ML17229A902

LER 98-008-00:on 981008,inadequate Reactor Protection Sys Trip Bypass TS Was Noted.Caused by Poorly Worded Ts. Submitted LAR to Clarify Power Requirements for High Rate of Power Trips.With 981104 Ltr

ML17229A902
Person / Time
Site:	Saint Lucie
Issue date:	11/04/1998
From:	FREHAFER K W, STALL J A FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-98-280, LER-98-008, LER-98-8, NUDOCS 9811130285
Download: ML17229A902 (8)

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CATEGORY1REGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9811130285DOC.DATE:98/11/04NOTARIZED:NOFACZL:50-335St.LuciePlant,Unit1,FloridaPower6LightCo.AUTH.NAMEAUTHORAFFILIATIONFREK<FER,K.W.FloridaPower&LightCo.STALL,J.A.FloridaPower6LightCo.RECZP.NAME.RECIPIENTAFFILIATIONDOCKET05000335

SUBJECT:

LER98-008-'00:on981008,inadequatereactorprotectionsystripbypassTSwasnoted.CausedbypoorlywordedTS.SubmittedLARtoclarifypowerrequirementsforhighrateofpowertrips.With981104ltr.DISTRIBUTIONCODE:IE22TCOPIESRECEIVED:LTRENCLSIZE:TITLE:50.73/50.9LicenseeEventReport(LER),ncidentRpt,etc.NOTES:ERECIPIENTIDCODE/NAMEPD2-3PDINTERNAL:ACRSAEOD/SPD/RRABNRR/DE/ECGBNRR/DE/EMEBNRR/DRCH/HOHBNRR/DRPM/PECBRES/DET/EIBEXTERNAL:LSTLOBBYWARDNOACPOORE,W.NRCPDRCOPIESLTTRENCL1111111111111111111111RECIPIENTZDCODE/NAMEGLEAVES,WAEOD/SPD/RABCDEEELBNRR/DRCH/HZCBNRR/DRCH/HQMBNRR/DSSA/SPLBRGN2FILE01LZTCOBRYCE,JHNOACQUEENER,DSNUDOCSFULLTXTCOPIESLTTRENCL11221111111111111'1111RD0MI'NOTETOALE"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083FULLTEXTCONVERSIONREQUIREDTOTAL,NUMBEROFCOPIESREQUIRED:LTTR23ENCL23 FloridaPower&LightCompany,6351S.OceanDrive,JensenBeach.FL34957APLNovember4,1998L-98-28010CFRg50.73U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555Re:St.LucieUnits1and2DocketNos.50-335/389ReportableEvent:1998-008-00DateofEvent:October8,1998InadequateReactorProtectionemTriBTechni1ificationh.,';",f~.~".;":".+eattachedLicŽenseeEve.'.,;j~>v>.".p~l0,CFR$50,73toprovideanttotherequirementsofntReport1998-008isbeingsubmittedpursunotificationofthesubjectevent.ia,-P~Verytrulyyours,J.A.StallVicePresidentSt.LucieNuclearPlantJAS/EJW/KWFAttachmentcc:RegionalAdministrator,USNRCRegionIISeniorResidentInspector,USNRC,St.LucieNuclearPlant98ii13028598ii04PDRAMCK05000:335SPDRanFPLGroupcompany

