ML17059A522
| ML17059A522 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/04/1994 |
| From: | BRANLUND B J, GORDON B M, RANGANATH S GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML17059A520 | List: |
| References | |
| GENE-523-A161-1, GENE-523-A161-1094, NUDOCS 9411160239 | |
| Download: ML17059A522 (84) | |
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GENE-523-A161-1094DRF137-0010-06StructuralEvaluationandJustificationoftheNineMilePoint1CoreShroudforContinuedOperationPerformedBy:BettyI.undSe'EngineerStructuralMechanicsProjectsBarryM.GordonPrincipalEngineerBWRTechnologyApprovedBy:SampathRanganPhDManager,EngineeringandLicensingConsultingServicesGENuclearEnergySanJose,CAT94ilih023994ii04PDRADQCK05000220PDR 0
GEiVudcarEnergyGENE-$23-Al6l-lopsIMPORTANTNOTICEREGARDI1VGCONTElVTSOFTHISREPORTPleaseReadCarefullyTheonlyundertakingsoftheGeneralElectricCompany(GE)respectinginformationinthisdocumentarecontainedinthecontractbetweenNiagaraMohawkPowerCompanyandGE,andnothingcontainedinthisdocumentshall,beconstnledaschangingthecontract.TheuseofthisinformationbyanyoneotherthanNiagaraMohawkPowerCompanyorforanypurposeotherthanthatforwhichitisintendedundersuchcontractlsnotauthorized;andwithrespecttoanyunauthorizeduse,GEmakesnorepresentationorwarranty,andassumesnoliabilityastothecompleteness,accuracy,orusefulnessoftheinformationcontainedinthisdocument,orthatitsusemaynotinfringeprivatelyownedrights.
GErVuclcarEnergyGEJYFS23-A361-1094TableofContentsl.1NTRODUCTION....,.....,......~~\~oo~o~o~o~too~~~~~o~~112.DESCRIPTIONOFINDICATIONS.......,...~.....,...,....2.1REFERENCES.~tttteo~oottoootto212-23.COMPARISONBETWEENNMP-1ANDOYSTERCREEKCORESHROUDS.....................3-13.1WATERCHEMISTRY3.2SHROUDEVALUATION.3.3SHROUDCOMPARISONCONCLUSION.3.4REFERENCES.4.CRACKGROWTHESTIMATE....,.4.1SLIP-DISSOLUTIONMODEL4.2CALCULATIONOFPARAMETERS4.3CRACKGROWTHPREDICTION
4.4CONCLUSION
..4.5REFERENCE5.FLAWEVALUATION....,.........,..,...,.,3-13-33-33o4~o~o~o~o~oo~ooeoo~o~o~o~o~e~o~~~~~~~~ooeee~o~o~o~~~eoe44-14-24-44-544~ooooooeeoooooooooootoo515.1LIMITLOADMETHOD..5.2EVALUATIONOFPART-THROUGHWALLCRACKS.5.3SAFETYFACTORS..5.4APPLICATIONOFFLAWEVALUATIONMETHODOLOGYTONMP-1SHROUD.5.4./LimitLoad.5.4.2LEFM.5.5REFERENCES5-15-35-45-55-55-55-66oCONCLUSIONSoeeoeeootooootooootoeo~ooooooo~eeeto~ooooteo~o~o~e~oooooooee~~o~~o~o~~~~eettott
GE(YndearEnergy<EWE-$23-Al6l-tOygI.INTRODUCTIONThisreportpresentsthestructuralevaluationandjustificationforcontinuedoperationoftheNineMilePointUnit1(NMP-1)plantuntilFebruaryof1995.Recently,inspectionoftheOysterCreekcoreshroudrevealedsignificantindicationsatthemid-beltlineweld,H4.DuetosimilaritiesbetweenOysterCreekandNMP-1,itisprudenttodetermineifsimilarcrackingcouldbeexpectedinNMP-1.ItisalsoprudenttodeterminethatiftheOysterCreekcrackingwerepresentinNMP-1,thecrackingisstructurallyacceptableforoperationuntiltheplannedoutageinFebruaryof1995.InspectionoftheNMP-1coreshroudisplannedforthisnextoutage.Thestructuraljustificationforcontinuedoperationispresentedinthisreportedasoutlinedinthefollowinganalyses:1.DiscussionofcomparisonofNMP-1andOysterCreekbasedonwaterchemistry,fluenceandon-lineyears.ThiscanbeusedasabasistoestablishthatanycrackingintheNMP-1coreshroudislikelytobeboundedbythatobservedintheOysterCreekcoreshroud.2.GEPLEDGEcrackgrowthratemodelingtoestimateaNMP-1specificcrackgrowthrate.ThiscalculationwillshowthattheestimatedcrackgrowthrateintheNMP-1coreshroudislessthanSxl0'n/hr,whichhasbeentypicallyusedforcoreshroudcracking.3.FlawevaluationusingtheOysterCreekindicationsandconsideringcrackgrowthduringthecurrentoperatingcycleuntilFebruaryof1995.ResultsofthecomparisonbetweenNMP-1andOysterCreekshowthatthecrackinginOysterCreekislikelytoboundthatwhichmaybeexpectedintheNMP-1shroud.Inaddition,theflawevaluationandcrackgrowthrateevaluationdemonstratethatthestructuralintegrityoftheNMP-1coreshroudweldH4isassuredassumingthatthesameindicationsintheOysterCreekH4weldarepresentintheNMP-1H4weld.1-1
