ML17332A751
| ML17332A751 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 04/25/1995 |
| From: | FITZPATRICK E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17332A752 | List: |
| References | |
| AEP:NRC:1166R, NUDOCS 9505010273 | |
| Download: ML17332A751 (27) | |
Text
RIORITY1CCELERATEDRIDSPROCI'.SSIiG)REGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9505010273DOC.DATE:95/04/25NOTARIZED:NODOCKETFACIL:50-315DonaldC.CookNuclearPowerPlant,Unit1,IndianaM05000315AUTH.NAMEAUTHORAFFILIATIONFITZPATRICK,E.IndianaMichiganPowerCo.(formerlyIndiana&MichiganEleRECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)
SUBJECT:
ApplicationforamendtolicenseDPR-58,incorporating2.0voltinterimSGtubesupportplatepluggingcriterionforfuelcycle15.DISTRIBUTIONCODE:AOOIDCOPIESRECEIVED:LTRJENCLLSIZE:I++8-TITLE:ORSubmittal:GeneralDistributionNOTESRECIPIENTIDCODE/NAMEPD3-1LAHICKMAN,JINTERNA~@IL~ENPEINRR/DE/EMCBNRR/DSSA/SPLBNUDOCS-ABSTRACTEXTERNAL:NOACCOPIESLTTRENCL11111111111111RECIPIENTIDCODE/NAMEPD3-1PDNMSS/DWM/LLDPNRR/DRCH/HICBNRR/DSSA/SRXBOGC/HDS2NRCPDRCOPIESLTTRENCL112211111011ENVOTETOALL"RIDS"RECIPIEV'TS:PLEASEHELPUSTOREDUCEO'KSTE!COVTACT'I'IIEDOC!:KIEV.I'OVTROLDESK,ROOKIPI-37(EXT.504-OS3)TOELDIIiATEYOURNAi!L'ROilDISI'RIBUTIONLIS'ISI:ORDOCUh,IEi'I'SYOUDOi"I'L'I'.D!TOTALNUMBEROFCOPIESREQUIRED:LTTR14ENCL13 itjC IndianaMichiganPowerCompanyP.O.Box16631Columbus,OH432168April25,i995DocketNos'0-315AEP:NRC:1166RU.S.NuclearRegulatoryCommissionATTN:DocumentControlDeskWashington,D.C.20555Gentlemen:DonaldC.CookNuclearPlantUnit1TECHNICALSPECIFICATIONCHANGESTOINCORPORATE2.0VOLTINTERIMSTEAMGENERATORTUBESUPPORTPLATEPLUGGINGCRITERIONFORFUELCYCLE15ThisletteranditsattachmentsprovidesupplementalinformationinresponsetotheMarch15,1995,telephonediscussionswithyourstaffregardingourFebruary3,1995,letter,AEP:NRC:1166Q,concerningapplicationforamendmenttothetechnicalspecifications(T/Ss)ofDonaldC.CookNuclearPlantUnitl.Specifically,thissupplementalinformationaddressestheapplicablerequirementsofdraftNRCGenericLetter(GL)94-XX,"Voltage-BasedRepairCriteriafortheRepairofWestinghouseSteamGeneratorTubesAffectedbyOutsideDiameterStressCorrosionCracking."Foryourconvenience,allattachmentspreviouslysubmittedwithAEP:NRC:1166Qarebeingre-submittedandsupersedethosecontainedinthatsubmittal.Attachment1providesatechnicalsummaryofthespecificinspectionpracticesandcalculationalmethodologiesoutlinedinGL94-XXthatwillbeappliedtotheUni.t1interimpluggingcriteriaprogramandthe10CFR50.92nosignificanthazardsevaluation.Theevaluationandresultssupportcontinueduseof2voltinterimpluggingcriteriaforfuelcycle15.Attachment2containsexistingT/Spagesmarkedtoreflecttherequestedchanges.Attachment3providestheproposedrevisedT/Spages./95050i0273950425PDRADOCK05000315PDR J45 U.S.NuclearRegulatoryCommissionPage2AEP:NRC:1166RWebelievetheproposedchangeswillnotresultin(1)asignificantchangeinthetypesofanyeffluentthatmaybereleasedoffsite,or(2)asignificantincreaseinindividualorcumulativeoccupationalradiationexposure.TheseproposedchangeshavebeenreviewedbythePlantNuclearSafetyReviewCommitteeandwillbereviewedbytheNuclearSafetyandDesignReviewCommitteeatthenextregularlyscheduledmeeting.Incompliancewiththerequirementsof10CFR50.91(b)(1),copiesofthisletteranditsattachmentshavebeentransmittedtotheMichiganPublicServiceCommissionandtotheMichiganDepartmentofPublicHealth.TheT/SpagesaffectedbythoseproposedchangesarealsoimpactedbytheT/SpagessubmittedwithourApril13,1995,letterAEP:NRC:1129D,UseofLaserWeldedSleevesforSteamGeneratorTubes.Sincerely,E.E,FitzpatrickVicePresidentSWORNTOANDSUBSCRIBEDBEFOREMETHIS4~DAYOF1995NoryPublicehAttachmentscc:A.A.BlindG.CharnoffJ.B.MartinNFEMSectionChiefNRCResidentInspector-BridgmanJ.R.Padgett f't4V'tr~va4 ATTACHMENT1TOAEP:NRC:1166RDESCRIPTIONOFCHANGESTOTHEDONALDC.COOKNUCLEARPLANTUNIT1TECHNICALSPECIFICATIONS10CFR50.92EVALUATION
