ML17221A601

LER 87-007-01:on 871125,reactor Tripped on Loss of Load Due to Turbine Trip.Caused by Personnel Error.Permanent Magnet Generator & Exciter Bearing Replaced & Exciter Bearing Thermocouple removed.W/880129 Ltr

ML17221A601
Person / Time
Site:	Saint Lucie
Issue date:	01/29/1988
From:	JOHNSON A B, WOODY C O FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
L-88-41, LER-87-007, LER-87-7, NUDOCS 8802020148
Download: ML17221A601 (6)

Text

REGULA,YINFORMATIONDISTRIBUTIYSTEM(RIDS)ACCESSIONNBR:8802020148DOC.DATE:88/01/29NOTARIZED:NOFACIL:50-389St.LuciePlant>Unit2>FloridaPoeer5LightCo.AUTH.NAMEAUTHORAFFILlATIONJOHNSON'.B.FloridaPoeer5LightCo.WOODY.C.O.FloridaPower5LightCo.RECIP.NAMERECIPIENTAFFILIATIONDOCKET¹05000389,

SUBJECT:

LER87-007-01:on871125.reactortrippedonlossofloadduetoturbinetrip.Causedbgpersonnelerror.Permanentmagnetgenerator5exciterbearingreplacedZcexciterbearingthermocoupleremoved.W/880129ltr.DISTRIBUTIONCODE:IE22DCOPIESRECEIVED:LTRENCLSIZE:TITLE:50.73LicenseeEventReport(LER)iIncidentRptietc.NOTES:RECIPIENTIDCODE/NAMEPD2-2LATOURIGNYiECOPIESLTTRENCL1111RECIPIENTIDCODE/NAMEPD2-2PDCOPIESLTTRENCL11INTERNAL:ACRSMICHELSONAEOD/DOAAEOD/DSP/ROABARM/DCTS/DABNRR/DEST/ADSNRR/DEST/ELBNRR/DEST/MEBNRR/DEST/PSBNRR/DEST/SGBNRR/DLPG/GABNRR/DREP/RABA)R/SIBREGFILE02IBRGN2FILE01EXTERNAL:EG5GGROHiMHSTLOBBYWARDNRCPDRNSICMAYSTG11112211011111111111111111155111111ACRSMOELLERAEOD/DSP/NASAEOD/DSP/TPABDEDRONRR/DEST/CEBNRR/DEST/ICSBNRR/DEST/MTBNRR/DEST/RSBNRR/DLPG/HFBNRR/DOEA/E*BNRR/DREP/RPBNRR/PMAS/ILRBRESTELFORDiJRES/DRPSDIRFORDBLDGHOY>ALPDR"NSICHARRIS>J2211111111111111111211111111111TOTALNUMBEROFCOPIESREQUIRED:LTTR46ENCL45

