RIS 2000-21, Changes to the Unplanned Scram and Unplanned Scram with Loss of Normal Heat Removal Performance Indicators

Changes to the Unplanned Scram and Unplanned Scram with Loss of Normal Heat Removal Performance Indicators

ML003754093
Person / Time
Issue date:	09/26/2000
Revision:	0
From:	Matthews D B Division of Regulatory Improvement Programs
To:
Sanders S
References
RIS-00-021
Download: ML003754093 (10)

OMBControlNo.:3150-0195UNITEDSTATESNUCLEARREGULATORYCOMMISSIONOFFICEOFNUCLEARREACTORREGULATIONWASHINGTON,D.C.20555-0001October31,2000NRCREGULATORYISSUESUMMARY2000-21CHANGESTOTHEUNPLANNEDSCRAMANDUNPLANNEDSCRAMWITHLOSSOFNORMALHEATREMOVALPERFORMANCEINDICATORS

ADDRESSEES

Allholdersofoperatinglicensesfornuclearpowerreactors,exceptthosewhohavepermanentlyceasedoperationsandhavecertifiedthatfuelhasbeenpermanentlyremoved fromthereactorvessel.

INTENT

TheU.S.NuclearRegulatoryCommission(NRC)isissuingthisRegulatoryIssueSummary(RIS)toinformpowerreactorlicenseesthata6-monthpilottestwillbeconductedtoevaluate changestothe"unplannedscramsper7,000criticalhours"andthe"unplannedscramswith lossofnormalheatremoval"performanceindicators(PIs)thatareintendedtominimizethe potentialforunintendedconsequences.ThisRISalsoprovidesinformationontheprocessto beusedbylicenseesparticipatinginthepilottesttovoluntarilysubmitPIdatatotheNRC beginningDecember21,2000.SubmittalofPIinformationisavoluntaryactivity;therefore,this RISrequiresnoactionorwrittenresponseonthepartoftheaddressees.

BACKGROUND

INFORMATIONTheReactorOversightProcess(ROP)isbuiltuponaframeworkdirectlylinkedtotheAgency'smission.Thatframeworkincludescornerstonesofsafety.Withineachcornerstone,abroad sampleofinformationonwhichtoassesslicenseeperformanceinrisk-significantareasis gatheredfromPIdatasubmittedbylicenseesandfromtheNRC'srisk-informedbaseline inspections.ThePIsarenotintendedtoprovidecompletecoverageofeveryaspectofplant designandoperation,buttheyareintendedtobeindicativeofperformancewithinrelated cornerstones.ThedatasubmittedbyeachlicenseeisusedtocalculatethePIvalues,which arethencomparedtorisk-informed,objectivethresholds.ReportingofPIdatatotheNRCisavoluntaryprograminwhichalllicenseesparticipate.HistoricaldatanecessarytobegintheprogramwassubmittedonJanuary21,2000,usingthe guidelinesofRIS99-06,"VoluntarySubmissionofPerformanceIndicatorData,"andNEI99-02, DraftRev.D,"RegulatoryAssessmentPerformanceIndicatorGuideline."NEI99-02contains thegeneralreportingguidelinesusedbythelicenseetoreportPIdatatotheNRC.