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PsAttachment1toAEP:NRC:1166RPage1I.INTRODUCTIONThisamendmentrequestproposesachangetoCookNuclearPlantUnit1steamgenerators(SG)T/Ss4.4.5.2,4.4.5.3,4.4.5.4,4.4.5.5,3.4.6.2andBases3/4.4.5and3/4.6.2toallowcontinueduseofSGtubesupportplateinterimpluggingcriteria(IPC)forfuelcycle15.Becauseofthechanges,textshiftandrepagenationarerequired.ThechangeallowsSGtubeswithbobbincoileddycurrentindicationslessthanorequalto2voltsattubesupportplateintersectionstoremaininservice,regardlessofapparentdepthoftubewallpenetration,ifasaresult,theprojectedend-of-cycle(EOC)distributionofcrackindicationsisshowntoresultinprimary-to-secondaryleakagelessthan12.6gpminthefaultedloopduringapostulatedsteamlinebreakevent.Indicationsgreaterthan2voltsbutlessthanorequalto5.6voltsmayremaininserviceifamotorizedrotatingpancakecoil(MRPC)probeinspectiondoesnotdetectdegradation.Thisamendment,specifictofuelcycle15,wouldreducethenumberofSGtubespluggedduetoindicationsatsupportplateintersections.ReducingthenumberofpluggedtubesprovidesAD@Abenefitsandmaintainsreactorcoolantsystem(RCS)flowmargin.AnassessmentreportaddressingtheeffectivenessoftheIPCmethodologydescribedinWCAP-13187,Revision0,wascompletedfollowingfuelcycle13andreportedinsubmittaldocumentAEP:NRC:1166J.ThereportconcludedthatthevoltagedistributionfoundbyinspectionatEOC13in1994isingoodagreementwiththeprojectionsmadeatEOC12in1992.Thevoltagegrowthratescontinuetobeverysmall,withamaximumgrowthof0.4voltsforfuelcycle13comparedto0.49voltsforfuelcycle12.Notubeswerefoundforwhichthebobbincoilvoltageexceededthe2voltIPCrepairlimitatEOC13.ThemaximumprojectedEOC14voltagebasedonEOC13voltagedistributionis2.0voltsusingtheNRCmodeland1.9voltsusingtheindustrymodel.Consideringtheresultsofthisreport,continuationof2voltIPCisjustifiedforfuelcycle15.SimilarassessmentandprojectionreportswillbepreparedatEOC14basedonGL94-XXreportingrequirements.II'PPLICATIONOFDRAFTGL94-XXREUIREMENTSTOTHCOOKNUCLARPLANTUNIT1SGIPCLICENSEAMENDMENTREVESTFORCYCLE15TheCookNuclearPlantUnit1,2voltIPCwillbeimplementedpertheguidanceofGL94-XXalongwiththelatestindustrydataforburstandleakagedatabases.NRCGL94-XXwillbefactoredintotheCookNuclearPlantUnit1IPCasfollows:
Attachment1toAEP:NRC:1166RPage2Analystswillbebriefedregardingthepossibilityofprimarywaterstresscorrosioncracking(PWSCC)attubesupportplateintersections.IfPWSCCisfoundatthesupportplateintersectionsitwillbereportedtotheNRCstaffpriortostartup.2)ThesupportingdatasetsforcalculationofburstprobabilityandestimationofprimarytosecondaryleakageduringapostulatedmainsteamlinebreakwillbethoselistedinSections2.a.land2.b.3(1),respectively,oftheGL.3)MainsteamlineburstprobabilityandleakagecalculationswillbeperformedfollowingtheguidanceofGL94-XX,Section2,"TubeIntegrityEvaluation."Calculationsperformedinsupportofthevoltage-basedrepaircriteriawillfollowthemethodologydescribedinWCAP-14277,"SteamLineBreakLeakRateandTubeBurstProbabilityAnalysisMethodsforOutsideDiameterStressCorrosionCrackingatTubeSupportPlateIntersections,"datedJanuary1995'hecalculationswillbeperformedpriortoreturningtheSGstoserviceusingtheas-foundEOC14voltagedistribution.TheprojectedEOC15voltagedistributionresultswillbereportedinthe90dayreport.NodistributioncutoffwillbeappliedtothevoltagemeasurementvariabilitydistributionforcalculationoftheprojectedEOCvoltagedistribution.4)Inspectionscope,dataacquisition,anddataanalysiswillbeperformedfollowingtheguidanceofGL94-XX,Section3,"InspectionCriteria"andAppendixA,"NDEDataAcquisitionandAnalysisGuidelines"submittedbyourletterAEP:NRC:1166Hforthecycle14IPC.Motorizedrotatingpancakecoilinspectionwillbedoneonallindicationsexceeding1.5volts.Motorizedrotatingpancakecoilinspectionwillalsobedoneonallintersectionswherecoppersignals,largemixedresiduals,ordentslargerthan5voltsinterferewithdetectionofflaws.Probewearinspectionsandre-inspectionswillbeperformedusingtheguidelinesofAppendixA,SectionA.2.3,assubmittedbyourletterAEP:NRC:1166H.Ifanyofthelastprobewearstandardsignalamplitudespriortoprobereplacementexceedthe+/-15$limit,byavalueof"X%",thenanyindicationsmeasuredsincethelastacceptableprobewearmeasurementthatarewithin"XS"oftheplugginglimitwillbereinspectedwiththenewprobe.Forexample,ifanyofthelastprobewearsignalamplitudespriortoprobereplacementwere17%aboveorbelowtheinitialamplitude,thentheindicationsthatarewithin2%(17%-15%)oftheplugginglimitmustbereinspectedwiththenewprobe.Alternatively,thevoltagecriterionmaybeloweredtocompensatefortheexcessvariation;forthecaseabove,amplitudesz0.98timesthevoltagecriterioncouldbesubjecttorepair.
