Press Release-96-085, the Nuclear Regulatory Commission Has Received the Attached Report from Its Advisory Committee on Reactor Safeguards

Press Release-96-085, the Nuclear Regulatory Commission Has Received the Attached Report from Its Advisory Committee on Reactor Safeguards

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UnitedStatesNuclearRegulatoryCommissionOfficeofPublicAffairsWashington,DC20555Phone301-415-8200Fax301-415-2234 Internet:opa@nrc.govNo.96-85FORIMMEDIATERELEASE(Monday,June17,1996)NOTETOEDITORS:TheNuclearRegulatoryCommissionhasreceivedtheattachedreportfromitsAdvisoryCommitteeonReactorSafeguards(ACRS).

Thereport,intheformofaletter,providescommentsonthe potentialuseofindividualplantexaminationsforexternal eventsindeterminingwherethecurrentnumberofnuclearplants inoperationfallinrelationtoradiologicalriskandtheNRC's safetygoals.Inaddition,theNRC'sexecutivedirectorforoperationsreceivedfourACRSreports.Theyprovidecommentson:--Aproposedruleonoperationsatnuclearpowerplantsduringshutdowns;--Regulatoryguidancedocumentsrelatedtodigitalinstrumentationandcontrolsystems;--TheadequacyoftheNRC'smultiplesystemresponsesprograminresolvingsafetyissues;and--ImplementationofNRC'sregulatoryreviewgroup recommendations.

1. Attachments:Asstated June6,1996TheHonorableShirleyAnnJackson Chairman U.S.NuclearRegulatoryCommission Washington,D.C.20555-0001

SUBJECT:

POTENTIALUSEOFIPE/IPEEERESULTSTOCOMPARETHERISKOFTHECURRENTPOPULATIONOFPLANTSWITHTHESAFETY

GOALSThisreportisinresponsetoaStaffRequirementsMemorandumdatedSeptember20,1994,inwhichtheCommissionrequested furtherguidanceandinsightondeterminingwherethecurrent populationofoperatingplants,bothindividuallyand collectively,fallinrelationtothesafetygoals.Ourintent indevelopingaresponsewastoexaminetheIndividualPlant Examinations(IPEs)/IndividualPlantExaminationsofExternal Events(IPEEEs)resultstoseeiftheycanbeextendedsoasto comparetheriskofthecurrentpopulationofplantswiththe safetygoals.Duringthe431stmeetingoftheAdvisoryCommitteeonReactorSafeguards,May23-25,1996,wecompletedourdiscussionsonthis subject.Duringthe418th,February1995,and419th,March1995 meetings,weheardpresentationsbyanACRSSeniorFellowonan approachforestimatingtheriskassociatedwithsomeofthe missingorincompleteelementsoftheIPEs.Duringour431st meeting,wereviewedastudybytheBrookhavenNational Laboratory(BNL)(performedaspartoftheIPEInsightsProgram) thatinvestigatedtheuseofsomeoftheIPEstocomparethe plantrisktothesafetygoals.Wealsohadthebenefitofthe documentsreferenced.Thepromptfatalityandlatenthealtheffectsquantitativesafetygoalsareposedinriskterms.Consequently,toestablishthe statusofthepopulationofplantswithrespecttothesegoals,a full-scopeLevel3probabilisticriskassessment(PRA)of acceptablequalityforeveryplantwouldseemtoberequired.

SuchPRAswouldneedtoincludeallinternalandexternalevents (includinglow-powerandshutdownoperations)andwouldalsoneed totakeintoconsiderationtheindividualsitecharacteristics.Inalmostallcases,theIPEsandIPEEEsarenotandwerenotintendedtobefull-scopePRAs.Forexample,alargenumberof IPEEEsusedtheFireInducedVulnerabilityEvaluation(FIVE)