GEivnckurEnergyGEE-$33-A16l-l0962.DESCRIPTIONOFINDICATIONSTheindicationsfoundintheOysterCreekcoreshroudH4weldareusedinthisstructuralevaluation.TheresultsoftheOysterCreekH4inspectionareshowninAppendixA.Thesefiguresillustratetheindicationdepthsatvariousazimuthallocationsinthecoreshroud.Atsomelocations,indicationswerefoundinboththeIDandOD(Insomecasesonecrackwasabovetheweldandtheotherwasbelowtheweld).Forthiscase,theindicationswereanalyzedasacombineddepthofthetwoflaws.Fortheareaswhichwerenotinspected,through-wallindicationswereassumed.Figure2-1isaschematicshowingtheligamentconfigurationbasedontheOysterCreekresults.Figure2-1showstheligamentconfigurationafterapplicationoftheproximitycriteria;thisconfigurationisusedforcalculatingthelimitloadcriteria.Thefollowingconservativeassumptionwereusedtodeterminetheassumedindications:l.Eachindicationwascharacterizedbythemaximumdepthoftheindicationovertheentirelengthoftheindication.2.Acrackdepthuncertaintyfactorof0.3"wasaddedtothedepthofeachcrack.3.AnestimatedcrackgrowthuntilthenextinspectionwithacrackgrowthrateofSx10'n/hrwasaddedtoeachcrackdepth.4.AtlocationswhereindicationswerefoundonboththeIDandOD,thedepthwasassumedtobethesumofthetwoindications.5.Whenflawswerecombinedduetoproximity,themaximumdepthofthecombinedindicationswasused.Inaddition,theestimatedcrackgrowthuntilthenextinspectionwasaddedforthisevaluation.Theshadedareascorrespondtoassumedindications.TheseresultsweredeterminedusingtheproximitymethodologypresentedinReference2-1.2-1
gE>VudcurEnergyGENE-$23-A161-10942.1References2-1BWRCoreShroudInspectionandFlawEvaluationGuidelines,PreparedfortheBWRVesselandInternalsProjectAssessmentSubcommittee,GENE-523-A113-0894,August1994.2-2
GESugarEnergyGEM-$23-8161-1094AT10TFIGURE2-1SCHEMATICOFOYSTERCREEKINDICATIONS2-3
GE.VuclearFungyGEM-S23-lil6I-l0943.COMPARISONBET%'EENNMP-1ANDOYSTERCREEKCORESHROUDSAcomparisonbetweentheNMP-1andOysterCreekcoreshroudsispresentedinthissection.TheintentistodemonstratethatanycrackingintheNMP-1shroudH4weldislikelyboundedbythatobservedintheOysterCreekH4weld.Theevaluationconsiderswaterchemistry,fluence,on-lineyears,andmaterialaspects.3.1WaterChemistryForthefirstfourcycleofhotoperation,NMP-1operatedwithrelativelyhighprimarywaterconductivity.AsseeninTable3-1andFigure3-1,thecyclicconductivitymeanvaluesexceeded0.43p,S/cm.Therewasadramaticconductivityimprovementduringthefifthfuelcyclewheretheconductivitydecreasedtolessthan0.3pS/cm.Sincethefourthcycle,conductivityvalueshavesteadilyimprovedandwereexcellentatlessthan0.09pS/cmduringthelastthreeoperatingcycles.Earlysteadystatechloridelevelsrangedbetween30and58ppb.Inadditiontohighearlylifesteadystateconductivity,therewereafewdocumentedwaterchemistrytransientsatNMP-1:l.September3,1971-NMP-1conductivityreached30pS/cmatpowerduetohighconductivitywaterinthe,condensatestoragetank.2.November25,1974-NMP-1conductivityreached1.4pS/cmatpowerduetoavalvingerrorduringresintransfer.ThepHdroppedto5.6and81ppbchloridewas-identifiedinthewater.3.March9,1977-683ppbchloridewasidentifiedinthewaterduringshutdown.OysterCreek'searlywaterchemistrywasconsiderablymoreimpurethanNMP-1's.OysterCreekwascharacterizedbyanaveragefirstsevencyclemeanof0.465ij.S/cm.Onlyafterfuelcycleten,wheredataisagainavailable,didthereactorwaterconductivity3-1
