RG1.024 PWR放射气体贮存箱失效的潜在放射性后果评估 1972

U.S.NUCLEARREGULATORYCOMMISSIONMarch1972Revision0REGULATORYGUIDEOFFICEOFNUCLEARREGULATORYRESEARCHREGULATORYGUIDE1.24(DraftwasissuedasSafetyGuide24)ASSUMPTIONSUSEDFOREVALUATINGTHEPOTENTIALRADIOLOGICALCONSEQUENCESOFAPRESSURIZEDWATERREACTORRADIOACTIVEGASSTORAGETANKFAILUREA.INTRODUCTIONSection50.34of10CFRPart50,“ContentsofApplications:TechnicalInformation,”requiresthateachapplicantforaconstructionpermitoroperatinglicenseprovideananalysisandevaluationofthedesignandperformanceofstructures,systems,andcomponentsofthefacilitywiththeobjectiveofassessingtherisktopublichealthandsafetyresultingfromoperationofthefacility.Radioactivegasstoragetanksareusedatpressurizedwaterpowerreactorstopermitdecayofradioactivegasesasameansofreducingorpreventingthereleaseofradioactivematerialstotheatmosphere.Theaccidentalreleaseofthecontentsofoneofthesetanksresultingfromaruptureofthetank,orofaninletordischargepipe,orbecauseofoperatorerrororvalvemalfunction,isoneofthepostulatedaccidentsusedtoevaluatetheadequacyofthesecomponentswithrespecttothepublichealthandsafety.Thissafetyguidelistsacceptableassumptionsforuseinevaluatingtheradiologicalconsequencesofthispostulatedaccident.Insomecasesunusualsitecharacteristics,plantdesignfeatures,orotherfactorsmayrequiredifferentassumptionswhichwillbeconsideredonanindividualcasebasis.B.DISCUSSIONRadioactivegasstoragetanksareusedatpressurizedwaterpowerreactorstopermitdecayofradioactivegasesasameansofreducingorpreventingthereleaseofradioactivematerialstotheTheNRCissuesregulatoryguidestodescribeandmakeavailabletothepublicmethodsthattheNRCstaffconsidersacceptableforuseinimplementingspecificpartsoftheagency’sregulations,techniquesthatthestaffusesinevaluatingspecificproblemsorpostulatedaccidents,anddatathatthestaffneedsinreviewingapplicationsforpermitsandlicenses.Regulatoryguidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired.MethodsandsolutionsthatdifferfromthosesetforthinregulatoryguideswillbedeemedacceptableiftheyprovideabasisforthefindingsrequiredfortheissuanceorcontinuanceofapermitorlicensebytheCommission.Thisguidewasissuedafterconsiderationofcommentsreceivedfromthepublic.Regulatoryguidesareissuedin10broaddivisions:1,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(xenon-133).Thus,storageofthesegasesforaperiodof60dayswillessentiallyeliminatebydecayalloftheradionuclidesexceptkrypton-85.Theprobabilityofagasdecaytankrupturingislow.However,theprobabilityofanaccidentalreleaseresultingfromsuchthingsasoperatorerrorormalfunctionofavalveortheoverpressurereliefsystemisconsideredtobesufficientlyhighthatthecalculatedoffsitewholebodyexposuresthatmightresultfromasinglefailureduringnormaloperationshouldbesubstantiallybelowtheguidelinesof10CFRPart100.Inconsideringtheprobabilityandconsequencesofsuchasinglefailureoccurring,itisrecognizedthatgreatervolumesofradioactivegaseswillbegeneratedbythelargerplantspresentlybeingconstructedthanthevolumesgeneratedbymostpresentlyoperatingplants.Thisincreasedquantityofradioactivegaswillnecessitateasubstantialincreaseinthenumberorsizeofgasstoragetanksused.Consideringthepotentialwhichexistsforaninadvertentreleaseandthehighnoblegascontentofthetankstogetherwiththefactthatsuchgasdecaytanksarenormallylocatedoutsidethereactorcontainment,everyreasonableeffortshouldbemadetoreducetheprobabilityofsuchanaccidentalrelease.Thus,thereisaneedforastrongqualityassuranceprogram,asrequiredbyAppendixBto10CFRPart50,to“providecontroloveractivitiesaffectingthequalityoftheidentifiedstructures,systems,andcomponents,toanextentconsistentwiththeirimportancetosafety…Theprogramshalltakeintoaccounttheneedforspecialcontrols,processes,testequipment,tools,andskillstoattaintherequiredquality,andtheneedforverificationofqualitybyinspectionandtest.Theprogramshallprovideforindoctrinationandtrainingofpersonnelperformingactivitiesaffectingqualityasnecessarytoassurethatsuitableproficiencyisachievedandmaintained.”Inthefollowingparagraphs,somepotentialproblemareasaren