ImplementationoftheROPbeganonApril2,2000,usingtheguidelinesofRIS00-08

"VoluntarySubmissionofPerformanceIndicatorData,"andNEI99-02,Rev0.Thefirst submissionofPIdataforalloperatingreactorplantsoccurredonApril21,2000.ML003754093 RIS2000-21Page2of4NRChasestablishedaformalprocessto(1)addressquestionsandfeedbackfrominternalandexternalstakeholders,(2)makechangestoexistingPIsandthresholdsbasedonlessons learned,and(3)developnewPIsandassociatedthresholds.Thisformalprocessisbeingused toevaluatethechangesdescribedinthisRIS,andwillbedocumentedinInspectionManual Chapter0608,"PerformanceIndicatorProgram,"whichwillbeissuedsoon.SUMMARYOFISSUESomeindustryrepresentativeshaveexpressedconcernwithincludingmanualscramsinthe"unplannedscramsper7,000criticalhours"and"unplannedscramswithlossofnormalheat removal"PIs.CommentershavestatedthatincludingmanualscramsinthePIscouldsendthe wrongmessagetolicenseemanagersandoperationspersonnel.Thiscouldpotentiallyresultin non-conservativedecisionmakingduringaplanteventforwhichamanualscrammaybe warranted.NRCisusingitsformalPIchangeprocesstoevaluatealternativePIsthattrack initiatingeventsinawaythatisintendedtominimizethepotentialforunintended consequences.Asapartofthechangeprocess,numerouspublicmeetingswereheldtodiscussandrefineindustryproposalsforthesealternativePIs.NRChasagreedtopilottestthe"unplanned reactorshutdownsper7,000criticalhours"and"unplannedreactorshutdownswithlossof normalheatremoval"PIs(seeattachedforadetaileddescription).Thefollowingplantshavevolunteeredtoparticipateinthepilottest:JamesA.FitzPatrick;Salem,Units1&2;HopeCreek;ShearonHarris;JosephM.Farley,Units1&2;Vogtle,Units 1&2;EdwinI.Hatch,Units1&2;DresdenUnits2&3;PrairieIsland,Units1&2;PaloVerde, Units1,2,&3;DiabloCanyonUnits1&2;andFortCalhoun.ThepurposeofthispilottestistocollectdatatodetermineifthealternativePIsareaseffectiveastheexistingPIsatprovidinganindicationofperformanceintheinitiatingeventscornerstone, whilereducingthepotentialforunintendedconsequences.InreachingitsdeterminationregardingtheefficacyoftheproposedPIs,theNRCwillconsiderthefollowing:1.differencesbetweendatacollectedforthe"unplannedreactorshutdownsper7000criticalhours"andthe"unplannedscramsper7000criticalhours"PIs;2.comparabilityofthedatareportedforthe"unplannedreactorshutdownswithlossofnormalheatremoval"andthe"unplannedscramswithlossofnormalheatremoval"PIs.

Additionally,theNRCwillcomparetherateofoccurrenceof"unplannedreactor shutdownswithlossofnormalheatremoval"andtheresultspresentedinNUREG/CR-

5750,"RatesofInitiatingEventsatU.S.NuclearPowerPlants:1987-1995,"Sections:

LossofFeedwaterandLossofHeatSinkEvents,toidentifydifferences; RIS2000-21Page3of43.theabilityoflicenseestoreporttherequesteddataaccuratelyandwithminimalneedforclarification;4.theabilityofeachalternatePItoreducethepotentialforunintendedconsequenceswithoutintroducingotherunintendedconsequences;5.whetherthereareminimalchangesinreportingburdenforlicensees.SincethepilotplantswillcontinuetobeassessedusingtheexistingPIsandnottheproposedalternatePIs,nothresholdswillbeappliedtothedatareportedinthispilottest.Thresholdsare expectedtobethesameasthosefortheexistingPIs,butwillbedeterminedsubsequenttothe pilot.Basedontheresultsofthispilotprogram,includingconsiderationofstakeholderfeedback,theNRCwilldecidewhethertoreplaceeachcurrentPIwiththealternatePI.VOLUNTARYACTION

