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{{#Wiki_filter:ACCELERATEDDISTRIBUTIONDEMONSTTIONSYSTEMREGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9205180236DOC.DATE:92/05/14NOTARIZED:NOFACIL:50-389St.LuciePlant,Unit2,FloridaPower&LightCo.AUTH.NAME.AUTHORAFFILIATIONSAGER,D.A.FloridaPower&LightCo.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)
{{#Wiki_filter:ACCELERATED DISTRIBUTION DEMONSTTION SYSTEMREGULATORY INFORMATION DISTRIBUTION SYSTEM(RIDS)ACCESSION NBR:9205180236 DOC.DATE:
92/05/14NOTARIZED:
NOFACIL:50-389 St.LuciePlant,Unit2,FloridaPower&LightCo.AUTH.NAME.AUTHORAFFILIATION SAGER,D.A.
FloridaPower&LightCo.RECIP.NAME RECIPIENT AFFILIATION DocumentControlBranch(Document ControlDesk)


==SUBJECT:==
==SUBJECT:==
Specialrept:on920421,turbinegeneratorfailedtotripfollowingmanualreactortrip.Causedbyfailuresinredundant&electricallyindependentturbinetrippingschemes.I&Cdisassembled&trxpblockinspected.DISTRIBUTIONCODE:IE22DCOPIESRECEIVED:LTRENCLSIZE:TITLE:50.73/50.9LicenseeEventReport(LER),IncidentRpt,etc.NOTESDOCKET05000389RECIPIENTIDCODE/NAMEPD2-2LANORRIS,JINTERNAL:ACNWAEOD/DOAAEOD/ROAB/DSPNRR/DLPQ/LHFB10NRR/DOEA/OEABNRR/DST/SELB8DRR/LB8D1REGFIL02RGN2FILE01EXTERNAL:EG&GBRYCE,J.HNRCPDRNSICPOORE,W.COPIESLTTRENCL1111221-12211111111111133.1111RECIPIENT'IDCODE/NAMEPD2-2PDACRSAEOD/DSP/TPABNRR/DET/EMEB7ENRR/DLPQ/LPEB10NRR/DREP/PRPB11NRR/DST/SICB8H3NRR/DST/SRXB8ERES/DSIR/EIBLSTLOBBYWARDNSICMURPHY,G.ANUDOCSFULLTXTCOPIESLTTRENCL112211111122111111111111NOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEV'ASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOiilPl-37(EXT.20079)TOELlilllNATEYOURNN!EFROivIDISTRIBUTIONLISTSFORDOCUMENTSYOUDONTNEED!TOTALNUMBEROFCOPIESREQUIRED:LTTR32ENCL-32  
Specialrept:on920421,turbine generator failedtotripfollowing manualreactortrip.Causedbyfailuresinredundant
'P.O.Box128,Ft.Pierce,FL34854-0128FPLMay14,1992L-92-149U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555Re:St.LucieUnit2DocketNo.50-389EventDate:April21,1992TurbineTriFailureUdateAttachedpleasefindtheupdatedversionofaplantproblemreportwhichdiscussesaneventwhichoccuredonApril21,1992.Includedisthecurrentstatusofouranalysisoftheevent.Pursuantto10CFR50.73aLicenseeEventReportwillbesubmittedwithin30daysoftheeventdate.Verytrulyyours,D.A.SVicePrSt.LgersidentePlantDAS/JWH/kwAttachmentcc:StewartD.Ebneter,RegionalAdministrator,USNRCRegionIISeniorResidentInspector,USNRC,St.LuciePlantDAS/PSL1697-9292051802369205i4PDRADOCK050003898PDRanFPLGroupcompany ST.LUCIEPLANTINHOUSEEVENTREPORT92-023REV.9TURBINEGENERATORFAILEDTOTRIPFOLLOWINGMANUALREACTORTRIPUNIT'DATE:APRIL21,1992I.INITIALPLANTCONDITIONSOnApril21,1992,St.LucicUnit2wasshuttingdownforascheduledrefuelingoutage.Reactorpowerwasatapproximately12%.II.EVENTDESCRIPTIONAscheduledreactor-turbineshutdownwasinprogressonUnit2.Duringtheshutdown,powermovedtothetopofthereactorcore.Existingproceduralguidanceonaxialshapeindex(ASI)wasbeingemployedtominimizethiseffect.However,whenthreeoutoffourlocalpowerdensityprc-tripsonthereactorprotectionsystemactuated,thcnuclearplantsupervisor(NPS)instructedthereactorcontroloperatorstomanuallytriptheUnit.Amanualreactortripwasinitiated,buttheturbinedidnottrip.Severalunsuccessfulattemptswerethenmadetotriptheturbineusingtheturbinetrippushbutton.Thenuclearwatchengineerwasthendispatchedandtrippedtheturbinelocallyfromtheturbinefrontstandard.III.EVENTSEQUENCESt.LucieUnit2wasperformingascheduledreactorshutdownforrefuelingpurposes.DuringtheplantshutdownASIapproacheditsupper(negative)limit.CoordinationatcontrollingASIwithinlimitsandmaintainingreactorcoolanttemperatureduetoXenonbuildupbecameincreasinglydifficult..Whenreactorpowerwasdecreasedtoabout12%,controlrodinsertionnolongeihadanyeffectonmakingASIlessnegativeandthreeofthefourreactorprotectionsystemlocalpowerdensitypre-tripsalarmed.At0238,theNPSinstructedthereactorcontroloperatorstomanuallytriptheunitandthemanualreactortrippushbuttonsonRTGB(reactorturbinegeneratorboard)204andRTGB.201weredepressed.TwosecondslatertheturbinetrippushbuttononRTGB201wasdepressed;however,thcturbinedidnottrip.StandardposttripactionsfromEmergencyOperatingProcedure(EOP)1wereimplemcnted.Whentheturbinetrippushbuttonwasdepressed,theturbinegovernorvalvesindicatedclosedbutthethrottlevalves,reheatvalves,andinterceptvalvesindicatedopen.Autostopoilandtheemergencytripheaderindicatedpressuresofapproximately100psiand2000psi,respectively.Themegawattrecorderindicatedninetymegawatts.Several"additionalattemptsweremadetotripthcturbineusingthepushbutton,buteachwasunsuccessful.Atthispoint,thereactorcontroloperatoropenedgeneratoroutputbreakers8W52and8W49,securedthevoltageregulator,stoppedthcdigitalelectro-hydraulic(DEH)pumps,closedthemainsteamisolationvalves(MSIV),andbrokecondenservacuum.IHE892-023,5/14/921of5 III.EVENTSEQUENCE(cont'd)TheassistantnuclearplantsupervisorinstructedtheNWEtotriptheturbinefromtheFrontStandard.At0241alltheturbinevalvesclosed.EOP-2,ReactorTripRecovery,wasthencarriedout,twosetsofsatisfactorysafetyfunctionstatuscheckswerccompleted,theplantwasstabilized,andtheTurbineShutdownProcedurewasre-entered.IV.EVENTEVALUATIONA)Withtheexceptionofthefailureoftheturbinetotrip,theplantresponsetothiseventwasasexpected.Uponinitiationofthereactortripsignal,thefollowingshouldhaveoccurred.Thefourcontrolelementdrivemechanism(CEDM)busundervoltagcrelaysshoulddc-energize.Thisshouldenergize(open)the20ETsolenoidvalveanddraintheelectro-hydraulicfluidfromtheemergencytripheader(Seeattachment¹I).The20ASTtripsolenoidcoilshouldsimultaneouslyenergize,pulldownthemechanicaltriplever,anddumptheautostopoilheader.Decreasingautostopoilpressureallowstheinterfacevalvetoopenanddumptheelectro-hydraulicfluidemergencytripheader.Whenautostopoilprcssuredecreasesto45psi,pressureswitches63-1ASTand63-2ASTshouldlockin,actuatingageneratorprimarylockoutwhichtripsthcgeneratoroutputbreakers.Thesameresultshouldbeobtainedwhenattemptingtotriptheturbineviatheturbinetrippushbutton.Theoverspeedprotectionsystem(OPC)didnotandshouldnothaveactuatedbecauseitwasnotchallenged.Themaximumturbinerpmobservedduringthiseventwas1850rpm.ThisisbelowtheOPCsetpointof1854rpm.Amulti-disciplineteamisinvestigatingtodeterminewhytheturbinefailedtotripwhenthetripsignalswereinitiated.RefertoFigures1,2,&3formoredetails.B)FETYIIFfTheplantresponsetothiseventisboundedbysection15.1.5oftheSt.LucieUnit2FinalSafetyAnalysisReport(FSAR),"IncreasedHeatRemovalbytheSecondarySystem"asfurtherdescribedbelow..Analysisofthreescenariossimilartobutwithdifferentparametersthantheactualeventwereconducted.Ineachcasetheeventswerewithintheplant'sdesignbasisandarcsummarizedbelow.1.12%PowerTrip,NoOperatorActionScenario.*AutomaticMSIVclosureat600psig.Cooldownterminated.*CooldownrateboundedbylimitingFSARcooldownevent.IHE¹92-023,5/14/922of5 IV.EVENTEVALUATION(cont'd)B)NIFI2.100%PowerTr'ip,NoOperatorActionScenario.*PossibleSafetyInjectionActuationSignal(SIAS)butnoactualinjection.*AutomaticMSIVclosureat600psig.Cooldownterminated.~CooldownrateisboundedbytheFSARcooldowneventasconfirmedbyin-houseRETRANanalysis.3.100%PowerTripwithFSARChapter15AccidentScenario.*FSARChapter15Analysisconsiderssinglefailureofturbinestopvalvesto~close.Operatorstrainedonthesimulatorfordesignbasisaccidents.MultiplefailuresaresimulatedandprocedurallyaddressedbyEOPs.Theseinclude"ExcessSteamDemand".C)ALYILAAmulti-disciplineinvestigationteamisperformingarootcauseanalysisofthisevent.MembersofthisgroupincludeSystemEngineers,andrepresentativesfromOperations,Maintenance,Engineering,andtheTurbinevendor.Thcredundantdesignofthcturbinetripschemesuggeststhatatleasttwofailureswercnecessarytoexplaintheinabilitytotripobservedduringthe04/21/92event.Accordinglythefailureanalysisplanisevaluatingboththe20ETandthe20ASTturbinetrips.Extensiveturbinevendorinputwasobtainedforthefailureanalysisplan.ParticularattentionwaspaidtothelessonslcarncdintheSalemoverspeedevent.ALetterofInstruction,2-LOI-T-67,"EvaluationofTurbineSolenoidTripFunction,"waswrittentoevaluatetheoperationofalltripfunctions.Attachment1isthefailureanalysis.8QQILJl5-Thefailureoftheturbinetotripwascausedbyunrelatedfailuresintheredundantandelectricallyindependentturbinetrippingschemes.(moredetailslater.....)Turbinetrip20ASTfailedduetoanintermittentlossofcircuitcontinuity.Eitheroftwodeficienciesnotedatrelay62ASTX(item¹6ofattachment1"FailureAnalysisPlan")couldcausesuchafailure.(moredetailslater.....)Resultsofthc20ETsolenoidvalveautopsy.(moredetailslater.....)Becausethesetwounrelatedfailurescouldnotbedetectedwiththcexistingsystemdesignandsurveillanceprogram,atotallossoftripcapabilityresulted.(moredetailslater.....)IHE¹92-023,5/14/923of5 V.CORRECTIVE-ACTIONSA)RAIVITI1.Theoriginal20ET,20OPC-1and20OPC-2Solenoidvalveshavebeenremovedandweresenttoanindependentlaboratoryforanalysis.Resultsareduebackon05/18/922.I&Ciscontinuingtoinvestigatethcrootcauseoftheintermittentelectricalproblemsofthe20ASTtripsolenoidunderPWO7356.Thecircuitsofthe20ETand20OPC1and2solenoidsarealsobeingevaluatedforsimilarproblems3.I&Cwillevaluateprovidingcoilmonitoringlightsfor20ASTand20ETtoindicatecontinuityofthefieldcableandsolenoidcoil.4.OperationsisevaluatingadditionalguidanceforEOP-1,"StandardPostTripActions",onactionstotakeforareactortripwithnosubsequentturbinetrip.5.Engineeringwillevaluateprovidingalatch-incircuitforthe20ETsolenoidvalve.Thelatch-inwillbcprovidedonlyacrossthePB710contacts.6.Engineeringwillevaluateprovidinga30secondtimedelaybetweenaturbinetripandageneratortriptoactivatethereversepowerrelays.7.Engineeringwillevaluateprovidingthecapabilitytoexercisethc20ASTsolenoidvalvewhileonline.8.Operationswillevaluatemodifyingtheirprocedurestoallowindividualtripfeaturetesting.9.PCM032-292M"TurbineLubeOilConditionerConnections"willinstallvalvesandfittingstoallowconnectionofanup-gradedlubeoilconditioner.10.I&CwilldisassembleandinspectthetripblockunderPWO7356.11.Engineeringwillevaluateprovidingimproved20ASTcoilsuppressiontolimitarcingacross62ASTXrelaycontacts.12.NuclearFuelsisevaluatingadditionalguidanceforASIcontrolattheendofcorelife.B)MAIVITI13.EngineeringwillevaluateenhancementstothefiltrationsystemfortheturbineEHfluid.14.Engineeringwillevaluatetheuseofastainlesssteelsolenoidvalvebodytoreplacetheexistingcarbonsteelbody.IHE¹92-023,5/14/924of5 V.CORRECTIVEACTIONS(cont'd)B)AI15.EngineeringwillevaluateuseofanalternativeDEHfluidtoreducematerialincompatibilities.16.Engineeringwillevaluateprovidinganadditional20ASTvalveofdiversemanufacturewhichcanbetestedonlinebytheuseofthemanualtripbuttons.17.Engineeringwillevaluateprovidingameansoftestingthe20ETsolenoidvalvewhileonline.IHE¹92-023,5/14/925of5 Attachment1PFTFAILUREANALYSISPLANFTII1of2Frfr1.20ET(valve)-sticking,binding-removedfromsystemin"asfound"conditiontopreserveanycvidenccoffailuremode;senttoanindependentlab.