ML17262A758

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LER 92-002-00:on 920203,reactor Trip Occurred W/Reactor at Approx 23% Full Power Just Subsequent to Turbine Trip While at 47% Power.Caused by Lo Lo Level in SG a Due to Design Perturbations.New Setting calculated.W/920304 Ltr
ML17262A758
Person / Time
Site: Ginna Constellation icon.png
Issue date: 03/04/1992
From: BACKUS W H, MECREDY R C
ROCHESTER GAS & ELECTRIC CORP.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-002, LER-92-2, NUDOCS 9203110291
Download: ML17262A758 (28)


Text

!+ACCELERATEDDISTRIBUTIONDEMONSTRATIONSYSTEMREGULATORINFORMATIONDISTRlBUTIONpTEM(RIDS)ACCESSIONNBR:9203110291DOC.DATE:92/03/04NOTARIZED:NODOCKET¹FACIL:50-244RobertEmmetGinnaNuclearPlant,Unit1,RochesterG05000244AUTH.NAMEAUTHORAFFILIATIONBACKUSiW.H.RochesterGas&ElectricCorp.MECREDY,R.C.RochesterGas&ElectricCorp.RECIP.NAMERECiPIENTAFFILIATION

SUBJECT:

LER92-002-00:on920203,reactortripoccurredw/reactoratapprox23%fullpowerjustsubsequenttoturbinetripwhileat47%power.CausedbylololevelinSGAduetodesignperturbations.Newsettingcalculated.W/920304ltr.DISTRIBUTIONCODE:IE22TCOPIESRECEIVED:LTRENCLSIZE:TITLE:50.73/50.9LicenseeEventReport(LER),IncidentRpt,etc.NOTES:LicenseExpdateinaccordancewith10CFR2,2.109(9/19/72).RD/05000244ARECIPIENTIDCODE/NAMEPDl-3LAJOHNSON,ACOPIESLTTRENCL1111RECIPIENTIDCODE/NAMEPD1-3PDCOPIESLTTRENCL11DDINTERNAL:ACNWAEOD/DSP/TPABNRR/DET/EMEB7ENRR/DLPQ/LPEB10NRR/DREP/PRPBllNRR/DST/SICB8H3NRR/DST/SRXB8ERES/DSIR/EIBEXTERNAL'G&GBRYCEiJ~HNRCPDRNSICPOOREiW.AEOD/DOAAEOD/ROAB/DSPNRR/DLPQ/LHFB10"NRR/DOEA/OEABNRR/DST/SELB8DgNR~D-.LB8Dl-G~02RGN1FILE0133LSTLOBBYWARD1111NSICMURPHYgG.A111.1NUDOCSFULLTXT112211112211111111221~1'111111111111DNOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMPl-37(EXT.20079)TOELIMINATEYOURNAMEFROMDISTRIBUTIONLISTSFORDOCUMENTSYOUDON'TNEED!ADDSFULL'TEXTCONVERSIONREQUIREDTOTALNUMBROFCOPIESREQUIRED:LTTR30ENCL30 I

rrf~'I~zotrr.sT4MROCHESTERGASANDELECTRICCORPORATION489EASTAVENUE,ROCHESTERN.K-74649-0001ROBER't(,hlECRjtpYVrr<VresidenlCrnnaNo<lcmProdursrorrTELE&>0'MEARErrCOM716546'2700March4,1992U.S.NuclearRegulatoryCommissionDocumentControlDeskWashington,DC20555

Subject:

LER92-002,FeedwaterTransient,DueToLossOfExcitationInducedTurbine/GeneratorTrip,CausesLoLoSteamGen'eratorLevelReactorTrip-R.E.GinnaNuclearPowerPlantDocketNo.50-244Inaccordancewith10CFR50.73,Licensee.EventReportSystem,item(a)(2)(iv),whichrequiresareportof,"anyeventorconditionthatresultedinmanualorautomaticactuationofanyEngineeredSafetyFeature(ESF),includingtheReactorProtectionSystem(RPS)",theattachedEventReportLER92-002isherebysubmitted.Thiseventhasinnowayaffectedthepublic'shealthandsafety.Verytrulyyours,RobertC.Mecredy.xcoU.S.NuclearRegulatoryCommissionRe'gionI475AllendaleRoadKingofPrussia,PA19406GinnaUSNRCSeniorResidentInspectorf)~g(4~(q'l92031i0291'720304PDRADOCK050002445PDR It'l