pGEiVnckarEnergyGENE-$23-A16I-f094improve.Infact,in1991OysterCreekbeganoperatingonhydrogenwaterchemistry(HWC).ThelastthreefuelcyclereactorwaterconductivityatOysterCreekhasbeenexcellent.OysterCreek'searlysteadystatechloridelevelsrangedoveraslightlywiderrangethanÃvP-1,i.e.,between25and74ppb.Inadditiontolongtermhighearlylifesteadystateconductivity,therewasasingledocumentedwaterchemistrytransientexperiencedatOysterCreek(Reference3-1).:1.June6,1972-730ppbchloridewasidentifiedinthewaterduetodepletedreactorwaterclean-upsystemdemineralizer.Becauseofthehighearlylifeconductivityhistory,itislikelythatintergranularstresscorrosioncracking(IGSCC)initiationwasacceleratedinsusceptibleareasoftheprimarysystem,includingtheshroud.TheeFectsofconductivity(sulfate)oncrackinitiationinuncrevicedmaterialispresentedinFigure3-2.Itisclearthatanincreaseinconductivityresultsinanaccelerationincrackinitiationasmeasuredbytheconstantextensionratetest(CERT).Asimilartypeofinitiationaccelerationisobservedforchlorideions.ThestrongcorrelationbetweenconductivityandIGSCCsusceptibilityinuncrevicedsensitizedstainlesssteelhasalsobeenexaminedinvariousotherlaboratorystudies(Reference3-2through3-4)anditisevidentthatasignificantdecreaseincrackinitiationtimeisexpectedwithincreasedconcentrationsofcertaindeleteriousanionicimpurities,inparticularchloridesandsulfates.ForcrevicedBWRcomponents,thestrongcorrelationofSCCsusceptibilitywithactualBWRplantwaterchemistryhistoryhasbeenDocumented(Reference3-5).3-2
GEivudcarEnergyGEISTE-$23-Aldl-l0943.2ShroudEvaluationFollowingisaone-on-onecomparisonbetweentheNMP-1andOysterCreekcoreshrouds:~NMP-1'sfirstfive-cyclemeanconductivitywas0.457pS/cmcomparedtoOysterCreekat0.526pS/cm.~NMP-1'stotalmeanconductivityis0.280pS/cmcomparedto0.316p,S/cmforOysterCreek.~NMP-1ischaracterizedby15.5on-lineyearscomparedto15.7forOysterCreek.~NMP-1peakfastfluenceisapproximately4.2x10"n/cm.Thiscomparesagainst6.6x10'/cmforOysterCreek.~NMP-1'scoreshroudmaterialandOysterCreekcoreshroudmaterialisessentiallythesamewithbothplantsusingthesameheatsofType304stainlesssteel.~BothNMP-1andOysterCreekshroudsweremanufacturedbyP.F.Avery.3.3ShroudComparisonConclusionBasedontheexperienceofshroudcrackinginBWRswithrelativelygoodwaterchemistryqualityandatlowfluencelocations,independentofmanufacturer,materialofconstructionandrelativeage,crackinginNMP-1'sH4shroudweldcannotberuledout.However,aon-on-onecomparisonbetweentheoperatinghistoryofNMP-1'sandOysterCreekstronglysuggeststhatNMP-1'sshroudisboundedbyOysterCreek'sshroudcondition.Althoughthematerialofshroudconstructionisidenticalinthetwoplants,theNMP-1shroudcorrosionconsiderationsarefavoredbythelowerfirstfivecyclemeanconductivityoftheplant,lowertotalmeanconductivityandlowerfluenceattheshroud.3-3
GE,VuelearEnergyGENE-$23-Al61-l0943.4References3-1.B.H.Dillmanetal,"MonitoringofChemicalContaminantsinBWRs,"EPRINP-4134,July1985.3-2.DavisandM.E.Indig,"TheEffectofAqueousImpuritiesontheStressCorrosionCrackingofAusteniticStainlessSteelinHighTemperatureWater,"paper128presentedatCorrosion83,Anaheim,CA,NACE,April1983.3-3.Ljungberg.D.CubicciotiandM.Tolle,"EffectofImpuritiesontheIGSCCofStainlessSteelinHighTemperatureWater,"Corrosion,Vol.44,No.2,February1988.3-4.Ruther,W.K.SoppetandT.F.Kassner,"EffectofTemperatureandIonicImpuritiesatVeryLowConcentrationsonStressCorrosionCrackingofType304StainlessSteel,"Corrosion,Vol.44,No.11,November1988.3-5.BrownandG.M.Gordon,"EffectsofBWRCoolantChemistryonthePropensityforIGSCCInitiationandGrowthinCrevicedReactorInternalsComponents,"paperpresentedattheThrdInt.Symp.ofEnvironmentalDegradationofMaterialsinNuclearPowerSystems-WaterReactors,TransverseCity,MI,August1987,publishedinproceedingsofthesame,TMS-AIME,Warrendale,PA,1988.34
GE'h'uCharEnergyGENE.SZ3-AI61-f094Table3-1.NineMilePoint-1andOysterCreekWaterChemistryHistoryCycleNMP-1CycleMeanValueConduct.pS/cmOysterCrCycleMeanValueConduct.pS/cmOCCl-ppbCl-ppbNMP-ISO4=,ppbOCSO4=,ppb101213140.4320.5250.5910.4450.2910.2250.1810.1330.0870.0820.0840.4260.8690.3290.2940.7140.2980.3240.1430.1440.0880.090.06730465844332726251840742724372825443-5