-resultsduc05/18/922.20ET(circuit)-loosewire-opencoil-impropersupplyvoltage-continuitycheck-resistancecheck~-voltagemeasuredandrecorded-satisfactory/PWO7356-noopen/2-LOI-T-67-acceptable/2-LOI-T-673.20AST(valve)4.20AST(TripBlock)5.20AST(circuit)-sticking,binding'pluggedorifice-loosewire-valveoperatedduringtest-disassembleandinspect-continuitycheck-noindicationofstickingorbinding/2-LOI-T-67-scheduled5/12/92-looseterminalconnectionfoundatposition¹6on63ASTX/PWO7356-opencoil-impropervoltagesupply-resistancecheck-voltagemeasuredandrecorded-noopen/2-LOI-T-67-acceptable/2-LOI-T-676.62ASTX(Relay)-setpointdrift-digitalrecorder-setpointverified/2-LOI-T-67-loosewire-continuitycheck-looseterminalconnectionatposition¹6/2-LOI-T-67*PotentialFailureCause-degradedcontacts-visualexamination-slightarcingonbothsetsofcontactswithburnresidueevident*PotentialFailureCause Attachment1FAILREANALYIPLAN2of27.20-1OPC(valve)-sticking,binding-valveoperatedduringtest-noindicationofsticking,binding/2-LOI-T-67,valvesenttoanindependentlab,resultsduc05/18/928.20-1OPC(circuit)9.20-2OPC(valve)-loosewire-sticking,binding-continuitycheck-valvesenttoanindependentlab-noopens/PWO7356-resultsdue05/18/9210.20-2OPC(circuit)11.FCV-22-148(interface-loosewire-sticking,binding-continuitycheck-valveoperatedduringtest-noopens/PWO7356-noindicationofsticking,binding/2-LOI-T-67valve)12.63-1AST(pressureswitch)13.63-2AST(pressureswitch)14.PB710-contacts-contacts-contacts-contactalignment-digitalrecorderandvisually-acceptable/2-LOI-T-67-digitalrecorderand-visually-acceptable/2-LOI-T-67I'continuitychecks,disassembly,andinspection-topcontactsrequiredmoremovementthanbottomcontacts,switchreplaced/PWO7356-switchoperatedduringtest-acceptable/2-LOI-T-67-NotaCauseoftheFailure15.EFIfluid16.Turbinelubeoil-contamination-contamination-waterandparticulate-waterandparticulate-inspecification/PredictiveMaintenanceperiodictestingprogram-inspecification/PredictiveMaintenanceperiodictestingprogram Attachment2EELLIEKPL1of11.ManualReactortripduetoalossofASIcontrol-IneffectiveASIcontrolmethod-ImprovedASIcontrolprocedure2.Looseleadat62ASTX-Lackofmeanstodetectalossofcontinuity-Designchangestoaddcircuitmonitoringlights-Designchangestoallowperiodicon-linetestingofboth20ASTand20ET3.Burntcontactson62ASTX-Inadequatearcsuppression-Designchangetoupgradearcsuppressionin20ASTcircuit(MORELATER......  
&electrically independent turbinetrippingschemes.I&Cdisassembled
}IESTINGHOUSEELECTRO-HYDRAULICCONTROLSYSTEHANDAUTO-STOPOILSYSTEtlaaetttc~eeee~p+AApwooa~wetweeelcatvasCcecal~electeeM(ll~eee~~elel~ttettVIa~atvttwIIIII-III~ataatIW3IIIIIIIII~atoOtIWIIIIIIIIlataatlWIIIIteeet~eatIWI~1~e~e~II~tcSOLENOIDTRIPSREACTORTRIP(A)2.ELECTRICALOVERSPEED3.LOHEHFLUIDPRESSURE4.flANUAL5.ETC.eeccva'ftieAUTOSTOPOILPRESSURESKITCHES~'~e~~aieeeeea~20AsTcaaaeaSL~tallltag~at~tvwtfatecaaeaacEMERGENCYTRIPS1.LOWAUTO-STOPOILPRESSURE(2/3)2.REACTORTRIP(0)3.HANUALTRIP4.ttl-HILEVELlftANYS/G2o-i0PcBo-2opcla~aaeQrtaftVaeeeeeefa,EtfFLIIIOSTSfittOVERSPEEDPROTECTIONCONTROLLER103KOFNOR)lALSPEED2.GENERATOROUTPUTBREAKERSOPENABOVEAPRESETPOMERLEVEL3.CHANGEINGENERATOROUTPUTANDTURBINEINLETPRESSUREAUfOSfOPOILSYSflN ASTO)Manual)GDIERATOR~~lOCKOUTTURBINETRIPSOVERSPEEOIAUTOISTEAI4IETHDEHDCRECTOR[SIOP[<~'HOOPTAILUREOILs.EASELIIHPijsuezZW4~FZ-oag0OVIII.zLI0In26IL-7IO6PB2710.25TDI%56862~P'2CSH.~.86GBSH..885~14GADOO685SECORAT56r-4I0IN-Id74R4'r3II~25SECII14L12Tppo60.25SEC.IEHlXH7.(5ILlll)It74DITXTDDODCF4rasses~25SEC~su-4cg-e,lo93109ISC23CIs'5'23Bs0RB5l5OA2OOWSETATI25Tl.4irvjISP23PosATaR(TYP)62ASTXTPOIDgECISA.Lh&P3234is%2SA62ASTXISC2SC'A00IOSB:0~63-1IAST2663K0RA5T063t363LVgE3b63,74C62AASTX-(56747105H.TIIASTH0gOAST34..I3I4CSC.1CSBTieIIlos1IXCWP4il5,6s20~.;~cs-p414d63XS<g6883LI6S6SdS6d74~74IBO74LV74TBEASTXOS6r66L2TDPLI6R6B'jrvvzasra+vrll<&#x17d;rQ'CAUTOSTOPesapeerlLowBr8Loss'tuustTdpTslpSlopTR1PFAII.UIIESolenolsIKnes8~"2~r~iy';,'.-"...~.."-63T63YCw0109I22'-'."':26'ILV/1rsrt'.I747BO16747TB6I6P4R",r2dj"l810"'"'lSEHTI(7~sitsrs''stR'~g'55laIEIeLATlaPi"jQL-tg+6Ip8624'-4IIl"k..t.:.IEbASCOS1~INCORPORAFLORIDAPOWERIST.LUCEPLANT-EX..';(,.'SGHEMATll;Di,TURBIHEAUTO.STOPTNI485'f5CfIV5.Vr'jul@'f63T6%83fg',,'.W$Ilr6;:eaIo..v.Z-..q.rVVIAVI44V>>s"'.OFQ:s'rI~CWP.Tr'-SNi41:IO-203,~REVPATEAPPROVEP,APPROVfP~e~r'rrrr~alep--~r"LTIr..i.-s;I;Ie>>r:y:pg:.g!"'.pgal@~rsrni~na)so-'gQ-les9re'8M)Wy~Aj~~~rl,"'j~"P4'sr~'"g+~+~jRki~TT""'"-'g'>>'vrs.rmrsrqvrvcsvrsrrrrrv6e.!l,rvss.rsv-svv~"-srrvrms"'4'>';.',t,"4>>....".;".(:I":.i",'i(q"r'"."rt$p~+8OTESFOICC570>+SCRAPPEVELOpQRI4Tg5Q~RCV477~..ss4isN  
&trxpblockinspected.
DISTRIBUTION CODE:IE22DCOPIESRECEIVED:LTR ENCLSIZE:TITLE:50.73/50.9 LicenseeEventReport(LER),IncidentRpt,etc.NOTESDOCKET05000389RECIPIENT IDCODE/NAME PD2-2LANORRIS,JINTERNAL:
ACNWAEOD/DOAAEOD/ROAB/DS PNRR/DLPQ/LHFB10 NRR/DOEA/OEAB NRR/DST/SELB 8DRR/LB8D1REGFIL02RGN2FILE01EXTERNAL:
EG&GBRYCE,J.H NRCPDRNSICPOORE,W.COPIESLTTRENCL1111221-12211111111111133.1111RECIPIENT
'IDCODE/NAME PD2-2PDACRSAEOD/DSP/TPABNRR/DET/EMEB 7ENRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICB8H3 NRR/DST/SRXB 8ERES/DSIR/EIB LSTLOBBYWARDNSICMURPHY,G.A NUDOCSFULLTXTCOPIESLTTRENCL112211111122111111111111NOTETOALL"RIDS"RECIPIENTS:
PLEASEHELPUSTOREDUCEV'ASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOiilPl-37(EXT.20079)TOELlilllNATE YOURNN!EFROivIDISTRIBUTION LISTSFORDOCUMENTS YOUDONTNEED!TOTALNUMBEROFCOPIESREQUIRED:
LTTR32ENCL-32  
'P.O.Box128,Ft.Pierce,FL34854-0128 FPLMay14,1992L-92-149U.S.NuclearRegulatory Commission Attn:DocumentControlDeskWashington, D.C.20555Re:St.LucieUnit2DocketNo.50-389EventDate:April21,1992TurbineTriFailureUdateAttachedpleasefindtheupdatedversionofaplantproblemreportwhichdiscusses aneventwhichoccuredonApril21,1992.Includedisthecurrentstatusofouranalysisoftheevent.Pursuantto10CFR50.73aLicenseeEventReportwillbesubmitted within30daysoftheeventdate.Verytrulyyours,D.A.SVicePrSt.LgersidentePlantDAS/JWH/kw Attachment cc:StewartD.Ebneter,RegionalAdministrator, USNRCRegionIISeniorResidentInspector, USNRC,St.LuciePlantDAS/PSL1697-929205180236 9205i4PDRADOCK050003898PDRanFPLGroupcompany ST.LUCIEPLANTINHOUSEEVENTREPORT92-023REV.9TURBINEGENERATOR FAILEDTOTRIPFOLLOWING MANUALREACTORTRIPUNIT'DATE:APRIL21,1992I.INITIALPLANTCONDITIONS OnApril21,1992,St.LucicUnit2wasshuttingdownforascheduled refueling outage.Reactorpowerwasatapproximately 12%.II.EVENTDESCRIPTION Ascheduled reactor-turbine shutdownwasinprogressonUnit2.Duringtheshutdown, powermovedtothetopofthereactorcore.Existingprocedural guidanceonaxialshapeindex(ASI)wasbeingemployedtominimizethiseffect.However,whenthreeoutoffourlocalpowerdensityprc-trips onthereactorprotection systemactuated, thcnuclearplantsupervisor (NPS)instructed thereactorcontroloperators tomanuallytriptheUnit.Amanualreactortripwasinitiated, buttheturbinedidnottrip.Severalunsuccessful attemptswerethenmadetotriptheturbineusingtheturbinetrippushbutton.Thenuclearwatchengineerwasthendispatched andtrippedtheturbinelocallyfromtheturbinefrontstandard.