Addressees

thatareparticipatinginthispilotprogramshouldconformtotheguidancecontainedinthisRISforthevoluntarysubmissionofPIdata.SendthePIdataasan attachmenttoane-mailmessageaddressedto<pidata@nrc.gov>onorbeforeDecember21,2000,toincludedataforOctoberandNovember2000,andbythe21stofthemonthfollowingtheendofeachmonththereafter.ThedatareportingphaseofthepilottestendsonApril21, 2001,withthesubmissionofdatafromtheprecedingmonth.BACKFITDISCUSSIONThisRISrequiresnoactionorwrittenresponse.AnyactiononthepartofaddresseestocollectandtransmitPIdatainaccordancewiththeguidancecontainedinthisRISisstrictlyvoluntary and,therefore,isnotabackfitunder10CFR50.109.Therefore,thestaffdidnotperforma backfitanalysis.FEDERALREGISTERNOTIFICATIONAnoticeofopportunityforpubliccommentonthisRISwasnotpublishedintheFederalRegisterbecausetheNRChasworkedcloselywithNEI,industryrepresentatives,membersofthepublic,andotherstakeholderssinceearly1998onthedevelopmentofNRC'sROP, includingthecollectionofPIdata.TheNRChassolicitedpubliccommentsonitsintentto collectPIdatainfiveFederalRegisternotices(datedJanuary22,April19,May26,July19,andAugust11,1999),twoRegulatoryIssueSummaries:RIS99-06and00-08,"Voluntary SubmissionOfPerformanceIndicatorData,"andatnumerouspublicmeetings.TheNRCwill alsoissueaFederalRegisternoticesolicitingpubliccommentontheproposedPIsthataredescribedinthisRI RIS2000-21Page4of4PAPERWORKREDUCTIONACTSTATEMENTThisRIScontainsavoluntaryinformationcollectionthatissubjecttothePaperworkReductionActof1995(44U.S.C.3501etseq.).TheNRCmaynotconductorsponsor,andapersonis notrequiredtorespondto,acollectionofinformationunlessitdisplaysacurrentlyvalidOffice ofManagementandBudget(OMB)controlnumber.Thecollectionofthisinformationis coveredbyOMBclearancenumber3150-0195whichexpiresonOctober31,2002.Pleasecontactthepersonlistedbelowwithanyquestionsaboutthismatter./RACharlesE.AderActingfor/DavidB.Matthews,DirectorDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationTechnicalContact:SeritaSanders,NRR301-415-2956 E-mail:sxs5@nrc.gov

Attachments:

1.UnplannedReactorShutdownsper7,000CriticalHours2.UnplannedReactorShutdownswithLossofNormalHeatRemoval 3.ListofRecentlyIssuedNRCRegulatoryIssueSummaries RIS2000-21Page4of4PAPERWORKREDUCTIONACTSTATEMENTThisRIScontainsavoluntaryinformationcollectionthatissubjecttothePaperworkReductionActof1995(44U.S.C.3501etseq.).TheNRCmaynotconductorsponsor,andapersonis notrequiredtorespondto,acollectionofinformationunlessitdisplaysacurrentlyvalidOffice ofManagementandBudget(OMB)controlnumber.Thecollectionofthisinformationis coveredbyOMBclearancenumber3150-0195whichexpiresonOctober31,2002.Pleasecontactthepersonlistedbelowwithanyquestionsaboutthismatter./RACharlesE.AderActingfor/DavidB.Matthews,DirectorDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationTechnicalContact:SeritaSanders,NRR301-415-2956 E-mail:sxs5@nrc.gov

Attachments:

1.UnplannedReactorShutdownsper7,000CriticalHours2.UnplannedReactorShutdownswithLossofNormalHeatRemoval 3.ListofRecentlyIssuedNRCRegulatoryIssueSummariesDistribution:PUBLIC RISFileAccessionNo.:ML003754093TemplateNo.:NRR-052Toreceiveacopyofthisdocument,indicateintheboxC=Copyw/oattachment/enclosureE=Copywithattachment/enclosureN=Nocopy*seepreviousconcurrenceOFFICEREXB:DRIPTechEditorIIPB:DIPMIIPB:DIPMNAMESSanders*JBeeson*MJohnson*WDean*

