ML17059B241

NMP-1 Core Shroud Repair Mod Summary Rept.

ML17059B241
Person / Time
Site:	Nine Mile Point
Issue date:	08/13/1996
From:	GLEASON T E, RANGANATH S, SCHRAG M R GENERAL ELECTRIC CO.
To:
Shared Package
ML17059B240	List: ML17059B239 ML17059B241 ML17059B242 ML17059B243 ML17059B244 ML18040A180
References
GENE-B13-01739, GENE-B13-01739-31-R0, GENE-B13-1739, GENE-B13-1739-31-R, NUDOCS 9608210135
Download: ML17059B241 (30)

Text

ENCLOSMILEPOINT1CORESHROUDREPAIRMODIFICATIONSARYREPORT96082iOi359608i4'DRADQCK,05000220,.P~',PDR

GENuclearfnerqyGENEB13-P1739-31Revision0August1996NineMilePoint1CoreShroudRepairModificationSummaryReportPreparedfor.NiagaraMohawkPowerCorporationPreparedby:GENuclearEnergyReactorModificationServices175CurtnerAvenue,N/C571SanJose,California95125

GENuclearE'nergyGENEB13-01739-31Revision0August1996NineMilePoint1CoreShroudRepairModificationSummaryReportPreparedby:&-/Z-K,TE.Gleason,PrincipalEngineerReactorModificationServicesReviewedby:Approvedby:N.R.Schrag,IncipalEngineerReactorModificationServices<l~jg,S.Ranganath,EngineeringFellowGENuclearEnergy

GENEB13-01739-31Revision0August1996REVISIONSTATUSSHEETRevisionApprovalS.RanganathDateInitialIssueDescription

GENEB13-P1739-31Revision0August1998IMPORTANTNOTICEREGARDINGCONTENTSOFTHISREPORTPleaseReadCarefullyThisreportwaspreparedbyGeneralElectricsolelyfortheuseoftheNiagaraMohawkPowerCorporation.TheinformationcontainedinthisreportisbelievedbyGeneralElectrictobeanaccurateandtruerepresentationofthefactsknown,obtainedorprovidedtoGeneralElectricatthetimethisreportwasprepared.TheonlyundertakingsoftheGeneralElectricCompanyrespectinginformationinthisdocumentarecontainedinthecontractgoverningthiswork,andnothingcontainedinthisdocumentshallbeconstruedaschangingsaidcontract.Theuseofthisinformationexceptasdefinedbysaidcontract,orforanypurposeotherthanthatforwhichitisintended,isnotauthorized;andwithrespecttoanysuchunauthorizeduse,neitherGeneralElectricCompanynoranyofthecontributorstothisdocumentmakesanyrepresentationorwarranty(expressorimplied)astothecompleteness,accuracyofusefulnessoftheinformationcontainedinthisdocumentorthatsuchuseofsuchinformationmaynotinfringeprivatelyownedrights;nordotheyassumeanyresponsibilityforliabilityofdamageofanykindwhichmayresultfromsuchuseofsuchinformation.

GENEB13-01739-31Revision0August1996CONTENTSl.INTRODUCTION2.SUMMARYANDCONCLUSIONS3.TIERODREPLACEMENTMODIFICATION4.H6ACONTACTEXTENSION5.DISPLACEMENTSUMMARY6.DESIGNBASIS7.SAFETYCONSIDERATIONS8.ATTACHMENTS