NRCFORM366IS-1999)U.S.NUCLEARREGULATORYCOMMISSIONLICENSEEEVENTREPORT(LER){Seereverseforrequirednumberofdigits/charactersforeachblock)APPROVEDBYOMBNO.3150.0104EXPIRES06I30l2001Estimatedburdenperresponsetocomplywiththismandalorybtfcrmagoncollecbonrequesl:50hrs.ReportedlessonslearnedareincorporatedintoIhelicensingprocessandfedbacktoIndusby.FonvardcommentsregardingburdenestimatelotheRecordsManagementBranch(TWF33),US.NudearRegulatoryCommission.Washington.DC205554001~andloIhePapenvrskRedudionProiect(31500104]OlrceofManagementandBudget,Washington.OC20503.IfaninformationcogecgondoesnoldisplayacurrentlyvalidOMBcontrolnumber,theNRCmaynotconductorsponsor,sndapersonisnolrequiredtorespondlo,thehformationcollection.FACIUTYNAME(1)St.LucieUnit1DOCKETNUMBER{2)05000335PAGE(3)Page1of4TITLE(4)InadequateReactorProtectionSystemTripBypassTechnicalSpecificationMONTHDAY10081998EVENTDATE(5LERNUMBER6REPORTDATE7)SEQUENTIALREVISIONMONTHNUMBERNUMBER1998-008-00OAY041998DOCKETNUMatn05000389DOCKETNUMSERFACIUTVNAMESt.LucieUnit2FACIUTVNAMEOTHERFACILITIESINVOLVED6OPERATINGMODE(9)POWERLEVEL{10)10020.2201(b)20.2203(a){I)20.2203(a)(2)(i)20.2203(e)(2)(ii)20.2203(a)(2)(iii)20.2203(a)(2)(iv)20.2203(e){2)(v)20.2203(a)(3)(i)20.2203(e)(3)(Ii)20.2203(a){4)50.36(c)(1)50.36(c)(2)50.73(a)(2)(i)50.73(a)(2)(ii)50.73(a)(2)(iii)50.73(a)(2)(iv)50.73(a)(2)(v)50.73{a)(2)(vii)50.73(a)(2)(viii)50.73(a)(2)(x)73.71OTHERSpecifyInAbstractbeloworInNRCForm3SSAUIREMENTSOF10CFR9:(Checkoneormoro){11)THISREPORTISSUBMITTEDPURSUANTTOTHEREQNAMEUCENSEECONTACTFORTHISLER12TELEPHONENUMBERSncludeAresCocci~K.W.Frehafer,LicensingEngineer(561)467-7748COMPLETEONELINEFOREACHCOMPONENTFAILUREDESCRIBEDINTHISREPORT13CAUSESYSTEMCOMPONENTMANUFACTURERREPORTABLETOEPIXCAUSESYSTEMCOMPONENTMANUFACTURERREPORTABLETOEPIXJCn/aN/ANO6PPTALRORTXPECTED(14)YES(IfYoe,completeEXPECTEDSUBMISSIONDATE).NOEXPECTEDSUBMISSIONDATE(15)ABSTRACT[Limitto1400spaces,ie.,approximately15singlespecedtypewrittenlines/{16)OnOctober8,1998,St.LucieUnits1and2wereinMODE1at100percentreactorpower.FPLdeterminedthattheTechnicalSpecificationgoverningthetripbypasssetpointsforthehighrateofchangeofpowerreactorprotectionsystemtripwasinerror.TheexplicittermTHERMALPOWERusedintheaffectedTechnicalSpecificationtablenotationrelativetothehighrateofchangeofpowertripbypassfunctioncannotbesatisfiedpriortoent'ryintoMODE2fromaMODE3conditionduetothenormallevelofheattransfertothereactorcoolantasaresultofreactorcoredecayheat.Thetermsofthespecificationcannotbeachievedsincedecayheatisnotadirectlymeasurableparameterandthe.operativeparameterforremovalofthebypassisexcoreneutronfluxthatismeasuredbythewiderangelogarithmicneutronfluxmonitors.Duringpastreactorstartups,literalcompliancewiththeTechnicalSpecificationsforthehighrateofchangeofpowertripwasnotmet.ThecauseofthiseventwasapoorlywordedTechnicalSpecificationthatdidnotexplicitlyexcludedecayheatfromthepowerlevelatwhichthehighrateofchangeofpowertripbypassisrequiredtoberemoved.Asacorrectiveaction,St.Luciehasdevelopedandsubmittedanamendmenttothelicensetoclarifythepowerrequirementsforthehighrateofchangeofpowertrip.Therevisionensuresthatthemeaningof'explicittermsusedintheaffectedTechnicalSpecificationsareconsistentwiththeintentofthestatedrequirementsbasedoneachSt.LuciePlantdesign.NACFORM3SSIS.1999)