DATE9/26/009/29/0010/4/0010/5/00D:DIPMOGCREXBC:REXB:DRIPD:DRIPBBoger*JEuchner*JShapaker*LMarsh*DMatthews/CEAfor10/6/0010/23/0010/27/0010/30/0010/31/00OFFICIALRECORDCOPY Attachment1RIS2000-21 Page1of2UnplannedReactorShutdownsper7,000CriticalHoursPurposeThisindicatormonitorsthenumberofunplannedshutdownsofthereactorinresponsetooff-normalconditionsorevents.Itmeasuresthefrequencyofunplannedshutdownsper7,000 criticalhoursandprovidesanindicationofinitiatingeventfrequency.IndicatorDefinitionThenumberofunplannedshutdownsofthereactorinresponsetooff-normalconditionsoreventsduringthepreviousfourquarterswhilecriticalper7,000hours.DataReportingElementsThefollowingdataarereportedforeachreactorunit:*thenumberofunplannedshutdownsofthereactorinresponsetooff-normalconditionsoreventswhilecriticalinthepreviousquarter*thenumberofhoursofcriticaloperationinthepreviousquarterCalculationTheindicatorisdeterminedusingthevaluesforthepreviousfourquartersasfollows:(numberofunplannedreactorshutdownswhilecriticalinprevious4qtrs)value=--------------------------------------------------------------------------------------------------X7,000hrs(totalnumberofhourscriticalinprevious4qtrs)DefinitionofTermsUnplannedreactorshutdownmeanstheshutdownofthereactorinresponsetooff-normalconditionsoreventsbytheunplannedadditionofnegativereactivitybyanymeans,(e.g.,