GENEB13-01739-31Revision0August1998l.INTRODUCTIONAcoreshroudrepairmodificationwasinstalledinNineMilePoint1NuclearPowerPlanttoprovideanalternateloadpathfortheType304stainlesssteelcircumferentialwelds,HlthroughH7.ThecoreshroudrepairensuresthestructuralintegrityofthecoreshroudbyreplacingthefunctionofweldsHlthroughH7with4stabilizerassemblies,andfourcoreplatewedges.Inthecourseofthepost-installationinspectionoftheshroudrepair,threedeviationswereidentified,evaluatedandwerefoundacceptableforcontinuedplantoperationthroughthenextcycle.Afteradditionalreviewandevaluation,twoadditionalmodificationsareproposedtoprovidethelongtermcorrectiveactions.1.1Modification1:270'ieRodReplacementThelowerspringofonestabilizerassemblybearsontheblendradiusofthe270'ecirculationnozzle.Theproposedmodificationistoreplacethetierodandspringassemblywithonehavingthespringontheoppositesideofthetierod.ThisproposedmodificationrelocatesthespringtobearontheRPVasintended.1.2ThelowerspringcontactwiththeshrouddoesnotextendbeyondweldH6Aatanyofthefourlocations.Asaresult,ifweldH6Aisfullycracked,andifthedesignconditionofasteamlineLOCAplusseismiceventweretooccur,theshroudwouldnotbelaterallyconstrainedtotheextentintendedbydesign.TheproposedmodificationaddsanextensionpiecetoextendthespringcontactbeyondweldH6Aandrestorethisfeaturetoitsintendedfunction.Theextendedcontactandthecoreplatewedgesalsoprovidearedundantloadpathbetweenthecoreplateandthelowerspringaswasintendedintheoriginaldesign.Thismodificationappliestothe90',166'nd350'tabilizerassemblies.Thedeviationiscorrectedforthereplacementassemblyat270'.2.SUMMARYANDCONCLUSIONS2.1270'ieRodReplacementTheshroudrepairstabilizerassembliesaredesignedwiththelowerspringlocatedonthesideofthetierod.Theproposedmodificationistoreplacethetierodandspringassemblywithonehavingthespringontheoppositeside.ThemodificationmovesthespringsufficientlysuchthatitwillbearontheRPVasintended.Themodificationutilizes

GENEB13-01739-31Revision0August1998existinghardwarewhichwasbuiltasasparealongwiththeotherstabilizerassemblies.Onlyminorreworkisrequiredtorelocatethelowerspringandthereworkhasnoaffectonthehardwarefunction.ThemodificationdoesnotrequireadditionalpenetrationsthroughtheshroudsupportconeoranyadditionalEDMwork.Themodificationusesthesamelowersupportandupperspringassembliesandthereisnochangetotheactualtierodlocation.Additionalanalysishasbeendonetoaddressthedesignwherethelowerspringsarenolongerlocated90'part.Thenon-uniformlowerspringspacingaffectsthenetspringcharacteristicwhenthehorizontalseismicloadisdirectedbetweentwosprings.Theanalysisshowtheloadsanddisplacementsremainacceptableforallconditions.2.2H6AContactExtensionThelowerspringcontactswiththeshrouddonotextendabovetheH6Aweldaswasintended.ThedesignfunctioncanberestoredbyaddingaUshapedextensionpiecetoextendbeyondweldH6A.Theextensionpiecefitsovertheexistinglowercontactandiscapturedonthelowerextensioninalldirections.Theextensionisdesignedtoprovideapositivespringclampingforceagainstthesidesofthelowercontact.Thespringforceisnotrequiredtocapturethepartbutissufficienttopreventanyfreemovementorvibrations.Withthisarrangement,theaddedextensionpieceiscapturedinalldirectionsandisheldsecurebythespringloadedclampingforce.2.3ConclusionsThemodificationstotheshroudrepairstabilizersatNineMilePoint1willrestorethemtotheirintendeddesignfunction.Theplantlicensingbaseshavebeenreviewed.Thisreviewdemonstratesthatthesemodificationscanbeinstalled(1)withoutanincreaseintheprobabilityorconsequencesofanaccidentormalfunctionpreviouslyevaluated,(2)withoutcreatingthepossibilityofanaccidentormalfunctionofanewordifferentkindfromanypreviouslyevaluated,(3)andwithoutreducingthemarginofsafetyinthebasesofaTechnicalSpecification.3.TIERODREPLACEMENTMODIFICATION3.1BackgroundThelowerwedgeonthe270'ierodwasfoundtobearagainsttheblendradiusonarecirculationnozzleratherthanonthe'vesselwall.ThissituationisdocumentedperFDDREAl-0032andfurtherevaluatedinGElKB13-01739-25.Thatreportaddressedconcernsaboutthecontactareaandthestabilityofthecontactontheinclinedsurfaceofthenozzleblendradius.