10.001.00ET<<+00.10OEproonetaryhaonnaoonleaiaNoevenaeeaoaDenan-+MaxWeektyMeanValue<ydeQCydeMeanVa(ueawithStd.Oev.21AoH109e0.010FuelCycleFigure3-1NineMilePoint-1ReactorWaterConductivityMeanYaluci3-6 0
Figure3-2.EffectofSulfateonIGSCCInitiationAccelerationforFSType304IAcceleration'Factor00.2030~~030.101002.30.~0.00.101~0Conductivity(uS/cm)H+0N10CrackinitiationdatabasedonCERT100Sulfate{ppb)100010000so4wcoN
GEgVaclaarEItargyGENE-S23-AI6l-l0944.CRACKGRO%THESTIMATEThebasisforthecrackgrowthrateusedinthescreeningcriteriaisprovidedinthissectionTheNMP-1shroudcylinderswerefabricatedfromType304stainlesssteelplate.Therefore,theweldheat-affected-zone(HAZ)islikelysensitized.Theshroudisalsosubjectedtoneutronfluenceduringthereactoroperationwhichfurtherincreasestheeffectivedegreeofsensitization.Theotherside-effectofneutronfluenceinducedirradiationistherelaxationofweldresidualstresses.Theslip-dissolutionmodeldevelopedbyGEquantitativelyconsidersthedegreeofsensitization,thestressstateandthewaterenvironmentparameters,inpredictingastresscorrosioncracking(SCC)growthrate.Thecrackgrowthratepredictionsofthismodelhaveshowngoodcorrelationwithlaboratoryandfieldmeasuredvalues.Thismodelwasusedtopredictacrackgrowthrateandaconservativevaluewasthenselected.Theslip-dissolutionmodeldoesnotexplicitlyconsideranycontributiontocrackgrowthduetonewcrackinitiations.Whilenewcrackinitiationsduringthenextfuelcycleofoperationcannotberuledout,considerablerelaxationinweldresidualstressmagnitudesduetoirradiationislikelytominimizecrackinitiation.Thisissupportedbylimitedfieldevidencefromanoverseasplantwherethesamecrackedregionoftheshroudwasexaminedoverthreerefuelingcyclesfollowingthediscoveryoffirstincidenceofcracking.SThesubsequentexaminationsshowedsomegrowthoftheexistingcrack,butdidnotshowevidenceofnewinitiations.Evenifanynewinitiationsdooccur,itislikelythatonlyshallowcrackingwilloccurduringonecycleofoperation.4.1Slip-DissolutionModelFigure4-1schematicallyshowstheGEslip-dissolutionfilm-rupturemodel(Reference4-1)forcrackpropagation.ThecrackpropagationrateVtisdefinedasafunctionoftwoconstants(Aandn)andthecracktipstrainrate,s.V,=As"where:s=CK"(forconstantload)A=7.8x10n(fromReference4-2)n=(ef(K)/(eftK)+ef(qi)c))APR)(fromReference4-2)4-1
gg,VackarEnergyGENE523rl16l1094Theconstantsaredependentonmaterialandenvironmentalconditions.Thecracktipstrainrateisformulatedintermsofstress,loadingfrequency,etc.Whenaradiationfield,suchasthecasefortheshroud,ispresent,thereisadditionalinteractionbetweenthegammafieldandthefundamentalparameterswhichaffectintergranularstresscorrosioncracking(IGSCC)ofType304stainlesssteel(seeFigures4-2and4-3).Theincreaseinsensitization(i.e.,ElectrochemicalPotentiokinematicReactivation,EPR)andthechangesinthevalueofconstantAandnasafunctionofneutronfluence(>1MeV)isgivenasthefollowing:EPR=EPR0+3.36x1024(fluence)117(4-2)where,EPRisinunitsofC/cm2,fluenceisinunitsofn/cm2andthecalculatedvalueofEPRhasanupperlimitof30.TheconstantCisdefinedasthefollowing:forfluence<1.4x1019n/cm2:C=4.1x10-14(4-3a)forfluence>1.4x1019n/cm2but<3x1021n/cm2:C=1.14x10-13ln(fluence)-4.98x101(4-3b)forfluence<3.0x1021n/cm:C=6.59x1013(4-3c)ThevariableKisthestressintensityvialinearelasticfracturemechanicsandistobeusedwiththeaboveexpressionsintheunitsofMPa~m.4.2CalculationofParametersTheparametersneededforthecrackgrowthcalculationbytheGEmodelare:stressstateandstressintensityfactor,effectiveEPR,waterconductivity,andelectro-chemicalcorrosionpotential(ECP).ThestressstaterelevanttoIGSCCgrowthrateisthesteadystatestresswhichconsistsofweldresidualstressandthesteadyappliedstress.Figure4-4showsobservedthrough-'allweldresidualstressdistributionforlarge"diameterpipes.TheresidualstressistensileJ4-2