Attachment1toAEP:NRC:1166RPage3Bobbincoilprobecalibrationwillbeperformedusingfour20%holesintheASMEcalibrationstandardinsteadofthe100%throughwallholes.ThisapproachwasconcurredwithbytheNRCstaffattheJanuary18,1995,NRC/Industrymeeting.5)GL94-ZX,Section5,"OperationalLeakageRequirements,"willbecontinued.TheSGtubeleakagelimitof150gallonsperdaythrougheachSGwillbemaintainedaspreviouslyapprovedbytheNRCforourlastfuelcycle.CookNuclearPlantleakagemonitoringmethodsprovidetimelyleakdetection,trending,andresponsetorapidlyincreasingleaks.6)GL94-XX,Section6,"ReportingRequirements,"willbeimplemented.Itshouldbenoted,asstatedpreviouslyforSection2,thatthecalculationofleakageandburstprobabilityrequiredpriortoreturningtheSGstoservicewillbeperformedbyuseoftheas-foundEOCvoltagedistribution.AEPSCCOMMENTSEXCEPTIONSTOGL94-XXANDASSOCIATEDMPACTTOEPSCLICENSEAMENDMENTREVESTFORSGPCFORCYCLE15GL94-ZX,Sectionl,b:AnalysesperformedbyWestinghousehaveshownthatnotubesintheCookNuclearPlantUnit1SGswouldbesubjecttocollapseduringalossofcoolantaccident(LOCA)+safeshutdownearthquake(SSE)event.Therefore,notubesareexcludedbasedonthiscriteria.Itemsl.b.2andl.b.3arenotapplicablesincetheseconditionsdonotexistintheCookNuclearPlantUnit1'SGs.Series51SGsdesignedbyWestinghousedonothaveflowdistributionbaffleplates.2)GL94-ZX,Section3.b.2:BasedontubepullresultsfromCookNuclearPlantUnit1,copperdepositsarenotpresentonthetubeoutsidediameter(OD)surfacesorinthetubesupportplate(TSP)crevicecorrosionproduct.Similarly,CookNuclearPlantUnit1doesnothaveevidenceof"largemixedresidualsignals."CookNuclearPlantUnit1doesnothaveahistoryofeddycurrentdatawhichisdifficulttointerpret.3)GL94-ZX,Section3.c.2:Bobbincoilprobeswillcontinuetobecalibratedagainstthe20%holesintheASMEcalibrationstandardtoremainconsistentwiththemethodologyusedtodevelopthecriteria.GL94-ZX,Section3.c.4:Therequirementtoreinspectalltubespriortothelastprobechangeoutifthewearmeasurementexceeds15%isunnecessary.As'acknowledgedintheGL,a5.6voltrepaircriterionisjustified,however,therepaircriterioniscurrentlylimitedto2.0volts.Suchindicationsareexpectedtobewell Attachment1toAEP:NRC:1166RPage4withinstructurallimitsatEOC15conditions,particularlywhenUnit1growthratesareconsidered.ReinspectionofindicationsnecessitatedbyoutofspecificationprobewearwillbeconductedaccordingtoItem4ofpage2ofthisattachment.5)GL94-XX,Section4,addressestheneedtoperformtubepulls.Tubepullscausesignificantoutageextension,occupationalradiationexposure,andsignificantdirectcost.(Asanexample,removalofthreetubesamplesduringtheupcomingCookNuclearPlantUnit1refuelingoutageisestimatedtoaddtwotothreedaystotheoutagecriticalpath,havedirectcostsintherangeof$0.8-$1.3million,andincurfrom2-5manremexposure.)Therefore,tubesselectedforpullingshouldbejudiciouslychosenandshouldjustifythemonetaryexpenseandradiologicalexposure.Tubesshouldnotbepulledmerelytosatisfyachronologicalrequirement.AEPSCbelievesthattheimpositionofthisrequirementduringthenextscheduledrefuelingoutagewillnotenhancethecurrentburstandleakagedatabasessufficientlytowarranttheaddedcost.JustificationfornotperformingatubepullduringthenextoutageatCookNuclearPlantUnit1issuppliedbelow.A)In1992,nineCookNuclearPlantUnit1TSPintersectionswereremovedformetallographicexamination,bursttestingandleaktesting.Fieldbobbincoilvoltagesrangedfrom1.0to2.0volts,includingfourintersectionsreportedasNDD.Burstpressuresrangedfrom9,100to11,200psig.forthereportedindicationsandnointersectionsleakedduringtestingat2560psid.ExaminationoftubesafterbursttestingshowedcombinationsofaxiallyorientedintergranularstresscorrosioncrackingandintergranularcellularcorrosionoriginatingfromthetubeOD.Degradationmorphologywasdominatedbytheaxiallyorienteddegradation.InadditiontotheUnit1tubepullssupportingSGIPC,significantnumbersofintersectionswereremovedfromUnit2in1984and1986.Inallcases,circumferentiallyorienteddegradationwasnotdetected.B)Outsidediameterstresscorrosioncracking(ODSCC)degradationgrowthrateforCookNuclearPlantUnit1hasdecreasedoverthelasttwocyclesandnointersectionsduringthelastoutagehadTSPintersectionvoltagesexceeding2.0volts.Thishighlevelofperformanceisattributedtotheunitoperatingatreducedtemperatureandpressure,improvedsecondarysidechemistrycontrolandsludgeremoval,andaconservativeinspection/repairprogram.BasedonthelowgrowthratesatUnit1andchemistrycontrolinitiatives,EOC14voltagesareexpectedtobewellbelow3.0volts,andmostlikelylessthan2.0volts.Recenttubepullsatotherplants