<<ACcrea<<I4ASILICENSEEEVENTREPORTLER)Ug,IRILSARRIRVLATCATcoe>>e<<voceAeeaavlaOeetNO,$1<<.aiavISIIAISI/SQISeACILITYNAeelIllR.E.in'naNuclearPowerPlant:OOCRtTIA>>eOIRQlAo6ooo244>ot'"FeedwaterTransient,DuetoLossofExcitationnucedTurz.neGeneratorTrip,CausesLoLoSteamGeneratorLevelReactorTripIVINSOATSIIILtRNueettAIIIAIMRTOATIIIIOTHIAeACILITISIINVOLVIONlVO<<THOAYYIA1YIAR0239292~save<<ewe<<vee~IA002AevorceeIrueee~A0IIONTH03OAY04YIAR92eACIUTY<<AeeeeOOCAIT<<uee~SAISI0600O06000Oel1*TINOeeOOIItl~Oeel1LlvlL023THIS1leOATNSuteeITTIOeuAWANTI$Lea$4ISO.NQNlllIIISa.calleIIIIIIISt.eleIIIIIRI$OAOllelllIl<<lSO.OOSlelllllelSt.cellel~OMWIII~OMWQI~O.TSNIQIII~O.TtieIQIIIIIO.TSNIQIIVO~O.TSNIQII<<I~O.TSlalQ)lel~O.TSlalQlleOIIO.TIlelQlleraIAI~0.$SIeIQIleetlQISO.TSWQllel0THI1$ovl1tlelNTIOeItel1$."lceeeeerrercereeleeeeeeeree>>IlllM714ITLTllelOTHSRlteeeeVIeAeeeeeeererereeeTeeL<<RC/>>4<<AUILICINSIICONTACTMRTHQLSAllllTILteleONINVLQIAWesleyJI.BackusARIACOOlTechnicalAssist:anttotheOperationsManager31552444CCAVLSTIONSLINC>ORtACHCaeeMNINTOAILUAI0tlCAIllaIelTHISRIMATlltlCAUSISYSTINCOIIMNINTVA<ACrTVAIAIMRTAILI'gent,~H<@tToNeRosr~P4;":~QjCVSISYSTSNcoeeMNINTHANVSA4TVAIRIMATAILTONOAOSXBTBW315g~NAN$3'.~e'rterr%g~rr3>vVjj~4~e:.II~I,>>~C.~,y;$$4SVTTLININT*LAIMATtteICTIOIIAIVIIIllTee.er<<e>>NSRJSCTSOSVINISSIO>>OATIIAJSTA*cTILeevl4Iecoeeeer.IA,eeereee<<e>>reAY>>eeree>>eeeeeeeoer<>e<<eevlltlttetCTSOLVINISSIONOA'llll~IeeONTHCAYYIAROnFebruary3,1992withthereactoratapproximately23%fullpower,justsubsequenttoaturbinetripwhileat474reactorpower,areactortripoccurredduetoLoLoLevel(</=17%)inthe"A"SteamGenerator(S/G).TheControlRoomoperatorsimmediatelyperformedtheappropriateactionsofEmergencyOperatingProceduresE-0(ReactorTriporSafetyInjection)andES-0.1(ReactorTripResponse).BothMainSteamIsolationValves(MSIVs)weresubsequentlyclosedtolimitaReactorCoolantSystem(RCS)cooldownandtheplantwasstabil-izedathotshutdown.Theunderlyingcauseoftheeventwastheinabilitytocontrolthe"A"S/Glevelabovethereactortripsetpointduetodesignandtransientinducedperturbations.(ThiseventisNUREG-1022(x)CauseCode).CorrectiveactiontakenorplannedarediscussedinSectionVofthetext.<<ACe<<r<<I44$I If IIACtv'040ILICENSEEEVENTREPORTILER)TEXTCONTINUATIONVl.4VCLlAAAIOVLATOAVCeaWIllIISIA>>AOVlO0+14OIIQI~IQAl)et<AllII)I'lSSACILITYIIAIAlIII"OOCIIKZIIVIACCAIll%lAALlAIIIAAI~IIIllS~QMA4TIAL'VUAACVOIOHVIA~AOlIlIR.E.GinnaNuclearPowerPlanttlXTOr~aeOee~.~~~AAC~~'sIIlllosooo2449200200020F].PRE-L?V1?NTPLANTCONDITIONSTheplantwasatapproximately47%reactorpowerduetoaloadreductionearlierintheday.Partofthisload.reduction(i.e.toapproximately60%reactorpower)wasrequestedbytheRochesterGasandElectricCorporation(RG&E)PowerControlDispatchertoremoveamajortrans-missionlinefromservice(circuit908)forrepair.Theremainderofthisloadreduction(from60%to47%reactorpower)wasmadetoreducereactorpowerbelowpermissiveP-9(i.e.ReactorTripFromTurbineTripBlocked)toperformcondenserwaterboxmaintenanceandturbineon-linetriptestingandvalvetesting.ThemaingeneratorvoltagecontrolwasinthemanualmodeduetovoltageoscillationsexperiencedearlierintQeday.Thereactorcontrolrodswerealsointhemanualmodetomaintainthecoreaxialfluxwithinitsoperatingband.Turbineon-linetriptestingand'alvetestingwasinprogresswiththelasttest'sinitialconditionsbeingverifiedpriortoperformanceofthetest.IIDESCRIPTIONOFEVENTA.DATESANDAPPROXIMATETIMESOPMAZOROCCUEGU9iCES:oFebruary3,1992,2220EST:duetolossofexcitation.MainGenerator.Trip0February3,1992,2220EST:MainTurbinetripdue=tomaingeneratortrip.0February,3,1992,2224EST:Eventdateandtime.0February3,1992,2224EST:Discoverydateandtime.0February3,'992,2224EST:ControlRoomoperatorsverifybothreactortripbreakersopen,andallcontrolandshutdownrodsinserted.VAC~QALIlAAAIl4$I

IIACSvv~(041ILICENSEEEVENTREPORTILERITEXTCONTINUATIONUl,vUCLSAAAl<<ULATOAY<<OvvlllIOAISArrrovlOOvlvOIISO~IOsl)erirf5llII%$CSACILITYVAVlIllCO<<IICTIIUVClrl1ILlAlsUVCSAlll$I4vSr7IAI.rvASVISIOHV1~AOlIllR.E.GinnaNuclearPowerPlantosooo244TlxTIII~vSSSrrrsrvr.vvSrrrrAvIvrcsvrl~'llIITI92-002-00030>12oFebruary3,1992,2229EST:ControlRoomoperatorsclosebothMainSteamIsolationValves(MSIVs)tolimitaReactorCoolantSystem(RCS)cooldown.oFebruary3,1992,2307EST:Plantstabilizedathotshutdowncondition.B.EVENT:OnFebruary3,1992atapproximately2220EST,withthereactoratapproximately47%stablereactorpower,theControlRoomreceivedturbinetripfirstoutannunciatoralarmK-26(GeneratorLockoutRelay).Asreactorpowerwaslessthan50%fullpowerwiththemaincondenseravailable,(i.e.lessthanpermis-siveP-9),reactortripfromturbinetripwasautomaticallyblocked.TheControlRoomoperatorsimmediatelyentered-AbnormalProcedureAP-TURB.'1(TurbineTripWithoutReactorTripRequired)andperformeditsapplicableactions.TheresponsesoftheSteamGenerator(S/G)FeedwaterRegulatingValves(FRVs)fordifferentcontrolconfigurationsarenotedhereforclarityofsubsequentevents:oWhenallFRVs(MainandBypass)areintheautomaticmode,theywillgofullopenonaturbinetripwithRCSaveragetemperature(Tavg)greaterthan554F.Whentemperaturegoesbelow554F,thesevalveswillgofullclosed.0AllFRVs,bothmainandbypass,willfullycloseuponreceivingaHIS/GLevel()/=674)orsafetyinjectionsignalregardlessoftheirauto/manualstatus(feedwaterisolation).'WhentheMainFRVsareplacedinthe,manualmodefromtheaboveconfiguration,theywillassumethepositionabasedonthecurrentcontrollermanualdemandsignalandstaythereuntiladjustedbytheresponsibleoperator.AssumingthatthebypassFRVsareleftinauto,thebypassFRVswillcontinuetorespondtotheautomaticfeedwatercontroldemand.VACsOAvSCCA<l4$I tl HISCTerm~IMMIeLICENSEEEVENTREPORTILERITEXTCONTINUATIONU.S.HUclcAAitoUUAToircossssls$loi/ASSAOVCOOH$HO$1$OWIOS$Ilr<A$5IISI'$$AACIUI'TYHAMII1IOOCIICTHUMOIA111CliHUMOtiI~ISSOU~HTIAI,ASvlQIOrMrSA0$1$1R.E.GinnaNuclearPowerPlantRATlrmarMSrsrHssrsr.