GEqvualaarEuerg+GEÃE-$23-A26l-1094atboththeinsideandoutsidesurfacesandcompressiveinthemiddle.Thistypeofdistribution(characterizedbyacosinefunction)isaconservativerepresentationforweldsinlargediameterpipesandplates(seeReference4-3).Themaximumstressatthesurfacewasnominallyassumedas35ksi.Thesteadyappliedstressontheshroudisduet'ocorediQerentialpressureanditsmagnitudeissmallcomparedtotheweldresidualstressmagnitude.Figure4-5showstheassumedtotalstressprofileusedintheevaluation.Figure4-6showsthecalculatedvaluesofstressintensityfactor(K)assuminga360'.circumferentialcrack.ItisseenthatthecalculatedvalueofKreachesamaximumofapprox.25ksi~in.TheaveragevalueofKwasestimatedas20ksi~inandwasusedinthecrackgrowthratecalculations.Theweldresidualstressmagnitudeisexpectedtodecreaseasaresultofrelaxationproducedbyirradiation-inducedcreep.Figure4-7showsthestressrelaxationbehaviorofType304stainlesssteelduetoirradiationat550'.Sincemostofthesteadystressintheshroudcomesfromtheweldresidualstress,itwasassumedthattheKvaluesshowninFigure4-6decreaseinthesameproportionasindicatedbythestressrelaxationbehaviorofFigure4-7.ThesecondparameterneededintheevaluationistheEPR.Inthemodel,theinitialEPRvalueisassumedas15fortheweldsensitizedcondition.UsingEquation(4-2),thepredictedincreaseinEPRvalueasafunctionoffiuenceisshowninFigure4-8.ThethirdparameterusedintheGEpredictivemodelisthewaterconductivity.AwaterconductivityofO.1gS/cmwasusedinthiscalculationwhichisareasonablevalueformanyplants.ThereactorwaterconductivityatNMP-1isexcellent(approx.0.084p,S/cm).ThishasasignificantimpactonthepredictedcrackgrowthratebytheGEmodelasseeninFigure4-9,asshownforadomesticBWR/4.TodemonstratethattheGEmodelconservativelyrefiectstheeffectofconductivity,Figure4-10showsacomparisonoftheGEmodelpredictionswiththemeasuredcrackgrowthratesinthecrackadvanceverificationsystem(CAVS)unitsinstalledatseveralBWRs.ThecomparisonwithCAVSdatainFigureA-10alsodemonstratestheconservativenatureofcrackgrowthpredictionsbytheGEmode).TThelastparameterneededintheGEpredictionmodelistheECP.Figure4-11showsthemeasuredvaluesofECPattwolocationsinthecore.TheECPvaluesatzeroH2injectionarerelevantinFigureA-11fornohydrogeninjection.ItisseenthattheECP4-3
GEÃuckarEnergy~ELFSZS-~is-iOWvaluesatzeroH2injectionraterangefrom150mVto225mV.Therefore,avalueof200mVwasusedinthecalculation.4.3CrackGrowthPredictionBasedonthediscussionintheprecedingsection,thecrackgrowthratecalculationswereconductedasafunctionoffluenceassumingthefollowingvaluesofparameters:InitialKEPR0Cond.ECP=20ksi~in=15C/cm2=0.1pS/cm=200mVFigure4-12showsthepredictedcrackgrowthrateasafunctionoffluence.ItisseenthatthepredictedcrackgrowthrateinitiallyincreaseswiththefluencevaluebutdecreaseslaterasaresultofsignificantreductionintheKvalueduetoirradiationinducedstressrelaxation.Thecrackgrowthratepeaksat4.5x10-5in/hratafluenceoflx10n/cm2.Thus,aboundingvalueofSxl05in/hrcanbeconservativelyusedinthestructuralintegrityevaluationfortheshroud.TheactualrecentwaterconductivityforNMP-1is0.084pS/cm.ANMP-1plantspecificcalculationwasalsoperformedusingtheNMP-1waterconductivityandcurrentfluenceattheH4weld.ResultsofthiscalculationshowedthattheNMP-1crackgrowthratewas2.6x10'n/hr.Forpurposesofthisevaluation,aconservativecrackgrowthrateofSx10'n/hrisused.ThisboundingcrackgrowthrateisquiteconservativeascanbeshowninFigureA-13fromNUREG-0313,Rev.2.ItisseenthatthecrackgrowthrateofSx10-5in/hrat20ksi~inisconsiderablyhigherthanwhatwouldbepredictedbyusingtheNRCcurve.Thisfurtherdemonstratestheconservatisminherentintheassumedboundingvalueofcrackgrowthrate.44
GEJVuckarEu~gYGENE-$23-Al6l-l0944.4ConclusionAcrackgrowthratecalculationusingtheGEpredictivemodelwasconductedconsideringthesteadystatestress,EPR,conductivityandECPvaluesforatypicalshroud.TheevaluationaccountedfortheeffectsofirradiationinducedstressrelaxationandtheincreaseineffectiveEPR.TheevaluationshowedthataboundingcrackgrowthrateofSx10-5in/hrmaybeusedinthestructuralintegrityevaluationoftheNMP-1shroud.4-5