Attachment1toAEP:NRC:1166RPage5wheretheindicationvoltagewasgreaterthan2.0voltsandwherealargernumberofbeginningofcycle(BOC)indicationswereinthe2.0voltrangeindicatednounexpecteddegradationmorphology.TheexpectedEOC14voltagesatUnit1arewellbelowthethresholdforthroughwalldegradationof2.8volts(determinedfromatubepullatanotherplant)andwellbelowthethresholdforSLBleakageofapproximately6.0volts.Duringthecurrentoperatingcycle,Unit1hasnotexperiencedanysecondarysidechemistry"excursions"whichmightsupportunexpectedvoltagegrowthorinitiationof"non-typicaldegradationmorphologies.C)ThecurrentrequirementtoperformanMRPCinspectionofindicationsover1.5voltsissufficienttoidentifynon-typicalmorphologies.Forcasesofsignificantcellularcorrosion(identifiedatotherplants),metallographic.examinationhasshownthataxiallyorienteddegradationhasdominatedthemorphologyandbursttestresults.Forsuch"caseswheresignificantcircumferentialcomponentsinacellularmorphologycaninfluenceburst,associatedaxialcomponentswouldyieldvoltagesfarinexcessofthe5to6voltrange,andsuchcircumferentiallyorienteddegradationwouldbeofsufficientdepthtobedetectedbytheRPCprobe.IV,10CFR5092EVALUATIONBACKGROUNDCookNuclearPlantUnit1T/SAmendment178permittedtheimplementationofa2.0voltSGtubeIPCforthe14thoperatingcycleoftheCookNuclearPlantUnit1SGs.Thatlicenseamendment,applicableonlyforthecurrentoperatingcycle(cycle14),requiredtherepairofflaw-likebobbinindicationsabove2.0volts.Weareproposinguseofasimilar2voltinterimrepaircriterionfortheupcomingcycle15.TheproposedIPCprogramfortheCookNuclearPlantUnit1SGsfollowstheguidanceandgeneralintentofGL94-XXtomaintaintubestructuralandleakageintegrity.DESCRIPTIONOFTHEIPCREQUESTAsrequiredby10CFR50.91(a)(l),ananalysisisprovidedtodemonstratethattheproposedlicenseamendmenttoimplementanIPCforthetubesupportplateelevationODSCCoccurringintheCookNuclearPlantUnit1SGsinvolvesanosignificanthazardsconsideration.TheIPCutilizes
Attachment1toAEP:NRC:1166RPage6correlationsbetweeneddycurrentbobbinprobesignalamplitude(voltage)andtubeburstandleakagecapability.ThepluggingcriterionisbasedontestingoflaboratoryinducedODSCCspecimensandonextensiveexaminationofpulledtubesfromoperatingSGs(industrywide-includingthreetubespulledin1992representingnineintersectionsfromCookNuclearPlantUnit1SGs.)CConsistentwithGL94-ZX,theIPCprogramforCookNuclearPlantUnit1willincludethefollowingelementsaslistedunder"1.OverviewoftheVoltageRepairLimitApproach",page3ofGL94-ZX.Performanenhancedinspectionoftubes,particularlyattheTSPintersections.A100%bobbincoilinspectionofhotlegtubesupportplateintersectionsandcoldlegintersectiondowntothelowestcoldlegsupportplatewithknownODSCCindicationswillbeperformed.Allflawindicationswithbobbinvoltagesgreaterthan1.5voltswillbeinspectedbyMRPC.UtilizeNDEdataacquisitionandanalysisproceduresthatareconsistentwiththemethodologyusedtodevelopthevoltage-basedrepairlimits.TheCookNuclearPlantUnit1IPCprogramwillutilizeproceduresandtechniquesconsistentwiththemethodologiesusedtoestablishtheIPCasdescribedinSection3ofEnclosure1oftheGL,withtheexceptionthat20%.throughwallholeswillbeusedinthestandard(Section3.c.2ofGL94-XX).Repairorplugtubesthatexceedthevoltagelimits.Flaw-likesignalsadjacenttotheTSPwithbobbinvoltageslessthanorequalto2.0voltswillbeallowedtoremaininservice.Flaw-likeindicationsadjacenttotheTSPwithabobbinvoltageofgreaterthan2.0voltsbutlessthanorequalto5.6voltsmayremaininserviceifMRPCinspectiondoesnotdetectaflaw.'lawindicationswithavoltageofgreaterthan5.6voltswillberepaired.DeterminetheBOOvoltagedistribution.BeginningofCycle15voltagedistributionwillbeestablishedfromtheactualtubeinspectionstobeperformedduringthenextoutageandwillbeestablishedusingcurrentprogrammethodology.ProjecttheEOC15distribution.