III.EVENTSEQUENCESt.LucieUnit2wasperforming ascheduled reactorshutdownforrefueling purposes.
DuringtheplantshutdownASIapproached itsupper(negative) limit.Coordination atcontrolling ASIwithinlimitsandmaintaining reactorcoolanttemperature duetoXenonbuildupbecameincreasingly difficult..
Whenreactorpowerwasdecreased toabout12%,controlrodinsertion nolongeihadanyeffectonmakingASIlessnegativeandthreeofthefourreactorprotection systemlocalpowerdensitypre-trips alarmed.At0238,theNPSinstructed thereactorcontroloperators tomanuallytriptheunitandthemanualreactortrippushbuttons onRTGB(reactorturbinegenerator board)204andRTGB.201weredepressed.
Twosecondslatertheturbinetrippushbutton onRTGB201wasdepressed; however,thcturbinedidnottrip.StandardposttripactionsfromEmergency Operating Procedure (EOP)1wereimplemcnted.Whentheturbinetrippushbutton wasdepressed, theturbinegovernorvalvesindicated closedbutthethrottlevalves,reheatvalves,andintercept valvesindicated open.Autostopoilandtheemergency tripheaderindicated pressures ofapproximately 100psiand2000psi,respectively.
Themegawattrecorderindicated ninetymegawatts.
Several"additional attemptsweremadetotripthcturbineusingthepushbutton, buteachwasunsuccessful.
Atthispoint,thereactorcontroloperatoropenedgenerator outputbreakers8W52and8W49,securedthevoltageregulator, stoppedthcdigitalelectro-hydraulic (DEH)pumps,closedthemainsteamisolation valves(MSIV),andbrokecondenser vacuum.IHE892-023,5/14/921of5 III.EVENTSEQUENCE(cont'd)Theassistant nuclearplantsupervisor instructed theNWEtotriptheturbinefromtheFrontStandard.
At0241alltheturbinevalvesclosed.EOP-2,ReactorTripRecovery, wasthencarriedout,twosetsofsatisfactory safetyfunctionstatuscheckswerccompleted, theplantwasstabilized, andtheTurbineShutdownProcedure wasre-entered.
IV.EVENTEVALUATION A)Withtheexception ofthefailureoftheturbinetotrip,theplantresponsetothiseventwasasexpected.
Uponinitiation ofthereactortripsignal,thefollowing shouldhaveoccurred.
Thefourcontrolelementdrivemechanism (CEDM)busundervoltagc relaysshoulddc-energize.
Thisshouldenergize(open)the20ETsolenoidvalveanddraintheelectro-hydraulic fluidfromtheemergency tripheader(Seeattachment
&#xb9;I).The20ASTtripsolenoidcoilshouldsimultaneously
: energize, pulldownthemechanical triplever,anddumptheautostopoilheader.Decreasing autostopoilpressureallowstheinterface valvetoopenanddumptheelectro-hydraulic fluidemergency tripheader.Whenautostopoilprcssuredecreases to45psi,pressureswitches63-1ASTand63-2ASTshouldlockin,actuating agenerator primarylockoutwhichtripsthcgenerator outputbreakers.
Thesameresultshouldbeobtainedwhenattempting totriptheturbineviatheturbinetrippushbutton.
Theoverspeed protection system(OPC)didnotandshouldnothaveactuatedbecauseitwasnotchallenged.
Themaximumturbinerpmobservedduringthiseventwas1850rpm.ThisisbelowtheOPCsetpointof1854rpm.Amulti-discipline teamisinvestigating todetermine whytheturbinefailedtotripwhenthetripsignalswereinitiated.
RefertoFigures1,2,&3formoredetails.B)FETYIIFfTheplantresponsetothiseventisboundedbysection15.1.5oftheSt.LucieUnit2FinalSafetyAnalysisReport(FSAR),"Increased HeatRemovalbytheSecondary System"asfurtherdescribed below..Analysisofthreescenarios similartobutwithdifferent parameters thantheactualeventwereconducted.
Ineachcasetheeventswerewithintheplant'sdesignbasisandarcsummarized below.1.12%PowerTrip,NoOperatorActionScenario.
*Automatic MSIVclosureat600psig.Cooldownterminated.
*CooldownrateboundedbylimitingFSARcooldownevent.IHE&#xb9;92-023,5/14/922of5 IV.EVENTEVALUATION (cont'd)B)NIFI2.100%PowerTr'ip,NoOperatorActionScenario.
*PossibleSafetyInjection Actuation Signal(SIAS)butnoactualinjection.
*Automatic MSIVclosureat600psig.Cooldownterminated.
~CooldownrateisboundedbytheFSARcooldowneventasconfirmed byin-houseRETRANanalysis.
3.100%PowerTripwithFSARChapter15AccidentScenario.
*FSARChapter15Analysisconsiders singlefailureofturbinestopvalvesto~close.Operators trainedonthesimulator fordesignbasisaccidents.
Multiplefailuresaresimulated andprocedurally addressed byEOPs.Theseinclude"ExcessSteamDemand".C)ALYILAAmulti-discipline investigation teamisperforming arootcauseanalysisofthisevent.MembersofthisgroupincludeSystemEngineers, andrepresentatives fromOperations, Maintenance, Engineering, andtheTurbinevendor.Thcredundant designofthcturbinetripschemesuggeststhatatleasttwofailureswercnecessary toexplaintheinability totripobservedduringthe04/21/92event.Accordingly thefailureanalysisplanisevaluating boththe20ETandthe20ASTturbinetrips.Extensive turbinevendorinputwasobtainedforthefailureanalysisplan.Particular attention waspaidtothelessonslcarncdintheSalemoverspeed event.ALetterofInstruction, 2-LOI-T-67, "Evaluation ofTurbineSolenoidTripFunction,"
waswrittentoevaluatetheoperation ofalltripfunctions.
Attachment 1isthefailureanalysis.
8QQILJl5-Thefailureoftheturbinetotripwascausedbyunrelated failuresintheredundant andelectrically independent turbinetrippingschemes.(moredetailslater.....)
Turbinetrip20ASTfailedduetoanintermittent lossofcircuitcontinuity.
