RG1.121 PWR蒸发器降级传热管的堵管基准 1976

August1976U.S.NUCLEARREGULATORYCOMMISSIONREGULATORYGUIDEOFFICEOFSTANDARDSDEVELOPMENTREGULATORYGUIDE1.121BASESFORPLUGGINGDEGRADEDPWRSTEAMGENERATORTUBESA.INTRODUCTIONGeneralDesignCriteria14,ReactorCoolantPressureBoundary,and31,FracturePreventionofReactorCoolantPressureBoundary,ofAppendixA,GeneralDesignCriteriaforNuclearPowerPlants,to10CFRPart50,LicensingofProductionandUtilizationFacilities,requirethatthereactorcoolantpressureboundaryhaveanextremelylowprobabilityofabnormalleakage,ofrapidlypropagatingfailure,andofgrossrupture.GeneralDesignCriterion15,ReactorCoolantSystemDesign,requiresthatthereactorcoolantsystemandassociatedauxiliary,control,andprotectionsystemsbedesignedwithsufficientmargintoassurethatthedesignconditionsofthereactorcoolantpressureboundaryarenotexceededduringanyconditionofnormaloperation,includinganticipatedoperationaloccurrences.Furthermore,GeneralDesignCriterion32,InspectionofReactorCoolantPressureBoundary,requiresthatcomponentsthatarepartofthereactorcoolantpressureboundarybedesignedtopermitperiodicinspectionandtestingofcriticalareastoassesstheirstructuralandleaktightintegrity.Rupture1of*thesteamgeneratortubes,whichconstituteaportionofthereactorcoolantpressureboundary,couldpermitflowofreactorcoolantintothesecondarycoolantsystemorviceversa.Inaddition,theweakeningofthesetubesduetoservice-inducedtubedegradationprocessescould,intheeventofapostulatedloss-of-coolantaccident(LOCA),resultinruptureoftubesandreleaseoffluidenergyfromthesecondarysystemintothecontainmentorthereactorvessel.Theruptureofanumberofsingletubewallbarriersbetweenprimaryandsecondaryfluidhassafetyconsequencesonlyiftheresultingfluidflowexceedsanacceptableamountandrate.1Ruptureisdefinedasanyperforationofthetubepressureboundaryaccompaniedbyaflowoffluideitherfromtheprimarytothesecondarysideofthetubesorviceversa,dependingonthedifferentialpressureconditionprevailingduringnormalplantoperationordevelopedintheeventofpostulatedpipebreakaccidentswithineithertheprimaryreactorcoolantpressureboundaryorthesteamsystempressureboundary.USNRCREGULATORYGUIDESCommentsshouldbesenttotheSecretaryoftheCommission.U.S.NuclearRegulatoryGuidesareissuedtodescribeandmakeavailabletothepublicRegulatoryCommission.Washington.D0C20566.AttentionDocketingandmethodsacceptabletotheNRCstaffofimplementingspecificpartsoftheServgeSctionCommission'sregulations,todelineatetechniquesusedbythestaffinevaluTheguidesareIssuedInthefollowingtenbroaddivisionsstingspecificproblemsorpostulatedaccidents,ortoprovideguidancetoapplicants.RegulatoryGuidesarenotsubstitutesforregulations.andcomplianceIPowerReactors6.ProductswiththemIsnoirequired.Methodsandsolutionsdifferentfromthoaesetoutin2ResearchandTeatReactors7Transportationtheguideswillbeacceptableiftheyprovideabasisforthefindingsrequisiteto3.FuelsandMaterialsFacilities.OccupationalHealththeissuanceofcontinuanceofapermitorlicensebytheCommission4.EnvironmentalandSiting9.AntitrustReviewCommentsandsuggestionsforimprovementsintheseguidesareencouraged5.MaterialsandPlantProtection10Generalatalltimes,andguideswillberevised,asappropriate,toaccommodatecommentsandtoreflectnewinformationorexperience.However.cummetirronCopiesofpublishedguidesmaybeobtainedbywrittenrequestindicatingthethisguide.ifreceivedwithinabouttwomonthsafteritsissuancewillh-pardivisionsdesiredtotheU.SNuclearRegulatoryCommissionWashington0Cticularlyusefulinevaluatingtheneedforanearlyrevision20666,Attention.Director.OfficeofStandardsDevelopmentThisguidedescribesamethodacceptabletotheNRCstaffforestablishingthelimitingsafeconditionsoftubedegradationofsteamgeneratortubing,beyondwhichdefectivetubesasestablishedbyinserviceinspectionshouldberemovedfromservicebyweldingplugsateachendofthetube.Thisguideappliesonlytopressurizedwaterreactors(PWRs).B.DISCUSSIONTheheattransferareaofthesteamgeneratorsassociatedwithpressurizedwaterreactorscancomprisewellover50%ofthetotalprimarysystempressure-retainingboundary.Thesteamgeneratortubingthereforerepresentsanintegralpartofamajorbarrieragainstfissionproductreleasetotheenvironment.ThesteamgeneratortubingalsorepresentsabarrieragainststeamreleasetothecontainmentintheeventofapostulatedLOCA.Thedesigncriteriausedtoestablishthestructuralintegrityofthesteamgeneratortubingshouldincludeanalysesthatdefinetheminimumtubewallthicknessthatcansustain,withadequatemarginsandundernormalplantoperatingconditions,thepressureandthermalloadresultingfrompostulatedaccidentconditions,includingasafeshutdownearthquake(SSE)2incombinationwithaLOCAbreak,asteamlinebreak,orafeedwaterlinebreak.RegulatoryGuide1.83,InserviceInspectionofPressurizedWaterReactorSteamGeneratorTubes,definesdefectivetubes(i.e.,tubeswithwallthicknesslessthantheminimumacceptablethickness)asbeingunacceptableforcontinuedserviceandrecommendsthattheseandleakingtubesbeplugged.Partiallydegradedtubeswithawallthicknessgreaterthantheminimumacceptabletubewallthicknessareacceptableforcontinuedservice,providedtheminimumrequiredtubewallthicknessincludesanoperationalallowancefortubedegradationthatmayoccurbeforethenextscheduledtu