Attachment1toAEP:NRC:1166RPage7AnEOCvoltagedistributionwillbeestablishedbasedontheEOC14ECTdata.EOC15voltagedistributionwillbeprojectedusingMonteCarlotechniquesasdescribedinWCAP-14277andwillincludeallowanceforeddycurrentuncertaintyasdefinedintheGLandaconservativevoltagegrowthrateallowance.FortheprojectedEOC'voltagedistribution,calculateleakageandconditionaltubeburstprobability(andrepairtubesifnecessary).Steamlinebreakleakagewillbecalculated,asdescribedinWCAP-14277,basedontheEOC15projectedvoltagedistribution.Projectedleakagemustremainbelow12.6gpminthefaultedloopforoffsitedoseestimatestoremainwithin10$ofthe10CFR100guidelines.Thisvaluewascalculated,usingStandardReviewPlanmethodology,priortotheCycle14licenseamendmentrequestandwillnotchangefortheupcomingcycle.ConditionaltubeburstprobabilitywillbecalculatedaccordingtothemethodologydescribedinWCAP-14277.ConsistentwiththeGL,ifburstprobabilityisfoundtobegreaterthan1x102,theNRCwillbeconsulted.AsprescribedinGL94-XX,anevaluationofprimarytosecondaryleakage(andsubsequentlyoffsitedose)isrequiredforallplantsimplementingtheIPC.Allbobbinindicationsareincludedinthesteamlinebreakleakageanalyses,alongwithconsiderationoftheprobabilityofdetection.Iftheprojectedleakageexceeds12.6gpminthefaultedloopduringapostulatedsteamlinebreakevent,thenumberofindicationsinwhichtheIPCareappliedisreducedthroughtuberepairuntiltheprimary-to-secondaryleakagelimitsaresatisfied.EVALUATIONTubeDegradationCharacterizationIngeneral,thedegradationmorphologyoccurringatthetubesupportplateintersectionsatplantsintheU.S.canbedescribedasaxiallyorientedODSCC.ThedegradationmorphologyatCookNuclearPlantUnit1isentirelycompatiblewiththeoverallindustrydatabase.SteamGeneratorTubeIntegrityInthedevelopmentofanIPCforCookNuclearPlantUnit1,RegulatoryGuide(RG)1.121,"BasesforPluggingDegradedPWRSteamGeneratorTubes"andRG1.83,"InserviceInspectionofPWRSteamGeneratorTubes"areusedasthebasesfordeterminingthatSGtubeintegrityconsiderationsaremaintainedwithinacceptablelimits.RegulatoryGuide1.121describesamethodacceptabletotheNRCstaffformeetingGeneralDesignCriteria
~~4*1~~1t Attachment1toAEP:NRC:1166RPage8(GDC)14,15,31,and32byreducingtheprobabilityandconsequencesofSGtuberupturethroughdeterminingthelimitingsafeconditionsoftubewalldegradationbeyondwhichtubeswithunacceptablecracking,asestablishedbyinserviceinspection,shouldberemovedfromservicebyplugging.ThisregulatoryguideusessafetyfactorsonloadsfortubeburstthatareconsistentwiththerequirementsofSectionIIIoftheASMECode.For-the.tubesupportplateelevationdegradationoccurringintheCookNuclearPlantUnit1SGs,tubeburstcriteriaareinherentlysatisfiedduringnormaloperatingconditionsbythepresenceofthetubesupportplate.Thepresenceofthetubesupportplateenhancestheintegrityofthedegradedtubesinthatregionbyprecludingtubedeformationbeyondthediameterofthedrilledhole,thusprecludingtubeburst.Conservatively,nocreditistakeninthedevelopmentofthepluggingcriteriaforthepresenceofthetubesupportplateduringaccidentconditions.Basedontheexistingdatabasefor7/8inchtubing,bursttestingshowsthatthesafetyrequirementsfortubeburstmarginsduringaccidentconditionloadingscanbesatisfiedwithEOCbobbincoilsignalamplitudeslessthan9.6volts,regardlessofthedepthoftubewallpenetrationofthecracking.UponimplementationoftheseIPC,tubeleakageconsiderationsmustalsobeaddressed.Itmustbedeterminedthatthecrackswillnotleakexcessivelyduringallplantconditions.Forthe2voltinterimtubepluggingcriteriadevelopedfortheCookNuclearPlantUnit1SGtubes,noleakageisanticipatedduringnormaloperatingconditionsevenwiththepresenceofpotentialthroughwallcracks.Theexpectedvoltagewhichwouldsupportprimary-to-secondaryleakageatnormaloperatingconditionsisapproximately10volts.Noprimary-to-secondaryleakageattheTSPhasbeendetectedinU.S.plants.Relativetotheexpectedleakageduringaccidentconditionloadings,thelimitingeventwithrespecttodifferentialpressureexperiencedacrosstheSGtubesisapostulatedsteamlinebreakevent.For7/8inchtubing,pulledtubedatasupportsnoleakageupto2.81voltsandlowprobabilityofleakagebetween2.81and6.0volts,forbothpulledtubesandmodelboilerspecimens,attheboundingsteamlinebreakpressuredifferentialof2560psi.SteamlinebreakprimarytosecondaryleakagewillbecalculatedasprescribedinGL94-XXandWCAP14277,usingEOC14eddycurrentdata.Thiscalculatedleakagemustbeshowntobelessthan12.6gpminthefaultedloop.AdditionalConsiderationsTheproposedamendmentwouldprecludeoccupationalradiationexposurethatwouldotherwisebeincurredbypersonnelinvolvedintubepluggingorrepairoperations'yreducingnon-essentialtubeplugging,theproposedamendmentwouldminimizethelossofmargininthereactorcoolantflowthroughtheSGinLOCAanalyses.Theproposedamendmentwouldavoidlossofmargininreactorcoolantsystemflowand,therefore,assistinmaintainingminimumflowratesinexcessofthatrequiredforoperationat