Eitheroftwodeficiencies notedatrelay62ASTX(item&#xb9;6ofattachment 1"FailureAnalysisPlan")couldcausesuchafailure.(moredetailslater.....)
Resultsofthc20ETsolenoidvalveautopsy.(moredetailslater.....)
Becausethesetwounrelated failurescouldnotbedetectedwiththcexistingsystemdesignandsurveillance program,atotallossoftripcapability resulted.
(moredetailslater.....)
IHE&#xb9;92-023,5/14/923of5 V.CORRECTIVE
-ACTIONSA)RAIVITI1.Theoriginal20ET,20OPC-1and20OPC-2Solenoidvalveshavebeenremovedandweresenttoanindependent laboratory foranalysis.
Resultsareduebackon05/18/922.I&Ciscontinuing toinvestigate thcrootcauseoftheintermittent electrical problemsofthe20ASTtripsolenoidunderPWO7356.Thecircuitsofthe20ETand20OPC1and2solenoids arealsobeingevaluated forsimilarproblems3.I&Cwillevaluateproviding coilmonitoring lightsfor20ASTand20ETtoindicatecontinuity ofthefieldcableandsolenoidcoil.4.Operations isevaluating additional guidanceforEOP-1,"Standard PostTripActions",
onactionstotakeforareactortripwithnosubsequent turbinetrip.5.Engineering willevaluateproviding alatch-incircuitforthe20ETsolenoidvalve.Thelatch-inwillbcprovidedonlyacrossthePB710contacts.
6.Engineering willevaluateproviding a30secondtimedelaybetweenaturbinetripandagenerator triptoactivatethereversepowerrelays.7.Engineering willevaluateproviding thecapability toexercisethc20ASTsolenoidvalvewhileonline.8.Operations willevaluatemodifying theirprocedures toallowindividual tripfeaturetesting.9.PCM032-292M"TurbineLubeOilConditioner Connections" willinstallvalvesandfittingstoallowconnection ofanup-graded lubeoilconditioner.
10.I&Cwilldisassemble andinspectthetripblockunderPWO7356.11.Engineering willevaluateproviding improved20ASTcoilsuppression tolimitarcingacross62ASTXrelaycontacts.
12.NuclearFuelsisevaluating additional guidanceforASIcontrolattheendofcorelife.B)MAIVITI13.Engineering willevaluateenhancements tothefiltration systemfortheturbineEHfluid.14.Engineering willevaluatetheuseofastainless steelsolenoidvalvebodytoreplacetheexistingcarbonsteelbody.IHE&#xb9;92-023,5/14/924of5 V.CORRECTIVE ACTIONS(cont'd)B)AI15.Engineering willevaluateuseofanalternative DEHfluidtoreducematerialincompatibilities.
16.Engineering willevaluateproviding anadditional 20ASTvalveofdiversemanufacture whichcanbetestedonlinebytheuseofthemanualtripbuttons.17.Engineering willevaluateproviding ameansoftestingthe20ETsolenoidvalvewhileonline.IHE&#xb9;92-023,5/14/925of5 Attachment 1PFTFAILUREANALYSISPLANFTII1of2Frfr1.20ET(valve)-sticking, binding-removedfromsystemin"asfound"condition topreserveanycvidenccoffailuremode;senttoanindependent lab.-resultsduc05/18/922.20ET(circuit)
-loosewire-opencoil-improper supplyvoltage-continuity check-resistance check~-voltagemeasuredandrecorded-satisfactory
/PWO7356-noopen/2-LOI-T-67
-acceptable
/2-LOI-T-673.20AST(valve)4.20AST(TripBlock)5.20AST(circuit)
-sticking, binding'pluggedorifice-loosewire-valveoperatedduringtest-disassemble andinspect-continuity check-noindication ofstickingorbinding/2-LOI-T-67
-scheduled 5/12/92-looseterminalconnection foundatposition&#xb9;6on63ASTX/PWO7356-opencoil-improper voltagesupply-resistance check-voltagemeasuredandrecorded-noopen/2-LOI-T-67
-acceptable
/2-LOI-T-67 6.62ASTX(Relay)-setpointdrift-digitalrecorder-setpointverified/2-LOI-T-67-loosewire-continuity check-looseterminalconnection atposition&#xb9;6/2-LOI-T-67
*Potential FailureCause-degraded contacts-visualexamination
-slightarcingonbothsetsofcontactswithburnresidueevident*Potential FailureCause Attachment 1FAILREANALYIPLAN2of27.20-1OPC(valve)-sticking, binding-valveoperatedduringtest-noindication ofsticking, binding/2-LOI-T-67, valvesenttoanindependent lab,resultsduc05/18/928.20-1OPC(circuit) 9.20-2OPC(valve)-loosewire-sticking, binding-continuity check-valvesenttoanindependent lab-noopens/PWO7356-resultsdue05/18/9210.20-2OPC(circuit) 11.FCV-22-148 (interface
-loosewire-sticking, binding-continuity check-valveoperatedduringtest-noopens/PWO7356-noindication ofsticking, binding/2-LOI-T-67 valve)12.63-1AST(pressure switch)13.63-2AST(pressure switch)14.PB710-contacts
-contacts
-contacts
-contactalignment
-digitalrecorderandvisually-acceptable
/2-LOI-T-67-digitalrecorderand-visually-acceptable
/2-LOI-T-67I'continuity checks,disassembly, andinspection
-topcontactsrequiredmoremovementthanbottomcontacts, switchreplaced/PWO7356-switchoperatedduringtest-acceptable
/2-LOI-T-67
-NotaCauseoftheFailure15.EFIfluid16.Turbinelubeoil-contamination
-contamination
-waterandparticulate
-waterandparticulate
-inspecification
/Predictive Maintenance periodictestingprogram-inspecification
/Predictive Maintenance periodictestingprogram Attachment 2EELLIEKPL1of11.ManualReactortripduetoalossofASIcontrol-Ineffective ASIcontrolmethod-Improved ASIcontrolprocedure 2.Looseleadat62ASTX-Lackofmeanstodetectalossofcontinuity
-Designchangestoaddcircuitmonitoring lights-Designchangestoallowperiodicon-linetestingofboth20ASTand20ET3.Burntcontactson62ASTX-Inadequate arcsuppression
-Designchangetoupgradearcsuppression in20ASTcircuit(MORELATER......  
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~~lOCKOUTTURBINETRIPSOVERSPEEO IAUTOISTEAI4IETHDEHDCRECTOR[SIOP[<~'HOOPTAILUREOILs.EASELIIHPijsuezZW4~FZ-oag0OVIII.zLI0In26IL-7IO6PB2710.25TDI%56862~P'2CSH.~.86GBSH..885~14GADOO685SECORAT56r-4I0IN-Id74R4'r3II~25SECII14L12Tppo60.25SEC.IEHlXH7.(5ILlll)It74DITXTDDODCF4rasses~25SEC~su-4cg-e,lo93109ISC23CIs'5'23Bs0RB5l5OA2OOWSETATI25Tl.4irvjISP23PosATaR(TYP)62ASTXTPOIDgECISA.Lh&P3 234is%2SA62ASTXISC2SC'A00IOSB:0~63-1IAST2663K0RA5T063t363LVgE3b63,74C62AASTX-(56747105H.TIIASTH0gOAST34..I3I4CSC.1CSBTieIIlos1IXCWP4il5,6s20
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Revision as of 15:13, 29 June 2018