GENEB13-01739-31Revision0August1998Thelowerwedgecanberelocatedtoapositionwithmorecompletedcontact(Figure3.1)onthevesselbymovingthelowerspringtotheoppositesideofthestabilizerassembly.Byrelocatingthelowerspring,theconcernsaboutcontactstabilityandcontactareaareresolvedandthestabilizerassemblymaintainsitsintendedfunctionalrequirements.IIIIIIIIIIII1i\'IiNozzleBoundary[2'ldLncaIion//I/Nc~LocnlionII.2ln.FIGURE3.13.2.DescriptionNiagaraMohawkPowerCorporationpurchasedasparetierodassemblyandthisassemblyisintendedtobemodifiedtothealternateconfiguration.Applicabledesignandassemblydrawingsarerevisedtoincludethenewpartsandgroupswhichdefinethealternateconfiguration.Alladditionalpartsandassembliesaredesignedandfabricatedtothesamedesignbasisastheoriginalshroudrepairhardware.Movingthelowerspringtotheoppositesideofthestabilizerassemblyisaccomplishedbythestepslistedbelow.a.Removethelowerspringfromtheexistingspareassemblyandthelowercontactfromtheexistinglowerspring.Thestakedlockingpinswillhavetoberemovedtoaccomplishthis.Newlockingpinswillhavetobeinstalledinslightlydifferentlocations,butthiswillnotaffectthefunctionofthepart.

GENEB13-01739-31Revision0August1998b.Modifythelowerspringbyaddingcounterborestotheoppositesideoftheboltholes.Havingcounterboresonbothsidesdoesnotaffectthefunctionofthepart.c.ModifytheC-springbyextendingthe1.125diameterholethroughthepart.d.Fabricateanewlowercontactwiththeshroudsidedsurfacetaperedtofitontheoppositesideofthestabilizerassembly.ThenewlowercontactisalsodesignedtoextendbeyondtheH6Aweldtoavoidinstallationofthecontactextensionpiece.e.Re-assemblethetierodassembly.f.Sincethelowerwedgeisatanewposition,newannulusmeasurementsarerequiredandthenewlowerwedgemachinedtofitperthemodificationdrawing.g.Allchangeswillberecordedonamodificationdrawingrevision.Nochangesarerequiredfortheuppersupport,theupperspringandthemidsupport.3.3.FunctionThelowerspringisdesignedtorestrictthecoreplatedisplacementduringaseismicevent.Thestabilizerassemblyisdesignedforasinglelowerspringtocarrytheentirehorizontalseismicloadatthecoresupport.However,thedirectionoftheloadmaybesuchthatmorethanonespringsharestheload.Thelimitingspringdeflectionandspringloadsoccurwhenonlyoneofthelowerspringsreactstotheentirehorizontalload.Relocatingthespringhasnoaffectonthemaximumspringloadormaximumspringdeflection.Relocatingthelowerspringdoeschangethespacingbetweenadjacentspringsandthespacingdoesaffectthenetreactionwhentwospringssharethelateralload.ThelowerspringcontactwiththeRPVischangedbyabout4'ymovingittotheoppositesideoftheuerod.The4'hangefromtheas-installedlocationresultsinamaximum108'pacingbetweenadjacentlowersprings.Theminimumspacingbetweenadjacentlowerspringsis76'.Whenthefourlowerspringsare90'part,theequivalentspringconstantisthesameforalldirectionsoftheappliedload.Theequivalentspringconstantisthetotalloadappliedbythelowerspringsdividedbythedisplacementinthedirectionoftheappliedload.Becauseofthenon-uniformspringspacing,thevariationinequivalentspringconstantis 1

GENEB13-D1739-31RevisionDAugust1998from+24%to-31%.Anincreaseintheequivalentspringconstanttendstoincreasethetotalreactionloadanddecreasethetotaldisplacement.Althoughthetotalreactionloadincreases,theloadissharedbytwospringsandtheloadoneitherspringisboundedbythecasewhereonespringcarriestheentireload.Adecreaseinequivalentspringconstantresultsinalargerdisplacementinthedirectionoftheload.AdditionalanalysisinAttachments8.1and8.2showallloadsanddisplacementsremainacceptableforthismodification.4.H6ACONTACTEXTENSION4.1.BackgroundThelowercontactsdonotextendabovetheH6Aweldaswasintendedtosatisfytheintendeddesignrequirements.TheReactorModificationDrawing,107E5679Revision6,showstheas-installedpositionofthelowercontactsandtheH6Aweld.Thesituationresultedfrominsufficientmargininthelowercontactdesigntoaccountfortheuncertaintiesintheas-builtgeometryoftheshroudsupportcone.ThisabovedeviationfromtheintendeddesignconditionisdescribedandevaluatedinFDDREAl-0031.TheevaluationshowedthecoreplateboltsaresufficienttomaintainthecoreplatealignmentwithoutthelowercontactextendingaboveweldH6A.Theevaluationconsideredtheboltclampingloadandtheelasticpropertiesoftheboltstoshowallowablecoreplatedisplacementwasnotexceeded.'ddingtheextensionpieceprovidesadditionaldesignmarginandassurancethatthecoreplatealignmentismaintained.4.2DescriptionThelowercontactsatazimuths90',166'nd350'remodifiedtoextendbeyondtheH6AweldbyaddingaUshapedextensionpieceshowninFigure4.1.TheextensionpiecefitsovertheexistinglowercontactwiththelegsoftheUextendingaroundthesidesoftheexistinglowercontact.Thestepsattheendsofthelegsfitunderthelowercontacttopreventaxialmovement.Atangatthetopextensionfitsinthegapbetweenthelowercontactandthelowerspringtorestrictthehorizontalmovement.Theaddedextensionpieceiscapturedinalldirectionsontheexistinglowercontact.Thelegsoftheextensionprovideapositivespringclampingforce(40lbto50lb)againstthesidesofthelowercontact.Thisforceissufficienttopreventanyfreemovementorvibrations.Withthisarrangement,theaddedextensionpieceiscapturedinalldirectionsandisheldsecurebythespringloadedclampingforce.