INRCFORM366AI8-I888)LICENSEEEVENTREPORT(LER)TEXTCONTINUATIONU.S.NUCLEARREGULATORYCOMMISSIONFAGIUTYNAMEI1)St.LucieUnit1DocKETNUMBER205000335LERNUMBER(6)SEQUENTIALREVISIONNUMBERNUMBER1998-008-00PAGEI3)Page2of4TEXT(ffmorespeceisrequired,useedditionelcopiesofNRCForm366A/I17)DescriptionofEventOnOctober8,1998,St.LucieUnits1and2wereinMODE1at100percentreactorpower.FPLdeterminedthattheTechnicalSpecificationgoverningthetripandbypasssetpointsforthehighrateofchangeofpower(HRCP)reactorprotectionsystem(RPS)[BZISIJC]tripbypasswasinerror.Specifically,theTechnicalSpecificationincorrectlydefinestheHRCPtripbypassasafunctionofTHERMALPOWER,insteadofindicatedwiderangelogrithmicpower.Therateofchangeofreactorpowerismeasuredbyfourwiderangelogarithmicchannels.Eachchannelindependentlymonitorstheneutronfluxbyprocessingsignalsfromfissionchamberslocatedexternaltothereactorcoreandcoversatendecaderangefromapproximately10percenttoover100percentoffullpower.Theexcoreneutronfluxinthevicinityofthefissionchambersisproportionaltotheincorenuclearfissionrateandisnotsignificantlyinfluencedbyheattransferfromthecoretothecoolantfromthelong-termdecayofradioactivefissionproducts.Thelogarithmicpowerlevelsignalisdifferentiatedtoproviderateofchangeofpowerinformation.fromapproximately-1to+7decadesperminute(DPM)~TheratesignalisprocessedandinputtoabistablethatactuatestheHRCPtripwhentherateofchangeofreactorpowerexceeds2.49decadesperminute.Areactortripisinitiatedwhenreactorpowerexceedsthesetpointasmeasuredbyanytwowiderangechannels.Eachwiderangelogarithmicneutronfluxmonitoralsooperatesabistabletodisablethistripbelow10percentpowerand,conversely,ensurethatthisbypassisautomaticallyremovedatgreaterthanorequalto10percentpower.Thetripfeaturemayalsobebypassedabove15percentpower,butsettingandremovingthisbypassisaccomplishedbythepowerrangechannels(linear,narrowrangeneutronfluxmonitors)whichalsomonitortheexcoreneutronflux.TheTechnicalSpecificationsdefineTHERMALPOWERasthetotalreactorcoreheattransferratetothereactorcoolant.Inadditiontotheheatgeneratedbytheincorefissionrate,thisdefinitionofTHERMALPOWBRincludesdecayheatwhichisproducedfromtheradioactivedecayofcorefissionproducts.Forapreviouslyoperatedreactor,decayheatcontinuestoexistduringreactorshutdownandwouldtakeseveralyearstodecaytoalevelwherethecoreheattransferratecorrespondsto10percent,orless,ofRATEDTHERMALPOWER.Decay'heatisnotadirectlymeasureableparameter,doesnotreflectthereactivityconditionofthereactor,andisnotavariablenormallyassociatedwiththerateofchangeofreactorpower.Therefore,decayheatisnotsuitableforuseasanoperativeparameterforautomaticprotectiveactionsandthereisnoevidencetoindicatethatdecayheatwasconsideredinthedesignoftheHRCPtripfunction.CauseoftheEventThecauseofthiseventwasapoorlywordedTechnicalSpecificationthatdidnotexplicitlyexcludedecayheatfromthepowerlevelatwhichtheHRCPtripbypassisrequiredtoberemoved.AnalysisoftheEvent,Thiseventisreportableunder10CFR50.73(a)(2)(i)(B)as"anyoperationorconditionprohibitedbytheplant'sTechnicalSpecifications."ThefollowingNRCFORM388A(8.1888)

