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{{#Wiki_filter:ACCELERATEDDl/RIBUTIONDEMONSTRATIONSYSTEMREGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9205010133DOC.DATE:92/04/24NOTARIZED:NOFACIL:50-389St.LuciePlant,Unit2,FloridaPower&LightCo.AUTH.NAME.AUTHORAFFILIATIONSAGER,D.A.FloridaPower&LightCo.RECIP.NAMERECIPIENTAFFILIATION-DocumentControlBranch(DocumentControlDesk)DOCKET05000389
{{#Wiki_filter:ACCELERATED Dl/RIBUTION DEMONSTRATION SYSTEMREGULATORY INFORMATION DISTRIBUTIONSYSTEM(RIDS)ACCESSION NBR:9205010133 DOC.DATE:
92/04/24NOTARIZED:
NOFACIL:50-389 St.LuciePlant,Unit2,FloridaPower&LightCo.AUTH.NAME.AUTHORAFFILIATION SAGER,D.A.
FloridaPower&LightCo.RECIP.NAME RECIPIENT AFFILIATION
-DocumentControlBranch(Document ControlDesk)DOCKET05000389


==SUBJECT:==
==SUBJECT:==
In-HouseEventRept92-023:on920421,turbinegeneratorfailedtotripduringmanualreactortrip.Rootcauseanalysisstillinprogress.Solenoidvalvesremoved&senttoindependentlabforanalysis..DISTRIBUTIONCODE:IE22DCOPIESRECEIVED:LTRIENCLlSIZE:TITLE:50.73/50.9LicenseeEventReport(LER),IncidentRpt,etc.NOTES:RECIPIENTIDCODE/NAMEPD2-2LANORRIS,JINTERNAL:ACNWAEOD/DOAAEOD/ROAB/DSPNRR/DLPQ/LHFB10NRR/DOEA/OEABNRR/DST/SELB8D~/~S.TPLB8D1REGFILE02FILE01EXTERNAL:EG&GBRYCE,J.HNRCPDRNSICPOORE,W.COPIESLTTRENCL11112,21122111".'111,111111331111RECIPIENTIDCODE/NAMEPD2-2PDACRSAEOD/DSP/TPABNRR/DET/EMEB7ENRR/DLPQ/LPEB10NRR/DREP/PRPB11NRR/DST/SICB8H3NRR/DST/SRXB8ERES/DSIR/EIBLSTLOBBYWARDNSICMURPHY,G.ANUDOCSFULLTXTCOPIESLTTRENCL11221111112211111'"111111DDDNOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEiVASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMPl-37(EXT.20079)TOELIMINATEYOURNAMEFROMDISTRIBUTIONLISTSFORDOCUMENTSYOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:LTTR32ENCL32DD P.O.Box128,Ft.Pierce,FL34954.0128ggI4-8Q.L-92-129U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555'E:St.LucieUnit2DocketNo.50-389EventDate:April21,1992TurbineTriFailurePleasefindattachedthepreliminaryinternalproblemreportofourplanteventwhichoccurredonApril21,1992.Pursuantto10CFR50.73aLicensedEventReportwillbesubmittedwithin30daysoftheeventdate.Pleasecontactusifthereareanyquestionsaboutthissubmittal.Verytrulyyours,VicePresidentSt.LuciePlantDAS/JJB/kwcc:StewartD.Ebneter,RegionalAdministrator,RegionII,USNRCSeniorResidentInspector,USNRC,St.LuciePlantDAS/PSL4681-925'2050101335'20424PDRADOCK05000385'PDRanFPLGroupcompany ST.LUCIEPLANTINHOUSEEVENTREPORT92-023TURBINEGENERATORFAILEDTOTRIPFOLLOWINGMANUALREACTORTRIPUNIT:2DATE:APRIL21,1992I.INITIALPLANTCONDITIONSOnApril21,1992,St.LucieUnit2wasshuttingdownforascheduledrefuelingoutage.Reactorpowerwasatapproximately12%.II.EVENTDESCRIPTIONAscheduledReactor-TurbineshutdownwasinprogressonUnit2.Duringtheshutdown,powermovedtothetopofthecoreasexpected.ExistingproceduralguidanceonAxialShapeIndex(ASI)wasbeingemployedtominimizeitsaffects.WhenthreeoutoffourLocalPowerDensityPre-TripsonthcReactorProtection.Systemcamein,theNuclearPlantSupervisor(NPS)instructedtheReactorControlOperatorstomanuallytriptheUnit.Amanualreactortripwasinitiated,buttheturbinedidnottrip.SeveralattemptsweremadetotriptheturbineusingtheTurbineTrippushbuttonwithnosuccessandthcNuclearWatchEngineertrippedtheturbinefromthefrontstandard.III.EVENTSEQUENCESt.LucieUnit2wasperformingascheduledreactorshutdownforrefuelingpurposes.DuringtheplantshutdownASIapproacheditsupper(negative)limit.CoordinationatcontrollingASIwithinlimitsandmaintainingreactorcoolanttemperatureduetoXenonbuildinginbecamemoredifficult.Whenreactorpowerwasdecreasedtoabout12%,controlrodinsertionhadnoeffectonmakingASIlessnegativeandthreeofthefourReactorProtectionSystemLocalPowerDensitypre-tripscamein.Atthispoint,theNPSinstructedtheReactorControlOperatorstomanuallytriptheunitandthemanualreactortrippushbuttonsonRTGB(ReactorTurbineGuageBoard)204andRTGB201weredepressedat0238withtheturbinetrippushbuttononRTGB201beingdepressedapproximatelytwosecondslater;however,theturbinedidnottrip.StandardPostTripActionsfromEmergencyOperatingProcedure(EOP)1wereimplemented.Whentheturbinetrippushbuttonwasdepressed,thcGovernorValvesindicatedclosedbuttheThrottleValves,ReheatValves,andInterceptValvesindicatedopen.AutoStopOilandtheEmergencyTripHeaderindicatedpressuresofapproximately100psiand2000psi,respectively.Themegawattrecorderindicatedninetymegawatts.Severalmorcattemptsweremadetotriptheturbineusingthepushbutton,buttheywereunsuccessful.Atthispoint,theReactorControlOperatoropenedtheGeneratoroutputBreakers8W52and8W49,securedthevoltageregulator,stoppedtheDigitalElectrohydraulic(DEH)pumps,closedtheMainStcamIsolationValves(MSIV),andbrokecondenservacuum.IHE¹92-023,4-24-92SHEET1OF3 III.EVENTSEQUENCE(cont'd)TheAssistantNuclearPlantSupervisorinstructedtheNuclearWatchEngineertotriptheturbinefromtheFrontStandard.At0241alltheturbinevalvesclosed.EOP-2,ReactorTripRecovery,wasthencompletedwi'thtwosetsofsatisfactorySafety'unctionStatusChecks,theplantwasstabilized,andtheTurbineShutdownProcedure'asre-entered.IV.EVENTEVALUATIONA)PLANTRESPONSETheplantresponsetothiseventwasasexpectedwiththeexceptionofthefailureoftheturbinetotrip.Uponthereactortripsignal,thefourControlElementDriveMechanism(CEDM)Busundervoltagerelaysshouldde-energize.Thisshouldenergize(open)the20ETsolenoidvalveanddraintheelectro-hydraulicfluidfromtheemergencytripheader(Secattachment¹I).The20ASTtripsolenoidcoilshouldsimultaneouslyenergize,pulldownthemechanicaltriplever,anddumptheautostopoilheader.DecreasingautostopoilpressureallowstheInterfacevalvetoopenanddumptheelecto-hydraulicfluidemergencytripheader.Whenautostopoilpressuredecreasesto45psi,pressureswitches63-1ASTand63-2ASTshouldlockin,actuatingageneratorprimarylockoutwhichtripsthegeneratoroutputbreakers.ThesameresultshouldbeobtainedwhenattemptingtotriptheturbineviatheTurbineTripPushbutton.Amulti-disciplineteamisinvestigatingtodeterminewhytheturbinefailedtotripwhenthetripsignalswereinitiated.B)SAFETYSIGNIFICANCETheplantresponsetothiseventisboundedbysection15.1.5ofthePSLUnit2FinalSafetyAnalysisReport(FSAR),"IncreasedHeatRemovalbytheSecondarySystem"asfurtherdescribedbelow..12%PowerTrip,NoOperatorActionScenario.MSIV'sautocloseat600psig.Cooldownterminated.CoredecayheatreleasedviaMainSteamSafetyValves(MSSV)CooldownrateboundedbylimitingFSARcooldownevent.100%PowerTrip,NoOperatorActionScenario.PossibleSafetyInjectionActuation-Signal(SIAS)butnoactualinjection.AutomaticMSIVclosureafter66seconds.FuelsRETRANanalysisvalidatesthatnocoredamagewilloccur.100%PowerTripwithmultipleFSARChapter15AccidentScenario.Operatorstrainedonthesimulatorformultiplefailureeventsbeyonddesignbasis.ExcessstcamdemandeventsaresimulatedandprocedurallyaddressedbytheEOP's.IHE¹92-023,4-24-92SHEET2OF3 