ML18040A254

Forwards Proprietary & non-proprietary Repts from GE Re GL 94-03, Intergranular Stress Corrosion Cracking in Bwrs. List of Repts,Encl.Encls Withheld,Per 10CFR2.790(b)(i)

ML18040A254
Person / Time
Site:	Nine Mile Point
Issue date:	04/08/1997
From:	MCCORMICK M J NIAGARA MOHAWK POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17059B487	List: ML17059B486 ML17059B488 ML17059B489 ML17059B493 ML18040A254
References
GL-94-03, GL-94-3, NMP1L-1200, NUDOCS 9704100242
Download: ML18040A254 (94)

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4,~+rI-CATEGORY2REGULATZNPORMATZONDISTRIBUTION'STEM(RIDE)ACCESSIONNBR:9704100242DOC.DATE:97/04/08NOTARIZED:YESFACIL:50-220NineMilePoint.,NuclearStation,Unit1,NiagaraPoweAUTH;NAME-AUTHORAFFIL'I'ATIONIMCCORMICK,M.J.NiagaraMohawkPowerCorp.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)DOCKET05000220

SUBJECT:

Forwardsproprietaryanon-proprietaryreptsfromGEreGL94-03,"IntergranularStressCorrosionCrackinginBWRs."Listofrepts,encl.Enclswithheld,perC10CFR2.790(b)(i).~ADISTRIBUTIONCODE:APOIDCOPIESRECEIVED:LTR/ENCLLSIZE:TITLE:ProprietaryReviewDistribution-PreOperatingLicense&OperatingRTNOTES:RECIPIENTIDCODE/NAMEPDl-1LAHOOD,DCOPIESLTTRENCL1111RECIPIENT.IDCODE/NAMEPD1-1PDCOPIESLTTRENCL11INTERNAL:ACRSOGC/HDS3EXTERNAL:NRCPDRILECENTER011110S1Z(.Prop11DC.ENNOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083(PTOTALNUMBEROFCOPIESREQUIRED:LTTR7ENCL

NIAGARAMOHAWKCENERATI0NBUSINESSCROUPNINEMILEPOINTNUCLEARSTATION/LAKEROAD,P.O.BOX63,LYCOMING,NEWYORK13093/TELEPHONE(315)349-2660FAX(315)349-2605MARTINJ.McCORMICKJR.P.E.VicePresidentNuclearEngineeringApril8,1997NMP1L1200U.S.NuclearRegulatoryCommissionAttn:DocumentControlClerkWashington,DC20555RE:NineMilePointUnit1Docket50-220

Subject:

GenericLetter94-03"IntergranularStressCorrosionCracking(IGSCC)inBoilingWaterReactors"Gentlemen:BylettersdatedJanuary6,1995andJanuary23,1995,NiagaraMohawkPowerCorporation(NMPC)submittedanapplicationforrepairstotheNineMilePointUnit1(NMP1)coreshroud.Theshroudrepairsanduseofstabilizerassemblies(tierods)weresubmittedasanalternatetotherequirementsoftheASMECode,SectionXI,asallowedby10CFR50.55a(a)(3)(i).ThestaffprovidedapprovaloftheproposedalternaterepairbyletterdatedMarch31,1995.TheapprovalletterandattachedsafetyevaluationrequiredNMPCtosubmitre-inspectionplansfortheshroudandrepairassembliespriortothenextrefuelingoutageplannedfor1997.ByletterdatedFebruary7,1997,NMPCsubmittedplansforre-inspectionofthecoreshroudverticalweldsandrepairassembliesinaccordancewiththecriteriaprovidedbythe"BWRVesselandInternalsProgram"(BWRVIP)documentBWRVIP-07.Duringthe1997refuelingoutage,NMPCconductedcoreshroudverticalweldinspectionspertheapproveddocumentsandobservedverticalweldcrackingwhichexceededthescreeningcriteria.Additionally,inspectionsofthefourtierodassembliesfoundthetierodnutstohavelostsomepreloadandidentifieddamagetothelowerwedgeretainerclipsonthreetierods.FurtherdetailsoftheasfoundconditionsareprovidedinEnclosures1and2.l(ByphonecallsonMarch20,1997andApril2,1997,NMPCinformedthestaffoftheinspectionfindingsandindicatedthatanalysisoftheverticalweldcrackingandrestorationplanoftheshroudtierodassemblieswouldbesubmittedtotheNRCpriortorestartoftheunit.Thisletterandtheattachedenclosuresproviderootcause,correctiveactionsandthefinaldesigndocumentationwhichestablishestheacceptabilityoftheasfoundverticalweld$5OOigoAl3.3,llll3ll]llllGlllllll3lllllK'Illl',tlHllll,Wo'ILQo2Llg,.ti(IR,(s(ist'p lg.t Page2crackingforaminimumof10,600operatinghours(above200'F),determinesanappropriateweldre-inspectionschedule,providesdetailsoftheactionstakentorestorethetierodstotheasdesignedconditionanddescribesamodificationofthelowerwedgeretainerclipdesign.Themodifiedlowerwedgeretainerclipsarepartofthetierodassemblieswhich,asnotedabove,arenotincludedundertheASMECodeSectionXIdefinitionforrepairorreplacement.Assuch,thedesigndetailsofthemodifiedretainerclipsarebeingsubmittedtothestaffforreviewandapprovalasanalternativerepairpursuantto10CFR50.55a(a)(3)(i).Theenclosedanalysesprovidejustification'forcontinuedoperationofNMP1duringtheupcomingcycleutilizingtheupdated10CFR50.55aapprovalasproposedherein.Enclosures1,2and5areconsideredbytheirpreparer,GeneralElectric(GE),tocontainproprietaryinformationexemptfromdisclosurepursuantto10CFR2.790.Therefore,onbehalfofGE,NMPCherebymakesapplicationtowithholdthesedocumentsfrompublicdisclosureinaccordancewith10CFR2.790(b)(1).AnaffidavitexecutedbyGEdetailingthereasonsfortherequesttowithholdtheproprietaryinformationhasbeenincludedinEnclosure7.Anon-proprietaryversionofthesedocumentshasbeenincludedwiththisletterasEnclosure8.I.CoreShroudTheNMP1coreshroudhasfourGEcoreshroudstabilizerassembliesinstalled.TheseassemblieswereinstalledduringtheRFO-13(1995)refuelingoutage.Theinstallationwasdoneasapre-emptiverepairofthecoreshroudhorizontalweldsHlthroughH7inlieuofbaselineshroudinspectionofthesehorizontalwelds.TheGEshroudstabilizerdesignrequiresverticalweldintegrityinorderfortheshroudstabilizerstosatisfythedesignbasisassumptionofhorizontalweldsHlthroughH7beingthroughwallcracked360'.Thepre-andpost-shroudrepairinstallationinspectionscopeduringRFO-13,includedasampleinspectionoftheverticalweldsattheintersectionofaselectedhighfluenceweld(theH5weld).Theinspectionincluded6inchesaboveandbelowtheH5locationalongtheV9,V10,V11andV12welds.Theinspectionwasanenhancedvisualexaminationperformedfromtheinsidediameter(ID).Thisvisualexaminationwasintendedasasampleinspection.ThisinspectionscopewasapprovedbytheNRCaspartofthesafetyevaluationreport(SER)issuedfortheNMP1coreshroudstabilizerdesign.TheinspectionoftheNMP1verticalweldsinthecurrentrefuelingoutage(RFO-14)wasperformedconsistentwiththeBWRVIP-07guidelinesforthereinspectionofBWRcoreshrouds.Theseguidelinesalsoutilizedasampling

