ML17037B906
| ML17037B906 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 03/08/1978 |
| From: | Varga S A Office of Nuclear Reactor Regulation |
| To: | Rhode G K Niagara Mohawk Power Corp |
| References | |
| NUREG-0313 | |
| Download: ML17037B906 (24) | |
Text
MAR08f978DocketNo2,50-43.0NiagaraMohawkPowerCorporationATXM:Ikr.Gerlad.K.DiodeVicePresident-Mrgineering300ErieBoulevardNestSyracuse,New,York13202Gentlemen:
SUBJECT:
NBCSTAFFPOSXTICMOHTHEUSEOFAUSTEMXTICSTAINLESSSTEELINBOILIHGPPZERREACTORFACXLITXESWIHEBILEHHbJTNU~+SZATIC8,UNIT2Duringthepastseveralyears,theMCanditspredecessoragency,theABC,haveconductedanextensiveinvestigationtoevaluatethecrackingofausteniticstainlesssteelpiping.Thiseffortwasinitiatedfollowingthedetectioninlate1974andearly1975ofaseriesofcracksinthepipingofboilingwaterreactorfacilities.Asaresultofthisinvestigation,wehaveconcludedthatthetypesofausteniticstainlesssteelcurrentlyusedinboilingwaterreactorpipingaresusceptibletostresscorrosioncracking.Thestaffbelievestheprobabilityisextremelylowthatsuchstresscorrosioncracksvillpropagatefarenoughtocreateasignificantsafetyhazardtothepublic.However,wehavealsoconcludedthatstepsshouldbetakentoelimi-natethiscondition.Tothisend,wehavedevelopedapositiontosetforthacceptablereethodstoreducethesusceptibilityofboilingwaterreactorpipingtostresscorrosioncracking.ThispositioniscontainedinHUREG-0313,datedJuly1977,acopyofwhichisenclosed.PehavealsoincorporatedthepositioncontainedinNUREG-0313asBranchTechnicalPositionNTEB5-7andissueditas.arevisiontotheStandardReviewPlan.,Youshouldnotethattheimplen~tationschedulesetforthinthepositionprovidesforvaryingdegreesofconformance,dependinguponthestatusoftheapplication.1'equirethatyouprovideascheduleforyourresponsetothispositionwithin14daysofreceiptofthisletter.YourresponseshouldaddresseachofthesubsectionsinSectionIIandXIXoftheposition.Forty(40)c'opiesofyourresponseareneededforusebythestMf.OKKICK~SVRNAMKWOATS~NRCFORM318(9-76)NRCM02404UIS,OOVKRNMKNTPRINTINO,OI'PICK>1979429924 k~<<<<Ijk<<!<<!'-k<<V,'k.<<e NiagaraMohawkPowerCorporation.-2-MAR081978lfyourequireanyclarificationofthisrequest,pleasecontactthestaff'sassignedLicensingProject2~1anager.(ThisrequestforgenericinformationwasapprovedbyGEOunderablanketclearanceHo.R0071.ThisclearanceexpiresSeptember30,"1978.Sincerely,
Enclosure:
NUREG-0313,datedJuly1977Or<'lso'P~~"407/StevenA.Varga,ChiefLightRaterReactorsBranchNo.4DivisionofProjectt4anagementccvr/enclosure:Seepage3DFFICS~SURNAME~DATd~WcmSAIItja/oz,/780)/f/78NRCFORM318(9-76)NRCM02404U,S,OOVSRNMSNTFRINTINOOFFICSsISTSd2dd24 44ef>i9;y9RAMK)p)>Fdhole~(p(~~.gF'~s' NiagaraMohawkPowerCorporation--JAR08l9/9ccs.EugeneB.Thomas,Jr.LeBoeuf,Lamb,Leiby&MacRae1757NStreet,N.W.Washington,D.C.20036AnthonyZ.Roisman,Esq.Roisman,Kessler&Cashdan102515thStreet,NWWashington,D.C.20036Mr.RichardGoldsmithSyracuseUniversityCollegeofLawE.I.WhiteHallCampusSyracuse,"Sew"York'13210T.K.DeBoer,DirectorTechnologicalDevelopmentProgramsNewYorkStateEnergyOfficeSwanStreetBuildingCore1-2ndFloorEtrpireStatePlazaAlbany,NewYork12223 0~y1hJB NUREG-0313TECHNICALREPORTONMATERIALSELECTIONANDPROCESSINGGUIDELINESFORBWRCOOLANTPRESSUREBOUNDARYPIPINGManuscriptCompleted:July1977DatePublished:July1977DivisionofOperatingReactorsDivisionofSystemsSafetyOfficeofNuclearReactorRegulationU.S.NuclearRegulatoryCommissionWashington,D.C.20555
TABLEOFCONTENTSI."INTRODUCTIONII.SUMMARYOFACCEPTABLEMETHODSTOMINIMIZECRACKSUSCEPTIBILITYIII.INSERVICEINSPECTIONANDLEAKDETECTIONREQUIREMENTSFORBWRsWITHVARYINGCONFORMANCETOMATERIALSELECTIONANDPROCESSINGGUIDELINESIV.IMPLEMENTATIONOFMATERIALSELECTIONANDPROCESSINGGUIDELINESV.GENERALRECOMMENDATIONS~~1~\34~9.10
I.INTRODUCTIONSmall,hairlinecracksinausteniticstainlesssteelpipinginboilingwaterreactor(BWR)facilitieswereobservedasearlyas1965.Ineachcase,itwasbelievedthatthesituationhadbeencorrectedorsubstan-tiallyreducedbybettercontrolofwelding,contaminantsand/ordesignmodifications.InSeptember,1974,whenthefirstofaseriesofcracksinthepipingofthemoremodernBWRswasfoundatDresdenUnitNo.2.,thethenAtomicEnergyCommission(AEC)initiatedanintensiveinvestiga-tiontoevaluatethecause,extent,andsafety.implicationsoftheobservedcracking.InJanuary1975,aspecialPipeCrackingStudyGroupwasformedtocoordinateandacceleratethestaff'scontinuinginvest'iga-tionsoftheoccurrencesofpipecracking.Thisgroupincludedrepresen-tativesoftheNuclearRegulatoryCommission(NRC)andtheirconsultants.InOctober,1975,theStudyGroupissuedareport,NUREG-75/067"Tech-nicalReport,InvestigationandEvaluationofCrackinginAusteniticStainlessSteelPipingofBoilingWaterReactorPlants."Duringthesamegeneraltimespan,theGeneralElectricCompany(GE)conductedanindepen-dentevaluationofthecrackingoccurrencesandsubmittedtheirfindingsandrecommendationstotheNRC.ThispapersetsforththeNRCtechnicalpositionbasedontheinformationavailableatthistime.PlantoperatinghistoryindicatesthatType304and316austeniticstainlesssteelpipinginthereactorcoolantpressureboundaryofboilingwaterreactorsaresusceptibletostresscorrosion.cracking.