IV.EVENTEVALUATION(cont'd)C)ROOTCAUSEANALYSISAmulti-disciplineTurbineInvestigationTeamisperformingarootcauseanalysisofthisevent.ALetterofInstruction,2-LOI-T-67,"EvaluationofTurbineSolenoidTripFunction,"waswrittentoevaluatetheoperationoftheturbinemanualandautomatictripfunctions.Deficienciesidentifiedarenotedbelow.Rootcauseanalysisisstillinprogress.D)DEFICIENCIESIDENTIFIEDTestingofthc20ETTripsolenoid,20ASTsolenoidvalve,andthe20OPC1and2solenoidvalveswasperformedinaccordancewith2-LOI-T-67.Theresultsofthisevaluationareasfollows:1)20ETSolenoidvalveThcoriginalsolenoidvalvewasremovedtoprescrvcthe"asfound"conditionofthevalve.Anewsolenoidvalvewasinstalledandtestedsatisfactorily.Thisverifiedthe20ETelectricalcircuitsdidnotcontributetothefailures.2)20ASTTripSolenoidThesolenoidwastestednumeroustimeswithtwoofthctestsindicativeofintermittentcircuitproblems.Alooseconnectionwasfoundonrelay62ASTX/pin6.Thisconnectionisinthecircuitforall20ASTtripfunctions.Furthertroubleshootingiscontinuing.3)20OPC1and2SolenoidValvesOneOPCsoleniodvalvewasremovedpriortotestingforpotentialfailuremodeanalysis.TestingofoneoriginalandoncreplacementOPCsolenoidvalveindicatedacceptableoperationoftheOPCcircuits.V.CORRECTIVEACTIONS1.Theoriginal20ET,20OPC-1and20OPC-2Solenoidvalveshavebeenremovedandweresenttoanindependentlaboratoryforanalysis.2.Maintenanceiscontinuingtoinvestigatethcrootcauseoftheintermittentelectricalproblemsofthc20ASTTripSolenoid.Thecircuitsofthe20ETand20OPC1and2Solenoidsarealsobeingevaluatedtoensuresimilarproblemsdonotexist.3.NuclearFuelsisevaluatingadditionalguidanceforASIcontrolattheendofcorelife.4.OperationsisevaluatingadditionalguidanceforEOP-1,"StandardPostTripActions",onactionstotakeforareactortripwithnosubsequentturbinetrip.IHE¹92-023,4-24-92SHEET3OF3 eWESTINGHOUSEELECTRO-HYDRAULICCONTROLSYSTEMANDAUTO-STOPOILSYSTEM~esattttTrtvttvvaalralSCOPL5'7~\rtactttvatvttvtaltarwaavtawaTJtrttvtattaawwwatalarTTLTagZ~~4la~stasttw~slasILWTatTttasttwSavtrgEMERGENCYTRIPSIIIIIIII3IIIlIIIlIIIIIlIIIIIIIlIItwaatwrI~~QOg7~Ttawtaa~aII~tsttataca'vaLvaAUTOSTOPOILPRESSURESWITCHES(3)~acevaLTC~vaatratatalaI~tLava~I~avt1.LOWAUTO-STOPOILPRESSURE(2/3)2.REACTORTRIP('I)3.MANUALTRIP4.HI-HlLEVELINANYS/GSOLENOIDTRIPS1.REACTORTRIP(A)2.ELECTRICALOVERSPEED~3.LOWEHFLUIDPRESSURE4.MANUAL5.ETC.vaccwtavLaoaaa.OL~tattatat/2o-iOPcQo-2opg0roasf0Itat~tLOvsaaaaatvaOVERSPEEDPROTECTIONCONTROLLER103KOFNORMALSPEED2.GENERATOROUTPUTBREAKERSOPENABOVEAPRESETPOWERLEVEL3.CHANGEINGENERATOROUTPUTANDTURBINEINLETPRESSUREAVIOIIOPOILSY5ICII}}
In-HouseEventRept92-023:on 920421,turbine generator failedtotripduringmanualreactortrip.Rootcauseanalysisstillinprogress.
Solenoidvalvesremoved&senttoindependent labforanalysis.
.DISTRIBUTION CODE:IE22DCOPIESRECEIVED:LTR IENCLlSIZE:TITLE:50.73/50.9 LicenseeEventReport(LER),IncidentRpt,etc.NOTES:RECIPIENT IDCODE/NAME PD2-2LANORRIS,JINTERNAL:
ACNWAEOD/DOAAEOD/ROAB/DSP NRR/DLPQ/LHFB10 NRR/DOEA/OEAB NRR/DST/SELB 8D~/~S.TPLB8D1REGFILE02FILE01EXTERNAL:
EG&GBRYCE,J.H NRCPDRNSICPOORE,W.COPIESLTTRENCL11112,21122111".'111,111111331111RECIPIENT IDCODE/NAME PD2-2PDACRSAEOD/DSP/TPAB NRR/DET/EMEB 7ENRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICB8H3 NRR/DST/SRXB 8ERES/DSIR/EIB LSTLOBBYWARDNSICMURPHY,G.A NUDOCSFULLTXTCOPIESLTTRENCL11221111112211111'"111111DDDNOTETOALL"RIDS"RECIPIENTS:
PLEASEHELPUSTOREDUCEiVASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMPl-37(EXT.20079)TOELIMINATE YOURNAMEFROMDISTRIBUTION LISTSFORDOCUMENTS YOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:
LTTR32ENCL32DD P.O.Box128,Ft.Pierce,FL34954.0128 ggI4-8Q.L-92-129U.S.NuclearRegulatory Commission Attn:DocumentControlDeskWashington, D.C.20555'E:St.LucieUnit2DocketNo.50-389EventDate:April21,1992TurbineTriFailurePleasefindattachedthepreliminary internalproblemreportofourplanteventwhichoccurredonApril21,1992.Pursuantto10CFR50.73aLicensedEventReportwillbesubmitted within30daysoftheeventdate.Pleasecontactusifthereareanyquestions aboutthissubmittal.