Page3approachfortheverticalcoreshroudwelds.TheoptionselectedbyNMPCwastocompleteavisualinspectionof25%oftheequivalenttotalverticalweldlengthfromeithertheoutsidediameter(OD)orID.Aspartoftheinspectionplan,GEdefinedscreeningcriterionforminimumrequireduncrackedverticalweldsonaperweldbasis.TheringsegmentweldswereexcludedfromtheverticalweldsrequiringinspectionbasedonGEanalysisoftheringsegmentweldssubmittedtothestaffforreviewbyletterdatedFebruary7,1997.Asaresultofinspectionfindings,theinspectionscopewasexpandedusinganenhancedvisualinspectionmethodsupplementedbyultrasonicinspection(UT).B.TheinitialRFO-14inspectionoftheverticalweldsidentifiedcrackingovertheentireODlengthoftheV10weldusingenhancedvisualinspectiontechniques.Theinspectionplanswerethenexpandedtoestablishminimumrequireduncrackedligamentontheverticalweldswhicharerequiredtomeettheshroudstabilizerrepairdesignbasisassumptions.TheverticalweldcrackingevidentontheODofboththeV9andV10weldswasextensive.TheextentofcrackingidentifiedontheODhadnotpreviouslybeenidentifiedatotherBWRs.Asaresult,acompletebaselineinspectionoftheNMP1accessibleportionsofcertaincoreshroudhorizontalandverticalweldswasperformedinordertoestablishanoverallmaterialconditionassessmentoftheNMP1coreshroud.DetaileddescriptionsofbothverticalandhorizontalweldscrackingisprovidedinEnclosure1.TheindividualinspectionresultshavereceivedN.D.E.LevelIIIreviewbyGEandNMPCpersonnel.Thedocumentationofinspectionresultsisbeingcompiledforfinalqualityassurancereview.ThisreviewwillbecompletedbyApril20,1997.C.ThisshroudbaselineinspectionhasenabledNMPCtoestablishthatthecrackingattheverticalweldsV9andV10isconsistentwiththeexpectedIGSCCcrackingofBWRcoreshrouds.BoththehorizontalweldcrackinginthebeltlineH4weldandtheverticalweldcrackinginthebeltlineV9andV10weldsisoccurringintheheataffectedzone(HAZ)ofthewelds.TheassessmentoftheIGSCCcrackingisincludedinenclosedanalysesandreports.SeveralindependentevaluationswerealsoperformedforNMPCtoobtainanaccurateassessmentofthecauseandacceptabilityofverticalweldcracking.TheseevaluationshaveconcludedthatthecrackingnotedontheverticalweldsV9andV10isIGSCC.Thestressesthatcausecrackingintheverticalweldsareweldresidualandfabricationstressesandtoalesserextentthestressresultingfrominternalpressure(hoopstress).TheNMP1shroudhorizontalandverticalweldsareclearlysusceptibletoIGSCC.ThehighcarbonType304 t

Page4stainlesssteelmaterialwasinitiallysensitizedbytheweldingprocess.Thematerial'ssusceptibilitywasfurtherenhancedbysurfacecoldworkandsurfacestrainsfromthefabricationprocess.Irradiationwouldalsoaddtothesusceptibilityovertheoperatingtime.Finally,thetensilesurfaceresidualstressesandsurfacefabricationstressesledtotheIGSCCinitiation.TheinspectiondatafromUToftheseweldshasestablishedthecrackingdepth.Thepatternofcrackdepthisconsistentwiththecalculatedfluenceaxialandradialprofiles,Theestimatedfluencefortheseweldsisinthe2to4.5x10"n/cm~()1MEV).ThisfluenceplacestheseweldsinarangeforwhichtheradiationenhancedIGSCCconditionsexist.TheevaluationsperformedhaveconcludedthattheobservedcrackingisassociatedeitherwithweldHAZorsiteswherefabricationrelatedweldingorgrindingwasapparent.Theoverallconclusionisthatthiscrackingisnotuniqueandcanbeattributedtoweldingresidualstressesandfabricationfitupinducedstresses.D.ThebaselineinspectionhasidentifiedonelocationattheintersectionofH5andV9whereahorizontalcrackintheHAZofH5haslinkedwithaverticalcrackintheHAZofV9.Thiscaseisisolatedandhasnotbeenidentifiedinotherlocations.Infact,themajorityofthecrackingappearstostartapproximately6to10inchesdownfromthehorizontalH4weldHAZ.TheshroudhorizontalandverticalweldbaselineinspectionoftheNMP1coreshroudwhichhasbeenperformedprovidesapointofreferenceforfuturesampleinspectionofthecoreshroud.ThisbaselineandfuturesampleinspectionswillallowNMPCtomonitortheactualIGSCCcrackgrowthratewhichwillbeusedtomaintaintherequireddesignbasismargins.GEhascompletedanalysesregardingthepotentialimpactthecoreshroudstabilizerassembliescouldhaveonverticalweldcracking.Theresultshaveshownthatanyhoopstressinducedattheverticalweldsduetoshroudstabilizerthermalpreloadisnegligible.TheoverallconclusionisthattheshroudstabilizershadnoeffectontheshroudverticalweldcrackingidentifiedatV9andV10.Theverticalweld9andV10crackingwasreviewedbyindependentexpertsinIGSCCcrackingofBWRcoreshrouds.Enclosure3containstheresultsofaqualitativeassessmentofthevisuallyobservedcrackingontheH4,V9,V10andH5welds.ThisevaluationhasconcludedthattheIGSCCcrackingissimilarinnaturetothecracksseeninotherBWRsandthatthespecificconditionsfortheparticularcrackingpatternscanbeexplainedbynormalfabricationpracticesusedinmanufacturingthecoreshroud.Inanefforttobetterdefinehowthesefabricationprocessescanexplainthecracking,detailedfiniteelementmodelinghavebeenperformed.Overalltheresultsshowthatthe

