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

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Changes to the Unplanned Scram and Unplanned Scram with Loss of Normal Heat Removal Performance Indicators
ML003754093
Person / Time
Issue date: 09/26/2000
From: Matthews D
Division of Regulatory Improvement Programs
To:
Sanders S
References
RIS-00-021
Download: ML003754093 (10)
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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,andbythe21 stofthemonthfollowingtheendofeachmonththereafter.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 alsoissueaFederalRegisternoticesolicitingpubliccommentontheproposedPIsthataredescribedinthisRIS.

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 Page1of2UnplannedReactorShutdownsper7,000CriticalHours PurposeThisindicatormonitorsthenumberofunplannedshutdownsofthereactorinresponsetooff-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-thisconditionwouldcountasanunplannedreactorshutdown.

-2-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 procedureinwhichthereisahighprobabilityofashutdownbuttheshutdownisnotintended.

Attachment2RIS2000-21 Page1of3UnplannedReactorShutdownswithLossofNormalHeatRemoval PurposeThisindicatormonitorsthatsubsetofunplannedreactorshutdownsinwhichanunplannedlossofthenormalheatremovalpathoccursshortlybeforeorshortlyafteranunplannedreactor 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 whetherornotthenormalheatremovalpathis available,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 beenplacedinserviceorhasbeenremovedfromservice.

______________________________________________________________________________________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


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