Studieshaveshownthatsuchcrackingiscausedbyacombinationof.thepresenceofsignificantamountsofoxygeninthecoolant,highstresses,andsomesensitizationofmetaladjacenttowelds.Suchcrackshaveoccurredintheheataffectedzonesadjacenttoweldsbutarenotexpectedtooccuroutsidetheseareas,providedthatthepipematerialisproperlyannealed.Piperunscontainingstagnantorlowvelocityfluidshavebeenobservedtobemoresusceptibletostresscorrosioncrackingthanpipescontainingacontinuouslyflowingfluidduringplantoperation.Historically,thesecrackshavebeenidentifiedeitherbyvolumetricexamination,byleakdetectionsystems,orbyvisualinspection.Becauseoftheinherenthighmaterialtoughnessofausteniticstainlesssteelpiping,stresscorrosioncrackingisunlikelytocausearapidlypropagatingfailureresultinginaloss-of-coolantaccident.Althoughtheprobabilityisextremelylowthatthesestresscorrosioncrackswillpropagatefarenoughtocreateasignificantsafetyhazardttothepublic,thepresenceofsuchcracksisundesirable.StepsshouldthereforebetakentominimizestresscorrosioncrackinginBWRpipingsystemstoeliminatethisconditionandtoimproveoverallplantreliability.ItisthepurposeofthispositiontosetforthacceptablemethodstoreducethestresscorrosioncrackingsusceptibilityofBWRpipingandtherebyalsoprovideanincreasedlevelofreactorcoolantpressureboundaryintegrity.Recognizingthatthemoststraightforwardand desirableapproachormethodsmaynotbepracticable,orevenpossible,forallplants,thebasesforvaryingdegreesofconformancetoourguidelinesareprovided.Augmentedinserviceinspectionandleakdetec-tionrequirementsareestablishedforplantsthathavenotfullyimplementedtheprovisions.containedinPartIIofthisdocument.II.SUMMARYOFACCEPTABLEMETHODSTOMINIMIZECRACKSUSCEPTIBILITYThematerialselectionandprocessingguidelineslistedbelowidentifyalternativeacceptablemethodstominimizesusceptibilitytostresscorrosioninBWRpressureboundarypiping.Itisexpectedthatadoptionofthesepracticeswillresultinahighdegreeofprotectionagainststresscorrosioncracking.1.CorrosionResistantMaterialsAllpipeandfittingmaterialincludingweldmetalshouldbeofatypeandgradethathasbeenshowntobehighlyresistanttooxygen-assistedstresscorrosionintheas-installedcondition.Unstabilizedwroughtausteniticstainlesssteelwith>0.035/carbondoesnotmeetthisrequirementunlessallsuchpipingincludingweldsisinthesolutionannealedcondition.Theacceptabilityofalternativematerials,processes,orothermethodsftoprovideanadequatedegreeofcorrosionresistancewillbemadeonacase-by-casebasis.2.CorrosionResistant"SafeEnds"Allunstabilizedwroughtausteniticstainlesssteelpipingwithcarboncontents>0.0355shouldbeinthesolutionannealedcondition.
Ifweldsjoiningthesematerialsarenotsolutionannealed,theyshouldbemadebetweencase(orweldoverlaid)austeniticstainlesssteelsurfaces(5/minimumferrite)orothermaterialshavinghighresistancetooxygen-assistedstresscorrosion.Thejointdesignmustbesuchthatanyunstabilizedwroughtausteniticstainlesssteelcontaining>0.0351.carbon,whichmaybecomesensitizedasaresultoftheweldingprocess,isnotexposedtothereactorcoolant.3.Otherproposedmethodstoprovideprotectionagainststresscorrosioncrackingwillbereviewedonacasebycasebasis.RegulatoryGuide1.44"ControloftheUseofSensitizedStainlessSteel",datedMay,1973willberevisedtoprovideadditionalguidanceonacceptablepractices.III.INSERVICEINSPECTIONANDLEAKDETECTIONREUIREMENTSFORBWRsWITHVARYINGCONFORMANCETOMATERIALSELECTIONANDPROCESSINGGUIDELINES1..ForplantswhereallASMECodeClassIreactorcoolantpressureboundarypipingsubjecttoinserviceinspectionsunderSectionXImeetstheguidelinesstatedinPartII,noaugmentedinserviceinspectionorleakdetectionrequirementsarenecessary.2.Pipinginallotherplantsissubjecttoadditionalinserviceinspectionandleakdetectionrequirements,asdescribedbelow.Thedegreeofinspectionofsuchpipingdependsonwhetherthespecificpipingrunsareconformingornon-conforming,andonwhetherthespecificpipingrunsareclassifiedas"Service Sensitive"."ServiceSensitive"linesaredefinedasthosethathaveexperiencedcrackinginservice,orthatareconsideredtobeparticularlysusceptibletocrackingbecauseofhighstress,orbecausetheycontainrelativelystagnant,intermittent,orlowflowcoolant.Examplesofpipingrunsconsideredtobeservicesensitiveinclude,(butarenotlimitedto):corespraylines,recirculatingby-passlines(or"stubtubes"onplantsthathaveremovedtheby-passlines)CRDhydraulicreturnlines,isolationcondenserlines,andshutdownheatexchangerlines.A.Fornon-conforminglinesthatarenotservicesensitive:(1)Inserviceinspectionofthenon-conforminglinesshouldbeconductedinaccordancewiththeschedulespecifiedinASMECode,SectionXI-SubsectionIWB,asrequiredbytheapplicableexaminationCategoriesB-FandB-J,withtheexceptionthattherequiredexaminationshouldbecompletedinnomorethan80months(twothirdsofthetimeperscribedinthescheduleintheASNEBoilerandPressureVesselCodeSectionXI).Ifexaminationsconductedduringthefirst80monthperiodrevealnoincidenceofstresscorrosioncracking,theexaminationschedulethereaftercanreverttothescheduleperscribedinSectionXIoftheASMEBoilerandPressureVesselCode.