Page5weldingandfabricationprocesscanexplainthecrackingpatternobservedontheverticalwelds.Theseanalysescalculatedthrough-thicknessstressintensitysolutionsandcrackgrowthstudies.Theresultsclearlysupporttheboundinganalysisapproachbeingusedtodefinetheproposedoperatingintervalbetweeninspections.E.AnanalysisoftheverticalweldsusedtodefinetheproposedshroudverticalweldreinspectionintervalhasbeenperformedconsistentwithapprovedBWRVIPshroudanalysismethods.ThecriteriaappliedarethosesetforthintheBWRVIPcoreshroudinspectionandevaluationdocument.Theapproachbeingappliedfortheverticalweldsanalysisassumedthatallhorizontalweldsarecracked360'hroughwallconsistentwiththecoreshroudstabilizerdesignbasis.Theassumptionofhorizontalweld360'rackingrequiressufficientverticalweldintegritytoensurethatthedesignbasisassumptionofstackedrightcylindersismaintained.TheanalysisapproachreliesuponsizingofthethroughwallverticalweldcrackingwithUT.ThesethroughthicknesscrackshavebeenanalyzedconsistentwiththeBWRVIPcoreshroudinspectionandevaluationguidelinesaccountingforASMECodeSectionXIsafetyfactors,designbasisloads,inspectionuncertaintyconsistentwiththeBWRVIP-03guidelines,andthecurrentlyboundingNRCcoreshroudcrackgrowthassumptionof5x10~inches/hr.Basedontheseassumptions,therequiredcoreshroudre-inspectionintervalhasbeendeterminedtobeatleast10,600operatinghoursasdescribedinEnclosure1.Theattachedanalysisoftheverticalweldsincludesanassessmentofthepotentialleakagefrompostulatedthroughwallverticalcracking.Theoverallthermalhydraulicsassessmenthasconcludedthattheleakagewouldbenegligible.Theoverallconclusionisthatthisleakagehasnoimpactonthedesignbasisfornormalupsetoraccidentconditions.TheattachedEnclosure1providestherequireddetaileddiscussiononthissubject.Inconclusion,theverticalweldcrackingconditionhasbeenreviewedandbeendeterminedtonotrepresentanunreviewedsafetyquestionbasedonapplyingtheNRCapprovedcoreshroudinspectionandevaluationguidelines.TheseguidelinesprovidetheanalysisbasistodefineanacceptableinspectionintervalbasedonasfoundIGSCCcrackingofcoreshrouds.Therequiredintervalestablishedbytheattachedanalysesis10,600hoursofoperation.

