ML17332A745
| ML17332A745 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 04/13/1995 |
| From: | FITZPATRICK E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17332A746 | List: |
| References | |
| AEP:NRC:1129D, NUDOCS 9504260146 | |
| Download: ML17332A745 (24) | |
Text
RIQRITYCCELERATEDRlDSPROCl'.SSliCREGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9504260146DOC.DATE:95/04/13NOTARIZED:YESDOCKETNFACIL:50-315DonaldC.CookNuclearPowerPlant,Unit1,IndianaM05000315AUTH.NAMEAUTHORAFFILIATIONFITZPATRICK,E.IndianaMichiganPowerCo.(formerlyIndiana&MichiganEleRECIP.NAMERECIPIENTAFFILIAT10NDocumentControlBranch(DocumentControlDesk)
SUBJECT:
ApplicationforamendtolicenseDPR-58,modifyingTS3/4.4.5toallowuseoflaser-weldedsleevestorepairdefectiveSG~~tubes.Westinghousenonproprietary&proprietaryreptsdescribingrepairprocessencl.Proprietaryreptwithheld.DISTRIBUTIONCODE:APOIDCOPIESRECEIVED:LTRgENCLJSIZE:520TITLE:ProprietaryReviewDistribution-PreOperatingLicense&OperatingRNOTESRECIPIENTIDCODE/NAMEPD3-1LAHINTERNAFILECENTER01.EXTERNAL:NRCPDRCOPIESLTTRENCL11111110RECIPIENTIDCODE/NAMEPD3-1PDOGC/HDS2COPIESLTTRENCL1110DCUYOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEiVKSTE!COYTACT'I'IIEDOCL'ifEYTCONTROLDESK,ROOMPI-37IEXT.504.of63)TOI'.LIhflNATEYOI.'RXAifLPl<OilDISTRIBUTIONLIS'I'SI'ORDOCK'NlEX'I'SYOI.'ON"I'l.'I'.D!TOTALNUMBEROFCOPIESREQUIRED:LTTR6ENCL'
't'E IndianaMichiganPowerCompanyP.O.Box16631Columbus,OH43216IApril13,1995DocketNos.:50-315AEP:NRC:1129DU.S.NuclearRegulatoryCommissionATTN:DocumentControlDeskWashington,D.C.20555Gentlemen:DonaldC.CookNuclearPlantUnit1TECHNICALSPECIFICATIONCHANGESTOALLOWUSEOFLASER-WELDEDSLEEVESFORSTEAMGENERATORTUBESThisletteranditsattachmentsconstituteanapplicationforamendmenttothetechnicalspecifications(T/Ss)fortheDonaldC.CookNuclearPlantUnit1.Specifically,weareproposingtomodifyT/Ss3/4.4.5(SteamGenerators)andtheaccompanyingBasessectiontoallowuseoflaser-weldedsleevestorepairdefectivesteamgeneratortubes.AdetaileddescriptionoftheproposedchangesandouranalysisconcerningsignificanthazardsconsiderationsareincludedinAttachment1tothisletter.Attachment2containsmarkeduppagesofthecurrentT/Ss.Attachment3containstheproposedrevisedT/Sspages.Attachment4containsacopyoftheproprietaryreportpreparedbyWestinghouseElectricCorporation,WCAP-13088Revision3,describingthesleevingrepairprocess.Attachment5containsacopyofthenon-proprietaryversionofthesameWestinghouseElectricCorporationreport,WCAP-13089Revision3.Attachment6containsaWestinghouseauthorizationletter,CAW-95-786,ApplicationForWithholdingProprietaryInformationFromPublicDisclosureandaccompanyingaffidavit.Webelievetheproposedchangeswillnotresultin(1)asignificantincreaseintheamounts,andnosignificantchangeinthetypes,ofanyeffluentthatmaybereleasedoffsite,or(2)asignificantincreaseinindividualorcumulativeoccupationalradiationexposure.TheseproposedchangeshavebeenreviewedbythePlantNuclearSafetyReviewCommitteeandwillbereviewedatthenextregularlypu/'/(9504260i46950413PDRADOCK05000315PPDRscheduledNuclearSafetyandDesignReviewCommitteemeeting.:3gegpg/~/~
U.S.NuclearRegulatoryCommissionPage2AEP'NRC'1129DIncompliancewiththerequirementsof10CFR50.91(b)(1),copiesofthisletteranditsattachmentshavebeentransmittedtotheMichiganPublicServiceCommissionandtotheMichiganDepartmentofPublicHealth.TheT/SpagessubmittedwiththisletterwillbeimpactedbytheT/SpagechangesinourletterAEP:NRC:1166R,"2.0VoltInterimSteamGeneratorTubePluggingCriteriaforCycle15."Sincerely,VicePresidentSWORNTOANDSUBSCRIBEDBEFOREMETHIS~Z4DAYOF1995otaryPublicehAttachmentscc:A.A.BlindG.CharnoffJ.B.MartinNFEMSectionChiefNRCResident,Inspector-BridgmanJ.R.Padgett ATTACHMENT1TOAEPNRC'1129DDESCRIPTIONOFTHEPROPOSEDCHANGESANDANALYSISCONCERNINGSIGNIFICANTHAZARDSCONSIDERATIONS