Special Rept:On 920421,turbine Generator Failed to Trip Following Manual Reactor Trip.Caused by Failures in Redundant & Electrically Independent Turbine Tripping Schemes.I&C Disassembled & Trip Block Inspected
ML17227A424
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 05/14/1992
From: SAGER D A
FLORIDA POWER & LIGHT CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-92-149, NUDOCS 9205180236
Download: ML17227A424 (15)
v • d • e


Text

ACCELERATED DISTRIBUTION DEMONSTTION SYSTEMREGULATORY INFORMATION DISTRIBUTION SYSTEM(RIDS)ACCESSION NBR:9205180236 DOC.DATE:

92/05/14NOTARIZED:

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

FloridaPower&LightCo.RECIP.NAME RECIPIENT AFFILIATION DocumentControlBranch(Document ControlDesk)

SUBJECT:

Specialrept:on920421,turbine generator failedtotripfollowing manualreactortrip.Causedbyfailuresinredundant

&electrically independent turbinetrippingschemes.I&Cdisassembled

&trxpblockinspected.

DISTRIBUTION CODE:IE22DCOPIESRECEIVED:LTR ENCLSIZE:TITLE:50.73/50.9 LicenseeEventReport(LER),IncidentRpt,etc.NOTESDOCKET05000389RECIPIENT IDCODE/NAME PD2-2LANORRIS,JINTERNAL:

ACNWAEOD/DOAAEOD/ROAB/DS PNRR/DLPQ/LHFB10 NRR/DOEA/OEAB NRR/DST/SELB 8DRR/LB8D1REGFIL02RGN2FILE01EXTERNAL:

EG&GBRYCE,J.H NRCPDRNSICPOORE,W.COPIESLTTRENCL1111221-12211111111111133.1111RECIPIENT

'IDCODE/NAME PD2-2PDACRSAEOD/DSP/TPABNRR/DET/EMEB 7ENRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICB8H3 NRR/DST/SRXB 8ERES/DSIR/EIB LSTLOBBYWARDNSICMURPHY,G.A NUDOCSFULLTXTCOPIESLTTRENCL112211111122111111111111NOTETOALL"RIDS"RECIPIENTS:

PLEASEHELPUSTOREDUCEV'ASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOiilPl-37(EXT.20079)TOELlilllNATE YOURNN!EFROivIDISTRIBUTION LISTSFORDOCUMENTS YOUDONTNEED!TOTALNUMBEROFCOPIESREQUIRED:

