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May1973U.S.ATOMICENERGYCOMMISSIONREGULATORYGUIDEDIRECTORATEOFREGULATORYSTANDARDSREGULATORYGUIDE1.44CONTROLOFTHEUSEOFSENSITIZEDSTAINLESSSTEELA.INTRODUCTIONGeneralDesignCriteriaIand4ofAppendixAto10CFRPart50,GeneralDesignCriteriaforNuclearPowerPlants,requirethatcomponentsbedesigned,fabricated,erected,andtestedtoqualitystandardscommensuratewiththeimportanceofthesafetyfunctionstobeperformedandthattheybedesignedtoaccommodatetheeffectsofandbecompatiblewiththeenvironmentalconditionsassociatedwithnormaloperation,maintenance,testingandpostulatedaccidentconditions.AppendixBto10CFRPart50,QualityAssuranceCriteriaforNuclearPowerPlantsandFuelReprocessingPlants,requiresthatmeasuresbeestablishedtoassurematerialscontrolandcontrolofspecialprocessessuchasweldingandheattreatingandtoassureperformanceofreliabletestingprograms.Thisguidedescribesacceptablemethodsofimplementingtheaboverequirementswithregardtocontroloftheapplicationandprocessingofstainlesssteeltoavoidseveresensitizationthatcouldleadtostresscorrosioncracking.Thisguideappliestolight-water-cooledreactors.TheAdvisoryCommitteeonReactorSafeguardshasbeenconsultedconcerningthisguideandhasconcurredintheregulatoryposition.B.DISCUSSIONControloftheapplicationandprocessingofstainlesssteeltoavoidseveresensitizationisneededtodiminishthenumerousoccurrencesofstresscorrosioncrackinginsensitizedstainlesssteelcomponentsofnuclearreactors.Testdatademonstratethatsensitizedstainlesssteelissignificantlymoresusceptibletostresscorrosioncrackingthannon-sensitized(solutionheattreated)stainlesssteel.Ofspecificconcerninthisguidearetheunstabilizedausteniticstainlesssteels,whichincludeAmericanIronandSteelInstitute(AISI)types304and316normallyusedforcomponentsofthereactorcoolantsystemandothersafety-relatedsystems.Thisguidedoesnotcoverstabilizedstainlesssteels(e.g.,AISItypes321and347)whichalsoprovidesomeprotectionagainstsensitization,sincethesematerialsarenotcurrentlybeingselectedforuseinlight-water-cooledreactors.Processcontrolsshouldbeexercisedduringal,stagesofcomponentmanufacturingandreactor-constructiontominimizeexposureofstainlesssteeltocontaminantsthatcouldleadtostresscorrosioncracking.Sincesomedegreeofmaterialcontaminationisinevitableduringtheseoperations,halogensandhalogenbearingcompounds(e.g.,dielubricants,markingcompoundsandmaskingtape)shouldbeavoidedtothedegreepractical.Allcleaningsolutions,processingcompounds,degreasingagents,andotherforeignmaterialsshouldbecompletelyremovedatanystageofprocessingpriortoanyelevatedtemperaturetreatmentandpriortohydrotests.Reasonablecareshouldbetakentokeep(1)fabricationandconstructionareasclean,(2)componentsprotectedanddryduringstorageandshipment,and(3)allcrevicesandsmallopeningsprotectedagainstcontamination.Picklingofsensitizedstainlesssteelshouldbeavoided.Specialprecautionsshouldbetakentoavoidsurface-contaminationwithfluoridesfromweldingrodcoatingsandfluxes.ThequalityofwaterusedforfinalcleaningorflushingoffinishedsurfacesduringinstallationshouldbeinaccordancewithRegulatoryGuide1.37.Solutionheattreatingandtestingshouldnormallybeperformedonstartingmaterial.However,inordertoassurethepropersolutionheat-treatedconditionofthesurfaceareasoffinishedcomponents,itmaybepreferabletoperformthesolutionheattreatingandtestingoperationatalaterstageofcomponentmanufacturing.SolutionheattreatingshouldincludecoolingratessufficientlyrapidtopreventprecipitationofcarbidestoadegreethatthematerialisnotsusceptibletoUSAECREGULATORYGUIDESCopiesofpublishedguidesmaybeobtainedbyrequestindicatingthedivisionsdesiredtotheUS.AtomicEnergyCommission,Washington.D.C.20545.RegulatoryGuidesareissuedtodescribeandmakeavailabletothepublicAttention:DirectorofRegulatoryStanderds.CommentsendsuggestionsformethodsacceptabletotheAECRegulatorystaffofimplementingspecificpartsofImprovemaentsintheseguideswreencouragedandshouldbelenttotheSecretarytheCommission'sregulations,todelineatetechniquesusedbythestaffinoftheCommission,US.AtomicEnergyCommission.Washington,D.C.20545,evaluatingspecificproblemsorpostulatedaccidents,ortoprovideguidancetoAttention:Chief.PublicProceedingsStaff.applicants.RegulatoryGuidesarenotsubstitutesforregulationsandcompliancewiththemisnotrequired.MethodsandsolutionsdifferentfromthosesetoutinTheguidesareissuedinthefollowingtenbroaddivisions:theguideswillbeacceptableiftheyprovideabasisforthefindingsrequisitetotheissuanceorcontinuanceofapermitorlicensebytheCommission.1.PowerReactors6.Products2.ResearchardTestReactors7.Transportation3.FuelsandMaterialsFacilities8.OccupationalHealthPublishedguideswillberevisedperiodically,asappropriate,toaccommodate4.EnvironmentalandSiting9.AntitrustReviewcommentsandtoreflectnewinformationorexperience.5.MaterialsandPlantProtection10.Generalintergranularstresscorrosion.Waterquenching(usedforsimpleshapessuchasbarsandplates)shouldproduceanacceptablecoolingrate.However,coolingbymeansotherthanwaterquenchingisacceptableonlywhenthecoolingrateissufficientlyrapidtopreventsensitizationThisdeterminationismadebysubjectingthematerialtoasuitableintergranularcorrosiontestsuchas