insertionofcontrolrods,boron,oropeningreactortripbreakers).Unplannedreactor shutdownsarethosethatbringthereactorfromcriticalitytoashutdownmodewithin15 minutesofcommencingtoinsertnegativereactivity.Criticality,forthepurposesofthisindicator,typicallyexistswhenalicensedreactoroperatordeclaresthereactorcritical.Theremaybeinstancesinwhichatransientinitiatesfroma subcriticalconditionandisterminatedbyanunplannedreactorshutdownafterthereactoris critical-thisconditionwouldcountasanunplannedreactorshutdow ClarifyingNotesThevalueof7,000hoursisusedbecauseitrepresentsoneyearofreactoroperationataboutan80%availabilityfactor.2,400criticalhoursistheminimumnumberofcriticalhoursinfourconsecutivequartersforwhichanindicatorvalueiscalculated.Rateindicatorscanproducehighvaluesthatare misleadingwhenthedenominatorissmall;forcriticalhoursunder2,400,asingleshutdowncan produceavaluethatcrossesthegreen-whitethreshold.Therefore,thedisplayedvaluewillbe N/A.Alldataelementsmustneverthelessbereported.Unplannedreactorshutdownsincludethoseeventsthatarereportedunder10CFR50.72(b)(2)(iv)(B)whichrequiresreportingof"anyeventorconditionthatresultsinactuationof thereactorprotectionsystem(RPS)whenthereactoriscriticalexceptwhentheactuationresultsfromandispartofapre-plannedsequenceduringtestingorreactoroperation."Examplesofoff-normalconditionsoreventsinclude-TurbineTripLossofMainFeedwaterFlowLossofNormalHeatSink(maincondenser)MSIVClosureLossofOffsitePowerLossofElectricalLoad(includesgeneratortrip)ExcessiveFeedwater(overcoolingtransient)LossofAuxiliary/StationPowerSmallLossofCoolantAccident(includesreactor/recirculationpumpsealfailures)LossofServiceWater/ComponentCoolingWaterLossofVitalAC/DCbusSecondary/balance-of-plantPiping/ComponentRupturesReactivityControlAnomaly(e.g.,droppedormisalignedrod)OtherInitiatorsLeadingtoAutomaticActuationofReactorProtectionSystemUnplannedshutdownsmadeinresponsetoplantconditionsinaccordancewithoff-normalprocedures(e.g.,emergencyprocedures,abnormaloperatingprocedures,andalarmresponseprocedures)Reactorshutdownsthatarenotincluded:Reactorshutdownsthatareplannedtooccuraspartofatest(e.g.,areactorprotectivesystemactuationtest).Reactorshutdownsthatarepartofanormalevolutionmadeinaccordancewithnormalplantprocedures.Includedintheindicatorareunplannedreactorshutdownsthatoccurduringtheexecutionofa procedureinwhichthereisahighprobabilityofashutdownbuttheshutdownisnotintende Attachment2RIS2000-21 Page1of3UnplannedReactorShutdownswithLossofNormalHeatRemovalPurposeThisindicatormonitorsthatsubsetofunplannedreactorshutdownsinwhichanunplannedlossofthenormalheatremovalpathoccursshortlybeforeorshortlyafteranunplannedreactor shutdown.Theseshutdownsaremorerisk-significantthanuncomplicated,unplannedreactor shutdowns.IndicatorDefinitionThenumberofunplannedreactorshutdownswhilecriticalatorabovethepointofaddingheatduringtheprevious12quartersthatwerecausedbyorinvolvedanunplannedlossofthe normalheatremovalpathpriortoestablishingreactorconditionsthatallowuseoftheplant's normallongtermheatremovalsystems.DataReportingElementsThefollowingdataarereportedforeachreactorunit:*thenumberofunplannedreactorshutdownswhilecriticalatorabovethepointofaddingheatinthepreviousquarterthatwerecausedbyorinvolvedanunplannedlossofthe normalheatremovalpathpriortoestablishingreactorconditionsthatallowuseofthe plant'snormallong-termheatremovalsystems.CalculationTheindicatorisdeterminedusingthevaluesreportedfortheprevious12quartersasfollows:value=totalnumberofunplannedreactorshutdownswhilecriticalatorabovethepointofaddingheatduringtheprevious12quartersthatwerecausedbyorinvolvedan unplannedlossofthenormalheatremovalpathpriortoestablishingreactor conditionsthatallowuseoftheplant'snormallong-termheatremovalsystemsDefinitionofTermsNormalheatremovalpath:Thenormalheatremovalpath,forthepurposesofthisindicator,consistsofthepathfromthemaincondenserthroughthemainfeedwatersystemtothesteam generators(PWRs)orreactorvessel(BWRs),thenthroughthemainsteamisolationvalves, theturbinebypassvalves,andbacktothecondenser.Lossofthenormalheatremovalpath:Decayheatcannotberemovedthroughthemaincondenserwhenanyofthefollowingconditionsoccur(seeclarifyingnotesbelow):*completelossofallmainfeedwaterflow*completelossofcondenservacuum