Page6II.CoreShroudStabBizerAssemblies(TieRods)A.Duringthecurrentrefuelingoutage,post-operationalinspectionswereconductedonthecoreshroudstabilizer(tierod)assemblies,Tieroddeficiencieswerefound,includingimproperasfoundtorqueonthetierodnuts,anddamagetotheretainerclipsonthelowerspringwedges.Thesefindingsresultedinrootcauseevaluationsandadditionalinspectionsandtestingofthetierods.B.~~Enclosure2containsthedetaileddataontheas-foundcondition,rootcauseofthosedeficiencies,validationoftherootcauseandcorrectiveactionstaken.Gapswereidentifiedontheclevispintolowersupporthookcontactandunderthetierodnuttotopsupportcontact.Itwasdeterminedthatpreloadofthetierodshadbeenlost,tosomedegree,oneachtierod.Also,thelowerspringwedgeretainerclipwasbrokenatthe90'ierodlocationandvisiblydamagedatthe270'nd350'ierodlocations.The90'ierodlowerspringwedgewasfoundbottomedonitsguiderod,notincontactwiththevesselasoriginallyinstalled.Theremainingcontactpoints,springsandretainerclipswerefoundintheirproperpositions.C.Therootcauseforthetieroddegradationisattributedtorecognitionthatthetieroddesigndidnotconsidertheeffectofinstallationtolerancesforthelowersupportboltholes.Becauseofthis,theinstallationproceduresdidnotcontainspecificcriteriaforthelocationofthetoggleboltsduringinstallationofthelowersupport.Thelowersupporttoggleboltsarenominally4.000"indiameter.Themeasuredelectricdischargemachining(EDM)holesintheshroudconerangedfrom4.090"to4.110".Sincethepositionofthelowersupportboltswithinthemachinedholeswasnotprocedurallycontrolledduringinstallation,therelativepositionoftheboltswithintheholeswasvariable.Duringheatup,theexpansionoftheshroudandtierodsgeneratesaforcesufficientenoughtoovercometheinstalledfrictionforcesandmovethelowersupportuptheshroudcone.Thistranslatesintoaverticalmovementofthetierod.Thismovementwassufficienttoapplyaloadonthelowerspringwedgeretainerclipsuchthatitfailedwithinonecycleofoperation.Additionally,thelowerspringwedgeretainerclipwasnotdesignedtoaccommodatedifferentialmovementgiventhefrictionalloadsbetweenthevesselwallandthelowerspringwedgeduringnormalandtransientconditions.

Page7D.Subsequenttothesefindingsandrootcauseevaluation,aninstallationprocedurewasdevelopedtorestorethetierodstotheiroriginaldesignbasiscondition.Eachtierodwasjackedatthreelocationsduringtierodnuttorquingtoremoveanygapsassociatedwithinstallationtolerances.Jackswereplacedunderthelowersupport,onthevesselsideofthelowersupporttopushituptheshroudconetoremovetheclearancesbetweenthetoggleboltsandtheshroudsideoftheconeholes.Followingperformanceoftherevisedinstallationprocedureinspectionswerecompletedoneachtierodtoverifytheabsenceofgaps,propercontactandposition.Asaresultoftheseinspections,itwasdiscoveredthatthemiddlesupportwasnolongerincontactwiththevesselonthe90'nd166'ierod.Thiswascausedasaresultofthelowersupportassemblybeingmoveduptheconetowardstheshroud.Themiddlesupportdimensionsarebeingretakenandnewmiddlesupportswillbeinstalledpriortoreload.Otherlocationsonthetierodassemblieswiththepotentialforgapsandnon-conformingconditionswereinspected.Noadditionaldeficiencieswerenoted.AsummaryofNMPC's10CFR50.59safetyevaluationconcerningmodificationtothecoreshroudrepairtierodassembliesisprovidedinEnclosure4.E.Calculationswereperformedtoevaluatethemaximumpotentialdisplacementsofthetierodrelativetothelowerspringwedge.Thisresultedinaredesignofthelowerwedgeretainerclip.Themodifieddesignisdescribedbelowandaccommodatesexpectedmovements.Thenewretainerclipswillbeinstalledduringthecurrentrefuelingoutage.TheclipshavebeenfabricatedfromX-750,analyzedinaccordancewiththeASMECode,andmeetoriginaldesigncriteriaforthetierods.F.Thefunctionofthelowerwedgeretainerclipistoretainthelowerwedgeintheproperpositionduringinstallation.Itwasnotdesignedtoexperienceoperationalloads.Lowerwedgetovesselcontactwasassumedtomoveandaccommodatedifferentialthermalexpansionbetweenthetierodassemblyandthevessel.AsexplainedinEnclosure2,thefrictionforcebetweenthewedgeandthevesselwassufficienttopreventmovementofthewedgeduringthermalgrowthofthetierodassembly.Thelatchportionoftheretainerclipbecameloadedresultingintheoverstressedconditionoftheretainerclipanditssubsequentfailure.