Thepipingareassubjecttoexamination,themethodofexamina-tion,theallowableindicationstandardsandexaminationpro-ceduresshouldcomplywiththerequirementsoftheEditionandAddendaoftheASMECode,SectionXIidentifiedasapplicableby10CFRPart50,Section50.55a,Paragraph(g),"CodesandStandards."(2)ThereactorcoolantleakagedetectionsystemshouldbeoperatedunderthefollowingTechnicalSpecificationrequirementsinordertoenhancethediscoveryofunidentifiedleakagethatmayincludethrough-wallcracksdevelopedinausteniticstainlesssteelpiping:a.Thesourceofreactorcoolantleakageshouldbeidentifiabletotheextentpractical,usingleakagedetectionandcollec-tionsystemsthatmeetthepositiondescribedinSectionC,RegulatoryPositionofRegulatoryGuide1.45,"ReactorCoolantPressureBoundaryLeakageDetectionSystems,"oranacceptableequivalentsystem.b.Plantshutdownshouldbeinitiatedforinspectionandcorrectiveactionwhentheleakagesystemindicates,withinaperiodoffourhoursorless,anincreaseintherateofunidentifiedleakageinexcessoftwogallonsperminute,orwhenthetotalunidentifiedleakageattainsarateoffivegallonsperminute,whicheveroccursfirst.
c.Unidentifiedleakageshouldincludeallleakageotherthan:1.Leakageintoclosedsystems,suchaspumpsealorvalvepackingleakagethatiscaptured,metered,andconductedtoasumporcollectingtank,2.Leakageintothecontainmentatmospherefromsourcesthatarespecificallylocatedandknowneithernottointerferewiththeoperationoftheunidentifiedleakagedetectionsystem,nornottobefromathrough-wallcrackinthepipingwithinthereactorcoolantpressureboundary.B.Fornon-conforminglinesthatareservicesensitive:(1)TheleakagedetectionrequirementsdescribedinIII.Aabove,shouldbeimplemented.(2)Theweldsandadjoiningareasofbypasspipingofthedischargevalvesinthemainrecirculationloops,andoftheausteniticstainlesssteelreactorcorespraypipinguptoandincludingthesecondisolationvalveshouldbeexaminedateachreactorrefuelingoutageoratotherscheduledorunscheduledplantshutdowns.Successiveexaminationsneednotbe=closer'hansixmonths,ifshutdownsoccurmorefrequentlythansixmonths.Thisrequirementappliestoallbypasslineswhetherthe4-inchvalveiskeptopenorclosedduringoperation.