~srsrrrsAMHrcIlsrr~$111TIosooo24492--0.'2"-0'04osl2PriortotheturbinetripallFRVswereintheautomaticcontrolmodewiththebypassFRVsfullopenandthemainFRVscontrollingS/Glevelinsomemidposition.Subsequenttotheturbinetrip,thema'inFRVswentfullopenperdesign(thebypassFRVswerealreadyfullopen)andtheControlRoomoperatortransferredthemainFRVstomanualcontrolandadjustedthemtocontrolS/Glevels.ThebypassFRVswereleftintheautomaticcontrolmode.ThenarrowrangeS/Glevelswereatapproximately534andrapidlyincreasingwhenthemainFRVswereshiftedtothemanualmode.TheControlRoomoperatorclosed'ownthemainFRVstoapproximately10-134opentocontrolS/Glevels.Duringthistimethe"A"S/GFRVisolatedonHILevel(i.e.)/=67%narrowrangelevel).DuringapproximatelythissametimethefullopenbypassFRVsrapidlyclo".edbecausetheirautomaticcontrollingsetpointwasnow394S/Glevel.TheControlRoomoperator'continuedtomakeadjustmentstothemainFRVstocompensateforthetransientperturbations,butwasunsuccessful.At2224EST,February3,1992,withthereactoratapproximately234fullpowerareactortripoccurredduetoLoLoLevel((/=174)inthe"A"S/G.TheControlRoomoperatorsperformedtheimmediateactionsofEmergencyOperatingProcedureE-0(ReactorTripOrSafetyInjection)andtransitionedtoEmergencyOperatingProcedureES-O.l(ReactorTripResponse)whenitwasverifiedthatbothreactortripbreakerswereopen,allcontrolandshutdownrodswereinserted,andsafetyinjectionwasnotactuatedorrequired.BothMSIVsweresubsequentlyclosedat2229ESTtolimittheRCScooldown.TheclosingoftheMSIVssubsequentlymitigatedtheRCScooldownandtheplantwasstabilizedinhotshutdownat2307EST.MACsorvsAAAI$441 I

IIACSoew%CAI%45>LICENSEEEVENTREPORT{LER)TEXTCONTINUATIONy,l,IIUCLSAAAlOULATOAVCOSSMISCIOII/ASSAOVlOOulIOTISO&104l~>AllSINAI1$SACILITVIIASStIIIOOCKttIIUI&lAITIvSAALlllIIUSSCIAISIS~4USatiALU1SAOlISIR.E.GinnaNuclearPowerPlantTlXTIIT~~e~.WeeerCeW+ACArmWSSIUTIosooo244920200050vl2Equipmentproblemsthatoccurredduringtheeventwereasfollows:0'he"ALTSteamGeneratorMSIVMainControlBoardindicationshowedthevalvetobenotfullyclosed.Anauxiliaryoperatorwasimmediatelysentouttocheckandreportedthevalveclosedbasedonviewingthevalveexternalindicator.Subsequently,theMainControlBoardindicatedthevalvefullyclosedapproximately23minutesaftersignalreceipt.00FollowingthestartoftheTurbine,DrivenAuxiliaryFeedwater(TDAFW)pumponLoLoS/GLevels,itexhibitedsomeoscillationsinflow,howevertotalflowremainedabovetherequired400gallonsperminute(GPM)asrecordedonthePlantProcessComputerSystem(PPCS).TheIntermediateRangeNuclearInstrumentation,ChannelN-35,aftertrackingconsistantwithChannelN-36down'toapproximately10E-10amps,haditsindicationcontinuetodropbelow10E-11amps.TheN-35-channelreturnedtonormal(10E-11amps)approximatelytenhoursfollowingthetrip.C.INOPERABLESTRUCTURESgCOMPONENTSlORSYSTEMSTHATCONTRIBUTEDTOTHEKG9iT:D.None.OWNERSYSTEMSORSECONDARYFUNCTIONSAFFECTED:~None.E.METHODOFDISCOVERY:TheeventwasimmediatelyapparentduetoalarmsandindicationsintheControlRoom.hACSOAISSASAISASI 