MethodologytosearchforpotentialfirevulnerabilitiesandtheSeismicMarginsMethodologytosearchforseismic vulnerabilities,neitherofwhichgivesadirectexpressionof risk.Furthermore,shutdownriskwasnotapartofthe IPEs/IPEEEs.WhilemostlicenseesperformedsometypeofLevel2 containmentanalysis,thevastmajoritydidnotperformaLevel3 offsiteconsequencesanalysis.TheBNLstudyrepresentsagoodattempttoestimatetheeffectsofsomeofthemissingelementsintheIPEs/IPEEEs.Thisstudy didnotattempttoevaluatetheriskresultingfromseismicand fireevents,nordiditattempttoevaluateriskintheshutdown

mode.Informationisavailablethatarguablywouldmakeitpossibletoboundtheeffectsonriskofelementsmissingfromthe IPEs/IPEEEsandtodevelopanapproximatecomparisonwiththe safetygoals.Suchaboundwouldbeofquestionablevalueand wouldhaveverylargeuncertainties.Wedonotrecommendthat thisbedone.TheevidencefromtheBNLstudy,NUREG-1150,otherPRAs,andscopingstudiesofshutdownriskindicatesthat,onaverage,the populationofplantsmeetsthesafetygoals.Adefinitive determinationofthis,however,willonlybepossiblewhen acceptable,full-scopeLevel3PRAsareavailableforallthe plants.Webelievethattherequiredefforttodevelopsuch comprehensivePRAscannotbejustifiedforthesolepurposeof comparisonwiththesafetygoals.SuchPRAs,however,willbe neededinthelongruntomovetowardacoherentrisk-informed regulatorysystem.

Sincerely,/S/T.S.KressChairman,ACRS REFERENCES

1.MemorandumdatedSeptember20,1994,fromJohnC.Hoyle,ActingSecretary,NRC,toJohnT.Larkins,Executive Director,ACRS,

Subject:

StaffRequirements-Periodic MeetingwithACRS,Thursday,September8,19942.RichardSherry,ACRSSeniorFellow,"ASimplifiedApproachtoEstimationofSeismicCoreDamageFrequenciesfroma SeismicMarginsMethodsAnalysis"3.U.S.NuclearRegulatoryCommission,NUREG-1150,"SevereAccidentRisks:AnAssessmentforFiveU.S.NuclearPower Plants,"OfficeofNuclearRegulatoryResearch,December

1990 4.U.S.NuclearRegulatoryCommission,NUREG-XXXX,"IndividualPlantExaminationProgram:PerspectivesonReactorSafety andPlantPerformance,"DraftforCommentdatedApril19965.U.S.NuclearRegulatoryCommission,NUREG/CR-6144,"EvaluationofPotentialSevereAccidentsDuringLowPower andShutdownOperationsatSurry,Unit1,"Brookhaven NationalLaboratory,July19946.U.S.NuclearRegulatoryCommission,NUREG/CR-6143,"EvaluationofPotentialSevereAccidentsDuringLowPower andShutdownOperationsatGrandGulf,Unit1,"Sandia NationalLaboratories,March1995 June14,1996Mr.JamesM.TaylorExecutiveDirectorforOperations U.S.NuclearRegulatoryCommission Washington,D.C.20555-0001

SUBJECT:

PROPOSEDRULEONSHUTDOWNOPERATIONS Duringthe431stmeetingoftheAdvisoryCommitteeonReactorSafeguards,May23-25,1996,wehelddiscussionswith representativesoftheNRCstaffandtheNuclearEnergyInstitute (NEI),concerningthesubjectproposedruleandtheprobabilistic riskassessment(PRA)studiesthatwereperformedfortheSurry andtheGrandGulfNuclearPowerplants.OurSubcommitteeon PlantOperationsmetwiththestaff,NEI,andautility representativeonMay21,1996,todiscussthesematters.We alsohadthebenefitofthedocumentsreferenced.Wepreviously commentedonthestaffefforttoresolvetheshutdownoperations issueinourlettersdatedAugust13,1991,April9,1992, September15,1992,andMay13,1994.Accordingtothestaff,theproposedrulewillcontainperformance-basedelements.Sincethesupportingregulatory analysisandregulatoryguidearestillbeingdeveloped,we discussedonlytheproposedruleduringourmeeting.Thestaff hasheldseveralpublicmeetingswithNEItoobtainindustry inputontheformulationofthisrule.Wemadeanumberofcommentsontheriskbasisfortherule.Thestaffagreedtoconsiderourcommentsasitfinalizesthedraft rule,whichitplanstopublishforpubliccommentinSeptember 1996.Weplantoprovidecommentsontheproposedfinalrule afterthestaffhasreconciledthepubliccomments.Theconcernforriskassociatedwithshutdownoperationshasarisenfromincidentsthathaveoccurred.Ourquantitative understandingoftheriskposedbyplantsinlow-poweror shutdownmodesofoperationislimited.Riskassessmentsfor shutdownoperationswereperformedforSurry(athree-loopPWR withloopisolationvalvesandasub-atmosphericpressure containment)andGrandGulf(aBWR-6withaMarkIII containment).Neitheroftheseplantsisaparticularlygood surrogatefortheentirepopulationofPWRsandBWRs.