Intheeventtheseexaminationsfindthepipingfree.ofunacceptableindicationsforthreesuccessiveinspections,theexaminationmaybeextendedtoeach36monthperiod(plusorminusbyasmuchas12months)coincidingwitharefuelingoutage.Inthesecases,thesuccessiveexaminationmaybelimitedtoonebypasspiperun,andonereactorcorespraypipingrun~(3)Theweldsandadjoiningareasofotherservice.sensitivepipingshouldbeexaminedonasamplingbasis.Forexample,ifasystemconsistsofseveralbranchrunswithessentiallysymmetricpipingconfigurationsthatperformsimilarsystemfunctions,anacceptableinspectionprogramshouldincludeatleastone,butnotlessthan25K,ofthesimilarbranchruns.Thefrequencyofsuchexaminationsshouldbeasdescribedin2above.Ifunacceptableflawindicationsaredetectedinanybranchrun,theremainingbranchrunsamongthegroupshouldbeexamined.intheeventtheexaminationsrevealnounacceptableindica-tionswithinthreesuccessiveinspections,theexaminationschedulemayreverttotheASMEBoilerandPressureVesselCode,SectionXI,"InserviceInspectionofNuclearPowerPlant,Components"withtheexceptionthat.therequiredexaminationshouldbecompletedduringeach80monthperiod(two-thirdsthetimeperscribedinthescheduleintheASNECodeSectionXI).
(4)Themethodofexamination,theallowableindicationstandardsandexaminationproceduresshouldcomplywiththerequirementsoftheEditionandAddendaoftheASMECode,SectionXIidentifiedasapplicableby10,CFRPart50,Section50.55a,Paragraph(g),"CodesandStandards."IV.IMPLEMENTATIONOFMATERIALSELECTIONANDPROCESSINGGUIDELINES1.Forplantsthatapplyforaconstructionpermitaftertheissuedateofthisdocument,allASMECodeClassIreactorcoolantpressureboundarylinesshouldconformtotheguidelinesstatedinPartII.*2.Forplantsunde'rreview,butforwhichaconstructionpermithasnotyetbeenissued,allservicesensitivelinesshouldconformtotheguidelinesstatedinPartII.OtherASMECodeClassIreactor,coolantpressureboundarylinesshouldconformtoPartIII4to,theextentpracticable.3.Forplantsthathavebeenissuedaconstructionpermit,ASMECodeClassIreactorcoolantpressureboundarylinesshouldconformtotheguidelinesstatedinPartIItotheextentpracticable.*Afterrevision,RegulatoryGuide1~44maybeusedasguidanceforacceptablematerials,process,orothermethods. 4.Forplantsthathavebeenissuedanoperatinglicense,servicesensitivelinesshouldbemodifiedtoconformtotheguidelinesstatedinPartII,totheextentpracticable.LinesinwhichcrackingisexperiencedshouldbereplacedwithpipingthatconformstotheguidelinesstatedinPartII.V.,"GENERALRECOMMENDATIONSThemeasuresoutlinesinPartIIofthisdocumentprovideforpositiveactionsthatareconsistentwiththecurrenttechnology.Theimplemen-tationoftheseactionsshouldmarkedlyreducethesusceptibilitytostresscorrosioncrackinginBWRs.ItisrecognizedthatadditionaltechniquesareavailabletolimitthecorrosionpotentialofBWRcoolantpressureboundarymaterialsandimprovetheoverallsystemintegrity.Theseincludeplantdesignandoperationalconsiderationstoreducesystemexposuretopotentiallyaggressiveenvironment,improvematerialfabricationandweldingtechniquesandprovisionsforvolumetricinspec-tioncapabilityinthedesignofweldjoints.Specifically,considera-tionshouldbegivento:1.Minimizingthetotalextentofthecoolantpressureboundarywithspecialemphasisonstagnantorlowflowlines.2.Reducingtheoxygencontentoftheprimarycoolant.
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DISTRIBUTIONW/ENCLOSURE:DocketFilePDRLocalPDRLWR84FileM.ServiceProjectManagerWF'aneS.A.VargaDISTRIBUTIONW/0ENCLOSURE:R'.BoydR.DeYoungD.VassalloF.Williams.H.'Sm'ithR.MattsonJ.KnightS.PawlickiH.ConradI8E(3)ELDL.CrockerK.Gollerbcc:TICACRS(15)NSIC P+~~