Verytrulyyours,VicePresident St.LuciePlantDAS/JJB/kw cc:StewartD.Ebneter,RegionalAdministrator, RegionII,USNRCSeniorResidentInspector, USNRC,St.LuciePlantDAS/PSL4681-925'205010133 5'20424PDRADOCK05000385' PDRanFPLGroupcompany ST.LUCIEPLANTINHOUSEEVENTREPORT92-023TURBINEGENERATOR FAILEDTOTRIPFOLLOWING MANUALREACTORTRIPUNIT:2DATE:APRIL21,1992I.INITIALPLANTCONDITIONS OnApril21,1992,St.LucieUnit2wasshuttingdownforascheduled refueling outage.Reactorpowerwasatapproximately 12%.II.EVENTDESCRIPTION Ascheduled Reactor-Turbine shutdownwasinprogressonUnit2.Duringtheshutdown, powermovedtothetopofthecoreasexpected.
Existingprocedural guidanceonAxialShapeIndex(ASI)wasbeingemployedtominimizeitsaffects.WhenthreeoutoffourLocalPowerDensityPre-Trips onthcReactorProtection
.Systemcamein,theNuclearPlantSupervisor (NPS)instructed theReactorControlOperators tomanuallytriptheUnit.Amanualreactortripwasinitiated, buttheturbinedidnottrip.SeveralattemptsweremadetotriptheturbineusingtheTurbineTrippushbuttonwithnosuccessandthcNuclearWatchEngineertrippedtheturbinefromthefrontstandard.
III.EVENTSEQUENCESt.LucieUnit2wasperforming ascheduled reactorshutdownforrefueling purposes.
DuringtheplantshutdownASIapproached itsupper(negative) limit.Coordination atcontrolling ASIwithinlimitsandmaintaining reactorcoolanttemperature duetoXenonbuildinginbecamemoredifficult.
Whenreactorpowerwasdecreased toabout12%,controlrodinsertion hadnoeffectonmakingASIlessnegativeandthreeofthefourReactorProtection SystemLocalPowerDensitypre-tripscamein.Atthispoint,theNPSinstructed theReactorControlOperators tomanuallytriptheunitandthemanualreactortrippushbuttons onRTGB(ReactorTurbineGuageBoard)204andRTGB201weredepressed at0238withtheturbinetrippushbutton onRTGB201beingdepressed approximately twosecondslater;however,theturbinedidnottrip.StandardPostTripActionsfromEmergency Operating Procedure (EOP)1wereimplemented.
Whentheturbinetrippushbutton wasdepressed, thcGovernorValvesindicated closedbuttheThrottleValves,ReheatValves,andIntercept Valvesindicated open.AutoStopOilandtheEmergency TripHeaderindicated pressures ofapproximately 100psiand2000psi,respectively.
Themegawattrecorderindicated ninetymegawatts.
Severalmorcattemptsweremadetotriptheturbineusingthepushbutton, buttheywereunsuccessful.
Atthispoint,theReactorControlOperatoropenedtheGenerator outputBreakers8W52and8W49,securedthevoltageregulator, stoppedtheDigitalElectrohydraulic (DEH)pumps,closedtheMainStcamIsolation Valves(MSIV),andbrokecondenser vacuum.IHE¹92-023,4-24-92SHEET1OF3 III.EVENTSEQUENCE(cont'd)TheAssistant NuclearPlantSupervisor instructed theNuclearWatchEngineertotriptheturbinefromtheFrontStandard.
At0241alltheturbinevalvesclosed.EOP-2,ReactorTripRecovery, wasthencompleted wi'thtwosetsofsatisfactory Safety'unctionStatusChecks,theplantwasstabilized, andtheTurbineShutdownProcedure'as re-entered.
IV.EVENTEVALUATION A)PLANTRESPONSETheplantresponsetothiseventwasasexpectedwiththeexception ofthefailureoftheturbinetotrip.Uponthereactortripsignal,thefourControlElementDriveMechanism (CEDM)Busundervoltage relaysshouldde-energize.
Thisshouldenergize(open)the20ETsolenoidvalveanddraintheelectro-hydraulic fluidfromtheemergency tripheader(Secattachment
¹I).The20ASTtripsolenoidcoilshouldsimultaneously
: energize, pulldownthemechanical triplever,anddumptheautostopoilheader.Decreasing autostopoilpressureallowstheInterface valvetoopenanddumptheelecto-hydraulic fluidemergency tripheader.Whenautostopoilpressuredecreases to45psi,pressureswitches63-1ASTand63-2ASTshouldlockin,actuating agenerator primarylockoutwhichtripsthegenerator outputbreakers.
