RG1.077 控制棒弹棒事故使用的假设 1974

U.S.ATOMIC,ENERGYCOMMISSIONREGULATORYDIRECTORATEOFREGULATORYSTANDARDSMay1974GUIDEREGULATORYGUIDE1.77ASSUMPTIONSUSEDFOREVALUATINGACONTROLRODEJECTIONACCIDENTFORPRESSURIZEDWATERREACTORSA.INTRODUCTIONSection50.34,'Contentsofapplications:technicalinformation,of10CFRPart50,LicensingofProductionandUtilizationFacilities,requiresthateachapplicationforaconstructionpermitoroperatinglicenseprovideananalysisandevaluationofthedesignandperformanceofstructures,systems,andcomponentsofthefacilitywiththeobjectiveofassessingthepotentialrisktopublichealthandsafetyresultingfromoperationofthefacility.GeneralDesignCriterion28,ReactivityLimits,ofAppendixA,GeneralDesignCriteriaforNuclearPowerPlants,to10CFRPart50,requiresthereactivitycontrolsystemtobedesignedwithappropriatelimitsonthepotentialamountandrateofreactivityincreasetoassurethattheeffectsofpostulatedreactivityaccidentscanneitherresultindamagetothereactorcoolantpressureboundarygreaterthanlimitedlocalyieldingnorsufficientlydisturbthecore,itssupportstructures,orotherreactorpressurevesselinternalstoimpairsignificantlythecapabilitytocoolthecore.GeneralDesignCriterion28alsorequiresthatthesepostulatedreactivityaccidentsincludeconsiderationoftherodejectionaccidentunlesssuchanaccidentispreventedbypositivemeans.Thisguideidentifiesacceptableanalyticalmethodsandassumptionsthatmaybeusedinevaluatingtheconsequencesofarodejectionaccidentinuraniumoxide-fueledpressurizedwaterreactors(PWRs).Insomecases,unusualsitecharacteristics,plantdesignfeatures,orotherfactorsmayrequiredifferentassumptionswhichwillbeconsideredonanindividualbasis.TheAdvisoryCommitteeonReactorSafeguardshasbeenconsultedconcerningthisguideandhasconcurredintheregulatoryposition.B.DISCUSSIONTherateatwhichreactivitycanbeinsertedintothecoreofauraniumoxide-fueledwater-cooledpowerreactorisnormallylimitedbythe-designofthecontrolrodsystemtoavaluewellbelowthatwhichwouldresultinseriousdamagetothereactorsystem.However,apostulatedfailureofthecontrolrodsystemprovidesthepotentialforarelativelyhighrateofreactivityinsertionwhich,iflargeenough,couldcauseapromptpowerburst.ForU02fuel,alargefractionofthisgeneratednuclearenergyisstoredmomentarilyinthefuelandthenreleasedtotherestofthesystem.Ifthefuelenergydensitieswerehighenough,therewouldexistthepotentialforpromptruptureoffuelpinsandtheconsequentrapidheattransfertothewaterfromfinelydispersedmoltenU02.Promptfuelelementruptureisdefinedhereinasarapidincreaseininternalfuelrodpressureduetoextensivefuelmelting,followedbyrapidfragmentationanddispersaloffuelcladdingintothecoolant.Thisisaccompaniedbytheconversionofnuclearenergy,depositedasoverpowerheatinthefuelandinthecoolant,tomechanicalenergywhich,insufficientquantity,couldconceivablydisarrangethereactorcoreorbreachtheprimarysystem.TheRegulatorystaffhasreviewedtheavailableexperimentalinformationconcerningfuelfailurethresholds.Ingeneral,failureconsequencesforU02havebeeninsignificantbelow300cal/gforbothirradiatedandunirradiatedfuelrods.Therefore,acalculatedradialaverageenergydensityof280cal/gatanyaxialfuellocationinanyfuelrodasaresultofapostulatedrodejectionaccidentprovidesaconservativemaximumlimittoensurethatcoredamagewillbeminimalandthatbothshort-termandlong-termcorecoolingcapabilitywillnotbeimpaired.Forthepostulatedcontrolrodejectionaccident,amechanicalfailureofacontrolrodmechanismhousingisassumedsuchthatthereactorcoolantsystempressurewouldejectthecontrolrodanddriveshafttothefullywithdrawnposition.USAECREGULATORYGUIDESCopiesofpublishedguidesmaybeobtainedbyrequestIndicatingthedivisionsdesiredtotheUS.AtomicEnergyCommission.Washington,D.C.20545.RegulatoryGuidesweissuedtodescribeand'makeavailabletothepublicAttention:DirectorofRegulatoryStandards.CommentsandsuggestionsformethodsacceptaletotheAECRegulatorystaffofimplemnentingspecfifcpartsofImprovementsInthesguldesareencouragedandshouldbesenttotheSecretarytheCommission'sregulations,todelineatetechniquesused-bythestaffInoftheCommission.US.AtomicEnergyCommission,Washington,D.C.20645evaluatingspecificproblemsorpostulatedaccidents,ortoprovideguidancetoAttention.Chief,PublicProceedingsStaff.applicants.RegulatoryGuidesarenotsubstitutesforregulationsandcompliancewiththemIsnotrequired.MethodsandsolutionsdifferentfromthosesetoutInTheguideseraissuedinthefollowingtenbroaddivisions:theguideswillbeacceptableIftheyprovideabasisforthefindingsrequisitetotheIssuanceorcontinuanceofapermitorlicensebytheCommission.1.PowerRleactorsS.Products2.ResearchandTestReactors7.Transportation3.FuelsandMaterialsFacilities8.OccupationalHealthPublishedguideswillberevisedperiodically,asappropriate,toaccommodate4.EnvironmentalandSiting9.AntitrustReviewcommentsandtorflectnewInformationorexperience.L.MaterialsOndPlantProtection10.GeneralAsufficientnumberofinitialreactorstatestocompletelybracketallpossibleoperationalconditionsofinterestshouldbeanalyzedtoassureexaminationofupperboundsonultimatedamage.Inareasofuncertainty,theappropriateminimumormaximumparametersrelativetonominalorexpectedvaluesshouldbeusedtoassureaconservativeevaluation.Theinitialreact