Thestudiesofshutdownriskconsistedoftwophases.Thefirstphasewasadeliberatelyconservativescopinganalysis.The secondphasefocusedonasingle,high-riskplantoperational stateamongthemanythatexistduringshutdownoperation.Such anapproachcouldleadtoanincorrectassessmentofrisk(a historicalanalogueistheselectionofthelarge-break,loss-of-coolantaccidentasaboundingevent)ortotheadoptionof operatingpracticesthatmightincreaserisk.Theavailableevidencedoessuggestthatshutdownoperationscanmakeimportantcontributionstotheoverallrisktothepublic posedbynuclearpowerplants.Ontheeveofourentryintoan eraofrisk-informedrulemaking,therearenocomplete,reliable assessmentsofriskduringshutdownoperationsevenforafew representativeplants.Certainly,thereisnothingcommensurate withtheNUREG-1150studyofriskduringfull-poweroperation.Thestaffefforttowardaninterimsolutionbypromulgatingthisproposedruleisbasedonengineeringjudgmentandwillprobably lessenrisk.Arisk-informedunderstandingwillrequirea quantitativeevaluationofriskduringlow-powerandshutdown operations.Wethereforerecommendthatpriorityattentionbe giventoperformingLevel3PRAsforshutdownoperationsatthe NUREG-1150plantswithconsiderationofspentfuelpoolriskand uncertaintyassessments.

Sincerely,/s/T.S.KressChairman,ACRS References

1.MemorandumdatedApril5,1996,fromRobertC.Jones,OfficeofNuclearReactorRegulation,toJohnT.Larkins,ACRS,

Subject:

Developmentof§50.67,"ShutdownOperationof NuclearPowerPlants"2.U.S.NuclearRegulatoryCommission,PreparedbyBrookhavenNationalLaboratory,NUREG/CR-6144,"EvaluationofPotential SevereAccidentsDuringLowPowerandShutdownOperationsat Surry,Unit1,"SummaryofResults,October19953.U.S.NuclearRegulatoryCommission,PreparedbySandiaNationalLaboratories,NUREG/CR-6143,"Evaluationof PotentialSevereAccidentsDuringLowPowerandShutdown OperationsatGrandGulf,Unit1,"SummaryofResults,July

19954.NuclearManagementandResourcesCouncil,Inc.,NUMARC91-06,"GuidelinesforIndustryActionstoAssessShutdown Management,"December1991 June6,1996Mr.JamesM.TaylorExecutiveDirectorforOperations U.S.NuclearRegulatoryCommission Washington,D.C.20555-0001

SUBJECT:

REGULATORYGUIDANCEDOCUMENTSRELATEDTODIGITALINSTRUMENTATIONANDCONTROLSYSTEMSDuringthe429thand431stmeetingsoftheAdvisoryCommitteeonReactorSafeguards,March7-9andMay23-25,1996,wereviewed portionsoftheproposedStandardReviewPlan(SRP),Branch TechnicalPositions(BTPs),andRegulatoryGuidesrelatedto digitalinstrumentationandcontrol(I&C)systems.Weheld discussionswithrepresentativesoftheNRCstaffandits contractor,theLawrenceLivermoreNationalLaboratory(LLNL).