ATTACHMENT1TOAEP:NRC:1129DPage1INTRODUCTIONThisamendmentrequestproposesachangetoCookNuclearPlant(CNP)Unit1steamgeneratortechnicalspecification(T/S)4.4.5.2,4.4.5.4.a,4.4.5.4.c,4.4.5.5.b.l,andBasis3/4.4.5onpageB3/4.4-3,toallowsteamgeneratortubesleevingunderspecificconditions.ThechangepermitstheinstallationofAlloy690laser-weldedtubesleevesatdegradedtubesupportplate(TSP)intersectionsandwithinthetubesheet(TS)areaofCNPUnit1steamgenerators,.-Perthecurrenttechnicalspecifications,steamgeneratortubeswitheddycurrentindicationsexceedingthecurrentplugginglimitfortheselocationscanberepairedusingexistingsleevingrequirementsorberemovedfromservice.Thisproposedamendmentpermitslaser-weldedtubesleevestobeinstalledtorepairdegradedsteamgeneratortubeseitherattheTSPintersections(TSPsleeves),withintheTSarea(TSsleeves),oracombinationofbothwithinthesametube.DESCRIPTIONOFTHEAMENDMENTREQUESTAs'requiredby10CFR50.91(a)(1),thisanalysisisprovidedtodemonstratethataproposedlicenseamendmenttoimplementrepairoftubesusinglaser-weldedtubesleevesforCNPUnit1steamgeneratorsrepresentsnosignificanthazardsconsideration.Inaccordancewith10CFR50.92(c),implementationoftheproposedlicenseamendmentwasanalyzedusingthefollowingstandardsandfoundnotto:1)involveasignificantincreaseintheprobabilityorconsequencesforanaccidentpreviouslyevaluated,2)createthepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated,or3)involveasignificantreductioninamarginofsafety.Thelaser-weldedsleevingrepairmethodsecurestotheinsideoftheoriginaltubeashortlengthofsleevetubingwithanouterdiameterslightlysmallerthantheinsidediameterofthetube,spanningthedegradedareaoftheparenttube.TheTSPsleeveisattachedtothedegradedtubebyproducinganautogenousweldbetweentheoriginaltubeandsleeveateachendofthesleeve.TSPsleeveweldsareproducedinthefreespansectionsofthetubeabovethetopofthetubesheet.Thefreespanweldprovidesthestructuraljointbetweenthetubeandsleeve,and,sinceitisahermeticseal,italsoprovidespositive(leaktight)leakageintegrity.TheTSsleeveissecuredandsupportedstructurallyattheupperjointsectionbyafreespanautogenousweldperformedidenticallytotheTSPsleeveweldswhilethelowerjointissecuredbyamechanicalhardroll.AnoptionalsealweldcanalsobeincludedwithintheTSsleevelowerjointatanelevationcoincidentwiththeapproximatemidpointoftheTScladding.However,fortheTSsleevelowerjoint,thehardrollareasuppliesthenecessarystructuralrequirementsforthelowerjointsincethesealweldisoptionalforthislocation.Boththelowerhardroll 0~~'~'Pol ATTACHMENT1TOAEP:NRC:1129DPage2andfreespanlaserweldjointsprovidestructuralintegritycharacteristicswhichexceedthestructuralrequirementsforthesleeve.Therefore,itisexpectedthatalossofstructuralintegrityinoneofthesleevejointswillnotresultinalossofstructuralintegrityforthesleeve.ThesleevestructuralintegrityrequirementsincludesafetyfactorsinherenttotherequirementsoftheASMECode.InstallationofTSPsleevesand/orTSsleevesrestorestheintegrityoftheprimarypressureboundarytoaconditionconsistentwiththatoftheoriginallysuppliedtubing.AllweldsmustbeproducedaminimumdistancefromanydetectedtubedegradationasdescribedinWCAP-13088,Rev.3(Attachment4).Absentprovisionsfortuberepairbysleeving,tubeswithindicationsofdegradationinexcessofthepluggingcriteriaatTSPand/orTSlocationswouldhavetoberemovedfromserviceinaccordancewithtechnicalspecificationtubepluggingcriteria.Removalofatubefromserviceresultsinasmallreductionofreactorcoolantflowthroughthesteamgenerator.Thissmallreductioninflowhasanimpactonthemargininthereactorcoolantflowthroughthesteamgeneratorwithregardtocorecoolingcapacityandontheheattransferefficiencyofthesteamgenerator.Repairofatubebysleevingmaintainsthetubeinserviceandresultsinamuchsmallerflowreductionasopposedtoplugging.Therefore,theuseofsleevinginlieuofpluggingwouldminimizelossofmargininreactorcoolantsystemflowandassistinassuringthatminimumflowratesaremaintainedinexcessofthatrequiredforoperationatfullpower.AnycombinationofsleevingandpluggingutilizedatCNPUnit1uptoalevelsuchthattheeffectofsleevingwillnotreducetheminimumreactorcoolantflowratetobelowthecurrenttechnicalspecificationlimitisacceptable.Also,minimizingthereductioninflowhasoperationalbenefitsbylimitingtheincreaseinheatfluxacrossthetubesremaining'nservice.Increasedheatfluxeshavebeenassociatedwithanincreasedpotentialfortubecorrosion.TheproposedamendmentwouldmodifyTechnicalSpecifications3/4.4.5"SteamGenerators,"andBasesB3/4.4.5,"SteamGenerators,"topermittheuseofWestinghouselaser-weldedsleevesandwillprovidethesleeve/tubeinspectionrequirementsandacceptancecriteriatodeterminethelevelofdegradationwhichwouldrequirethesleevedtubetosubsequentlyberemovedfromservice.
~l ATTACHMENT1TOAEP'NRC'1129DPage3EVALUATIONSleeveTubeInteritDuringthedevelopmentoflaser-weldedsleeving,SectionIIIoftheASMECodewasusedfortheminimumwallthicknessdeterminationandboundingstressandfatiguelevelsforthesleeve.ByshowingthatthesleevedesignmeetstheapplicablesubsectionsofSectionIIIoftheCode,thesleevedesignmeetsthedesignrequirementsofthe.originaltubing.(Draft)RegulatoryGuide(RG)1.121,"BasesforPluggingDegradedPWRSteamGeneratorTubes,"isusedtodeveloptheplugginglimitofthesleevedeterminedbynon-destructiveexamination(NDE),shouldsleevewalldegradationsubsequentlyoccur.Potentiallydegradedsleevesattheplugginglevelwereshown(byanalysis)toretainburststrengthinexcessofthreetimesthenormaloperatingpressuredifferentialatendofcycleconditions,perRG1.121guidelines.ThestructuralanalysisoutlinedinAttachment4utilizesagenericsetofloadinginputswhichwasintendedtoboundtheoperatingregimesofallplantswithWestinghouseSeries44and51steamgenerators.ThecurrentnormaloperatingpressuredifferentialforCNPUnit1isapproximately1410psi,whichisboundedbythevalueusedinAttachment4of1530psifornormaloperatingconditions.DuetotherelativelylowsteampressuredevelopedinModel51steamgenerators,thenormaloperatingcondition(withappropriatesafetyfactorof3applied)resultsinthelimitingloadingconditionfordeterminationoftherequiredminimumwallthicknesstosatisfytheASMECode,andsubsequentlyRG1.121.Additionally,thesleevewallplugginglimitforCNPUnit1LWSshasbeenestablishedusinganormaloperatingconditionprimarytosecondarypressuredifferentialof1600psi(discussedlater).TherequirementsofRG1.83,"InserviceInspectionofPWRSteamGeneratorTubes,"areimplemented,andabaselineeddycurrentinspectionoftheinstalledsleevesisperformedpriortooperation.Anultrasonicinspectionofthefreespanweldjointsisalsoperformedpriortooperation.Theultrasonicinspectionisusedtoverifythattheminimumacceptablefusionzonethicknessoftheweldisachieved.AseparateminimumweldfusionzonethicknesshasbeenshownbyanalysistosatisfytherequirementsoftheASMECodewithregardtoacceptablestresslevelsduringoperatingandaccident,conditions'heacceptancecriteriafortheultrasonictesting(UT)inspectionoftheweldrequiresaminimumweldfusionzonewidth.ThisminimumUTbasedweldwidthisapproximately50Xlargerthantheminimumacceptableweldwidthbasedonstresslimitations,therefore,structuralmarginabovethatprovidedmerelybycompliancewiththeASMECodeisinherentlyprovidedforeachsleeveweld.Additionally,fieldexperiencehasindicatedthatnominalweldwidthsareapproximatelytwicetheminimumweldwidthrequiredforUTacceptance.