gt.fVuckarEnergyGEÃE-$23-gf6g/0944,5Reference4-1F.P.Fordetal,"PredictionandControlofStressCorrosionCrackingintheSensitizedStainlessSteeVWaterSystem,"paper352presentedatCorrosion85,Boston,MA,NACE,March1985.4-2F.P.Ford,D.F.Taylor,P.L.Andresen&R.G.Ballinger,"EnvironmentallyControlledCrackingofStainlessSteelandLowAlloySteelsinLWREnvironments,"1987,(EPRIReportNP50064M,ContractRP2006-6).4-3ASMESectionXITaskGrouponReactorVesselIntegrityRequirements,"WhitePaperonReactorVesselIntegrityRequirementsforLevelAandBConditions,"EPRI,PaloAlto,CA,January1993,(EPRIReportTR-100251,Project2975-13).4-6
GENudcarEnergyGENE-323-8161-1094CTVTCrack-tipadvancebyenhancedoxidationatstrainedcracktipVT--AgWhere:-A,ncrackpropagationrateconstants,dependentonmaterialandenvironmentalconditions,crack-tipstrainrate,formulatedintermsofstress,loadingfrequency,etc.Figure4-1:TheGEPLEDGESlipDissolution-FilmRuptureModelofCrackPropagation4-7
6'Egaclcar&erg+GELT-523-AI61-1094SOLUTIONRENEWALRATETOCRACK-TIPSTRESSOXIDERUPTURERATEATCRACK-TIP>/ANIONICTRANSPORTENVIRONMENTMICRO-STRUCTUREHARDENINGIRELAXATIONT-FIELDCRACKTIP4[A],pHPASSIVATIONRATEATCRACK-TIPN-FLUENCEG.B.DENUDATIONISEGREGATIONFigure4-2:EffectsofFastFluence,Flux&,GammaFieldonParametersAffectingIGSCCofType304StainlessSteel4-8
GEKuCkurEnergyGEIVE-$23-AI61-2094VT=Ai,",QxO~~"A"HoM'EPRP,S,NI~Si~necTz-~ef(x)~(ef(x)+ef(q)cof(EPR)Figure4-3:ParametersofFundamentalImportancetoSlipDissolutionMechanismofIGSCCinSensitizedAusteniticStainlessSteel4-9
GEendearEnergyGENE-$23-8161-1094INSIDEWALL50OUTSIDEWAU403020IOIc/llP-20Oa~ddd44~~QO44oCLd~8d~Q0.2040.60.8l.0Figure4-4:Through-wallLongitudinalResidualStressDataAdjacenttoWeldsin12to28inchDiameterStainlessSteelPiping4-10
GEivnckarEnagyGENE-$23-Al6l-l094STRESSKSIDOD3020TotalStressProfile10AppliedLoadStress0-10-20-30400.20.40.60.8DEPTH(INCHES)1.21.4Figure4-5:ConservativeRepresentationoftheShroudTotalThrough-wallStressProfile4-11
GE/udearEnergyGEÃE-$23-A161-1094262422201816141210STRESSINTENSITY,K(KSI'INCH"0.5)0.20.40.60.8CRACKDEPTH,A(INCHES)Figure4-6:ShroudThrough-wallStressIntensityFactor4-12
GE>VudaarEnergyGELT-529-8161-10'0.8C~~C~~C$EQa:0.6V)V)o04Q~~VC5u-0.2StressRelaxationBehaviorfromIrradiationCreepMinimumAverageData~~Type304StainlessSteel'.at288'Ci.e"g02010NeutronFluence,n/cm2(Eo1MeV}10Figure4-7:StressRelaxationBehaviorofType304StainlessSteelDuetoIrradiationat288'C4-13'
gE,VuclcarEnergyGEE-$23-rll6l-10943025a-20101E+191E+20FLUENCE1E+21Figure4-8:EPRVersusNeutronFluence4-14 eP GEivudaalEnergyGENE323ill6ll0960.00015.000E-05PL"0.00001UCl0.000001OFOIAl91992-19931975-1984100mV0mV100mV-200mV300mV0.000000100.10.20.30.40.50.60.70.80.9Conductivity,pS/cmPLEDGE:20ksiJin,15C/cm2Figure4-9:GENEPLEDGEModelPredictionforaBWR-4(SensitizedType304CrackGrowthRate)4-15
GEivnckarEnergyGENE-$23-itl61-10'.00015.000E-OS200mVe0.00001(90.000001O1E-07AGAG0C0CMM(9AG0TMMM0AJ0C0NN0.050.10150.20.25Conductivity,pS/cmPLEDGE:20ksigin,15C/cm2CAV:20-25ksigin,13C/cm2,100-160mV0.30.35Figure4-10:EffectofConductivityonSensitizedType304CrackGrowthRate4-16
GEivuclcarEnergyGM-$23-Al61-l094300200100llJ0E-100OuJ-200-300JustBelowTopGuideLevelJustAboveCorePlateLevel-4000102030405060708090FeedwaterH2,SCFMFigure4-11:In-CoreBypassECPversusFeedwaterHydrogenforBWR-44-17
GElVF-323-AI6I-I0941.00E-041.00E-061E+191E+20Fluence(n/cm2I1E+21StressIntensity=20ksigin,InitialEPR=15C/cm2Figure4-12:GrowthRateversusFluence4-18