Page8Theretainercliphasbeenredesignedtoaccommodatemovementduringnormalandtransientconditions.Theredesignedretainerclipswillbeinstalledpriortoreload.Enclosure5,"DesignReportforImprovedShroudRepairLowerSupportLatches,"providestheresultsofanevaluationperformedfortheredesignedlatchanddemonstratesacceptabilityoftheredesignedlatchanditsuseintheoriginaltierodassembly.III.FurtherActionsNMPChasanalyzedtheasfoundconditionoftheshroudverticalweldsandhasestablishedthattheplantcanbeoperatedsafely.Aconservativeintervalforre-inspectionoftheweldshasbeenestablishedasdescribedinEnclosure1.Re-inspection,includingtightnesschecksofthetierodnuts,willbeperformedafterapproximately10,600hoursofoperationandNMPCwillhaveplansforacontingencyrepairshouldonebeneededatthattime.NMPCplansadditionalanalyses,duringtheupcomingcycle,whichmayjustifyextensionofthere-inspectionintervalfortheshroudverticalwelds.TheresultsoftheseanalyseswillbesubmittedtotheNRC,ifappropriate.AboatsampleofcrackedmaterialwillbemechanicallyremovedfromashroudweldHAZatanappropriatelocationpriortorestartfromRFO-14.Asalongertermaction,NMPCplanstoperformanalysisonthesampletoestablishthepresenceofIGSCC,theageofthecracking,whethercrackgrowthhasarrestedandtoinvestigateanyotherpotentialcontributingmechanisms.ThismetallurgicalsampleistobeusedtohelpNMPCandtheindustrybetterunderstandtheIGSCCcrackingoftheBWRcoreshroudverticalwelds.IV.InspectionofOtherInternalsNMPChasperformedinspectionsovertheoperatinglifeoftheplanttomeetseveralASMECode,industry,BWRVIPandAugmentedRegulatoryrequirements.TheseinspectionsprovidethebasisforanoverallconditionassessmentoftheRPVinternals.Specifically,theinspectionsperformedduringthecurrentrefueloutageontheinternalcoresprayannuluspipingandcoresprayspargers,showednocrackgrowthofpreviouslyidentifiedindicationsonthespargers.Theannuluspipingwasfoundtobewithoutflaws,includingthecriticalweldsatcrevicedlocations.AsummaryofinspectionsperformedtodateofotherinternalsisprovidedinEnclosure6.NMPChasperformedanevaluationofthetierodrestorationactivitiesandtheasfoundconditionoftheverticalweldsandfoundthemacceptableforcontinuedservice.NMPCrequestsapprovalofthefinaldesigndocumentationfortheproposedmodificationofthetierodretainerclipsbyarevisiontotheexistingNRCshroudrepairsafetyevaluation

Page9submittedasanalternaterepairunder10CFR50.55(a)(2)(i).ReceiptofNRCapprovalisrequestedbyApril20,1997.Verytrulyyours,MartinJ.McCormickJr.VicePresident-NuclearEngineeringMJM/MSL/lmcEnclosuresxc:Mr.H.J.Miller,NRCRegionalAdministrator,RegionIMr.S.S.Bajwa,ActingDirector,ProjectDirectorateI-l,NRRMr.B.S.Norris,SeniorResidentInspectorMr.D.S.Hood,SeniorProjectManager,NRRRecordsManagement

UNITEDSTATESNUCLEARREGULATORYCOMMISSIONIntheMatterofNiagaraMohawkPowerCorporationNineMilePointUnitj.DocketNo.50-220MartinJ.McCormickJr.,beingdulysworn,statesthatheisVicePresident-NuclearEngineeringofNiagaraMohawkPowerCorporation;thatheisauthorizedonthepartofsaidCorporationtosignandfilewiththeNuclearRegulatoryCommissionthedocumentattachedhereto;andthatthedocumentistrueandcorrecttothebestofhisknowledge,informationandbelief.MartinJ.cCormickJr.VicePresident-NuclearEngineeringSubscribedandswornbeforeme,inandfortheStateofNewYorkandtheCountyofQ~~ethis8-dayofApril,997.NOTARYPUBLICJOHNCJOSHNoteyPublic,8teteofSeeYo4No.4837303CueINedInGsveeoCemtyCommissionExpfresFeb.28,19qe 88QL0ftHOt,CmY+wN4etatBAYRRytafaHaacrm~xigampo"~~0nlt."PiiHeuQPf<E~~3U"DOXIEfi