Inaddition,ourSubcommitteeonI&CSystemsandComputersmet withtheNRCstaffandLLNLtodiscussthesedocumentsonMarch6 andMay22,1996.Wealsohadthebenefitofthedocuments

referenced.ThestaffrequestedACRStoreviewtheSRPChapter7updateintheearlystagesofdevelopmenttoaccommodatethescheduleset forthintheDigitalI&CTaskActionPlan.Thestaffexpectsto completedevelopmentoftheSRPChapter7updateandassociated guidanceinSeptember1996,integratetherecommendationsfrom theNationalAcademyofSciences/NationalResearchCouncil (NAS/NRC)Phase2studyreportinOctober1996,publishtheDraft SRPChapter7andassociatedguidanceforpubliccommentin December1996,andissuethefinalSRPandrelatedguidancein May1997.ThestaffisrevisingtheSRP,addingtwonewsections,developingnewBTPs,andpreparingsixregulatoryguidesthat endorseeightindustrystandards.Thestaffpresentedasafety evaluationreport(SER)onanElectricPowerResearchInstitute (EPRI)topicalreportforelectromagnetic/radiofrequency interference(EMI/RFI)designrequirementsandtesting.A plannedBTPoncommercialoff-the-shelf(COTS)softwaremaybe replacedbyanSERonatopicalreportbeingdevelopedbyanEPRI workinggroup.WeconcurwiththestaffconclusionsintheSER associatedwiththeEPRItopicalreportonEMI/RFIandencourage thestafftocompleteanSERfortheEPRItopicalreportonCOTS.ConsideringthefactthatthestaffisusinggenerallyacceptedU.S.softwareengineeringpractices,itappearsthatthestaff approachisappropriatetoupdatetheSRPandassociatedguidancetocodifythecurrentregulatoryframeworkfordigitalI&C.We raisedseveralissues(e.g.,thelinkagebetweenSRPChapter7 andotherSRPchapters,andgradedapproachesbasedonimportance tosafety)thatweresubsequentlyclarifiedbythestaff.The staffagreedtodocumenttheseclarifications.Wehaveraisedotherissuesthatincludethelevelofdetailprovidedintheregulatoryguidesandthebalanceintheguidance betweenthereviewofthedesignprocessandtheassessmentof theproduct.WeplantoreportontheseandotherdigitalI&C issuesatalaterdate.Weplantoreviewthestaff'sremainingSRPsections,theBTPs,andtheSERontheEPRItopicalreportonCOTSwhentheybecome

available.

Sincerely,/S/T.S.KressChairman,ACRS References

1.U.S.NuclearRegulatoryCommission,StandardReviewPlan,Section7.0,"InstrumentationandControlsOverviewofReviewProcess,"DraftVersion3.0,February12,19962.U.S.NuclearRegulatoryCommission,StandardReviewPlan,Section7.1,"InstrumentationandControlsIntroduction,"DraftVersion7.0,February14,19963.U.S.NuclearRegulatoryCommission,StandardReviewPlan,Section7.2,"ReactorTripSystem,"DraftVersion6.0,April 17,19964.U.S.NuclearRegulatoryCommission,StandardReviewPlan,Section7.9,"DataCommunications,"DraftVersion4.1,April 18,19965.U.S.NuclearRegulatoryCommission,(Proposed)BranchTechnicalPositionHICB-14:"GuidanceonSoftwareReviews forDigitalComputer-BasedInstrumentationandControl SafetySystems,"Version9.0,February14,19966.U.S.NuclearRegulatoryCommission,(Proposed)BranchTechnicalPositionHICB-16:"GuidanceontheLevelofDetail RequiredforDesignCertificationApplicationsUnder10CFR Part52,"Version7.0,April12,1996 7.U.S.NuclearRegulatoryCommission,DraftRegulatoryGuides,transmittedbymemorandumdatedFebruary9,1996, fromM.WayneHodges,Director,OfficeofNuclearRegulatory Research,NRC,toJohnT.Larkins,ACRS:

ÿU.S.NuclearRegulatoryCommission,DraftRegulatoryGuideDG-XXXX,Version2.7.2,"Verification, Validation,Reviews,andAuditsforDigitalComputer SoftwareUsedinSafetySystemsofNuclearPower

Plants"ÿU.S.NuclearRegulatoryCommission,DraftRegulatoryGuideDG-XXXX,Version2.0.7,"ConfigurationManagement PlansforDigitalComputerSoftwareUsedinSafety SystemsofNuclearPowerPlants"8.U.S.NuclearRegulatoryCommission,DraftRegulatoryGuides,transmittedbymemorandumdatedApril26,1996,from M.WayneHodges,Director,OfficeofNuclearRegulatory Research,NRC,toJohnT.Larkins,ACRS:

ÿDraftRegulatoryGuideDG-XXXX,Version2.0,"SoftwareUnitTestingforDigitalComputerSoftwareUsedin SafetySystemsofNuclearPowerPlants"ÿDraftRegulatoryGuideDG-XXXX,Version2.0,"DevelopingSoftwareLifeCycleProcessesforDigital ComputerSoftwareUsedinSafetySystemsofNuclear PowerPlants"ÿDraftRegulatoryGuideDG-XXXX,Version2.0,"SoftwareRequirementsSpecificationsforDigitalComputer SoftwareUsedinSafetySystemsofNuclearPower

Plants"ÿDraftRegulatoryGuideDG-XXXX,Version2.0,"SoftwareTestDocumentationforDigitalComputerSoftwareUsed inSafetySystemsofNuclearPowerPlants"9.MemorandumdatedJanuary30,1996,fromF.Miraglia,OfficeofNuclearReactorRegulation,NRC,toE.Jordan,Committee toReviewGenericRequirements,NRC,

Subject:

Requestfor EndorsementoftheSafetyEvaluationReportonElectric PowerResearchInstituteTopicalReport,TR-102323, "GuidelinesforElectromagneticInterferenceTestingin PowerPlants" June3,1996Mr.JamesM.TaylorExecutiveDirectorforOperations U.S.NuclearRegulatoryCommission Washington,D.C.20555-0001

SUBJECT:

RESOLUTIONOFTHEMULTIPLESYSTEMRESPONSESPROGRAMISSUESDuringthe431stmeetingoftheAdvisoryCommitteeonReactorSafeguards,May23-25,1996,wecompletedourreviewofthe adequacyoftheresolutionoftheMultipleSystemResponses Program(MSRP)issues.Duringthe427thmeeting,December7-8, 1995,weheardpresentationsbyandhelddiscussionswith representativesoftheNRCstaffandanACRSSeniorFellow regardingthismatter.Wealsohadthebenefitofthedocuments

referenced.IntheprocessofreviewinganumberofUnresolvedSafetyIssues(USIs)duringthemid-1980s,theACRSexpressedconcernthat treatingeachsafetyissueinisolationmightnotidentify significantsysteminteractions.TheACRSalsoraisedanumber ofquestionsconcerningsysteminteractionsthatwerenot addressedintheproposedresolutionofcertainUSIs.

Subsequently,thestaffestablishedtheMSRPin1986toaddress ACRSconcernsandotherrelatedissues.TheMSRPidentified21potentialgenericissues.InAugust1995,theNRCstaffissuedafinalreportwhichconcludedthatnoneof theMSRPissuesposedneworseparatesafetyconcernsandthat theseissueswerebeingaddressedunderthescopeoftheexisting GenericSafetyIssue(GSI)process,orintheprogramsof IndividualPlantExaminations(IPEs)andIndividualPlant ExaminationofExternalEvents(IPEEEs).TheMSRPissueshavebeentreatedtoadegreeintheIPE/IPEEEprogramsandintheGSIprocess.Areviewofanumberof IPE/IPEEEsubmittals,however,failedtoidentifysatisfactory resolutionforsomeissues(e.g.,thetreatmentofinteractions betweennonsafetyandsafetysystems,seismicallyinduced interactions,andhydrogenlineruptures).Wealsonotethatthe issuesofnonsafety/safetysystemsinteractionsappeartobe bettertreatedintheIPEEEsubmittalsthatwerebasedon probabilisticriskassessmentsthaninthosethatwerebasedon SeismicMarginsMethodologyandFire-InducedVulnerability EvaluationMethodology.