NRCFDRM366A(6-1998)LlCENSEEEVENTREPORT(LER)TEXTCONTINUATIONU.S.NUCLEARREGULATORYCOMMISSIONFACILITYNAME(1)St.LucieUnit1DOCKETNUMBER(2)05000335LERNUMBER(8)SEQUENTIALREVISION'UMBERNUMBER1998-008-00PAGE(3)Page3of4TEXT(ifmorespeceisrequired,useedditionelcopiesofiIfRCForm366AI(17)FTechnicalSpecificationtablenotationsapplytothewiderangelogarithmicneutronfluxmonitorfunctionalunit:ForbothUnits:TS1.25:RATEDTHERMALPOWERshallbeatotalreactorcoreheattransferratetothereactorcoolantof2700MWt.TS1.33:THERMALPOWERshallbethetotalreactorcoreheattransferratetothereactorcoolant.TS1.20,OPERATZOMALMODE:AnOPBRATZOHALMODE(i.e.,MODE)shallcorrespondtoanyoneinclusivecombinationofcorereactivitycondition,powerlevel,andaveragereactorcoolanttemperaturespecifiedinTSTable1'.ZnTABLE1.2,theterm0RATEDTHERMALPOWERismodifiedwithafootnotethatstates,*Excludingdecayheat.Unit1:TABLE2.2-1,NOTE(4):Tripmaybebypassedbelow10%andabove15%ofRATEDTHERMALPOWERTABLE3.3-1,Note(d):Tripmaybebypassedbelow100andabove15%ofRATEDTHERMALPOWER)bypassshallbeautomaticallyremovedwhenTHERMALpowerisabove100orbelow15%ofRATEDTHBRKQPOWBR.Unit2:TABLE2.2-2,NOTE(4)andTABLE3.3-7,NOTE(e):Tripmaybebypassedbelow10andabove15%.ofRATEDTHERMALPOWBR;bypassshallbeautomaticallyremovedwhenTHERMALpowerisabove10%orbelow15%ofRATBDTHERMALPOWER.TheHRCPtripwasprovidedwiththeSt.LucieUnit1andUnit2analogRPSas"backupprotectionagainstpowerexcursioneventsinitiatedfromsubcriticalconditions.Thetripisrequiredtobeoperablei.nModes1and2,butmaybebypassedbelow10percentandabove15percentofreactorpower.Assuch,thetripisbasedonboththeOPBRATZONALMODBofthereactorandonhowfastthemeasuredparameterrepresentingreactorpowerchangesinagiventimeperiod.Thesetpointisspecifiedinunitsofreactorstartuprate,i.e.,indecadesperminute(DPM).Thestartuprateisobtainedfromthewiderangelogarithmicneutronfluxmonitorswhichmonitortheexcoreneutronflux.Theexcoreneutronfluxisproportionaltotheincorefissionrate,andtherefore,isproportionaltothereactorpowerproducedfromtheincorefissionrate.Duringstartupofacommercialnuclearreactorfromsubcriticalconditions,heattransfertothereactorcoolantasaresultofonlythefissionrateistypicallyinsufficienttosignificantlyaffectthereactorcoolanttemperaturewhenlessthanapproximately0.1percentoffullpowerandtherateofchangeofneutronfluxisessentiallytheonlymeasureableparameterthatprovidesrateofchangeofpowerinformation.Table1.2ofthefacilityTechnicalSpecificationsdefinestheOPBRATZOHALMODBSofplantoperationintermsofreactivity,thermalpower,andaveragecoolanttemperature.ThetermpercentRATEDTHERMALPOWERisclearlyannotatedandfootnotedwithanasterisktoclarifythatthenumericalvaluesusedinthetableexcludedecayheat.Thisexclusionappliestothepowerlevelthat,inpart,definesMODE2whereintheHRCPtripisrequiredtobeoperableduringreactorstartup.NAGFOAM386A(6-1998)