INDEXOFENCIOSURESENCLOSURE1AssessmentoftheVerticalWeldCrackingontheNMP1ShroudENCLOSURE2ShroudRepairAnomalies,NineMgePointUnit1,RFO14ENCLOSURE3NineMilePointUnit1CoreShroudCrackingEvaluationENCLOSURE410CFR50.59SafetyEvaluation96-018,Revision1ENCLOSURE5DesignReportforImprovedShroudRepairLowerSupportLatchesENCLOSURE6InspectionHistoryENCLOSURE7Affidavit(GE)ENCLOSURE8Non-ProprietaryVersionofReports ENCLOSURE2SHROUDREPAIRANOMALIESNINEMILEPOINTUNIT1RFO14..9704100242

ENCLOSURE410CFRSO.59SAFETYEVALUATION96-018,REVISION1 0

1050.59SAFETYEVALUATIONSURYMODIFICATIONTOTHECORESHROUDREPAIRSTABILIZERASSEMBLIESAshroudrepairmodificationwasinstalledinNineMilePoint1NuclearPowerPlanttoprovideanalternateloadpathfortheType304stainlesssteelcircumferentialwelds,HlthroughH7.ThemodificationensuresthestructuralintegrityofthecoreshroudbyreplacingthefunctionofweldsHlthroughH7with4stabilizerassembliesandfourcoreplatewedges.Inthecourseofthepost-installationinspectionoftheshroudrepair,threedeviationswereidentified,evaluatedandwerefoundacceptableforcontinuedplantoperationthroughthenextcycle.Afteradditionalreviewandevaluation,additionalmodificationsareproposedtoprovidethelongtermcorrectiveactions.Duringthespring1997refuelingoutage,twoadditionaldeficiencieswerefoundontheshroudrepairhardware.Eachofthefourshroudrepairstabilizerassemblieswerefoundtohavelessthantheoriginalinstallationpreloadandoneofthelowerwedgelatcheshadfailedinservice.Twootherlowerwedgelatchesalsoappearedtobedegraded.Thelatchisawishboneshapedpiece,thatisintendedtopreventrelativemotionbetweenthelowerwedgeandthelowerspringwiththeassumptionthatslidingwouldoccurbetweenthelowerwedgeandtheRPVwall.ThedeviationswerefoundduringrequiredaugmentedIn-serviceInspectionsgSI)anddu'ringtheplannedreplacementoftheshroudstabilizerassemblyat270'.Therootcauseofthestabilizerverticallossofpreloadwasduetoclearancesbetweenthelowersupporttoggleboltsandtheholesintheshroudsupportcone.Theimportanceoftheclearancebetweenthetoggleboltsandtheholewasnotrecognizedandnotincorporatedintotheinstallationengineeringdocumentation.Thisallowedthelowersupporttomoveuptheshroudsupportconetowardtheshroudwhentheplantreachednormaloperatingconditions.Therootcauseofthelatchfailureisanincorrectdesignassumptionregardingslidingatthevesseltolowerwedgeinterface.Adetaileddiscussionoftheas-foundconditionofthestabilizerassembliesandtherootcauseofthedeviationsisincludedinReference27.ThisevaluationconsiderstheadditionofthethreemodificationsdescribedbelowandhowthesemodificationsafreettheSafetyEvaluationfortheCoreShroudRepairDesign,Reference23,31and32.ThereferencesinPartEretainthesamenumberswithadditionalreferencesapplicabletothemodifications.~difzatiga3.Thelowerspringofonestabilizerassemblybearsontheblendradiusofthe270'ecirculationnozzle.Theproposedmodificationsistoreplacethetierodandspringassemblywithonehavingthespringontheoppositesideofthetierod.ThisproposedmodificationrelocatesthespringtobearontheRPVasintended.Madii@~2ThelowerspringcontactwiththeshrouddonotextendbeyondweldH6Aatanyofthefourlocations.Asresult,thebarrelsectionbetweenweldsH5andH6AisnotlaterallyrestrainedduringasteamlineLOCAcombinedwithaDBEaswasintended.TheproposedmodificationaddsanextensionpiecetoextendthespringcontactbeyondweldH6Aandrestorethisfeaturetoitsintendedfunction.Theextendedcontactandthecoreplatewedgesalsoprovideanredundantloadpathbetweenthecoreplateandthelowerspringaswasintendedintheintheoriginaldesign.Page1of17 