NRCForm3SSA19413lLICENSEEENTREPORT(LER)TEXTCONTINUAIONU.S,NUCLEARREGULATORYCOMMISSIONAPPROVEDOMBNO.3150&104EXPIRES:9/31/BBFACILITYNAMEIIISt.Lucie,Unit2OOCKETNUMBERIllYEARLERNUMBERIBI@~a.SFOVENT/ALNvMErrxo,:REvrsroNiMNVMEllPAGE0)TEXT/ifmoros/rscoisrsr/rr/rsd,rrsosddio'orrs/H/ICFonrr3////A'/(IT)osooo389'870070102OF04DESCRIPTIONOFENTENTEOn25November,1987,St.LucieUnitTwowasoperatingat50percentpowersteadystateinMode1.Theunitwasreturnedtoserviceon23Novemberfollowingarefuelingoutageandwasholdingat50percentpowerwhilerepairswereinprogressonthe2ASteamGeneratorFeedPump(SGFP)(EIIS:SJ)duetoasmallwaterleakthatdevelopedontheventlineatthepumpcasing.ThereactorwasbeingmaintainedinasteadystateconditionwithallautomaticcontrollersplacedinautomaticwiththeexceptionoftheControlRodDriveSystem(EIZS:JD)whichwasinOFF.At2331hours,theReactorProtectiveSystem(EIZS:JC)initiatedareactortriponlossofloadduetoaturbinetrip.Theturbinetrippedonamaingenerator(EIIS:TB)lockout.ThecontrolroomwasalertedwithinformationthatsmokewasseencomingoutoftheMainGeneratorExciter(EZIS:TL).TheAssistantNuclearPlantSupervisor(ANPS)instructedtheTurbineOperator(TO)tocheckforrubsontherotatingcomponentsoftheturbine-generator.TheTOreportedevidenceofturbine-generatorrubstothecontrolroomandtheANPSinstructedtheReactorControlRoomOperators(RCOs)toopenthevacuumbreakersonthemaincondenser(EIZS:SG)toaidinslowingdowntheturbine.Afireteamwasassembledandstationedwithfirefightingequipmentatthevicinityofthemaingeneratorexciter.Therewerenoreportsofanactualfire.Thetripwasanuncomplicatedtripandallsystemsfunctionednormally.TheSteamBypassControlSystem(SBCS)(EIIS:JI)operatedtoreduceprimaryaveragetemperature(T-avg)tothezeropercentpowersetpointof532degreesF.Auxiliaryfeedwater(EIZS:BA)wasinitiatedmanuallytocontrolthesteamgenerator(S/G)levelforReactorCoolantSystem(RCS)(EIZSEAB)heatremoval.ThestandardposttripactionswerecompletedandtheunitwasimmediatelystabilizedinHotStandby,Mode3.NRCFORM316A19831 NRCForm3ddA(983)LICENSEENTREPORT(LER)TEXTCONTINUONV.S.NUCLEARREGULATORYCOMMISSIONAPPROVEOOMSNO.3150MI(HEXP!RES:8/3(188FACILITYNAME(I)DOCKETNUMBER(3)LERNVMSER(8)PACE(3)St.Lucie,Unit2TERT(Ilmoro<<>>oobror)rrr'rod,Ir>>odds'onelNRCFarm3ddl3I()T)osoooYEAR@gSEQUENTIALNUMtR007REVISIONNUMER0103OF04CAUSEOFTBBEVENTSTheimmediatecauseofthemaingeneratorlockoutwaslossofthegeneratorfield.ThelossoffieldwascausedbydestructionoftheexciterPermanentMagnetGenerator(PMG)thatoccurredwhentheexciterbearingfailedallowingthePMGarmaturetorubonthePMGstator.Furtherinvestigationintothefailureoftheexciterbearingindicatedthatagroundwascausedbyacompletedelectricalcircuitbetweentheexciterbearingandtheexciterbase.Thiscompletedelectricalcircuitbypassedtheinsulationbetweenthebearingpedestalandtheexciterbase.Thegroundwascausedbyanimproperinstallationofaninstrumentcable(EIIS:IT).TheinstrumentcableprovidestheterminalconnectionfromthethermocoupleoftheN9exciterbearinghousingtoitsterminalbox,whichprovidesremotetemperatureindicationinthecontrolroom.Theas-foundconditionoftheinstrumentcableindicatedthatthebraidedwirecableshieldwasnotproperlypositionedintheclamp;therefore,agrounddevelopedattheexciterbearing.Examinationoftheexciterbearingrevealedpittingmarksonthebearingsurface,characteristicofcurrentflowingacrossthebearingjournaltothebearingpad,whichresultedinthebearingfailure.Theimproperarrangementoftheinstrumentcablecannotbeconclusivelyidentifiedasawiringerrorduringtheinstallationofthenewmaingeneratorexciter.ThePMGandtheinstrumentcableweremeggeredtodetectforpossiblegroundsandtheresultswereacceptable.Ithasbeenpostulatedthatoneoftwocircumstancesmayhaveoccurred:1)theinstrumentcablewasinstalledcorrectlywiththebraidedwireshieldintheclampwhenitwasmeggered;thenatsomelaterdate,theinstrumentcablewasaccidentlysteppedoncausingthecableshieldtobecomeseparatedfromtheclamp;or2)theinstrumentcable,beingclampedincorrectlytothepedestal,hadnotyetbeenconnectedtotheterminalboxwhenthemeggertestwasperformed.Afterplacingthemaingeneratorbackinservice,thegroundshouldhavebeendetectedduringtheperformanceoftheweeklygeneratorexcitergroundcheck.ThepreventativemaintenancePlantWorkOrder(PWO)requiresvoltagestobereadacrosstheN9bearingshafttogroundandacrossthe59bearingpedestaltoground.Thedataistobeevaluatedtoensurenogroundshavedevelopedinthemaingeneratorexciter.Earlyrecognitionofthegroundwouldhavepromptedimmediateactiontoremovethemaingeneratorfromserviceforthenecessaryrepairs.Therootcauseoftheeventwasacognitivepersonnelerrorbyautilitymain-tenancesupervisorinmisinterpretationofthemaingeneratorexcitergroundvoltagereadings.Theappropriateprocedurewasproperlyfollowed.However,lackofunderstandingofthesignificanceofthegeneratorexcitergroundcheckandinadequateacceptancecriteriainthePWOwerecontributingfactorsinthepersonnelerror.Therewerenounusualcharacteristicsoftheworklocationthatdirectlycontributedtothepersonnelerror.NRCfORM3ddA(983)