Thesameresultshouldbeobtainedwhenattempting totriptheturbineviatheTurbineTripPushbutton.
Amulti-discipline teamisinvestigating todetermine whytheturbinefailedtotripwhenthetripsignalswereinitiated.
B)SAFETYSIGNIFICANCE Theplantresponsetothiseventisboundedbysection15.1.5ofthePSLUnit2FinalSafetyAnalysisReport(FSAR),"Increased HeatRemovalbytheSecondary System"as furtherdescribed below..12%PowerTrip,NoOperatorActionScenario.
MSIV'sautocloseat600psig.Cooldownterminated.
CoredecayheatreleasedviaMainSteamSafetyValves(MSSV)CooldownrateboundedbylimitingFSARcooldownevent.100%PowerTrip,NoOperatorActionScenario.
PossibleSafetyInjection Actuation-Signal (SIAS)butnoactualinjection.
Automatic MSIVclosureafter66seconds.FuelsRETRANanalysisvalidates thatnocoredamagewilloccur.100%PowerTripwithmultipleFSARChapter15AccidentScenario.
Operators trainedonthesimulator formultiplefailureeventsbeyonddesignbasis.Excessstcamdemandeventsaresimulated andprocedurally addressed bytheEOP's.IHE¹92-023,4-24-92SHEET2OF3 IV.EVENTEVALUATION (cont'd)C)ROOTCAUSEANALYSIS Amulti-discipline TurbineInvestigation Teamisperforming arootcauseanalysisofthisevent.ALetterofInstruction, 2-LOI-T-67, "Evaluation ofTurbineSolenoidTripFunction,"
waswrittentoevaluatetheoperation oftheturbinemanualandautomatic tripfunctions.
Deficiencies identified arenotedbelow.Rootcauseanalysisisstillinprogress.
D)DEFICIENCIES IDENTIFIED Testingofthc20ETTripsolenoid, 20ASTsolenoidvalve,andthe20OPC1and2solenoidvalveswasperformed inaccordance with2-LOI-T-67.
Theresultsofthisevaluation areasfollows:1)20ETSolenoidvalveThcoriginalsolenoidvalvewasremovedtoprescrvcthe"asfound"condition ofthevalve.Anewsolenoidvalvewasinstalled andtestedsatisfactorily.
Thisverifiedthe20ETelectrical circuitsdidnotcontribute tothefailures.
2)20ASTTripSolenoidThesolenoidwastestednumeroustimeswithtwoofthctestsindicative ofintermittent circuitproblems.
Alooseconnection wasfoundonrelay62ASTX/pin6.Thisconnection isinthecircuitforall20ASTtripfunctions.
Furthertroubleshooting iscontinuing.
3)20OPC1and2SolenoidValvesOneOPCsoleniodvalvewasremovedpriortotestingforpotential failuremodeanalysis.
Testingofoneoriginalandoncreplacement OPCsolenoidvalveindicated acceptable operation oftheOPCcircuits.
V.CORRECTIVE ACTIONS1.Theoriginal20ET,20OPC-1and20OPC-2Solenoidvalveshavebeenremovedandweresenttoanindependent laboratory foranalysis.
2.Maintenance iscontinuing toinvestigate thcrootcauseoftheintermittent electrical problemsofthc20ASTTripSolenoid.
Thecircuitsofthe20ETand20OPC1and2Solenoids arealsobeingevaluated toensuresimilarproblemsdonotexist.3.NuclearFuelsisevaluating additional guidanceforASIcontrolattheendofcorelife.4.Operations isevaluating additional guidanceforEOP-1,"Standard PostTripActions",
onactionstotakeforareactortripwithnosubsequent turbinetrip.IHE¹92-023,4-24-92SHEET3OF3 eWESTINGHOUSE ELECTRO-HYDRAULIC CONTROLSYSTEMANDAUTO-STOP OILSYSTEM~esattttTrtvttvvaalralSCOPL5'7~\rtactttvatvttvtaltarwaavtawaTJtrttvtattaawwwatalarTTLTagZ~~4la~stasttw~slasILWTatTttasttwSavtrgEMERGENCY TRIPSIIIIIIII3IIIlIIIlIIIIIlIIIIIIIlIItwaatwrI~~QOg7~Ttawtaa~aII~tsttataca'vaLva AUTOSTOPOILPRESSURESWITCHES(3)~acevaLTC~vaatratatalaI~tLava~I~avt1.LOWAUTO-STOP OILPRESSURE(2/3)2.REACTORTRIP('I)3.MANUALTRIP4.HI-HlLEVELINANYS/GSOLENOIDTRIPS1.REACTORTRIP(A)2.ELECTRICAL OVERSPEED
~3.LOWEHFLUIDPRESSURE4.MANUAL5.ETC.vaccwtavLaoaaa.OL~tattatat/2o-iOPcQo-2opg0roasf0Itat~tLOvsaaaaatvaOVERSPEED PROTECTION CONTROLLER 103KOFNORMALSPEED2.GENERATOR OUTPUTBREAKERSOPENABOVEAPRESETPOWERLEVEL3.CHANGEINGENERATOR OUTPUTANDTURBINEINLETPRESSUREAVIOIIOPOILSY5ICII}}