GENEB13-01739-31Revision0August1996TANGLLAi4IPLEGSTEPSFIGURE4.1Theaddedextensionpiecesareinstalledwithaspecialtoolforhandlingandtokeepthelegssprungapart.Whenseatedinplace,thetoolreleasesthelegsallowingthemtoclamparoundthelowercontact.Thismethodallowsthepiecetobeinstalledwithoutslidingorhavingtoapplyexcessiveforce.Thesametoolcanbeusedtoremovetheextensionpieceifrequired.4.3FunctionThelowerspringsaredesignedtolimitthecoreplatedisplacementduringaseismicevent.ThelowerspringbearsagainsttheshroudatthecoresupportledgeandextendsabovetheH6AweldandbelowtheH6Bweld.WhentheH6Aweldremainsincontact,whetheritsfailedorothe+vise,thejointismodeledasahingeintheseismicmodelandiscapableofcarryingashearload.DuringasteamlineLOCA,thedploadontheshroudheadissufficienttoopena360'hroughwallcrackattheH6Alocation.Inthisevent,thejointismodeledasarollerintheseismicmodelandisnotcapableofcarryingashearload.IntheeventoffullseparationatweldH6Athecontactextensionlimitsthepossibleshroudmovementand,togetherwiththecoreplatewedges,providearedundantloadpathforthehorizontalseismicloads.(Thecoresupportstructureisalsoheldinposition

GENEB13-01739-31Revision0August1996bythecoresupportboltsandbythecoresupportalignerpins.)Withouttakingcreditforthecoresupportboltsoralignerpins,thelimitinglateraldesignloadontheextensionistheentire63,800Ibmaximumhorizontalseismicload.Theanalysisinattachments8.1and8.2showallloadsanddisplacementsremainacceptablewiththeextensionpiecesinstalled.5.DISPLACEMENTSUMMARYAlthoughallcoresupportdisplacementsremainacceptable,bothmodificationsdescribedin3and4abovedoaffectthedisplacementsandchangethevaluesreportedintheoriginalstressreport,GE-NE-B13-01739-04,Rev.0.Thedisplacementvaluesreportedbelowsupersedethedisplacementvaluesreportedintheoriginalstressreport.Theallowablepermanentandtransientdisplacementsaresummarizedbelow.Theshroudrepairhardwaredesignspecification,25A5583,providesthebasisfortheallowabledisplacementsandsafetyfactors.TopGuidePermanent=2.1/SFTopGuideTransient=notspecifiedCoreSupportPermanent=0.75/SFCoreSupportTransient=1.68/SFNormal/UpsetSF=2.25EmergencySF=1.50FaultedSF=1.1255.1TopGuideTheTopGuidealwaysremainsincontactwiththeupperspringandthereisnopermanentdisplacement.Thelimitingconditionforeacheventisthe"allhinge"conditionwhichhasanequivalentdisplacementtotheHlrollercase.Sincethereisonlyoneseismicevent,thedisplacementisthesamefortheUpset,EmergencyandFaultedevents.Thecalculatedmaximumtransientdesigndisplacementis0.904inchesforeachevent.Althoughthe0.904inchisatransientdisplacement,italsosatisfiesthemostrestrictiveallowablepermanentdisplacementrequirementforanUpseteventof0.93inches.5.2CoreSupportAfaultedeventwithseparationatweldH6Aistheonlyconditionwheretheremaybepermanentdisplacementatthecoresupport.Forallothereventsthedisplacementresultsfromthespringcompressionwhichreturnstotheoriginalpositionwhentheloadstops.The"allhinge"case(equivalenttothe"Hlroller"case)isapplicableforUpsetandEmergencyandFaultedevents.