URCForm366A(983)LICENSEENTREPORT(LER)TEXTCONTINUAONU.S.NVCLEARRECULATORYCOMMISSIONAPPROVEDOMBNO.3150WIOiEXPIRES:8/31/88FACILITYNAME(11St.Lucie,Unit2DOCKETNUMBER(2)YEARLERNUMBER(6)SEOUENTIALNUMBERREVISIONNUMEllPACE(3)TEXT/I/mortt/Mcoitror)rr/rtd.IhtotdChr/ont/HRCForrrr36(L('ti(17)p5ppp389870070104OF04ANALYSISOFTHEEVENT:Theeventisreportableunder10CFR50.73(a)(2)(iv),"anyeventorconditionthatresultedinmanualorautomaticactuationofanyEngineeredSafetyFeature,includingtheReactorProtectionSystem."Thiseventwasobservedtobearoutinereactortriponlossofload.TheresultingtransientwaswellenvelopedbytheSt.LucieUnitII2FinalUpdatedSafetyAnalysisReportsection15.2.1.2"LimitingReactorCoolantSystemPressureEvent-IsolationofTurbine(100%power)."AllPlantSafetyFunctionsweremetandtherewerenoadditionalcomplications.Consequently,thehealthandsafetyofthepublicwerenotaffectedbythisevent.CORRECTIVEACTIONS.1.ThePermanentMagnetGeneratorwasreplaced.2.TheExciterBearingwasreplaced.3.Anevaluationwasmadeand'theExciterBearingthermocouplewasdeterminedtobeunnecessaryanditwasremovedtopreventfutureincidentsofthistype.4.Thepreventativemaintenanceplantworkorderwasrevisedtoadequatelydefinetheacceptancecriteriaandtheproperactionswhentheacceptancecriteriaarenotmet.5.TrainingwasgiventoallElectricalMaintenancepersonneltoelaborateontheimportanceofproperlyevaluatingthedataduringperformanceoftheweeklygeneratorexcitergroundcheck.h6.Theplanttraininggroupwillevaluatethisitemtodetermineappropriatetrainingrequirementsandmethods.ADDITIONALINFORMATION:FAILEDCOMPONENTINFORMATION:WestinghouseExciterBearing(89bearing)PartI)613F432GOlPREVIOUSSIMILAREVENTS:SeeLER5389-84-011forapreviousreactortripduetoexciterbearingfailure.NRCFORM366*(983)

P.O.14000,JUNOBEACH,FL33408.0420SKNLI5291988L-88-4110CFR50,73U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555,Gentlemen:Re:St.LucieUnit2DocketNo.50-389ReportableEvent:87-07Revision1DateofEvent:November25,1987ReactorTriponLossofLoadCausedbyMainGeneratorExciterBearinFailureDuetoPersonnelErrorTheattachedLicenseeEventReport(LER)isbeingsubmittedpursuanttotherequirementsof10CFR50.73toprovideanupdateonthesubjectevent.Verytrulyyours,C.0.odyExecutiveVicePresidentCOW/GRM/gpAttachmentcc:Dr.J.NelsonGrace,RegionalAdministrator,RegionZI,USNRCSeniorResidentInspector,USNRC,St.LuciePlantGRM/022.LERanFPLGroupcompany