Revision as of 16:13, 29 June 2018

In-House Event Rept 92-023:on 920421,turbine Generator Failed to Trip During Manual Reactor Trip.Root Cause Analysis Still in Progress.Solenoid Valves Removed & Sent to Independent Lab for Analysis
ML17227A402
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 04/24/1992
From: SAGER D A
FLORIDA POWER & LIGHT CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
92-023, 92-23, L-92-129, NUDOCS 9205010133
Download: ML17227A402 (6)


Text

ACCELERATED Dl/RIBUTION DEMONSTRATION SYSTEMREGULATORY INFORMATION DISTRIBUTIONSYSTEM(RIDS)ACCESSION NBR:9205010133 DOC.DATE:

92/04/24NOTARIZED:

NOFACIL:50-389 St.LuciePlant,Unit2,FloridaPower&LightCo.AUTH.NAME.AUTHORAFFILIATION SAGER,D.A.

FloridaPower&LightCo.RECIP.NAME RECIPIENT AFFILIATION

-DocumentControlBranch(Document ControlDesk)DOCKET05000389

SUBJECT:

In-HouseEventRept92-023:on 920421,turbine generator failedtotripduringmanualreactortrip.Rootcauseanalysisstillinprogress.

Solenoidvalvesremoved&senttoindependent labforanalysis.

.DISTRIBUTION CODE:IE22DCOPIESRECEIVED:LTR IENCLlSIZE:TITLE:50.73/50.9 LicenseeEventReport(LER),IncidentRpt,etc.NOTES:RECIPIENT IDCODE/NAME PD2-2LANORRIS,JINTERNAL:

ACNWAEOD/DOAAEOD/ROAB/DSP NRR/DLPQ/LHFB10 NRR/DOEA/OEAB NRR/DST/SELB 8D~/~S.TPLB8D1REGFILE02FILE01EXTERNAL:

EG&GBRYCE,J.H NRCPDRNSICPOORE,W.COPIESLTTRENCL11112,21122111".'111,111111331111RECIPIENT IDCODE/NAME PD2-2PDACRSAEOD/DSP/TPAB NRR/DET/EMEB 7ENRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICB8H3 NRR/DST/SRXB 8ERES/DSIR/EIB LSTLOBBYWARDNSICMURPHY,G.A NUDOCSFULLTXTCOPIESLTTRENCL11221111112211111'"111111DDDNOTETOALL"RIDS"RECIPIENTS:

PLEASEHELPUSTOREDUCEiVASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMPl-37(EXT.20079)TOELIMINATE YOURNAMEFROMDISTRIBUTION LISTSFORDOCUMENTS YOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:

LTTR32ENCL32DD P.O.Box128,Ft.Pierce,FL34954.0128 ggI4-8Q.L-92-129U.S.NuclearRegulatory Commission Attn:DocumentControlDeskWashington, D.C.20555'E:St.LucieUnit2DocketNo.50-389EventDate:April21,1992TurbineTriFailurePleasefindattachedthepreliminary internalproblemreportofourplanteventwhichoccurredonApril21,1992.Pursuantto10CFR50.73aLicensedEventReportwillbesubmitted within30daysoftheeventdate.Pleasecontactusifthereareanyquestions aboutthissubmittal.