t41EVI ATTACHMENT1TOAEP:NRC:1129DPage4Asstatedpreviously,agenericsetofloadingconditionswasusedforstructuralanalysisofthesleevedtubeassemblyinAttachment4.Afatigueanalysiswasperformedforthesleevedtubeassembly,thecriticallocationbeingthefreespanlaserweld.Theloadingcyclesthatwereappliedtothesleeveassemblyanalysiswerethosefora40yearplantlifecycle.Therefore,thefatigueanalysisisconservativeforanoperatingplant.Theresultsofthefatigueanalysisindicateacceptableusagefactorsfortheentirerangeofpermittedweldthicknesses.Acomparisonofthenumberofloadingcyclesusedin.thegenericanalysisindicatesthat..thegenericinputsareconservativecomparedtoCNPUnit1inthisarea.Usingthegenericinputs,thecumulativefatigueusagefactorwasfoundtobemuchlessthan1.0(actualvaluelessthan0.10).ThepressuredifferentialsusedforthegenericanalysiswerefoundtobeconservativecomparedtoCNPUnit1valuesforthemajorityofthetransientcurvesevaluated.SeveraltransientsforCNPUnit1involvedslightlyhigherpressuredifferentialscomparedtotheinputsusedinthegenericanalysis.However,thedifferencewasdeterminedtobeinsignificantwithregardtotheappliedrangeofstressintensityandalsoinsignificantwithregardtoitsinputtocumulativefatigueusageloading.Recalculationofcumulativefatigueusageindicatesvirtuallynochangeinthecalculatedusagefactor(actualvalueforCNPUnit1remainslessthan0.1).AconservativesetoftransientsapplicabletoCNPUnit1wereusedforthecomparisonwiththetransientsetdefinedinAttachment4:TheCNPUnit1transientsareapplicableforplantoperationatboth2250psiand2100psiRCSpressure.ArangeofT><<valuesarealsoincludedintheCNPUnit1transientset.LeakagetestingunderconditionsconsideredtobemoreseverethanexpectedduringalloperatingplantconditionshasshownthattheLWSdoesnotintroduceadditionalprimarytosecondaryleakageduringapostulatedsteamlinebreakevent.Laser-weldedsleevedtubeassembliesweresubjectedtothermalandfatiguecyclingandthenleaktestedatpressuredifferencesofupto3110psi,whichfarexceedsthemaximumexpectedCNPUnit1feedlinebreak/steamlinebreak(FLB/SLB)pressuredifferentialofapproximately2335to2560psid.Noleakagewasdetectedinanyweldedjoint(bothfreespanandTSjoints).LeakagetestinghasalsoshownthatthesealweldoftheTSsleevelowerjointisnotrequiredinordertoprecludeleakageduringnormaloperationoraccidentconditionsat600oF.Non-weldedlowerjointTSsleeve/tubeleakagetestspecimensweresubjectedtobothfatigueandthermalcyclingtestspriortofinalleakrateevaluationtesting.Theloadlevelappliedduringthefatiguetestingexceededthemaximumaxialloadappliedtothesleeveduringthemostseverepressureloadingcondition.Thermalcyclingtestssimulatedastandardplantheatup/cooldowncycle.Noleakagewasdetectedinanynon-weldedTSsleevelowerjointat600oFafterboththermalandfatigueloading.Primarytosecondaryleakage
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ATTACHMENT1TOAEP:NRC:1129DPage5throughnon-weldedTSsleevelowerjointswouldnotbeexpectedatOXpower(Tarot547F).SleevtnofPreviouslPluedIndicationsThesleeveinstallationrequirementsapplicabletoactivetubeswhichhavebeenidentifiedascontainingdegradationwhichexceedstherepairlimitarenodifferentforthesleevingofpreviouslypluggedtubes.Anew"baseline"inspectionoftheentiretubelengthmustbe...performedpriortosleeveinstallationin'previouslypluggedtube.Thelocationoftheidentifiedtubedegradationmustbeverifiedtobeaminimumdistanceofone-inchfromtheweldjoints(sameforactivetubes).Historically,theareasofthetubewhichhavesufferedoutsidediameterinitiatedcorrosiondegradationaretheTSPintersectionsandthesectionsoftubewithinthethicknessoftheTSwheresecondarysidecontaminantshavecollectedduetotheoperatingcrevices'heexpansiontransitionregioncanexperienceeitherouterdiameterorinnerdiameterinitiatedcorrosion.Thesleevefreespan(structural)weldjointsarenotlocatedintheseareas,andshouldnotbeaffectedbyanypreviouslyidentifieddegradationmechanismwhichcausedthetubetoberemovedfromservice.Thestructuralanalysishasalsosupportedsleeveinstallationinacircumferentiallyseparatedtube,therefore,theextentofidentifieddegradationshouldnotaffectsleeveinstallationprovidedthedegradationisoneinchfromtheweldjoints.Additionally,theareaofthetubewherethetubeplugwasinstalledmustbevisuallyinspectedpriortosleeveinstallation.Surfacefinishrequirementsforthisareahavebeendevelopedwhichhelptomaintaintheabilityofthejointtoformaleaktightseal.Conformancetothesurfacefinishrequirementsforthelowerjointwillhelptoensurealeaktightsleevejoint,regardlessofwhetherornotthesealweldhasbeenproduced.Theabilityoftheweldtosufficientlypenetratethetubewallhasbeenshownbytestincaseswherealocalizedgap(upto2mils)existedbetweenthetubeandsleeve.Thepenetratingcapabilitiesoftheweldwillalsohelptoensurealeaktightjointincaseswhereslightsurfaceimperfectionsduetotubeplugremovalmaybepresent.FlowMarinConsiderationsByreducingthenumberoftubeplugsinstalledinthesteamgenerator,theproposedamendmentwouldminimizethelossofmargininreactorcoolantflowthroughthesteamgeneratorduringapostulatedeventswhencorecoolingcapacityisrequired.Also,sleevingwillprovidegreatermarginabovetherequiredminimumflowforfullpoweroperation,thanifequalnumbersoftubeswerepluggedasopposedtosleeved.
ATTACHMENT1TOAEP'NRC'1129DPage6Theinstallationofasleeveintoatuberesultsinanadditionalflowrestrictionwithintheprimarysystem,withanassociatedincreaseinpressuredropinthesteamgenerator.Theeffectsofthisflowrestrictiononplantoperationareevaluatedinthesamemannerthattubepluggingeffectsareanalyzed.Attachment4identifiesthereductioninprimarycoolantflowcausedbytheprojectedsleevingundernormaloperatingconditionsandidentifiesthenumberofsleevesorcombinationofsleeveswhichresultinaflowreductionequivalenttoonepluggedtube.Evaluationofcorecoolingcapabilityforthe.minimumreactorcoolantsystemflowratewillboundtheeffectsonallcoreandsystemparametersforacombinationofpluggingandsleevinguptotheequivalentresistanceassociatedwiththeminimumreactorcoolantflowrate.ThehydraulicequivalencyvaluescontainedinAttachment4canbeusedtoestimatetheimpactoflaser-weldedsleevingonRCSflowcapability.UsingworstcaseflowconditionsofAttachment4(judgedtobeconservativecomparedtoCNPUnit1conditions),asinglehotlegTSsleevewouldrepresentapproximately1/23oftheflowreductionofapluggedtube.AdditionalcombinationsofTSPsleevesandTSssleevesandtheirflowreductioneffectsareincludedinAttachment4.ANALYSISConformanceoftheproposedamendmentstothestandardsforadeterminationofnosignificanthazardasdefinedin10CFR50.92(threefactortest)isshowninthefollowing:1)OperationofCNPUnit1inaccordancewiththeproposedlicenseamendmentdoesnotinvolveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated.TheTSand/orTSPintersectionLWSconfigurationhasbeendesignedandanalyzedinaccordancewiththerequirementsoftheASMECodeandRG1.121.Fatigueandstressanalysesofthesleevedtubeassembliesproducedacceptableresults.MechanicaltestinghasshownthatthestructuralstrengthoftheAlloy690sleevesundernormal,faultedandupsetconditionsiswithinacceptablelimits,Leaktestinghasdemonstratedthatprimarytosecondaryleakageisnotexpectedduringallplantconditions,includingthecasewherethesealweldisnotproducedinthelowerjointoftheTSsleeve.Testingshowsthatnon-weldingTSsleevelowerjointsremainedleaktightattemperatureandpressureconditionsrepresentativeofnormalandaccidentconditions.Sincelaserweldingproducesahermeticsealbetweenthetubeandsleeve,noleakpathcanbe'ealizedunderanycondition.Therefore,installationofLWSswillnotinfluenceoffsitedosecalculationforapostulatedsteamlinebreakevent.
ATTACHMENT1TOAEP:NRC:1129DPage7TheproposedtechnicalspecificationchangetosupporttheinstallationofAlloy690LWSsdoesnotadverselyimpactanypreviouslyevaluateddesignbasisaccidentortheresultsofaccidentanalysesforthecurrenttechnicalspecificationminimumreactorcoolantsystemflowrate.Theresultsofthequalificationtesting,analyses,andplantoperatingexperiencedemonstratethatthesleeveassemblyisanacceptablemeansofmaintainingtubeintegrity.Theseaforementionedanalysesandtestsdemonstratethatinstallationofsleevesspanningdegradedareas,ofthetubewillrestorethetubetoaconditionconsistentwithitsoriginaldesignbasis.PlugginglimitcriteriaareestablishedusingtheguidanceofRG1.121.Furthermore,perRG1.83recommendations,thesleevedtubecanbemonitoredthroughperiodicinspectionswithpresenteddycurrenttechniques'onformanceofthesleevedesignwiththeapplicablesectionsoftheASMECodeandresultsoftheleakageandmechanicaltests,supporttheconclusionthatinstallationoflaser-weldedtubesleeveswillnotincreasetheprobabilityorconsequencesofanaccidentpreviouslyevaluated.Dependinguponthebreaklocationforapostulatedsteamgeneratortuberuptureevent,implementationoftubesleevingcouldacttoreducetheradiologicalconsequencestothepublicduetoreducedflowratethroughasleevedtubecomparedtoanon-sleevedtubebasedontherestrictionaffordedbythesleevewallthickness.2)Theproposedlicenseamendmentdoesnotcreatethepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated,Implementationoflaser-weldedsleevingwillnotintroducesignificantoradversechangestotheplantdesignbasis.StressandfatigueanalysisoftherepairhasshowntheASMECodeandRG1.121allowablevaluesaremet.Implementationoflaser-weldedsleevingmaintainsoveralltubebundlestructuralandleakageintegrityduringallplantconditionsatalevelconsistenttothatoftheoriginallysuppliedtubing.Leakandmechanicaltestingofsleevessupportstheconclusionsofthecalculationsthatthesleeveretainsbothstructuralandleakageintegrityduringallconditions.Sleevingoftubesdoesnotprovideamechanismresultinginanaccidentoutsideoftheareaaffectedbythesleeves.Anyhypotheticalaccidentasaresultofpotentialtubeorsleevedegradationintherepairedportionofthetubeisboundedbytheexistingtuberuptureaccidentanalysis.Sincethesleevedesigndoesnotaffectanyothercomponentorlocationofthetubeoutsideoftheimmediatearearepaired,inadditiontothefactthattheinstallationofsleevesandtheimpactoncurrentplugginglevelanalysesisaccountedfor,thepossibilitythatlaser-ATTACHMENT1TOAEP'NRC'1129DPage8weldedsleevingcreatesanewordifferenttypeofaccidentisnotsupported.ThedesignofthermallytreatedAlloy600andAlloy690sleevedtubeassemblieshaveperformedwellhistoricallywithregardtocorrosion.TherearenoreportedinstancesofAlloy600thermallytreatedorAlloy690sleevedegradationforthegreaterthan35,000sleevesthatWestinghousehasinstalledintheU.S.Acceleratedcorrosiontestresultsshowthefreespanlaser-weldedjoint(LWJ)(withpost-weldheattreatment)iscapableofexhibitingaresistanceto"corrosionofgreaterthan10timesthatofrolledtubetransitions.MostLWScorrosionspecimensdidnotexperiencedegradationandweresubsequentlyremovedfromthecorrosiontestmediaafterasubstantialtestingperiod(supportingthe10xfactorcomparedtorolltransitions)wasachieved.SeveralmillannealedAlloy600materialheatswereusedforcorrosionspecimenpreparation.AllweredocumentedbyprevioustesttohavebeenhighlysusceptibletoPWSCC.ThepostweldheattreatmentprocessappliedtoLWSfreespanjointsisdesignedtoachieveaminimumtubeODwalltemperatureof1400Fadjacenttotheweldandwithinthelaserweldheataffectedzone.Sincethetargettemperatureof1400FisachievedonthetubeOD,aslightlyhighertemperatureisachievedatthetubeIDsurface,wheretheweldcoolingstressesareconcentrated.Also,sincetheaxiallengthofthelaserweldandlaserweldheataffectedzonearerelativelynarrowcomparedtoothersleeveweldingprocesses,anarrowersectionoftubeisrequiredtobeheattreated.SincethelengthoftuberequiredtobeheattreatedisshorterintheLWSprocessthanwithothersleevingprocesses,lowerresidualstressesinthetubecanbeexpected.Acceleratedcorrosiontestsalsoshowthatnon-heattreatedlaser-weldedfreespanjointsexhibitresistancetostresscorrosioncrackingequaltoorgreaterthanrolledtubetransitions.AnextensivedatabaseexistsonLWSjointperformanceinforeignplantsinwhichthefreespanjointsarenotheattreated.Oftheapproximately18,000non-heattreatedjointsinservice,nonehasexhibitedarapidcorrosionpotential.CorrosiontestingoftheTSsleevelowerjointLWJsexhibitaresistancetocorrosioncrackingofthreetofourtimesthatofrolledtubetransitions.Thesefactorssuggestpostulatedsleeve/tubeassemblydegradationwouldoccurataratelessthanrolledtransitions,andthepotentialforasleeve/tubeassemblywithaccelerateddegradationratecharacteristicsmoreseverethanrolltransitionsisnegligible.Approximately800LWSsarecurrentlyinoperationintheU.S.SomeofthesehavebeeninservicesinceApril1992.Theplantsinwhichthesesleevesareinstalledhavenotexperiencedanyadverseoperationalissues(suchasprimaryto
~'lk'(~4)~4V4 ATTACHMENT1TOAEP'NRC'1129DPage9secondaryleakage)ashasbeendetectedatotherplantswithsleeveswhichhaveexperiencedrapidcorrosionoftheparenttube.3)Theproposedlicenseamendmentdoesnotinvolveasignificantreductioninamarginofsafety.Thelaser-weldedsleevingrepairofdegradedsteamgeneratortubesasidentifiedinWCAP-13088Rev.3hasbeendemonstratedtorestoretheintegrityofthetube'undleundernormalandpostulatedaccidentconditions.ThesafetyfactorsusedinthedesignofsleevesfortherepairofdegradedtubesareconsistentwiththesafetyfactorsintheASMEBoilerandPressureVesselCodeusedinsteamgeneratordesign.TheplugginglimitcriteriaforthesleevehasbeenestablishedusingthemethodologyofRG1.121.Thedesignofthesleevejointshavebeenverifiedbytestingtoprecludeleakageduringnormalandpostulatedaccidentconditions.Implementationoflaser-weldedsleevingwillreducethepotentialforprimarytosecondaryleakageduringapostulatedsteamlinebreakwhilemaintainingavailableprimarycoolantflowareaintheeventofaLOCA.Byremovingfromservicedegradedintersectionsthroughrepair,thepotentialfortubeleakageduringasteamlinebreakisreduced.Thesedegradedintersectionsnowarereturnedtoaconditionconsistentwiththedesignbasis.Whiletheinstallationofasleevecausesareductioninflow,thereductionisfarbelowthereductionincurredbyplugging.Therefore,fargreaterprimarycoolantflowareaismaintainedthroughsleeving.UseofRG1.121.criteriaassuresthatthemarginofsafetywithrespecttostructuralintegrityisthesameforthesleevesasfortheoriginalsteamgeneratortubes.Theportionsoftheinstalledsleeveassemblywhichrepresentthereactorcoolantpressureboundarycanbemonitoredfortheinitiationandprogressionofsleeve/tubewalldegradation,thussatisfyingtherequirementsofRG1.83.Portionsofthetubebridgedbythesleevejointsareeffectivelyisolatedfromthepressureboundary,andthesleevethenformsthepressureboundaryintheseareas.TheareasofthesleevedtubeassemblywhichrequireinspectionaredefinedinAttachment4.Inaddition,sincetheinstalledsleeverepresentsaportionofthepressureboundary,abaselineinspectionoftheseareasisrequiredpriortooperationwithsleevesinstalled.Asstatedpreviously,weldfusionzonewidthisestablishedusingUTtesting.TheminimumacceptableweldwidthasdeterminedbyUTexaminationisapproximately50XwiderthantheminimumweldwidthwhichsatisfiesthestressconditionsoftheASMECode.ThegenericevaluationusesthepressurestressequationofSectionNB3224.1oftheASMECodewhichisusedtoestablish 1~Eg(S\If~aeoIelf ATTACHMENT1TOAEP'NRC:1129DPage10theminimumrequiredwallthicknessforthesleevedesignandsubsequentlyusedtodeterminethelevel"ofsleevewalldegradation(depthbyeddycurrentdetermination)thatwouldrequirethesleevetoberemovedfromservice.UsingtheBPgoz~ppvalueof1530psifromAttachment4the1imitingminimumrequiredsleevewallthicknessisestablished.Thesleevewallplugginglimit(usingAttachment4)'f25Xissubsequentlyestablished,andincludesanallowanceof10Xforeddycurrentuncertaintyand10Xforgrowth,althoughsleevewalldegradationhasnotbeenobservedtodateinWestinghousesleeves.ThegenericevaluationusedtheASMECodeminimumpropertyvaluestoestablishthesleeveplugginglimit.CertifiedmaterialtestreportsindicatethatthesleevematerialpropertiesaresignificantlyhigherthantheASMECodeminimumvalues.Thegenericevaluationconsideredaprimarytosecondarypressuredifferentialof1530psia,withasteampressureof720psia,fornormaloperatingconditions.CNPUnit1canoperateatfullpowerwithareducedTh<<valueandRCSpressureof2250psi.Steampressurecanbemaintainedaslowas650psi(tokeepTh<<aslowaspossible),butcannotgolowerthan650psiorthesteamgeneratoroperatingrequirementofaprimarytosecondaryaPof1600psi(max)willbeexceeded.AtthisaP>o~ovalueof1600psi,thesleeveminimumwallthicknessrequfiement(andsubsequentlysleevepressureboundaryplugginglimit)usingASMECodeminimummaterialpropertiescanberecalculated.Forthiscondition(normaloperatinghPequalto1600psi),thesleeveminimumwallplugginglimitisdefinedtobe23X.Anallowanceforeddycurrentuncertaintyandcontinueddegradationareincludedinthisvalue.Theminimumrequiredwallthicknessisdetermined'yexaminingplantconditionsatnormal,upset,faulted,andtestconditions.ForModel51steamgenerators,thenormaloperatingconditionresultsinthelimitingminimumwallthicknessrequirement.CONCLUSIONBasedontheprecedinganalysisitisconcludedthatoperationofCNPUnit1followingtheinstallationofAlloy690LWSsatthetubesupportelevationsandwithintheTSregionofthesteamgenerators,inaccordancewiththeproposedamendmentdoesnotresultinthecreationofanunreviewedsafetyquestion,anincreaseintheprobabilityofanaccidentpreviouslyevaluated,createthepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated,norreduceanymarginstoplantsafety.Therefore,thelicenseamendmentdoesnotinvolveasignificanthazardsconsiderationasdefinedin10CFR50.92.