GE/One!earEnergyGENESZ3II/61109eI0-3I0-4Iin./yrNRCCURVE0-5LLJI-CLI-oI06CDhCCDCLCDI0-7/$8/j/Q~/4r0.04in.iyrIIIIIIIII--I8O.tpps0t',sensltlte4atIISO'f/th(Eth~ISC/cs)CEO.tPP<<'0tlsensltlte4at11$0'F/th(Kph~10C/cs)-CEQO.tpps0t'Isensltlte4at11$0'F/tlhCEO.tpps0t,seecrelysensltlte4Q0ppsOt.lsensltltHat11$0'F/tlhCEIHITACHICKHKOQNLCKCtO~4pps0t,se<<sltlte4byvol~l<<$;LfSat$)t'F/tlh(Sll)I01sensltltHat(lt$t'f/10eisn)a($$t'F/tlh)(EPO~lC/cs)0ppsOt,se<<sltltHat(lt$t'f/10min)e($)t'F/tlh)(Epn~lC/cs)f~O.lHt,H~0.$4*0pps0t,sensltlte4at(It$t'f/IOsin)a(4t'F/tSFh)(EPO~ISC/cs)p0~0,:sensstltHat(It$t'F/10ein)a(4t'F/t57h)(EPH~'ISC/cs)f~O.lHt,H~0.$i~0ppsOt'IsensltltHatlt$t'f/Ilh(EM~tOC/cs)f~0.000Ht,H~0.$$X0ppsOtlsensltltHatIt$tf/Ilh(EpnItOC/cs)f~0.00Ht,0~0.$$RECENTANLOATA0IO2030405060STRESSINTENSITY,K{I(sile.j70Figure4-13:NUREG-0313CrackGrowthRateData4-19
GEtVuclcarEltbargyGEtVE-$23-Al6l.l0945.FLAWEVALUATIONThissectionprovidesthemethodologyandevaluationoftheobservedindicationsintheOysterCreekH4weld.Thismethodincorporatestheconservativeassumptionthattheareasotherthantheinspectedligamentlengthsareassumedtobecrackedthroughwall,andconsidersproximityrules.Abriefdescriptionofthetechniquesisfirstprovidedfollowedbyadetaileddescriptionoftheevaluation.5.1LimitLoadMethodFigure5-1showsaschematicrepresentativeplanviewofanasymmetricdistributeduncrackedligament.Itisassumedthatthereare1,2,...i,....nligamentlengthsandthattheilengthisofthickness'tandextendsfromanazimuthof6;1to6;2.Theligamentlength'loftheithligamentisrelatedtoazimuthangles6;1and6i2bythefollowingrelationship:li=(D/2)~(6;1-6j2)(5-1)where,Disthediameteroftheshroud.Thecalculationofmoment'M'hatthisligamentconfigurationcanresist,issomewhatcomplicatedsinceitisnotaprioriclearastowhichazimuthalorientationoftheneutraVcentralaxiswouldproducetheleastvalueofbendingmoment,'M'.Therefore,thevalueofMiscalculatedforvariousorientationsofthecentralaxisfrom0'o360'.Thiscalculationisperformedintwosteps:(1)Inthimtep,acentralaxisorientation,e,isfirstselected.Thelocationoftheneutralaxis(whichisparalleltothecentralaxis)atadistance5fromthecentralaxisisdeterminedusingthefollowing(seeFigure5-1):where,IRt(8)d8gm-a+))gm-a+))JRt(6)d6=(am/af)(2nRtg(5-2)a+/AssumedazimuthangleofthecentralaxisAngleoftheneutralaxiswithrespecttocentralaxis,orsin1(5/R)5-1 0
GE.VuakarEnergyGEÃE-$23-rl16I-I0945=DistancebetweenthecentralaxisandtheneutralRt(e)tnamGfaxisMeanradiusoftheshroudt;(thicknessoftheithligament),ifangle8issuchthate;1<e<62,or0otherwise.NominalthicknessofshroudMembranestressMaterialflowstress=3SmThus,thisstephelpsdefinethelocationoftheneutralaxiswhenthecentralaxisisassumedtobeatanazimuthangleofa.(2)Oncethelocationoftheneutralaxisrelativetothecentralaxisisdetermined,themoment,M+,isthenobtainedbyintegratingthebendingmomentcontributionsfromindividualligamentlengths.Themathematicalexpressionusedisthefollowing:Ma=IafR>At(8)Sin(a-8)d8(5-3)where,A1.0,if-(n-e+P)<6<a+(,or-1.0,ifa+)<e<-(ii-u+P)Theorientation'e'hatproducestheleastvalueofMiscalled'e,min'nddefinestheaxiscapableofresistingthelimitingmoment.Whetherthespecifiedsetofuncrackedligamentlengthsprovidestherequiredstructuralmarginisverifiedbythefollowing:M(xminI'Z+Pm>SF(Pm+Pb)where,PmPbSFSectionmodulusoftheshroudbasedonuncrackedcrosssectionAppliedmembranestressAppliedbendingstressSafetyfactor5-2
GEunclearEnergyGENE-323-Al6l-l0945.2EvaluationofPart-ThroughWallCracksIfitisnotpossibleobtaintherequiredsafetyfactorsassumingthrough-wallindications,thenevaluationofacombinationofuncrackedligamentsandpartthrough-wallcracksmayberequiredtoassessstructuralmargins.Forthiscase,theangularlocationoftheuncrackedligaments,andthedepthoftheflaws,mustbedetermined.Proximityrulesareusedtodetermineeffectiveflawlength.ThedepthdeterminationmustalsoincludeanyuncertaintyassociatedwiththeNDEmethodused.Allowancesforcrackgrowtharealsofactoredin,includingeffectsonbothlengthofuncrackedligaments,anddepthofflawedportionsoftheareaexamined.Thisinformationcanthenbeanalyzedinaccordancewithpreviouslyoutlinedmethods.Themaximumobserveddepthsizingerrortodatehasbeen7.6mm.Basedonthis,theuncertaintyassignedtodepthmeasurementsis7.6mm,untilbetterinformationcanbeobtained.Itmaybepossibletoconservativelysimplifytheaboveapproachbyassumingaflawof360oatthemaximumobserveddepth,a.Thedepth'a'houldincludeanyuncertaintyassociatedwiththeNDEmethodused.Therequiredminimum360'igamentatacircumferentialweldcanbedeterminedbyiterativelycalculatingtheallowablecrackdepth,'d'singthefollowingequations(Reference5-1):(n(I-d/tn-Pm/af)}/(2-d/tn)Pb'(2ag'm)(2-d/tn)sinp(5-5)(5-6)(Pm+Pb)SF=Pb'+Pmwhere,PmPbdtnSFPrimarymembranestressatthesubjectweldPrimarybendingstressatthesubjectweldAllowablecrackdepthShroudwallthickness(awayfromafilletweld)SafetyfactorappropriatefortheoperatingconditionbeingevaluatedMaterialflowstress(=3Sm)5-3
GEivuckarEnergyGENE-$2$-Al61-l094Itshouldbenotedthatthestresses,PmandPb,arecalculatedusingthenominalshroudthickness.Thecurrentcrackdepth'a'sacceptableiftheprojectedcrackdepth,afteraccountingforcrackgrowthuntilthenextinspection,islessthantheallowablecrackdepth'd'.Thiscriteriaisgivenbythefollowingequation:(a+CG)<d(5-7)where,CGistheprojectedcrackgrowthuntilthenextinspection.5,3SafetyFactorsSafetyfactorsof2.8foroperationalconditionsand1.4forfaultedconditionswereusedintheevaluationofcircumferentialwelds.ThesesafetyfactorvaluesareconsistentwithSectionXIvalues.5-4
GEIIudaarEnergyGEM-S23-AI6l-I0945.4ApplicationofFlawEvaluationMethodologytoNMP-1ShroudTheapplicationoftheflawevaluationmethodologydescribedearlierispresentedinthissection.CrackgrowthassumingacrackgrowthrateofSx10Sin/hrwasaddedtotheassumedindications.5.4.1LimitLoadForlimitload,theflawdistributionpatterninSection2.0wasused.ThisflawdistributionpatternwasaresultofapplyingtheproximitycriteriagiveninReference2-1.Acomputer.programwasusedwhichusestheReference2-1methodology.Resultsofthisevaluationshowedsafetyfactorsinexcessofthoserequired.Theresultingsafetyfactorswere:ConditionCalculatedReuiredNormalandUpsetEmergencyandFaulted6.53.52.81.4Theseresultsillustratethatduetotherelativelylowloads,theshroudisveryflawtolerant.5.4.2LEFMTheLEFMcalculationisprovidedeventhoughtheresultsofthiscalculationmaynotbemeaningfulduetothefluenceattheNMP-1H4weldlocation.Thecurrentfluenceisjustabove3xlon/cm.ThefracturetoughnessusedtodeterminethecriticalflawsizecorrespondMomaterialwithafluenceof8x10'/cm.BasedontheOysterCreekflawresults,aconservativecombinationoftheindicationswasconsideredfortheLEFMcalculation.Usingthisconservativecombination,asafetyfactorof1.83wasobtained.Thiscomparesagainsttherequired1.4forfaultedconditions.5-5 0
GEPuckarEnergyGENEI-AI6I10945.5References5-1S.RanganathandH.S.Mehta,"EngineeringMethodsfortheAssessmentofDuctileFractureMargininNuclearPowerPlantPiping,"ASTMSTP803(1983).5-6
OoBll/B12CentralAxis'5?'(:C,.%?5eutraAxisrBuFigure5-1SchematicofNon-SymmetricigiamentDistribution
GEivudcarEnergyGElVE-$2$.1I6l.l0946.CONCLUSIONSAnevaluationoftheNMP-1coreshroudhasbeenperformed.TheobjectiveoftheevaluationwastodemonstratethatcontinuedoperationofNMP-1wasjustifiedonastructuralbasisbyapplyingtheOysterCreekinspectionresultstoNMP-1.Itwasconcludedthatbasedonaone-to-onecomparisonbetweenNMP-1andOysterCreek,theindicationsintheOysterCreekshroudwilllikelyboundthoseintheNMP-1shroud.Evenwiththisconservativeassumption,itwasdeterminedthatthesafetyfactorpresentintheNMP-1coreshroud(usingOysterCreekindications)exceededtherequiredsafetyfactorsuntilatleastFebruaryof1995.Thus,itwasconcludedthatcontinuedoperationoftheNMP-1plantisjustifiedbasedonstructuralevaluationofthecoreshroud.6-1
ATTACHMENT2NINEMILEPOINTUNIT1DOCKETNO.50-220LICENSENO.DPR-63GENERICLETTER94-03SUPPLEMENTALINFORMATION"FRACTUREMECHANICSASSESSMENTOFTHENINEMILEPOINTUNIT1SHROUDH4WELD"REPORTMPM-109439MPMRESEARCHRCONSULTINGOCTOBER1994 0