Attachment1toAEP:NRC:1166RPage9fullpower.ReductionintheamountoftuberepairrequiredcanreducethelengthofplantoutagesandreducethetimethattheSGisopentothecontainmentenvironmentduringanoutage.The100%eddycurrentbobbinprobeinspectionassociatedwithimplementationoftheIPCwillhelptoidentifynewareasofconcernwhichmayarisebyprovidingalevelofinserviceinspectionwhichisfarinexcessoftheT/Srequirementsutilizingthe.40%depth-basedplugginglimitforacceptabletubewalldegradation.SIGNIFICANTHAZARDSANALYSISInaccordancewiththethreefactortestof10CFR50.92(c),implementationoftheproposedlicenseamendmentisanalyzedusingthefollowingstandardsandfoundnotto1)involveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated;2)createthepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated;or3)involveasignificantreductioninmarginofsafety.Conformanceoftheproposedamendmenttothestandardsforadeterminationofnosignificanthazardsasdefinedin10CFR50.92(threefactortest)isshowninthefollowingparagraphs.1)OperationofCookNuclearPlantUnit1inaccordancewiththeproposedlicenseamendmentdoesnotinvolveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated.Testingofmodelboilerspecimensforfreespantubing(notubesupportplaterestraint)atroomtemperatureconditionsshowburstpressuresinexcessof5000psiforindicationsofouterdiameterstresscorrosioncrackingwithvoltagemeasurementsashighas19volts.BursttestingperformedonpulledtubesfromCookNuclearPlantUnit1withuptoa2.02voltindicationshows.measuredburstpressureinexcessof10,000psiatroomtemperature.Bursttestingperformedonpulledtubesfromotherplantswithupto7.5voltindicationsshowburstpressuresinexcessof6,300psiatroomtemperatures.Correctingfortheeffectsoftemperatureonmaterialpropertiesandminimumstrengthlevels(asthebursttestingwasdoneatroomtemperature),tubeburstcapabilitysignificantlyexceedsthesafetyfactorrequirementsofRG1.121.Asstatedearlier,tubeburstcriteriaareinherentlysatisfiedduringnormaloperatingconditionsduetotheproximityofthetubesupportplate.Testdataindicatesthattubeburstcannotoccurwithinthetubesupportplate,evenfortubeswhichhave100$throughwallelectric-dischargemachinednotches0.75inchlong,providedthetubesupportplateisadjacenttothenotchedarea.Sincetube-to-tubesupportplateproximityprecludestubeburstduringnormaloperatingconditions,useofthecriteriamust,therefore,retaintubeintegritycharacteristicswhichmaintaintheRG1121marginofsafetyof143timestheboundingfaultedcondition(steamlinebreak)pressuredifferential.
Attachment1toAEP:NRC:1166RPage10Duringapostulatedmainsteamlinebreak,theTSPhasthepotentialtodeflectduringblowdown,therebyuncoveringtheintersection.Basedontheexistingdatabase,theRG1.121criterionrequiringmaintenanceofasafetyfactorof1.43timesthesteamlinebreakpressuredifferentialontubeburstissatisfiedby7/8inchdiametertubingwithbobbincoilindicationswithsignalamplitudeslessthan9.6volts;-regardlessoftheindicateddepthmeasurement.A2.0voltpluggingcriteriacomparesfavorablywiththe9.6voltstructurallimitconsideringthepreviouslycalculatedgrowthratesforODSCCwithinCookNuclearPlantUnit1SGs.Consideringavoltagegrowthcomponentof0,8volts(40%voltagegrowthbasedon2.0voltsBOC)andanondestructiveexaminationuncertaintyof0.40volts(208voltageuncertaintybasedon2.0voltsBOC),whenaddedtotheBOCIPCof2.0volts,resultsinaboundingEOCvoltageofapproximately3.2voltsforcycle15operation.A6.4voltsafetymarginexists(9.6structurallimit-3.2voltEOC-6.4voltmargin).Forthevoltage/burstcorrelation,theEOCstructurallimitissupportedbyavoltageof9.6volts.Usingthisstructurallimitof9.6volts,aBOCmaximumallowablerepairlimitcanbeestablishedusingtheguidanceofRG1.121.TheBOCmaximumallowablerepairlimitshouldnotpermitasignificantnumberofEOCindicationstoexceedthe9.6voltstructurallimitandshouldassurethatacceptabletubeburstprobabilitiesareattained.ByaddingNDEuncertaintyallowancesandanallowanceforcrackgrowthtotherepairlimit,thestructurallimitcanbevalidated.ThepreviousIPCsubmittalestablishedtheconservativeNDEuncertaintylimitof20%oftheBOCrepairlimit.Forconsistency,a40$voltagegrowthallowancetotheBOCrepairlimitisalsoincluded.ThisallowanceisextremelyconservativeforCookNuclearPlantUnit1.Therefore,themaximumallowableBOCrepairlimit(RL)basedonthestructurallimitof9.6voltscanberepresentedbytheexpression:RL+(0.2xRL)+(0.4xRL)9.6volts,or,themaximumallowableBOCrepairlimitcanbeexpressedas,RL-9.6voltstructurallimit/1.6-6.0volts.Thisstructuralrepairlimitsupportsthisapplicationforcycle15IPCimplementationtorepairbobbinindicationsgreaterthan2.0voltsbasedonRPCconfirmationoftheindication.Conservatively,anupperlimitof5.6voltswillbeusedtorepairbobbinindicationswhichareabove2.0voltsbutdonothaveconfirmingRPCcalls.
