operability.

Testing determined the"A" phase firing control circuit board produced an unstable output voltage.All three (3)firing control circuit boards were replaced.Following satisfactory completion of post maintenance testing, HPCS-Cl-1 was declared operable on October 15", 1997 at 0150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> and Technical Specification 3.8.4 Action B.1 was exited.Immedia e rrective Action The HPCS System was immediately declared inoperable and Technical Specification LCOs 3.8.4 Action B.l and 3.5.1 Action D.1 were entered.Plant operators responded promptly to restore RCIC System operability and Technical Specification LCO 3.5.1 Action D.1 was exited.F rther Evalu ion This event is being reported per the requirement of 10CFR50.73(a)(2)(v)(D) as a condition that alone could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.The inoperability of the HPCS System is a unique event at WNP-2.Unlike the other Emergency Core Cooling Systems, HPCS System inoperability is reportable even though all requirements of Technical Specification LCO action statements are being complied with.As HPCS is a"single train" Emergency Core Cooling System, inoperability is reportable any time it is unable to perform its safety function when it is required to be able to do so by plant conditions.

FACILITY NAME{I)LICENSEE EVENT REPORT (LER)TEXT CONTINUATION DOCKET NUMBER I2)LER NUMBER (6)SEQUENTIAL NVHBER R6V!S)ON NUMBER PAGE I 3)Washington Nuclear Plant-Unit 2 50-397 97 011 00 3 oF 3 TEXT (If more space is required, use additional copies of NRC Form 366A)(I 7)~Roo ause The cause of the HPCS Battery Charger failure was failure of the"A" phase firing control circuit board due to component degradation (aging)during seven (7)years of operation.

Further Corrective Action Performed an infrared survey of the HPCS Batter;Charger and cleaned and retightened connections.

A Scheduled Maintenance System task for the replacement of all three (3)firing control circuit boards at intervals of five (5)years or less has been instituted to prevent recurrence.

A review of the preventative maintenance programs for other battery chargers and inverters to verify adequate inspection requirements and acceptable replacement intervals for key components has been implemented to ensure similar failures are avoided in other plant equipment.

Asses men f Safe on uences Offsite power remained available while HPCS-Cl-1 was inoperable.

Thus, HPCS was capable of performing its emergency core cooling safety function at all times using offsite power.Also, the HPCS design backup systems of ADS[SB]and the Low Pressure Core Spray (LPCS)[BM]were available to provide low-pressure spray to the reactor.RCIC was available as an alternate high-pressure injection system approximately 17 minutes after the HPCS Battery Charger failed.Although Safety Related, the RCIC System is not an Engineered Safety Feature (ESF)System and no credit is taken in the safety analyses for RCIC System operation.

However, based on the RCIC System contribution to the reduction of overall plant risk, with RCIC and HPCS inoperable the plant must be brought to at least Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.Plant operators responded quickly'to restore RCIC operability, avoiding the 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> plant shutdown required by Technical Specification LCO 3.5.1 Action D.1.The actions of the plant operators were prompt and correct to ensure the plant was maintained within the bounds of the Technical Specifications and;therefore, within the bounds of the operational safety analysis.Adequate core cooling was ensured.This event had no safety significance.

Similar Even There have been no recent LERs involving equipment inoperability as a result of degraded circuit boards.The corrective actions listed above will preclude recurrence of similar events.

I;