IncorporationofsomeMSRPissuesintotheIPE/IPEEEprocessmayhavebeenexpedient,butthestafffailedtoputintoplacea mechanismtoensurethatlicenseeshadevaluatedandresolved theseissuesinanadequatemanner.Additionalstaffreviewto determinetheadequacyoftheresolutionoftheseissuesis, therefore,warranted.AsstatedinourreporttotheCommission,datedAugust16,1988,wecontinuetoemphasizethat"systemsinteractions,someof whichmaybeadversetosafety,willcontinuetoberevealedby operatingexperienceinexistingplants.Theseshouldbe evaluatedbythestaffastheyoccur,andthelessonslearned incorporatedintotherequirementsandpracticesoftheagency." Sincerely,/s/T.S.KressChairman,ACRS References

1.U.S.NuclearRegulatoryCommission,NUREG/CR-5420,"MultipleSystemResponsesProgramIdentificationofConcernsRelatedtoaNumberofSpecificRegulatoryIssues,"

PreparedbyOakRidgeNationalLaboratory,October19892.MultipleSystemResponsesProgramFinalReport,transmittedbymemorandumdatedAugust2,1995fromL.C.

Shao,OfficeofNuclearRegulatoryResearch,toDavidL.

Morrison,OfficeofNuclearRegulatoryResearch3.MemorandumdatedJanuary12,1996,fromAugustW.Cronenberg,ACRSSeniorFellow,toACRSMembersandStaff,

Subject:

ObservationsfromReviewofMultipleSystem ResponsesProgram(MSRP)ReportsandMemoranda4.U.S.NuclearRegulatoryCommission,NUREG-0933,"APrioritizationofGenericSafetyIssues,"July19915.ReportdatedAugust16,1988,fromW.Kerr,ACRSChairman,toLandoW.Zech,Jr.,NRCChairman,

Subject:

Proposed ResolutionofUSIA-17,"SystemsInteractionsinNuclear PowerPlants" June5,1996Mr.JamesM.TaylorExecutiveDirectorforOperations U.S.NuclearRegulatoryCommission Washington,D.C.20555-0001

SUBJECT:

IMPLEMENTATIONOFTHEREGULATORYREVIEWGROUP RECOMMENDATIONSDuringthe431stmeetingoftheAdvisoryCommitteeonReactorSafeguards,May23-25,1996,wereviewedthestatusofthe implementationoftheRegulatoryReviewGrouprecommendations.

Duringourreview,wehadthebenefitofdiscussionswithrepre-sentativesoftheNRCstaffandthereferenceddocument.TheRegulatoryReviewGroupwasestablishedbyyouonJanuary4,1993,toconductacomprehensiveanddisciplinedreviewofpower reactorregulationsandrelatedNRCprocedures,programs,and practices.InAugust1993,theRegulatoryReviewGroupissued itsfinalreportcontainingrecommendationstoreducetheregula-toryburdenonlicenseesandtostrengthenNRCadministrative practices.Thestaffsubmitteditsplanforimplementingthese recommendationsinJanuary1994andissuedsubsequentsemiannual statusreports.WebelievethattheeffortbytheRegulatoryReviewGrouphasbeensuccessful.TheRegulatoryReviewGrouprecommendations havebeenimplementedorassignedtoappropriateNRCofficesfor implementation.Wewouldliketocomplimentthestaffonits

success.Sincerely,/s/T.S.KressChairman,ACRS

Reference:

SECY-96-024,datedFebruary2,1996,fromJamesM.Taylor, ExecutiveDirectorforOperations,NRC,fortheCommissioners,

Subject:

SemiannualStatusReportontheImplementationof RegulatoryReviewGroupRecommendations