-2-*completeclosureofatleastoneMSIVineachmainsteamline*failureofoneormoreturbinebypassvalvestomaintainreactorpressureandtemperatureatthedesiredoperatingconditionCompletelossofcondenservacuum:Alossofcondenservacuumthatpreventsthecondenserfromremovingdecayheatafteranunplannedreactorshutdown.Unplannedreactorshutdown:Theshutdownofthereactorinresponsetooff-normalconditionsoreventsbytheunplannedadditionofnegativereactivitybyanymeans(e.g.,insertionof controlrods,boron,oropeningreactortripbreakers).Unplannedreactorshutdownsarethose thatbringthereactorfromcriticalitytoashutdownmodewithin15minutesofcommencingto insertnegativereactivity.Criticality:Forthepurposesofthisindicator,criticalitytypicallyexistswhenalicensedreactoroperatordeclaresthereactorcritical.ClarifyingNotesUnplannedreactorshutdownswithlossofnormalheatremovalcanoccurintwoways:(1)Thelossofthenormalheatremovalpathcausestheunplannedshutdownor(2)thelossofthe normalheatremovalpathoccursaftertheunplannedshutdown.Ineithercase,thenormal heatremovalpathisconsideredunavailable.Thedeterminingfactorforthisindicatoris whetherornotthenormalheatremovalpathisavailable,notwhethertheoperatorschoosetousethatpathorsomeotherpath.Operatoractionsordesignfeaturestocontrolthereactorcooldownrateorwaterlevel,suchasclosingthemainfeedwatervalvesorclosingallMSIVs(aslongasthefeedwatervalvesor MSIVsarecapableofbeingreopenedbyoperatordemand)arenotincluded.However, operatoractionstomitigatetheevent(e.g.,closingMSIVstoisolateasteamleak)areincluded.Examplesofacompletelossofallmainfeedwaterflow:Tripoftheonlyoperatingfeedwaterpumpwhileoperatingatreducedpower;lossofastartuporanauxiliaryfeedwaterpump normallyusedduringplantstartup;lossofalloperatingfeedpumpsbecauseoftripscausedby lowsuctionpressure,lossofsealwater,orhighwaterlevel(BWRreactorlevelorPWRsteam generatorlevel);unplannedreactorshutdowncausedbythelossofalloperatingfeedpumps; unplannedreactorshutdowninresponsetofeedproblemscharacteristicofatotallossof feedwaterflow;andinadvertentisolationorclosureofallfeedwatercontrolvalvespriortoan unplannedreactorshutdown.Examplesoflossofcondenservacuum:tripofallcirculatingwaterpumps;travelingscreenblockage;condenserleakage;tripofallcondensatepumpsonhighcondensatetemperature causedbythelossofcondenservacuum.ExamplesofcompleteclosureofatleastoneMSIVineachmainsteamline:automaticclosureofallMSIVsaspartofanengineeredsafetyfeatureactuation;spuriousclosureofallMSIVs.-3- Exampleoflossofturbinebypasscapability:sustaineduseofoneormoreatmosphericdumpvalves(PWRs)orsafetyreliefvalvestothesuppressionpool(BWRs)afteranunplanned reactorshutdown.Examplesthatdonotcount:lossofallmainfeedwaterflow,condenservacuum,orturbinebypasscapabilitycausedbylossofoffsitepower;partiallossesofcondenservacuumorturbine bypasscapabilityafteranunplannedreactorshutdowninwhichsufficientcapabilityremainsto removedecayheat;momentaryoperationofPORVsorsafetyreliefvalves;andanunplanned shutdownatlowpowerwithinthecapabilityofthePORVsifthemaincondenserhasnotyet beenplacedinserviceorhasbeenremovedfromservic ______________________________________________________________________________________OL=OperatingLicense CP=ConstructionPermitAttachment3RIS2000-21 Page1of1LISTOFRECENTLYISSUEDNRCREGULATORYISSUESUMMARIES_____________________________________________________________________________________RegulatoryIssueDateofSummaryNo.SubjectIssuanceIssuedto_____________________________________________________________________________________2000-20AdvanceNoticeof

Intent

toPursueLicenseRenewal10//00Date pendingAllholdersofOLsfornuclearpowerreactors,exceptthose licenseeswhohavepermanently ceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel2000-19PartialReleaseofReactorSiteforUnrestrictedUseBeforeNRC ApprovaloftheLicense TerminationPlan10/24/00AllholdersofOLsfornuclearpowerreactors,includingthose licenseeswhohavepermanently ceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel2000-18GuidanceonManagingQualityAssuranceRecordsinElectronic Media10/23/00AllholdersofOLsfornuclearpowerplants,includinglicensees thathavepermanentlyceased operationsandhavecertifiedthat fuelhasbeenpermanently removedfromthereactorvessel.

Inaddition,thosematerials licensees,includingcertificate holdersandvendors,thatare requiredtohaveanNRC approvedqualityassurance program.2000-17ManagingRegulatoryCommitmentsMadebyPower ReactorLicenseestotheNRC Staff09/21/2000AllholdersofOLsfornuclearpowerreactors