LTTR32ENCL-32

'P.O.Box128,Ft.Pierce,FL34854-0128 FPLMay14,1992L-92-149U.S.NuclearRegulatory Commission Attn:DocumentControlDeskWashington, D.C.20555Re:St.LucieUnit2DocketNo.50-389EventDate:April21,1992TurbineTriFailureUdateAttachedpleasefindtheupdatedversionofaplantproblemreportwhichdiscusses aneventwhichoccuredonApril21,1992.Includedisthecurrentstatusofouranalysisoftheevent.Pursuantto10CFR50.73aLicenseeEventReportwillbesubmitted within30daysoftheeventdate.Verytrulyyours,D.A.SVicePrSt.LgersidentePlantDAS/JWH/kw Attachment cc:StewartD.Ebneter,RegionalAdministrator, USNRCRegionIISeniorResidentInspector, USNRC,St.LuciePlantDAS/PSL1697-929205180236 9205i4PDRADOCK050003898PDRanFPLGroupcompany ST.LUCIEPLANTINHOUSEEVENTREPORT92-023REV.9TURBINEGENERATOR FAILEDTOTRIPFOLLOWING MANUALREACTORTRIPUNIT'DATE:APRIL21,1992I.INITIALPLANTCONDITIONS OnApril21,1992,St.LucicUnit2wasshuttingdownforascheduled refueling outage.Reactorpowerwasatapproximately 12%.II.EVENTDESCRIPTION Ascheduled reactor-turbine shutdownwasinprogressonUnit2.Duringtheshutdown, powermovedtothetopofthereactorcore.Existingprocedural guidanceonaxialshapeindex(ASI)wasbeingemployedtominimizethiseffect.However,whenthreeoutoffourlocalpowerdensityprc-trips onthereactorprotection systemactuated, thcnuclearplantsupervisor (NPS)instructed thereactorcontroloperators tomanuallytriptheUnit.Amanualreactortripwasinitiated, buttheturbinedidnottrip.Severalunsuccessful attemptswerethenmadetotriptheturbineusingtheturbinetrippushbutton.Thenuclearwatchengineerwasthendispatched andtrippedtheturbinelocallyfromtheturbinefrontstandard.

III.EVENTSEQUENCESt.LucieUnit2wasperforming ascheduled reactorshutdownforrefueling purposes.

DuringtheplantshutdownASIapproached itsupper(negative) limit.Coordination atcontrolling ASIwithinlimitsandmaintaining reactorcoolanttemperature duetoXenonbuildupbecameincreasingly difficult..

Whenreactorpowerwasdecreased toabout12%,controlrodinsertion nolongeihadanyeffectonmakingASIlessnegativeandthreeofthefourreactorprotection systemlocalpowerdensitypre-trips alarmed.At0238,theNPSinstructed thereactorcontroloperators tomanuallytriptheunitandthemanualreactortrippushbuttons onRTGB(reactorturbinegenerator board)204andRTGB.201weredepressed.

Twosecondslatertheturbinetrippushbutton onRTGB201wasdepressed; however,thcturbinedidnottrip.StandardposttripactionsfromEmergency Operating Procedure (EOP)1wereimplemcnted.Whentheturbinetrippushbutton wasdepressed, theturbinegovernorvalvesindicated closedbutthethrottlevalves,reheatvalves,andintercept valvesindicated open.Autostopoilandtheemergency tripheaderindicated pressures ofapproximately 100psiand2000psi,respectively.

Themegawattrecorderindicated ninetymegawatts.

Several"additional attemptsweremadetotripthcturbineusingthepushbutton, buteachwasunsuccessful.

Atthispoint,thereactorcontroloperatoropenedgenerator outputbreakers8W52and8W49,securedthevoltageregulator, stoppedthcdigitalelectro-hydraulic (DEH)pumps,closedthemainsteamisolation valves(MSIV),andbrokecondenser vacuum.IHE892-023,5/14/921of5 III.EVENTSEQUENCE(cont'd)Theassistant nuclearplantsupervisor instructed theNWEtotriptheturbinefromtheFrontStandard.

At0241alltheturbinevalvesclosed.EOP-2,ReactorTripRecovery, wasthencarriedout,twosetsofsatisfactory safetyfunctionstatuscheckswerccompleted, theplantwasstabilized, andtheTurbineShutdownProcedure wasre-entered.

IV.EVENTEVALUATION A)Withtheexception ofthefailureoftheturbinetotrip,theplantresponsetothiseventwasasexpected.

Uponinitiation ofthereactortripsignal,thefollowing shouldhaveoccurred.

Thefourcontrolelementdrivemechanism (CEDM)busundervoltagc relaysshoulddc-energize.

Thisshouldenergize(open)the20ETsolenoidvalveanddraintheelectro-hydraulic fluidfromtheemergency tripheader(Seeattachment

¹I).The20ASTtripsolenoidcoilshouldsimultaneously

energize, pulldownthemechanical triplever,anddumptheautostopoilheader.Decreasing autostopoilpressureallowstheinterface valvetoopenanddumptheelectro-hydraulic fluidemergency tripheader.Whenautostopoilprcssuredecreases to45psi,pressureswitches63-1ASTand63-2ASTshouldlockin,actuating agenerator primarylockoutwhichtripsthcgenerator outputbreakers.

Thesameresultshouldbeobtainedwhenattempting totriptheturbineviatheturbinetrippushbutton.

Theoverspeed protection system(OPC)didnotandshouldnothaveactuatedbecauseitwasnotchallenged.

Themaximumturbinerpmobservedduringthiseventwas1850rpm.ThisisbelowtheOPCsetpointof1854rpm.Amulti-discipline teamisinvestigating todetermine whytheturbinefailedtotripwhenthetripsignalswereinitiated.

RefertoFigures1,2,&3formoredetails.B)FETYIIFfTheplantresponsetothiseventisboundedbysection15.1.5oftheSt.LucieUnit2FinalSafetyAnalysisReport(FSAR),"Increased HeatRemovalbytheSecondary System"asfurtherdescribed below..Analysisofthreescenarios similartobutwithdifferent parameters thantheactualeventwereconducted.

Ineachcasetheeventswerewithintheplant'sdesignbasisandarcsummarized below.1.12%PowerTrip,NoOperatorActionScenario.

  • Automatic MSIVclosureat600psig.Cooldownterminated.
  • CooldownrateboundedbylimitingFSARcooldownevent.IHE¹92-023,5/14/922of5 IV.EVENTEVALUATION (cont'd)B)NIFI2.100%PowerTr'ip,NoOperatorActionScenario.
  • PossibleSafetyInjection Actuation Signal(SIAS)butnoactualinjection.
  • Automatic MSIVclosureat600psig.Cooldownterminated.

~CooldownrateisboundedbytheFSARcooldowneventasconfirmed byin-houseRETRANanalysis.

3.100%PowerTripwithFSARChapter15AccidentScenario.

  • FSARChapter15Analysisconsiders singlefailureofturbinestopvalvesto~close.Operators trainedonthesimulator fordesignbasisaccidents.

Multiplefailuresaresimulated andprocedurally addressed byEOPs.Theseinclude"ExcessSteamDemand".C)ALYILAAmulti-discipline investigation teamisperforming arootcauseanalysisofthisevent.MembersofthisgroupincludeSystemEngineers, andrepresentatives fromOperations, Maintenance, Engineering, andtheTurbinevendor.Thcredundant designofthcturbinetripschemesuggeststhatatleasttwofailureswercnecessary toexplaintheinability totripobservedduringthe04/21/92event.Accordingly thefailureanalysisplanisevaluating boththe20ETandthe20ASTturbinetrips.Extensive turbinevendorinputwasobtainedforthefailureanalysisplan.Particular attention waspaidtothelessonslcarncdintheSalemoverspeed event.ALetterofInstruction, 2-LOI-T-67, "Evaluation ofTurbineSolenoidTripFunction,"

waswrittentoevaluatetheoperation ofalltripfunctions.

