RG1.174 在电站对取照基准的特定变更的风险预知决策中使用概率风险评价的一个方法 2002

1Thesearemodificationstoaplant'sdesign,operation,orotheractivitiesthatrequireNRCapproval.Thesemodificationscouldincludeitemssuchasexemptionrequestsunder10CFR50.11andlicenseamendmentsunder10CFR50.90.RegulatoryguidesareissuedtodescribeandmakeavailabletothepublicsuchinformationasmethodsacceptabletotheNRCstaffforimplementingspecificpartsoftheNRC’sregulations,techniquesusedbythestaffinevaluatingspecificproblemsorpostulatedaccidents,anddataneededbytheNRCstaffinitsreviewofapplicationsforpermitsandlicenses.Regulatoryguidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired.MethodsandsolutionsdifferentfromthosesetoutintheguideswillbeacceptableiftheyprovideabasisforthefindingsrequisitetotheissuanceorcontinuanceofapermitorlicensebytheCommission.Thisguidewasissuedafterconsiderationofcommentsreceivedfromthepublic.Commentsandsuggestionsforimprovementsintheseguidesareencouragedatalltimes,andguideswillberevised,asappropriate,toaccommodatecommentsandtoreflectnewinformationorexperience.WrittencommentsmaybesubmittedtotheRulesandDirectivesBranch,ADM,U.S.NuclearRegulatoryCommission,Washington,DC20555-0001.Regulatoryguidesareissuedintenbroaddivisions:1,PowerReactors;2,ResearchandTestReactors;3,FuelsandMaterialsFacilities;4,EnvironmentalandSiting;5,MaterialsandPlantProtection;6,Products;7,Transportation;8,OccupationalHealth;9,AntitrustandFinancialReview;and10,General.Singlecopiesofregulatoryguides(whichmaybereproduced)maybeobtainedfreeofchargebywritingtheDistributionServicesSection,U.S.NuclearRegulatoryCommission,Washington,DC20555-0001,orbyfaxto(301)415-2289,[e-mail]ideandotherrecentlyissuedguidesareavailableatNRC’shomepageat(DraftwasissuedasDG-1110)ANAPPROACHFORUSINGPROBABILISTICRISKASSESSMENTINRISK-INFORMEDDECISIONSONPLANT-SPECIFICCHANGESTOTHELICENSINGBASIS1.PURPOSEANDSCOPE1.1INTRODUCTIONTheNRC'spolicystatementonprobabilisticriskassessment(PRA)(Ref.1)encouragesgreateruseofthisanalysistechniquetoimprovesafetydecisionmakingandimproveregulatoryefficiency.TheNRCstaff'sRisk-InformedRegulationImplementationPlan(Ref.2)describesactivitiesnowunderwayorplannedtoexpandthisuse.Theseactivitiesinclude,forexample,providingguidanceforNRCinspectorsonfocusinginspectionresourcesonrisk-importantequipment.AnotheractivityunderwayinresponsetothepolicystatementisusingPRAtosupportdecisionstomodifyanindividualplant'slicensingbasis(LB).1ThisregulatoryguideprovidesguidanceontheuseofPRAfindingsandriskinsightsinsupportoflicenseerequestsforchangestoaplant'sLB,asinrequestsforlicenseamendmentsandtechnicalspecificationchangesunderSections50.90-92of10CFRPart50,DomesticLicensingofProductionandUtilizationFacilities.Itdoesnotaddresslicensee-initiatedchangestotheLBthatdoNOTrequireNRCreviewandapproval(e.g.,changestothefacilityasdescribedinthefinalsafetyanalysisreport(FSAR),thesubjectof10CFR50.59).Licensee-initiatedLBchangesthatareconsistentwithcurrentlyapprovedstaffpositions(e.g.,regulatoryguides,standardreviewplans,branchtechnicalpositions,ortheStandard1.174-2TechnicalSpecifications)arenormallyevaluatedbythestaffusingtraditionalengineeringanalyses.Alicenseegenerallywouldnotbeexpectedtosubmitriskinformationinsupportoftheproposedchange.Licensee-initiatedLBchangerequeststhatgobeyondcurrentstaffpositionsmaybeevaluatedbythestaffusingtraditionalengineeringanalysesaswellastherisk-informedapproachsetforthinthisregulatoryguide.Alicenseemayberequestedtosubmitsupplementalriskinformationifsuchinformationisnotsubmittedbythelicensee.IfriskinformationontheproposedLBchangeisnotprovidedtothestaff,thestaffwillreviewtheinformationprovidedbythelicenseetodeterminewhethertheapplicationcanbeapproved.Basedontheinformationprovided,usingtraditionalmethods,theNRCstaffwilleitherapproveorrejecttheapplication.However,licenseesshouldbeawarethatspecialcircumstancesmayariseinwhichnewinformationrevealsanunforeseenhazardorasubstantiallygreaterpotentialforaknownhazardtooccur,suchastheidentificationofanissuerelatedtotherequestedLBchangethatmaysubstantiallyincreaserisk.Insuchcircumstances,theNRChasthestatutoryauthoritytorequirelicenseeactionaboveandbeyondexistingregulationsandmayrequestananalysisofthechangeinriskrelatedtotherequestedLBchangetodemonstratethatthelevelofprotectionnecessarytoavoidunduerisktopublichealthandsafety(i.e.,adequateprotection)wouldbemaintaineduponapprovaloftherequestedLBchange.ThisregulatoryguidedescribesanacceptablemethodforthelicenseeandNRCstafftouseinassessingthenatureandimpactofLBchangeswhenthelicenseechoosestosupportorisrequestedbythestafftosupportthechangeswithriskinformation.TheNRCstaffwouldreviewtheseLBchangesbyconsideringengineeringissuesandapplyingriskinsights.Licenseeswhosubmitriskinformation(whetherontheirowninitiativeorattherequestofthestaff)shouldaddresseachoftheprinciplesofrisk-informedregulationdiscussedinthisregu