0~~1 HACSoreMI$4$ILICENSEEEVENTREPORTILERITEXTCONTINUATIONvt.IIUCLEA+AtOULATCAYcoooorlttrorrAssAOYEOOvtHO$I$0aIOo-t)eOIAEStrtI1$SACILITYHAlttIllOOCKETIIUoottAItlLt1HUOSOEAIII$$4v~rrYIOLMootveOI<o~AOEIEIR.E.GinnaNuclearPowerPlantTEXTlrsrrreoHIOoo~rotreoS.reoroorrorHPCAHe~$IIITIosooo24492-002-060F12OPERATORACTION:Afterthereactortrip,theControlRoomoperatorsperformedtheactionsofEmergencyOperatingProceduresE-O,(ReactorTripOrSafetyInjection)andES-0.1,(ReactorTripResponse).TheMSIVsweremanuallyactuatedclosedapproximatelyfour(4)minutesafterthetriptopreventfurtherplantcooldown.Theplantwassubsequentlystabilizedathotshutdown..Subsequently,theControlRoomoperatorsnotifiedhighersupervisionandtheNuclearRegulatoryCom-missionper10CFR50.72,non-emergency,4hournotification.G.SAFETXSXSTEMRESPONSES:The"A"S/GFRVsclosedautomaticallyfromafeedwatdrisolationsignal.III.CAUSEOFKGDFZA.IMMEDIATECAUSE:Thereactortripwasdueto"AttS/GLoLoLevel(</=>>4)B.ROOTCAUSE:Theunderlyingcauseofshe"A"S/GLoLoLevel~(</=174)wasdeterminedtobetheControlRoomoperator'sinabilitytocontrolthe"A"S/Glevelaboveitsreactortripsetpointduetothefollowingcontributingfactors:Thetransientperturbationsthatwereoccurringduetodesign(i.e.thedesignoftheFRVstogofullopen,wheninautomaticmode,followingaturbinetrip,andthedesignofhavingthebypassFRVsopenatthehigherpowerlevels).0TheshrinkandswellphenomenonoftheS/Gwaterlevelsduetotheabovedesigninducedperturba-tionsandthetransientinducedperturbations.HACSoaksttAArtttl 44 IINCNotes~I$4$I0LICENSEEEVENTREPORTILER)TEXTCONTINUATIONVl.1VCLlAA1$OVLATO1YCOMMI$$IO1NANNAOVlOOVNAO$I$O~IONlNNI1$$$I$I1$NACILITYIIANltIllOOCIIlZIIVINCCAIllLl1IIINNC$1I~IslavlseviALMalv+IOAOlI$IR.E.GinnaNuclearPowerPlantTEXTIN'1INNN1~.vNNOeeeaWIYNC/erat~$IIITI05IO0024492-002-00070'2,ANALYSISOFEV19iTThiseventisreportableinaccordancewith10CFR50.73,LicenseeEventReportsystem,item(a)(2)(iv),whichrequiresreportingof,"anyeventorconditionthatresultedinmanualorautomaticactuationofanyEngineeredSafetyFeature(ESF)includingtheReactor'rotectionSystem(RPS)".The"A"S/GLoLoLevelreactortripwasanautomaticactuationoftheRPS.Anassessmentwasperformedconsideringboththesafetyconsequences.andimplicationsofthiseventwiththefollowingresultsandconclusions:Therewerenosafetyconsequencesorimplicationsattributedtothereactortripbecause:oThetworeactortripbreakersopenedasrequired.oAllcontrolandshutdownrodsinsertedasdesigned.oTheplantwasstabilizedathotshutdown.TheGinnaUpdatedFinalSafetyAnalysisReport(UFSAR)Chapter15.2.2,"LossofExternalElectricalLoad",wasreviewedandcomparedtotheplantresponseforthisevent.Theplantisdesignedtoaccepta50%lossofelectricalloadwhileoperatingatfullpoweroracompletelossofelectricalloadwhileoperatingbelow50%,withoutinitiatingareactortrip.Althoughplantdesigncanaccepta50%lossofload,pastexperiencehas'hownavulnerabilitytoS/Gshrinkandswell.SincetheS/GmainFRVsareplacedinmanual,actualplantresponsewillbedependentuponoperatorresponsetoindicatedS/Glevel.GinnaUFSARChapter15.2.2evaluatestheplantbehaviorforacompletelossofloadfromfullpowerwithoutadirectreactortrip,primarilytoshowtheadequacyofthepressure-relievingdevicesandalsotoshowthatnocoredamageoccurs.CompletelossofloadanalysisshowsthatDNBRdoesnotdropbelow2.0andpressurizerpressuredoesnotexceed2500psia.Onlyasmallpressurespike(approxi-mately30psig)andasmalltemperaturespike(2.5F)wasencounteredduringthistransient.wACNOAIN$NAAI$44I

ISACTens444AI4431LICENSEEEVENTREPORTILER)TEXTCONTINUATIONU.S.HUCLSAAASOULATOAYCO>>>>ISSIOSIASSAOYSOOU4'SO)ISO~IOs4)ctiA4$41SISSFACILITYIIA>>4IllOOCIISTHUIS44AISIT~AALSAKUSA44AISISSQUSNT<ALUAASYhlORUSASAO4ISIR.E.GinnaNuclearPowerPlantTSXT/IT~>>S>>h>>SUse4.v>>>>h>>On>>hfISCA>>>>~'S11171I050002492002-0OF12Followingthereactortrip,pressurizer'leveldecreasedtoapproximately54levelasaresultofthecooldown.Thisisanexpectedobserved'ransient.TheS/Glevelsbothdecreasedtothenarrowrangetaps.ThisisanexpectedtransientbasedupontheencounteredshrinkintheS/Gs.Aslowcooldownresultedduringtheposttriprecoveryperiod.Thiscooldownisboundedbytheplantaccident'nalysisanddoesnotexceedtheTechnicalSpecificationlimitof100Fperhour.AdditionalprotectionwasprovidedbyclosureoftheMSIVs.Basedontheaboveandareviewofposttripdataandpastplanttransients,itcanbeconcludedthattheplanthasoperatedasdesignedandthatthere'asnounreviewedsafetyquestionsandthatthepublic'shealthandsafetywasassuredatalltimes.CORRECTIVEACTIONA.ACTIONTAKENTORRKZJBNAFFECTEDSYSTEMSTOPRE-&TENTNORMALSTATUS:0TheS/GlevelswerereturnedtotheirnormaloperatinglevelsbyadditionofAuxiliaryFeedwater,subsequenttothereactortrip.0The"A"MSIV,manufacturedbyAtwoodandMorrill,isa30inchairoperatedswingcheckvalve,installedinthereversedirectiontouseS/Gsteamflowtoensureproperclosure.Aswithanyswingcheckvalve,theclosingmomentmustbelargeenoughtoovercomethefrictiononthevalveshaftduetothevalvepacking-..Completeclosureisaccomplishedbytheforceofthefluidflowonthevalvedisc.The"A"MSIVwassubsequentlystrokedseveraltimessuccessfullytoensureoperabilityandadequateclosurecapability.Resultsofthesetestssupporttheconclusionthatfailureofthe"A"MSIVtofullyseatduringthereactortripwasnotduetointernalvalvedistortionandbending,butwastheresultofalackofflowacrossthevalvedisc.Failuretocloseisattributedtotheclosureoperationoccurringinaquiescentenvironment.'eACAOASI444AiSWI Lh 0IIACtovv%CA104llUCENSEEEVENTREPORT{LER)TEXTCONTINUATIONVl.IIVCLtAAAlCULATCAYCISALIIQQCII/AitAOVEOOVIW)ISOWIOCE)ctiACS~ITI%SS*CILITYIIANIIIIDOCKCTIIVINIAITIL41IILNNI1IIIvTAASICVINTiALVIVOS<V1V~ACEIelR.E.GinnaNuclearP'owerPlant0s00o24492-pp2ppftXTW~~1~vmeeeaaeVIIACAVVI~'llIITl090~12Valveclosureisdependentupontwofactors:Themoment,developedbytheweightofthevalvediscandthespringprovidedtoassistinvalve.closure,plussufficientsteamflowacrossthevalvedisc,withoutwhichthevalvewasnotcapableofcompletingitsclcgoperation.WhenthedemandsignalforMSI~=oclosewasger.atedd/pacrosstheAMSIVwaslowerthanth-.d/pacrosstheBMSIV.Thed/pacrosstheB=.IVwasenoughtofullyseatthevalvewhilethed/pacrosstheAMSIVdidnotprovideenoughforcetoovercomeshaftpackingfrictionalforces.Approximately23minuteslater,thed/pacrosstheAMSIVincreasedapproximately2psidwhichresultedincompleteclosureofthevalve.Foralldesignbasisaccidents,whereMSIVclosureisrequired,the=-accidenttransientswoulddevelopalargeenoughdifferentialpressuretoobtaincompletevalveclosure.RG&Eiscontinuingtoevaluatevariouspackingmaterialswhichhavealowfrictioncoefficientandcanperformtherequiredsealingfunction.oTheTDAFWpumpwassubsequentlytestedtodeterminethecauseoftheflowoscillations,butthetesthadtobeabortedduetoasteamleakonthegovernorvalve.Thegovernorvalvewasdisassembled,inspectedandplacedbackinservice.Thesteamleakwastheresultofgasketleak(probablycausedduetoexcessivetravelofthegovernorvalve).Thegasketwasreplacedwithaqualifiedspare.Thecauseoftheflowoscillationswasduetothe"hunting"ofthegovernorvalve.Thehuntingofthegovernorvalvewascausedbyafeedbacknutbeingoutofproperposition.,ThepositionofthefeedbacknutwascorrectedandtheTDAFWpumpwassubsequentlytestedsuccessfullyandreturnedtoservice.11CPCAIv~IIABI

IIACt<<<<~IS45ILICENSEEEVENTREPORTILER)TEXTCONTINUATIONM5,~IICLSAAAlauLASOAVCO<<AIISSIOIIAlt1OVSOOUINOSISO~IO45)cttII55SISI'SSFACILITYHAAISI'lOOCIIS7HUIAllAISILlllNIIIASSIII~ISSQMSleTILL~U8'IYCIOR<<SAAAOlISIR.E.GinnaNuclearPowerPlantosooo24492p2ppraXtW~eeaee~.v<<~+ACA<<~'iIIm1poi:1200AstheIntermediateRange"NISChannelN-35trackedNISChannelN-36for,itsnormaloperatingrange.andreturnedtonormalapproximatelyten(10)hoursafterthetrip,noimmediateactionwasdeemednecessary.ThisabnormalityhasbeenobservedandresearchedextensivelyinthepastincooperationwiththeNSSSvendor,Westinghouse.Notechnicalbasishasbeenidentifiedastowhythe10E-11idlecurrentdoesnotmaintainindicationat10E-11amps;RG&EandWestinghouseconcurredthatthechannelwasoperableandcapableofperformingallintendedfunctions.Furtherevaluationsoftheresponsecharacteris-ticsofNISchannelN-35willbeperformedduringthe1992AnnualRefuelingandMaintenanceOutage.Thiseventwasinitiatedbyamaingeneratortripduetolossofexcitation.Extensiveexamination,evaluationandtestingwasperformedonthemaingeneratorvoltagecontrolsystem,withthefollowingresultsandconclusions:Theautomaticandmanualvoltagecontrolunitswereextensivelytestedandfoundtooperatesatisfactorily.TheMinimumExcitationLimiter(MEL)datatakenduringthetestingindicatedthatthesettingwastooclosetonormaloperatingpointsofthegenerator.AnewMELsettingwascalculated,reviewedby.Westinghouse(thevendor)andimplemented.Therevisedsettingwillallowoperationtoapproximately190MVARunderexcitedat500MW.h1CBOA<<SASAil4$I l4 