GENEB13-D1739-31RevisionDAugust19965.2.1PermanentDisplacementThemaximumpermanentdisplacementisthedistancetheshroudmovesbeforecontactwithaspringmember.Themachineddistancebetweenthespringloadedshroudcontactsurfaceandtheuppercontactis0.15inches.ThelowercontactalsobearsagainstweldcrownatH68.Theweldcrownisestimatedtobelessthan0.13high.Ifthedisplacementisdirectedmidwaybetweenthetwocontactslocated108'part,thedisplacementisincreasedto0.48inches.(Attachment8.2)Theallowablepermanentdisplacementis0.67inches.5.2.2TransientDisplacementTheboundingtransientdisplacementisacombinationofthemaximumpermanentdisplacementandthemaximumspringcompression.ForUpset,andEmergencyconditions,thereisnopermanentdisplacementandthemaximumtransientdisplacementis0.256inches(Attachment8.1,Table1).TheallowableUpsettransientdisplacementis0.75inches.AssumingtheworstcasescenarioforloaddirectionandspringcharacteristicsforaFaultedevent,themaximumspringcompressionis0.368inches(Attachment8.1,Table1).Themaximumtransientdisplacementbecomes0.85incheswhenroundedtotwoplaces.TheallowableFaultedtransientdisplacementis1.49inches.6.DESIGNBASISThehardwareforbothmodificationsisdesignedandfabricatedtothesamedesignbasisastheoriginalshroudrepairhardware.Themodifiedstabilizerassemblyincludesthesamedesignfeaturesastheoriginalhardware.Allpartsarelockedinplaceorcapturedbymechanicaldevices.ThefabricationrequirementsforthetwoproposedmodificationswillbeinaccordancewiththepreviouslyapprovedfabricationrequirementsfortheNMP-Icoreshroudstabilizers.Thereisnoweldingrequiredduringfabricationorinstallation.Relocatingthelowerspringtotheoppositesideofthestabilizerassemblyisconsistentwiththecoreshroudrepairdesigncriteriaanddesignbasis.Theadditionalcounterboresandlockingpinholesneededtoutilizetheexistingpartshavenoaffectonthestabilizerassemblyfunctionorstresses.Thehandlingandinstallationtoolsarethesameasusedfortheoriginalinstallation.

GENEB13-D1739-31Revision0August19967.SAFETFCONSIDERATIONSThisevaluationhasinvestigatedmodificationstotheshroudrepairstabilizersatNineMilePoint1whichwillrestorethemtotheirintendeddesignfunction.Theplantlicensingbaseshavebeenreviewed.Thisreviewdemonstratesthatthesemodificationscanbeinstalled(1)withoutanincreaseintheprobabilityorconsequencesofanaccidentormalfunctionpreviouslyevaluated,(2)withoutcreatingthepossibilityofanaccidentormalfunctionofanewordifferentkindfromanypreviouslyevaluated,(3)andwithoutreducingthemarginofsafetyinthebasesofaTechnicalSpecification.TheGECoreShroudRepairDesignSafetyEvaluation,GE-NE-B13-01739-05,Rev.1hasbeenreviewedforpossibleadverseconsequencesofmovingthelowerspringtotheoppositesideofthestabilizerassembly.ThecoreplatedisplacementsreportedinB.2.1areupdatedtoincludetheaffectsofthelowerspringspacing.The0.75inchtemporarydisplacementduringafaultedeventremainswellthe1.49inchallowableforthisevent.GESafetyEvaluation,GE-NE-B13-01739-5.1,Rev.0,entitled,"ModificationtoGEShroudRepairDesign",wascompletedtoevaluatethetwoproposedmodificationsinaccordancewith10CFR50.59.Thesafetyevaluationconcludedthattheproposedmodificationsdonotinvolveanyunreviewedsafetyquestions.8.ATI'ACHMENTS8.1GENEB13-01739-03,Supplement1,NineMilePoint1SeismicAnalysis,CoreShroudRepairModification8.2GENEB13-01739-04,Supplement4,NineMilePoint1ShroudRepairHardwareStressAnalysis8.3Drawing107E5679Rev.7andPartsList107E5679Rev.5,ReactorModification8.4Specification25A5585Rev.4,StabilizerInstallation