Attachment1toAEP:NRC:1166RPagellTheconservatismofthisrepairlimitisshownbytheEOC13(Spring1994)eddycurrentdata.Theoverallaveragevoltagegrowthwasdeterminedtobeonly1.48(oftheBOCvoltage).Inaddition,theEOC13maximumobservedvoltageincreasewas0.40volts,andoccurredinatubewithaBOCindicationof0.96volts.Theapplicabilityofcycle14growthratesforcycle15operationwillbeconfirmedpriortoreturn.toserviceofCookNuclearPlantUnit1.Similarlargestructuralmarginsareanticipated.Relativetotheexpectedleakageduringaccidentconditionloadings,ithasbeenpreviouslyestablishedthatapostulatedmainsteamlinebreakoutsideofcontainmentbutupstreamofthemainsteamisolationvalverepresentsthemostlimitingradiologicalconditionrelativetotheIPC.InsupportofimplementationoftheIPC,itwillbedeterminedwhetherthedistributionofcrackindicationsatthetubesupportplateintersectionsattheendofcycle15areprojectedtobesuchthatprimarytosecondaryleakagewouldresultinsiteboundarydoseswithinasmallfractionofthe10CFR100guidelines.Aseparatecalculationhasdeterminedthisallowablesteamlinebreakleakagelimittobe12.6gpm.AlthoughnotrequiredbytheCookNuclearPlantdesignbasis,thiscalculationusestherecommendedIodine-131transientspikingvaluesconsistentwithNUREG-0800,andtheT/Sreactorcoolantsystemactivitylimitof1.0microcuriepergramdoseequivalentIodine-131.TheprojectedsteamlinebreakleakageratecalculationmethodologyprescribedinGL94-ZXandWCAP14277willbeusedtocalculateEOC15leakage,basedonactualEOC14distributionsandEOC15projecteddistributions.DuetotherelativelylowvoltagegrowthratesatCookNuclearPlantUnit1andtherelativelysmallnumberofindicationsaffectedbytheIPC,steamlinebreakleakagepredictionperGL94-ZXisexpectedtobesignificantlylessthantheacceptancelimitof12.6gpminthefaultedloop.PriortoissueofGL94-XX,projectedEOC14leakrateswerecalculated,basedondraftNUREG-1477,foratotaloftwelvecases,thecombinationofsixprobability-of-leakcorrelationsandtwoleakratecalculationmethodologies.ResultsofthecalculationsshowthattheprojectedEOC14leakratesrangedfrom0.001gpmto1.360gpm.Theseresultsarewellbelowthe12.6gpmallowable;therefore,implementationofthe2voltIPCduringcycle15wouldnotadverselyaffectSGtubeintegrityandresultsinacceptabledoseconsequences.CurrentGL94-ZXmethodologyrequiresonlythelog-logisticprobabilityofleakagecorrelationbeused.ProjectedEOC14SLBleakageusingthisfunctionwascalculatedtobeonly0.001gpm.BasedontherelativelyfewnumbersofintersectionsatCookNuclearPlantUnit1towhichtheIPCareapplied.andextremelysmallCook Attachment1toAEP:NRC:1166RPage12NuclearPlantUnit1plant-specificgrowthrate,asimilarvaluewouldbeexpectedbasedontheEOC14eddycurrentdata.TheinclusionofallIPCintersectionsintheleakagemodel,alongwithapplicationofaprobabilityofdetectionof0.6,willresultinextremelyconservativeleakageestimations,especiallysosincecloseexaminationoftheavailabledatashowsthatindicationsoflessthan2.8voltswillnotbeexpectedtoleakduringSLBconditions.AllUnit1IPCindicationsareexpectedtobebelow2.8voltsattheEOC15conditions.Theproposedamendmentdoesnotresultinanyincreaseintheprobabilityorconsequencesofanaccident.previouslyevaluatedwithintheCookNuclearPlantUnit1FSAR.2)Theproposedlicenseamendmentdoesnotcreatethepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated.ImplementationoftheproposedSGtubeIPCdoesnotintroduceanysignificantchangestotheplantdesignbasis.Useofthecriteriadoesnotprovideamechanismwhichcouldresultinanaccidentoutsideoftheregionofthetubesupportplateelevations.NeitherasingleormultipletuberuptureeventwouldbeexpectedinaSGinwhichthepluggingcriteriahasbeenapplied(duringallplantconditions).Specifically,wewillcontinuetoimplementamaximumleakageratelimitof150gpd(0.1gpm)perSGtohelpprecludethepotentialforexcessiveleakageduringallplantconditions.Thecycle15T/Slimitsimposedonprimarytosecondaryleakageatoperatingconditionsare:amaximumof0.4gpm(600gpd)forallSGs'withamaximumof150gpdallowedforanyoneSG.TheRG1.121criteriaforestablishingoperationalleakageratelimitsthatrequireplantshutdownarebaseduponleak-before-breakconsiderationstodetectafreespancrackbeforepotentialtuberuptureduringfaultedplantconditions.The150gpdlimitshouldprovideforleakagedetectionandplantshutdownintheeventoftheoccurrenceofanunexpectedsinglecrackresultinginleakagethatisassociatedwiththelongestpermissiblecracklength.RegulatoryGuide1.121acceptancecriteriaforestablishingoperatingleakagelimitsarebasedonleak-before-breakconsiderationssuchthatplantshutdownisinitiatediftheleakageassociatedwiththelongestpermissiblecrackisexceeded.Thelongestpermissiblecrackisthelengththatprovidesafactorofsafetyof1.43againstburstingatfaultedconditionsmaximumpressuredifferential.Avoltageamplitudeof9.6voltsfortypicalODSCCcorrespondstomeetingthistubeburstrequirementatalower95%predictionlimitontheburst