IIACIVnXWIS@)ILICENSEEEVENTREPORT(LERITEXTCONTINUATIONV,l.HVCLSAAASOULATOISYCOWHISSIOIIJAttrOvlOOUSeO)ISOMI04SIctirlSSI)I'ISAACILITYHAAISIIIOOCIIltHUUl1111LlrIIUMOlrI~I~AOlI)IR.E.GinnaNuclearPowerPlant05o0o2449tt)ITIItrrn~rnever.vnrrreenrrrCAttn~sIImS~Ovlrt<ALev-002-00110'2Theunitwassynchronizedtothesystemwiththe-voltageregulatorinmanualandnounusualeventswerenoted.Whenthevoltageregulatorwasplacedinthe-automaticmode,theloopwithinthevoltageregulatorsystemwasunstableandthevoltageregulatorwasreturnedtothemanualmode.Theoperationofthevoltageregulatordampingmodulewasverifiedandthegainwasreducedfrommaximumsettingtothemidpointonthepotentiometer.Thevoltageregulatorwasreturnedtotheautomaticmodeandoperatedsatisfactorily.Theplanthasnowoperatedatapproximatelyfullpowerandhasgonethroughseveralnormalvoltageadjustmentssuchasloweringthevoltaqeintheeveningandraisingthevoltageinthemorningasrequiredbysystemload.Noabnormalities.havebeenencountered.B.ACTIONTAKENORPLANNEDTOPREVENTRECURRENCE:AstheunderlyingcauseoftheeventwasdeterminedtobetheinabilityoftheControlRoomoperatortocontrolthe"A"S/Gleve~aboveitsreactortripsetpointduetodesignandtransientinducedlevelperturbation,thefollowingactionshavebeentakenorarebeingplanned:0ApplicableoperatingprocedureshavebeenchangedtorequirethatthebypassFRVsbeplacedinmanualclosedwhenincreasingaboveapproximately304reactorpower.0ApplicableoperatingprocedureshavebeenchangedtorequirereturningthebypassFRVstoautomaticcontrolwhendecreasingbelow304reactorpower.eACJOAN)SAAil4)1

IIACIsrselAAA104lILICENSEEEVENTREPORTILER)TEXTCONTINUATIONvl.eevCLlAIIAlOULATCAYcoseseeClloee/AASSOvloOvleeoIISOWIOel>eseAl5~rlITSI'ACILITYIIAIIlIIIOOCIIKTeeULQlA111LlAIIUAOlAI~IvTAASloulreveALSAVes~areverU~s~AolIQR.E.GinnaNuclearPower.Plant06<<o244TKXTrrrrsrers~r~.vmeseseeeerrrreCArse~'grIITI92-002-12o~12oAmodificationisplannedforthe1993AnnualRefuelingandMaintenanceOutagethatwouldmodifytheexistingfeedwaterisolationlogicforfail-openorfail-closedofthemainandbypassFRVsuponturbinetripwithmainFRVsinautomaticcontrolmode.Theplannedmodificationwilldeletetheexistingfail-openlogicandreplacethefail-closedlogicwithactuationuponreactortripasopposedtoturbinetrip.AstheeventwasinitiatedbytheMainGeneratortripduetolossofexcitation,thefollowingactionsareplannedtopreventrecurrence'.00RG&Eisplanningtopurchaseandinstallareplacementvoltageregulatorunit.IRoutinetestingandmaintenancewillbeperformedontheexistingvoltageregulatorunitduringthe1992AnnualRefuelingandMaintenanceOutagetoattainahighdegreeofconfidencethattheunitwilloperatewithoutincidentfortheentirefuelcycle.ADDITIONALINFORMATIONA.FAILEDCOMPONENTS:TheTDAFWpumpturbineisa465horsepowernoncondensingsteamturbine,serialnumber26635,manufacturedbytheWorthingtonCorporation.B.PREVIOUSLERsONSIMILAREVENTS:AsimilarLEReventhistoricalsearchwasconductedwiththefollowingresults:NodocumentationofsimilarLEReventswiththesameunderlyingcauseatGinnaStationcouldbeidentified.C.SPECIALCOMMENTS:None.~eACSOAee1AAArl4lI