搜索
U.S.NUCLEARREGULATORYCOMMISSIONREGULATORYGUIDEOFFICEOFSTANDARDSDEVELOPMENTREGULATORYGUIDE1.14REACTORCOOLANTPUMPFLYWHEELINTEGRITYA.INTRODUCTIONGeneralDesignCriterion4,EnvironmentalandMissileDesignBases,ofAppendixA,GeneralDesignCriteriaforNuclearPowerPlants,to10CFRPart50,LicensingofProductionandUtilizationFacilities,requiresthatnuclearpowerplantstructures,systems,andcomponentsimportanttosafetybeprotectedagainsttheeffectsofmissilesthatmightresultfromequipmentfailures.ThisguidedescribesamethodacceptabletotheNRCstaffofimplementingthisrequirementwithregardtominimizingthepotentialforfailuresoftheflywheelsofreactorcoolantpumpmotorsinlight-water-cooledpowerreactors.B.DISCUSSIONTheflywheelsonreactorcoolantpumpmotorsprovideinertiatoensureaslowdecreaseincoolantflowinordertopreventfueldamageasaresultofalossofpowertothepumpmotors.Duringoperationatnormalspeed,aflywheelhassufficientkineticenergytoproducehigh-energymissilesandexcessivevibrationofthereactorcoolantpumpassemblyiftheflywheelshouldfail.Overspeedofthepumprotorassemblyduringatransientincreasesboththepotentialforfailureandthekineticenerg3Toftheflywheel.Thesafetyconsequencescouldbesignificantbecauseofpossibledamagetothereactorcoolantsystem,thecontainment,orotherequipmentorsystemsimportanttosafety.Methodsofpredictingtheloss-of-coolantaccident(LOCA)overspeedconditionsareundercontinuinginvestigation.ThelimitonpredictedpumpoverspeedintheeventofaLOCAshouldbelessthanthecalculatedcriticalspeedforfailureoftheflywheel.Theconservatisminherentinthelattercalculation,coupledwitharealisticpredictionofmaximumrotationalspeed,isconsideredtoprovideadequatemarginbecauseofthelowprobabilityofoccurrenceofthespecificLOCAconditionsthatwouldcausesuchoverspeed.Methodsoflimitingpotentialpumpoverspeedarealsounderinvestigation.Iftheflywheelofthereactorcoolantpumpisconservativelydesignedandmadefromsuitablematerialswithcloselycontrolledquality,ifadequatedesignreviewofnewconfigurationsisprovided,andifadequateinserviceinspectionisprovided,theprobabilityofaflywheelfailureissufficientlysmallthattheconsequencesoffailureneednotbeprotectedagainst.Materialsforpumpflywheelsshouldbemanufacturedbyprocessesthatminimizeflawsandresultinadequatefracturetoughnessinboththetransverseandlongitudinalrollingdirections.Materialsproducedbyvacuummeltinganddegassingortheelectroslagremeltingprocessareknowntohaveimprovedcleanlinessandtoughness.PlatematerialshouldbecrossrolledtoaratioofatleastIto3,sufficienttoachieveacceptableisotropy.Fracturetoughnessisachievedmorereadilyinthinnerplates,andfabricationoflaminatedflywheelsbyassemblingthemfromseveralplatesisacceptable.Asanexample,pastevaluationshaveshownthatASMESA-533-BClass1andSA-508Classes2and3materialsgenerallyhavesuitabletoughnessfortypicalflywheelapplicationsprovidedstressconcentrationsarekeptwithinreasonablelimitsandthereferencetemperatureRTNDT,determinedinaccordancewithArticleNB-2331(a)ofSectionHIoftheASMECode,'isatleast500C(900F)belowthelowesttemperatureatwhichoperatingspeedisachieved.Forothermaterialsthatmaybeconsideredforflywheels,thestrengthandtoughnesspropertiesshouldbeevaluatedandjustifiedforthisapplication.'CopiesmaybeobbtinedfromtheAmericanSocietyofMechanicalEngineers,UnitedEngineeringCenter,345East47thStreet,NewYork,NewYork10017.USNRCREGULATORYGUIDESCommentsshouldbesenttotheSecretaryoftheCommission,U.S.NcilerRegulatoryGuidesareissuedtodescribeandmakeavailabletothepublicRegulatoryCommission.Washongton.D.C.2,Attention:DockelingendmethodsacceptabletotheNRCstaffofimplementingspecificpartsoftheCommission'sregulations,todelineatetechniquesusedbythestaffInevalu-Theguidesareissuedinthefollowingtenbroaddivisions:stingspecificproblemsorpostulatedaccidents.ortoprovideguidancetoapplicents.RegulatoryGuidesarenotsubstitutesforregulations,endcompliance1:PowerReactorsS.Productswiththemisnotrequired.Methodsandsolutionsdifferentfromthosesetoutin2.ResearchendTestReactors7.Transportationtheguideswillbeacceptableiftheyprovideabasisforthefindingsrequisiteto3'FuelsandMateriasiFacilities8.OccupationalHealththeissuanceorcontinuanceofapermitorlicensebytheCommission.4.EnvironmentalendSiting9.AntitrustReviewCommentsandsuggestionsforimprovementsintheseguidesareencouraged5.MaterialsandPlantProtection10.Generalatalltimes,andguideswillberevised.asappropriate,toaccommodatecommentsandtoreflectnewinformationorexperience.However.commentsonCopiesofpublishedguidesmaybeobtainedbywrittenrequeatindicatingthethisguide,ifreceivedwithinabouttwomonthsafteritsissuance,willbepar.divisionsdesiredtotheU.S.NuclearRegulatoryCommission.Washington.D.C.ticularlyusefulinevaluatingtheneedforanearlyrevision.21,Attention:Director,OfficeofStandardsDevelopment.Revision1Auust1975Thenon-ductilefractureanalysiscalledforinregulatorypositionC.2.dshouldbebasedonappropriateconservativeassumptionsforstresslevel,flawsize,temperature,andfracturetoughnessatthelocationofinterest.Thenon-ductilefracturecriterionusedtopredictthecriticalfracturespeedshouldbebasedoninitialinstabilityoftheflawasdefinedinASTME-399.Thejustificationforthes