Verytrulyyours,VicePresident St.LuciePlantDAS/JJB/kw cc:StewartD.Ebneter,RegionalAdministrator, RegionII,USNRCSeniorResidentInspector, USNRC,St.LuciePlantDAS/PSL4681-925'205010133 5'20424PDRADOCK05000385' PDRanFPLGroupcompany ST.LUCIEPLANTINHOUSEEVENTREPORT92-023TURBINEGENERATOR FAILEDTOTRIPFOLLOWING MANUALREACTORTRIPUNIT:2DATE:APRIL21,1992I.INITIALPLANTCONDITIONS OnApril21,1992,St.LucieUnit2wasshuttingdownforascheduled refueling outage.Reactorpowerwasatapproximately 12%.II.EVENTDESCRIPTION Ascheduled Reactor-Turbine shutdownwasinprogressonUnit2.Duringtheshutdown, powermovedtothetopofthecoreasexpected.

Existingprocedural guidanceonAxialShapeIndex(ASI)wasbeingemployedtominimizeitsaffects.WhenthreeoutoffourLocalPowerDensityPre-Trips onthcReactorProtection

.Systemcamein,theNuclearPlantSupervisor (NPS)instructed theReactorControlOperators tomanuallytriptheUnit.Amanualreactortripwasinitiated, buttheturbinedidnottrip.SeveralattemptsweremadetotriptheturbineusingtheTurbineTrippushbuttonwithnosuccessandthcNuclearWatchEngineertrippedtheturbinefromthefrontstandard.

III.EVENTSEQUENCESt.LucieUnit2wasperforming ascheduled reactorshutdownforrefueling purposes.

DuringtheplantshutdownASIapproached itsupper(negative) limit.Coordination atcontrolling ASIwithinlimitsandmaintaining reactorcoolanttemperature duetoXenonbuildinginbecamemoredifficult.

Whenreactorpowerwasdecreased toabout12%,controlrodinsertion hadnoeffectonmakingASIlessnegativeandthreeofthefourReactorProtection SystemLocalPowerDensitypre-tripscamein.Atthispoint,theNPSinstructed theReactorControlOperators tomanuallytriptheunitandthemanualreactortrippushbuttons onRTGB(ReactorTurbineGuageBoard)204andRTGB201weredepressed at0238withtheturbinetrippushbutton onRTGB201beingdepressed approximately twosecondslater;however,theturbinedidnottrip.StandardPostTripActionsfromEmergency Operating Procedure (EOP)1wereimplemented.

Whentheturbinetrippushbutton wasdepressed, thcGovernorValvesindicated closedbuttheThrottleValves,ReheatValves,andIntercept Valvesindicated open.AutoStopOilandtheEmergency TripHeaderindicated pressures ofapproximately 100psiand2000psi,respectively.

Themegawattrecorderindicated ninetymegawatts.

Severalmorcattemptsweremadetotriptheturbineusingthepushbutton, buttheywereunsuccessful.

Atthispoint,theReactorControlOperatoropenedtheGenerator outputBreakers8W52and8W49,securedthevoltageregulator, stoppedtheDigitalElectrohydraulic (DEH)pumps,closedtheMainStcamIsolation Valves(MSIV),andbrokecondenser vacuum.IHE¹92-023,4-24-92SHEET1OF3 III.EVENTSEQUENCE(cont'd)TheAssistant NuclearPlantSupervisor instructed theNuclearWatchEngineertotriptheturbinefromtheFrontStandard.

At0241alltheturbinevalvesclosed.EOP-2,ReactorTripRecovery, wasthencompleted wi'thtwosetsofsatisfactory Safety'unctionStatusChecks,theplantwasstabilized, andtheTurbineShutdownProcedure'as re-entered.

IV.EVENTEVALUATION A)PLANTRESPONSETheplantresponsetothiseventwasasexpectedwiththeexception ofthefailureoftheturbinetotrip.Uponthereactortripsignal,thefourControlElementDriveMechanism (CEDM)Busundervoltage relaysshouldde-energize.

Thisshouldenergize(open)the20ETsolenoidvalveanddraintheelectro-hydraulic fluidfromtheemergency tripheader(Secattachment

¹I).The20ASTtripsolenoidcoilshouldsimultaneously

energize, pulldownthemechanical triplever,anddumptheautostopoilheader.Decreasing autostopoilpressureallowstheInterface valvetoopenanddumptheelecto-hydraulic fluidemergency tripheader.Whenautostopoilpressuredecreases to45psi,pressureswitches63-1ASTand63-2ASTshouldlockin,actuating agenerator primarylockoutwhichtripsthegenerator outputbreakers.

Thesameresultshouldbeobtainedwhenattempting totriptheturbineviatheTurbineTripPushbutton.

Amulti-discipline teamisinvestigating todetermine whytheturbinefailedtotripwhenthetripsignalswereinitiated.

B)SAFETYSIGNIFICANCE Theplantresponsetothiseventisboundedbysection15.1.5ofthePSLUnit2FinalSafetyAnalysisReport(FSAR),"Increased HeatRemovalbytheSecondary System"as furtherdescribed below..12%PowerTrip,NoOperatorActionScenario.