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Attachment1toAEP:NRC:1166RPage13correlationcoupledwith95/95lowertolerancelimitmaterialproperties.Alternatecrackmorphologiescancorrespondto9.6voltssothatauniquecracklengthisnotdefinedbytheburstpressureversusvoltagecorrelation.Consequently,typicalburstpressureversusthrough-wallcracklengthcorrelationsareusedbelowtodefinethe"longestpermissiblecrack"forevaluatingoperatingleakagelimits.ConsistentwiththeCycle13andCycle14licenseamendmentrequestsforIPCandSection5ofEnclosure1oftheGL,operationalleakagelimitswillremainat150gpdperSG.Axialcracksleakingatthislevelareexpectedtoprovideleakbeforebreak(LBB)protectionatboththeSLBpressuredifferentialof2560psiand,whilenotpartofanyestablishedLBBmethodology,LBBprotectionwillalsobeprovidedatavalueof1.43timestheSLBpressuredifferential.Thus,the150gpdlimitprovidesforplantshutdownpriortoreachingcriticalcracklengthsforsteamlinebreakconditions.Additionally,thisleak-before-breakevaluationassumesthattheentirecreviceareaisuncoveredduringblowdown.'Partialuncoverywillprovidebenefittotheburstcapacityoftheintersection.3)Theproposedlicenseamendmentdoesnotinvolveasignificantreductioninmarginofsafety.TheuseofthevoltagebasedbobbinprobeinterimtubesupportplateelevationpluggingcriteriaatCookNuclearPlantUnit1isdemonstratedtomaintainSGtubeintegritycommensuratewiththecriteriaofRG1.121.RegulatoryGuide1.121describesamethodacceptabletotheNRCstaffformeetingGDC14,15,31,and32byreducingtheprobabilityortheconsequencesofSGtuberupture.ThisisaccomplishedbydeterminingthelimitingconditionsofdegradationofSGtubing,asestablishedbyinserviceinspection,forwhichtubeswithunacceptablecrackingshouldberemovedfromservice.Uponimplementationofthecriteria,evenundertheworstcaseconditions,theoccurrenceofODSCCatthetubesupportplateelevationsisnotexpectedtoleadtoaSGtuberuptureeventduringnormalorfaultedplantconditions.TheEOC15distributionofcrackindicationsatthetubesupportplateelevationswillbeconfirmedbyanalysisandcalculationtoresultinacceptableprimarytosecondaryleakageduringallplantconditionsandthatradiologicalconsequencesarenotadverselyimpacted.InaddressingthecombinedeffectsofaLOCAandSSEontheSGcomponent(asrequiredbyGDC2),ithasbeendeterminedthattubecollapsemayoccurintheSGsatsomeplants.Thisisthecaseasthetubesupportplatesmaybecomedeformedasaresultoflateral l
Attachment1toAEP:NRC:1166RPage14loadsatthewedgesupportsattheperipheryoftheplateduetothecombinedeffectsoftheLOCArarefactionwaveandSSEloadings.Then,theresultingpressuredifferentialonthedeformedtubesmaycausesomeofthetubestocollapse.'herearetwoissuesassociatedwithSGtubecollapse.First,thecollapseofSGtubingreducestheRCSflowareathroughthetubes.ThereductioninflowareaincreasestheresistancetoflowofsteamfromthecoreduringaLOCAwhich,inturn,maypotentiallyincreasepeakcladtemperature.Second,thereisapotentialthatpartialthrough-wallcracksintubescouldprogresstothrough-wallcracksduringtubedeformationorcollapse.Consequently,sincetheleak-before-breakmethodologyisapplicabletotheCookNuclearPlantUnit1reactorcoolantlooppiping,theprobabilityofbreaksintheprimarylooppipingissufficientlylowthattheyneednotbeconsideredinthestructuraldesignoftheplant.ThelimitingLOCAeventbecomeseithertheaccumulatorlinebreakorthepressurizersurgelinebreak.LossofcoolantaccidentloadsfortheprimarypipebreakswereusedtoboundtheCookNuclearPlantUnit1smallerbreaks.TheresultsoftheanalysisusingthelargerbreakinputsshowthattheLOCAloadswerefoundtobeofinsufficientmagnitudetoresultinSGtubecollapseorsignificantdeformation.AddressingRG1.83considerations,implementationofthebobbinprobevoltagebasedinterimtubepluggingcriteriaof2.0voltsissupplementedbyenhancededdycurrentinspectionguidelinestoprovideconsistencyinvoltagenormalization,a100$eddycurrentinspectionsamplesizeatthetubesupportplateelevationsperT/S,andMRPCinspectionrequirementsforthelargerindicationsleftinservicetocharacterizetheprincipaldegradationasODSCC.Asnotedpreviously,implementationofthetubesupportplateelevationpluggingcriteriawilldecreasethenumberoftubeswhichmustberepaired.TheinstallationofSGtubeplugsreducestheRCSflowmargin.Thus,implementationoftheIPCwillmaintainthemarginofflowthatwouldotherwisebereducedintheeventofincreasedtubeplugging.Basedontheabove,itisconcludedthattheproposedlicenseamendmentrequestdoesnotresultinasignificantreductioninmarginwithrespecttoplantsafetyasdefinedintheFinalSafetyAnalysisReportoranyBasesoftheplantT/Ss.