RG1.139 余热排出导则 1978

.,&Q~RREG(,0'-pAzS~U.S.NUCLEARREGULATORYCOMMISSIONMay1978REGULATORYGUIDEOFFICEOFSTANDARDSDEVELOPMENT-r..p:*I,i-rREGULATORYGUIDEGUIDANCEFORRESIOUAUSNRCREGULATORYGUIDESRegulatoryGuidesreIssuedtodescribeandmakeavailabletothePublicmethodsacteatabletotheNRCstaffofImolementingapecificPartsoftheCommiwon'sreouiationstodelineatettchniesueusedbytheetaffinteluatingseecificproblemsorpoetuiatdaccidents,ortoprovideguidancetoapplicants.RegulatoryGuidetarenotstbetitutesforregulations,andcompliancewiththemisnotrequird.MethodsandsolutionsdifferentfromthoseweeoutintheguidesvollbeacceptabeIttheyprovideabai,forthefindingsrequiaitetotheIsianceorcontinuanceofapermitorlicensebytheCommision.CommentsandaiessionsforimprosementsinthesguidesweencouragedIt11times,anduidenwillberevised.eneapropriate.toaccommodatecommentsandtoreflectnewInformationorexperience.However,commentsonthisguiderlfreceivedwithinabouttwomonthsafterItsieuance.willbeparticularlyusefulinevaluatingthenwedforaneartyreviaion.CommentsshouldbesenttotheSecretaryoftheCommi4nonUS.NuctavoAegu.tatoryCommisson,Washington.D.C.20555.Attention.DocketiungandServiceBrandc.Theguidertreinuedinthefollowingtenbroaddivrsions1.PowerReactors6.Productt2.ReseatchandTentReactors7.Transportation3.FuoisandMatelralsFacilitesS.OccuPationalHealth4.EnvironmentalndSiting9.AntirustReviewS.MaterialsandPlantProtection10.GenralRequetstforsingleconisofissuedguideslthichmayberegroducedlortorplace-mentonenautomaticdistributionlotforsingleconisoffutureuidesinsoecificdisisionsshouldbemaderinwritingtotheUS.NucleerRegulatoryCommisson.Washington,D.C.20555.Attention:DrectvorDivisonofDocumentControl.A.INTRODUCTIONGeneralDesignCriterion(GDC)19,ControlRoom,ofAppendixA,GeneralDesignCriteriaforNuclearPowerPlants,to10CFRPart50,LicensingofProductionandUtilizationFacilities,requiresthatitbepossibletotakeactionsfromthecontrolroomtomaintainthepowerplantinasafeconditionduringnormaloperationorinthecaseofanaccident.GDC34,ResidualHeatRemoval,requiresthatasystemtoremoveresidualheatbeprovided.GDC34definesthesystem'ssafetyfunctionasthetransferoffissionproductdecayheatandotherresidualheatfromthereactorcoreafterthereactorisshutdownsothatacceptabledesignlimitsofthefuelandthereactorcoolantpressureboundaryarenotexceeded.Furthermore,GOC34requiresthatthesystemsafetyfunctioncanbeaccomplishedassumingtheavailabilityofonlyonsiteoroffsitepower,coincidentwithasinglefailure.ThisguidedescribesamethodacceptabletotheNRCstaffforcomplyingwiththeCommission'sregulationswithregardtotheremovalofdecayheatandsensibleheatafterareactorshutdown.B.DISCUSSIONThesafeshutdownofanuclearpowerplantfollowinganaccidentnotrelatedtoaloss-of-coolantaccidentCLOCA)hasbeentypicallyinterpretedasahotstandby.Consequently,considerableemphasishasbeenplacedonthehot-standbyconditionofapowerplantincaseofanaccidentorabnormaloccurrence.Asimilardegreeofemphasishasbeenplacedonlong-termcooling,whichistypicallyachievedbytheresidualheatremoval(RHR)system.TheRHRsystemstartstooperatewhenthereactorcoolantpressureandtemperaturearesub-stantiallylowerthantheirhot-standbyconditionvalues.Itistheintentofthisguidetoplacethesamedegreeofemphasisontheentirerangeofreactorcoolanttemperaturesandpressures,includingtherangebetweenhotstandbyandRHRoperationconditions.Theimportanceofreliablesystemsthatremovedecayheatfromthereactorcoolantsystem(RCS)whilethelatterisatornearnormaloperatingtemperaturesisindicatedbytheresultsofWASH-1400,ReactorSafetyStudy(RSS).ThecapabilityofatypicalPWRplantandatypicalBWRplanttoremovedecayheatfollowingaplanttripwasevaluatedintheRSSonaprobabilisticbasis.Theevaluationincludedboththoseeventsinwhichthereactorprotectionsystem(RPS)failed(AnticipatedTransientsWithoutScram)andeventsinwhichtheRPSfunc-tionedasdesigned.Forthesetypesofevents,itwasconsideredacceptabletomaintainthereactoratornearnormaloperatingtemperatureandpressureforalongtime.However,intheeventofaplanttripevenwithasuccessfuloperationoftheRPS,systemsorequipmentfailuresthatledtotheinabilitytoremovedecayheatresultedinahigherproba-bilityofacoremeltthanthatpredictedforalargeLOCAforbothPWRsandBWRs.Conse-quently,asignificantsafetybenefitwillbegainedbyupgradingthosesystemsandequipmentneededtomaintaintheRCSatthehot-standbyconditionforextendedperiodsorthoseneededtocoolanddepressurizetheRCSsothattheRHRsystemcanbeoperated.1.139-1Furthermore,eventhoughitmaygenerallybeconsideredsafetomaintainareactorinahot-standbyconditionforalongtime,experienceshowsthatthei-ehavebeeneventsthatrequiredeventualcooldownandlong-termcoolinguntiltheRCSwascoldenoughtoperforminspectionandrepairs.ItisthereforeobviousthattheabilitytotransferheatfromthereactortotheenvironmentafterashutdownisanimportantsafetyfunctionforbothPWRsandBWRs.Consequently,itisessentialthatapowerplanthavethecapabilitytogofromhot-standbytocold-shutdownconditions(whenthisisdeterminedtobethesafestcourseofaction)underanyaccidentconditions.Theseaccidentconditionscanconceivablyincludeasafeshutdownearthquake(SSE)andanextendedlossofoffsitepowerthatmayhaveresultedfromthatSSE.Inthatcase,allcomponents