RG1.117 龙卷风设计分级 1978

U.S.NUCLEARREGULATORYCOMMISSIONREGULATORYGUIDEOFFICEOFSTANDARDSDEVELOPMENTREGULATORYGUIDE1.117TORNADODESIGNCLASSIFICATIONA.INTRODUCTIONGeneralDesignCriterion2,DesignBasesforProtectionAgainstNaturalPhenomena,ofAppendixA,GeneralDesignCriteriaforNuclearPowerPlants,to10CFRPart50,LicensingofProductionandUtilizationFacilities,requires,inpart,thatstructures,systems,andcomponentsimportanttosafetybedesignedtowithstandtheeffectsofnaturalphenomenasuchastornadoeswithoutlossofcapabilitytoperformtheirsafetyfunctions.Criterion2alsorequiresthatthedesignbasesforthesestructures,systems,andcomponentsreflect(1)appropriatecombinationsoftheeffectsofnormalandaccidentconditionswiththeeffectsofnaturalphenomenaand(2)theimportanceofthe.safetyfunctionstobeperformed.ThisguidedescribesamethodacceptabletotheNRCstaffforidentifyingthosestructures,systems,andcomponentsoflight-water-cooledreactorsthatshouldbeprotectedfromtheeffectsoftheDesignBasisTornado(seeRegulatoryGuide1.76,DesignBasisTornadoforNuclearPowerPlants),includingtornadomissiles,andremainfunctional.TheAdvisoryCommitteeonReactorSafeguardshasbeenconsultedconcerningthisguideandhasconcurredintheregulatoryposition.B.DISCUSSIONNuclearpowerplantsshouldbeprotectedfromtheeffectsoftornadostrikes.Thelikelihoodofacredibletornadostrikevariesfromabout10'-peryeartovaluesseveralordersofmagnitudehigher.Physicaldesignparametersoftornadoprotectionprovisionsaresuchthatdesignatedstructures,systems,andcomponentswillbeabletomaintaintheirnecessarycapabilitiesintheeventofaDesignBasisTornado(DBT),asdefinedinRegulatoryGuide1.76.Thisensuresthatprotectionofthedesignateditemsagainstallcredibletornadoeshasbeenadequately-Linesindicatesubstantivechangesfrompreviousissue.considered.Abasicprovisionoftornadoprotectioncriteriaisthatthosestructures,systems,andcomponentswhosefailurecouldresultinconservativelycalculatedexposurescomparabletotheguidelineexposuresof10CFRPart100,ReactorSiteCriteria,shouldbeprotectedagainstDBTeffectstopreventsuchfailure.Thisprovisionbyitself,however,wouldnotprovideprotectionforcertainotherstructures,systems,andcomponentswhichcouldbedamagedbyalesssevere,butmorelikely,tornado.Inordertoensureprotectionformoreprobableeventshavinglesssevereconsequences,theselectionofstructures,systems,andcomponentstobeprotectedagainsttheeffectsofaDBTisbasedonnotallowingoffsiteexposurestoexceedanappropriatefractionof10CFRPart100guidelines.Protectionofdesignatedstructures,systems,andcomponentsmaygenerallybeaccomplishedbydesigningprotectivebarrierstoprecludetornadodamage.Forexample,theprimarycontainment,reactorbuilding,auxiliarybuilding,andcontrolstructuresshouldbedesignedagainstcollapseandshouldprovideanadequatebarrieragainstmissiles.However,theprimarycontainmentneednotnecessarilymaintainitsleaktightintegrity.Ifprotectivebarriersarenotinstalled,thestructuresandcomponentsthemselvesshouldbedesignedtowithstandtheeffectsofthetornado,includingtornadomissilestrikes.Thephysicalseparationofredundantoralternativestructuresorcomponentsrequiredforthesafeshutdownoftheplantisgenerallynotconsideredacceptablebyitselfforprotectingagainsttornadoeffects,includingtornado-generatedmissiles.Thisisbecauseofthelargenumberandrandomdirectionofpotentialmissilesthatcouldresultfromatornadoaswellastheneedtoconsiderthesinglefailurecriterion.ItisnotnecessarytomaintainthefunctionalcapabilityofallSeismicCategoryIstructures,systems,andcomponentsbecausetheprobabilityofthejointoccurrenceoflow-probabilityevents(loss-of-coolantUSNRCREGULATORYGUIDESCommentsshouldbesenttotheSecretaryoftheCommission,US.NuclearRegulatoryCommission.Washington,D.C.20555,AttentionDocketingandServiceRegulatoryGuidesareissuedtodescribeandmakeavailabletothepublicmethodsBranch.acceptabletotheNRCstaffofimplementingspecificpartsoftheCommission'sregulations.todelineatetechniquesusedbythestaffinevaluatingspecificproblemsTheguidesareissuedinthefollowingtenbroaddivisionsorposlulatedaccidents,ortoprovideguidancetoapplicants.RegulatoryGuidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired1.PowerReactors6.ProductsMethodsandsolutionsdifferentfromthosesetoutintheguideswillbeaccept2.ResearchandTestReactors7.Traosporlationableiftheyprovideabasisforthefindingsrequisitetotheissuanceorcontinuance3FuelsandMaterialsFacilities8.OccupationalHealthofapermitorlicensebytheCommitsion.4EnvironmentalandSiting9.AntitrustReview5.MaterialsandPlantProtection10.GeneralCommentsandsuggestionsforimprovementsintheseguidesareencouragedatallRequestsforsinglecopiesofissuedguides(whichmaybereproduced)orforplacetimes,andguideswillberevised,asappropriate.toaccommodatecommentsandmentonanautomaticdistributionlistforsinglecopiesoffutureguidesinspecifictoreflectnewinformationorexperience.ThisguidewasrevisedasaresultofdivisionsshouldbemadeinwritingtotheUS.NuclearRegulatoryCommission.substantivecommentsreceived'fromthepublicandadditionalstaffreview.Washington.D.C.20555,AttentionDirector.DivisionofDocumentControl.Revision1April1978accidentwithDBTorsmallertornado,orearthquakewithDBTorsmallertornado)issuffici