NRCFORM366A18-1998)LICENSEEEVENTREPORT(LER)TEXTCONTINUATIONU.S.NUCUARREGULATORYCOMMlSSlONFACIUTYNAMEt1)0OCKETNUMBER2lt.ERNUMBER(6)PAGE(3)St.LucieUnit1SEQUENTIALREVISIONNUMBERNUMBER050003351998-008-00Page4of4TEXTllfmorespecsisreguired,useedditionelcopiesofNRCFerm36&i/I17)TheuseofexcoreneutronfluxasthemeasuredparametertoimplementtheHRCPtripfunctionisappropriate,andtheRPSnuclearinstrumentationchannelsdesignedtocoverthestartuprangesoftheSt.Luciereactorsarethewiderangelogarithmicneutronfluxmonitors.Similartodesignfeaturesofthetrip,thepowerlevelatwhichthetripfunctionbypassmustberemovedduringareactorstartupisassociatedwiththeOPERATIONALMODBofthereactorandmustbeinarangeofreactorpowerthatwillassuresuccessoftheprotectiveaction.TheonsetofoperabilityfortheHRCPtripinMODE2duringstartupisatanexcoreneutronfluxthatcorrespondstoapproximately10percentoftheincorefull-powerfissionrate.However,thethermalpowerproducedfromthisfissionrateistypicallybelowtheTHEMQPOWERdefinedbyTS1.33which,absentanexplicitmodifiertoindicateotherwise,includesdecayheat.IntheSt.LuciereactorsfollowingshutdownfromextendedpoweroperationstobelowMODE2,thethermalpowerproducedfromdecayheatistypicallyhigherthanthethermalpowerproducedonlybythefi.ssionrate.AlthoughtheexclusionofdecayheatfromtheHRCptripisimpliedbythedefinitionofOPERATIONALMODE,literalcompliancewiththeTechnicalSpecificationrequirementsfordefiningtheHRCPtripbypasssetpointasafunctionofTHERMALPOWERwasnotmet.AnalysisofSafetySignificanceTheTechnicalSpecificationinadequacydoesnotapplyduringshutdownreactoroperationsorMODB1reactoroperationabove15percentpower.Currently,bothSt.LucieunitsareoperatinginMIODE1above15percentpower,sonocurrentTechnicalSpecificationcomplianceissueexists.Duringpastreactorstartups,literalcompliancewiththeTechnicalSpecificationsfortheHRCPtripwasnotmet.However,thedesignoftheHRCPtripfunctionanditsautomaticbypassremovalfeatureareassociatedwiththereactorpowergeneratedonlybythefissionprocessandexcludesconsiderationofdecayheat.Decayheatisnotadirectlymeasureableparameter,doesnotreflectthereactivityconditionofthereactor,andisnotavariablenormallyassociatedwiththerateofchangeofreactorpower.Therefore,thehealthandsafetyofthepublicwerenotaffectedbythisevent.CorrectiveActions1.St.Luciehasdevelopedandsubmittedanamendmenttothelicensestoclarifythepowerrequirementsforthe'HRCPtrip.TheTechni.calSpecificationchangeswillneedtobeapprovedbytheNRCpriortoanysubsequentunitstartup.2.FPLreviewedtheTechnicalSpecificationsgoverningtheautomaticremovalof,andpermissivesfor,otherRPStripbypassesfortheincorrectuseofTHERMALPOWERanddecayheat.Thelicenseamendmentssubmittedinaction(1)abovealsoreplacesthetermTHERMALPOWERwiththepowermeasuredbytheappropriateneutronfluxmonitorforthetripbypassesassociatedwiththeRPSzeropowermodebypass,localpowerdensitytripbypass,andturbinetripbypass.AdditionalInformationNoneNRCFORM3BBA18-1998)