MSIV'sautocloseat600psig.Cooldownterminated.

CoredecayheatreleasedviaMainSteamSafetyValves(MSSV)CooldownrateboundedbylimitingFSARcooldownevent.100%PowerTrip,NoOperatorActionScenario.

PossibleSafetyInjection Actuation-Signal (SIAS)butnoactualinjection.

Automatic MSIVclosureafter66seconds.FuelsRETRANanalysisvalidates thatnocoredamagewilloccur.100%PowerTripwithmultipleFSARChapter15AccidentScenario.

Operators trainedonthesimulator formultiplefailureeventsbeyonddesignbasis.Excessstcamdemandeventsaresimulated andprocedurally addressed bytheEOP's.IHE¹92-023,4-24-92SHEET2OF3 IV.EVENTEVALUATION (cont'd)C)ROOTCAUSEANALYSIS Amulti-discipline TurbineInvestigation Teamisperforming arootcauseanalysisofthisevent.ALetterofInstruction, 2-LOI-T-67, "Evaluation ofTurbineSolenoidTripFunction,"

waswrittentoevaluatetheoperation oftheturbinemanualandautomatic tripfunctions.

Deficiencies identified arenotedbelow.Rootcauseanalysisisstillinprogress.

D)DEFICIENCIES IDENTIFIED Testingofthc20ETTripsolenoid, 20ASTsolenoidvalve,andthe20OPC1and2solenoidvalveswasperformed inaccordance with2-LOI-T-67.

Theresultsofthisevaluation areasfollows:1)20ETSolenoidvalveThcoriginalsolenoidvalvewasremovedtoprescrvcthe"asfound"condition ofthevalve.Anewsolenoidvalvewasinstalled andtestedsatisfactorily.

Thisverifiedthe20ETelectrical circuitsdidnotcontribute tothefailures.

2)20ASTTripSolenoidThesolenoidwastestednumeroustimeswithtwoofthctestsindicative ofintermittent circuitproblems.

Alooseconnection wasfoundonrelay62ASTX/pin6.Thisconnection isinthecircuitforall20ASTtripfunctions.

Furthertroubleshooting iscontinuing.

3)20OPC1and2SolenoidValvesOneOPCsoleniodvalvewasremovedpriortotestingforpotential failuremodeanalysis.

Testingofoneoriginalandoncreplacement OPCsolenoidvalveindicated acceptable operation oftheOPCcircuits.

V.CORRECTIVE ACTIONS1.Theoriginal20ET,20OPC-1and20OPC-2Solenoidvalveshavebeenremovedandweresenttoanindependent laboratory foranalysis.

2.Maintenance iscontinuing toinvestigate thcrootcauseoftheintermittent electrical problemsofthc20ASTTripSolenoid.

Thecircuitsofthe20ETand20OPC1and2Solenoids arealsobeingevaluated toensuresimilarproblemsdonotexist.3.NuclearFuelsisevaluating additional guidanceforASIcontrolattheendofcorelife.4.Operations isevaluating additional guidanceforEOP-1,"Standard PostTripActions",

onactionstotakeforareactortripwithnosubsequent turbinetrip.IHE¹92-023,4-24-92SHEET3OF3 eWESTINGHOUSE ELECTRO-HYDRAULIC CONTROLSYSTEMANDAUTO-STOP OILSYSTEM~esattttTrtvttvvaalralSCOPL5'7~\rtactttvatvttvtaltarwaavtawaTJtrttvtattaawwwatalarTTLTagZ~~4la~stasttw~slasILWTatTttasttwSavtrgEMERGENCY TRIPSIIIIIIII3IIIlIIIlIIIIIlIIIIIIIlIItwaatwrI~~QOg7~Ttawtaa~aII~tsttataca'vaLva AUTOSTOPOILPRESSURESWITCHES(3)~acevaLTC~vaatratatalaI~tLava~I~avt1.LOWAUTO-STOP OILPRESSURE(2/3)2.REACTORTRIP('I)3.MANUALTRIP4.HI-HlLEVELINANYS/GSOLENOIDTRIPS1.REACTORTRIP(A)2.ELECTRICAL OVERSPEED

~3.LOWEHFLUIDPRESSURE4.MANUAL5.ETC.vaccwtavLaoaaa.OL~tattatat/2o-iOPcQo-2opg0roasf0Itat~tLOvsaaaaatvaOVERSPEED PROTECTION CONTROLLER 103KOFNORMALSPEED2.GENERATOR OUTPUTBREAKERSOPENABOVEAPRESETPOWERLEVEL3.CHANGEINGENERATOR OUTPUTANDTURBINEINLETPRESSUREAVIOIIOPOILSY5ICII