Attachment 1isthefailureanalysis.

8QQILJl5-Thefailureoftheturbinetotripwascausedbyunrelated failuresintheredundant andelectrically independent turbinetrippingschemes.(moredetailslater.....)

Turbinetrip20ASTfailedduetoanintermittent lossofcircuitcontinuity.

Eitheroftwodeficiencies notedatrelay62ASTX(item¹6ofattachment 1"FailureAnalysisPlan")couldcausesuchafailure.(moredetailslater.....)

Resultsofthc20ETsolenoidvalveautopsy.(moredetailslater.....)

Becausethesetwounrelated failurescouldnotbedetectedwiththcexistingsystemdesignandsurveillance program,atotallossoftripcapability resulted.

(moredetailslater.....)

IHE¹92-023,5/14/923of5 V.CORRECTIVE

-ACTIONSA)RAIVITI1.Theoriginal20ET,20OPC-1and20OPC-2Solenoidvalveshavebeenremovedandweresenttoanindependent laboratory foranalysis.

Resultsareduebackon05/18/922.I&Ciscontinuing toinvestigate thcrootcauseoftheintermittent electrical problemsofthe20ASTtripsolenoidunderPWO7356.Thecircuitsofthe20ETand20OPC1and2solenoids arealsobeingevaluated forsimilarproblems3.I&Cwillevaluateproviding coilmonitoring lightsfor20ASTand20ETtoindicatecontinuity ofthefieldcableandsolenoidcoil.4.Operations isevaluating additional guidanceforEOP-1,"Standard PostTripActions",

onactionstotakeforareactortripwithnosubsequent turbinetrip.5.Engineering willevaluateproviding alatch-incircuitforthe20ETsolenoidvalve.Thelatch-inwillbcprovidedonlyacrossthePB710contacts.

6.Engineering willevaluateproviding a30secondtimedelaybetweenaturbinetripandagenerator triptoactivatethereversepowerrelays.7.Engineering willevaluateproviding thecapability toexercisethc20ASTsolenoidvalvewhileonline.8.Operations willevaluatemodifying theirprocedures toallowindividual tripfeaturetesting.9.PCM032-292M"TurbineLubeOilConditioner Connections" willinstallvalvesandfittingstoallowconnection ofanup-graded lubeoilconditioner.

10.I&Cwilldisassemble andinspectthetripblockunderPWO7356.11.Engineering willevaluateproviding improved20ASTcoilsuppression tolimitarcingacross62ASTXrelaycontacts.

12.NuclearFuelsisevaluating additional guidanceforASIcontrolattheendofcorelife.B)MAIVITI13.Engineering willevaluateenhancements tothefiltration systemfortheturbineEHfluid.14.Engineering willevaluatetheuseofastainless steelsolenoidvalvebodytoreplacetheexistingcarbonsteelbody.IHE¹92-023,5/14/924of5 V.CORRECTIVE ACTIONS(cont'd)B)AI15.Engineering willevaluateuseofanalternative DEHfluidtoreducematerialincompatibilities.

16.Engineering willevaluateproviding anadditional 20ASTvalveofdiversemanufacture whichcanbetestedonlinebytheuseofthemanualtripbuttons.17.Engineering willevaluateproviding ameansoftestingthe20ETsolenoidvalvewhileonline.IHE¹92-023,5/14/925of5 Attachment 1PFTFAILUREANALYSISPLANFTII1of2Frfr1.20ET(valve)-sticking, binding-removedfromsystemin"asfound"condition topreserveanycvidenccoffailuremode;senttoanindependent lab.-resultsduc05/18/922.20ET(circuit)

-loosewire-opencoil-improper supplyvoltage-continuity check-resistance check~-voltagemeasuredandrecorded-satisfactory

/PWO7356-noopen/2-LOI-T-67

-acceptable

/2-LOI-T-673.20AST(valve)4.20AST(TripBlock)5.20AST(circuit)

-sticking, binding'pluggedorifice-loosewire-valveoperatedduringtest-disassemble andinspect-continuity check-noindication ofstickingorbinding/2-LOI-T-67

-scheduled 5/12/92-looseterminalconnection foundatposition¹6on63ASTX/PWO7356-opencoil-improper voltagesupply-resistance check-voltagemeasuredandrecorded-noopen/2-LOI-T-67

-acceptable

/2-LOI-T-67 6.62ASTX(Relay)-setpointdrift-digitalrecorder-setpointverified/2-LOI-T-67-loosewire-continuity check-looseterminalconnection atposition¹6/2-LOI-T-67

  • Potential FailureCause-degraded contacts-visualexamination

-slightarcingonbothsetsofcontactswithburnresidueevident*Potential FailureCause Attachment 1FAILREANALYIPLAN2of27.20-1OPC(valve)-sticking, binding-valveoperatedduringtest-noindication ofsticking, binding/2-LOI-T-67, valvesenttoanindependent lab,resultsduc05/18/928.20-1OPC(circuit) 9.20-2OPC(valve)-loosewire-sticking, binding-continuity check-valvesenttoanindependent lab-noopens/PWO7356-resultsdue05/18/9210.20-2OPC(circuit) 11.FCV-22-148 (interface

-loosewire-sticking, binding-continuity check-valveoperatedduringtest-noopens/PWO7356-noindication ofsticking, binding/2-LOI-T-67 valve)12.63-1AST(pressure switch)13.63-2AST(pressure switch)14.PB710-contacts

-contacts

-contacts

-contactalignment

-digitalrecorderandvisually-acceptable

/2-LOI-T-67-digitalrecorderand-visually-acceptable

/2-LOI-T-67I'continuity checks,disassembly, andinspection

-topcontactsrequiredmoremovementthanbottomcontacts, switchreplaced/PWO7356-switchoperatedduringtest-acceptable

/2-LOI-T-67

-NotaCauseoftheFailure15.EFIfluid16.Turbinelubeoil-contamination

-contamination

-waterandparticulate

-waterandparticulate

-inspecification

/Predictive Maintenance periodictestingprogram-inspecification

/Predictive Maintenance periodictestingprogram Attachment 2EELLIEKPL1of11.ManualReactortripduetoalossofASIcontrol-Ineffective ASIcontrolmethod-Improved ASIcontrolprocedure 2.Looseleadat62ASTX-Lackofmeanstodetectalossofcontinuity

-Designchangestoaddcircuitmonitoring lights-Designchangestoallowperiodicon-linetestingofboth20ASTand20ET3.Burntcontactson62ASTX-Inadequate arcsuppression

-Designchangetoupgradearcsuppression in20ASTcircuit(MORELATER......

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