RG1.045 反应堆冷却剂压力边界泄漏检测系统 2008

TheNRCissuesregulatoryguidestodescribeandmakeavailabletothepublicmethodsthattheNRCstaffconsidersacceptableforuseinimplementingspecificpartsoftheagency=sregulations,techniquesthatthestaffusesinevaluatingspecificproblemsorpostulatedaccidents,anddatathatthestaffneedsinreviewingapplicationsforpermitsandlicenses.Regulatoryguidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired.MethodsandsolutionsthatdifferfromthosesetforthinregulatoryguideswillbedeemedacceptableiftheyprovideabasisforthefindingsrequiredfortheissuanceorcontinuanceofapermitorlicensebytheCommission.Thisguidewasissuedafterconsiderationofcommentsreceivedfromthepublic.Regulatoryguidesareissuedin10broaddivisionsC1,PowerReactors;2,ResearchandTestReactors;3,FuelsandMaterialsFacilities;4,EnvironmentalandSiting;5,MaterialsandPlantProtection;6,Products;7,Transportation;8,OccupationalHealth;9,AntitrustandFinancialReview;and10,General.ElectroniccopiesofthisguideandotherrecentlyissuedguidesareavailablethroughtheNRC=spublicWebsiteundertheRegulatoryGuidesdocumentcollectionoftheNRC=sElectronicReadingRoomat’sAgencywideDocumentsAccessandManagementSystem(ADAMS)at(DraftwasissuedasDG-1173,datedJune2007)GUIDANCEONMONITORINGANDRESPONDINGTOREACTORCOOLANTSYSTEMLEAKAGEA.INTRODUCTIONThisrevisiontoRegulatoryGuide1.45(Ref.1)describesmethodsthatthestaffoftheU.S.NuclearRegulatoryCommission(NRC)considersacceptableforuseinimplementingtheregulatoryrequirementsspecifiedbelowwithregardtoselectingreactorcoolantleakagedetectionsystems,monitoringforleakage,andrespondingtoleakage.Thisguideappliestolight-water-cooledreactors.GeneralDesignCriterion(GDC)14,“ReactorCoolantPressureBoundary,”assetforthinAppendixA,“GeneralDesignCriteriaforNuclearPowerPlants,”toTitle10,Part50,“DomesticLicensingofProductionandUtilizationFacilities,”oftheCodeofFederalRegulations(10CFRPart50),(Ref.2),requiresthatlicenseesorapplicantsdesign,fabricate,erect,andtestthereactorcoolantpressureboundary(RCPB)soastoensureanextremelylowprobabilityofabnormalleakage,rapidlypropagatingfailure,andgrossrupture.Asaresult,thedesignofthesenuclearcomponentsnormallyfollowsthecriteriaestablishedinSectionIIIoftheBoilerandPressureVesselCode(Ref.3)promulgatedbytheAmericanSocietyofMechanicalEngineers(ASME).Duringthedesignphase,degradation-resistantmaterialsarenormallyspecifiedforreactorcoolantsystem(RCS)components.However,materialscandegradeasaresultofthecomplexinteractionofthematerials,thestressestheyencounter,andthenormalandupsetoperatingenvironmentstheyexperience.Suchmaterialdegradationcouldleadtoleakageofthereactorcoolant.Consequently,GDC30,“QualityofReactorCoolantPressureBoundary”(Ref.2),requiresthatplantsprovidethemeansfordetectingand,totheextentpractical,identifyingthelocationofthesourceofreactorcoolantleakage.Rev.1ofRG1.45,Page2Additionally,10CFR50.55a,“CodesandStandards”(Ref.2),requirestheperformanceofinserviceinspectionandtestingofnuclearpowerplantcomponents.Thus,theconceptofdefenseindepthisappliedtoprovideassurancethatthestructuralintegrityoftheRCPBismaintained.B.DISCUSSIONBackgroundReactordesignandconstructionshouldincludeeveryefforttousematerialsandenvironmentsthatlimitthepotentialfordegradation.Duringtheoperationallifeofaplant,reactorcomponentscoulddegradethroughnormaloperationalwear,mechanicaldeterioration,corrosion,and/orfatigue.Thisdegradationcanleadtocoolantleakage.AlimitedamountofleakageinsidecontainmentmayoccurfromRCSsthatplantscannotpracticallyrender100-percentleaktight.ThesafetysignificanceofleakagefromtheRCScanvarywidely,dependingonthesourceoftheleakageaswellastheleakagerateandduration.Operatingexperienceandresearchhaveindicatedthatverylowlevelsofleakagecouldcause(orindicate)materialdegradationarising,forexample,asaresultofboricacidcorrosion,primarywaterstress-corrosioncracking,andintergranularstress-corrosioncracking.Suchformsofdegradationcouldpotentiallycompromisetheintegrityofasystem,leadingtoaloss-of-coolantaccident.TominimizetheprobabilityofrapidlypropagatingfailureattributabletomaterialdegradationandgrossruptureoftheRCPB,plantsshouldkeeptheleakagetoalevelthatisaslowaspracticalandtakepromptactioninrespondingtoleakagetolimitthesafetyconsequences.Promptcorrectiveactionrequirescontinuousonlinemonitoringforleakage.Continuousleakagemonitoringisimportanttoensuringthesafeoperationofafacilitybecauseitprovidesanindicatorduringreactoroperationthatapotentiallyadverseconditionmayexist.Inadditiontomonitoringforleakage,itisimportanttoquantifythereactorcoolantleakageandlocateitssourcetoassessitssafetysignificance.DetectingandeffectivelyrespondingtoleakageasearlyaspossibleprovidesdefenseindepthfortheintegrityoftheRCPB.TypesofLeakageRCSleakagefallsundertwomaincategories—identifiedleakageandunidentifiedleakage.Thedefinitionofidentifiedleakageisasfollows:$leakage(suchaspum