0'i TheabovetwonotedmoacationshavebeenreviewedandapprovebytheNRCinReference32.ggg*PIPg*gglPlddIdppPIPtheaxialtightnessofthestabilizerassemblies.Thelowerwedgelatchesmaybecomeloadedduetodifferentialverticaldisplacementgreaterthanintendedbytheoriginaldesignofthelatches.Therearetwocorrectiveactions.Thefirstistoremovetheclearancebetweenthetoggleboltsandtheshroudsupportcone.ThishasbeenaccomplishedwiththeReference28procedure.Theremovaloftheclearancesrestoresthestabilizerassembliestotheiroriginallyintendeddesignanddoesnotrepresentamodification.Thesecondcorrectiveactionwastoinstallnewmodifiedlatcheswhicharemoretolerantofdifferentialverticaldisplacement.A.l~0'ollowingtheinstallationofthecoreshroudrepairavisualinspectionoftheas-installedassemblyhardwareshowedthelowerspringwedgeonthe270'tabilizerassemblybearingontheblendradiusoftherecirculationnozzle.ThewedgewasintendedtobearontheRPVwall.Theproposedmodificationistoreplacethetierodandspringassemblywithonehavingthespringontheoppositeside.ThemodificationmovesthespringsufficientlysuchthatitwillbearontheRPVoriginallyasintended.Themodificationutilizes.existinghardwarewhichwasbuiltasasparealongwiththeotherstabilizerassemblies.Onlyminorreworkisrequiredtorelocatethelowerspringandthereworkhasnoaffectonthehardwarefunction.ThemodificationdoesnotrequireadditionalpenetrationsthroughtheshroudsupportconeoranyadditionalEDMwork.Themodificationusesthesamelowersupportandupperspringassembliesandthereisnochangetotheactualtierodlocation.Additionalanalysishasbeendonetoaddressthedesignwherethelowerspringsarenolongerlocated90'part.Thenon-uniformlowerspringspacingaffectsthenetspringcharacteristicwhenthehorizontalseismicloadisdirectedbetweentwosprings.Theanalysisshowtheloadsanddisplacementsremainacceptableforallconditions.A.2~6QQQQ~ThelowerspringcontactswiththeshrouddonotextendabovetheH6Aweldaswasintended.ThedesignfunctioncanberestoredbyaddingaUshapedextensionpiecetoextendbeyondweldH6A.TheextensionpiecefitsovertheexistinglowercontactwiththelegsoftheUextendingaroundthesidesoftheexistinglowercontact.Thestepsattheendsofthelegsfitunderthelowercontacttopreventaxialmovement.Atangatthetopextensionfitsinthegapbetweenthelowercontactandthelowerspringtorestrictthehorizontalmovement.Theaddedextensionpieceiscapturedinalldirectionsontheexistinglowercontact.Thelegsoftheextensionarespringloadedtoprovideapositiveclampingforceagainstthesidesofthelowercontact.Thespringforceisnotrequiredtocapturethepartbutissufficienttopreventanyfreemovementorvibrations.Withthisarrangement,theaddedextensionpieceiscapturedinalldirectionsandisheldsecurebythespringloadedclampingforce.Thehardwareforbothmodificationsisdesignedandfabricatedtothesamedesignbasis(Ref.1)astheoriginalshroudrepairhardware.Thedesignlifeofallrepairhardwarewillbefortwenty-fiveyears(theremaininglifeoftheplant,pluslifeextensionbeyondthecurrentoperatinglicense),toinclude20EffectiveFullPowerYears.Themodifiedstabilizerassemblyincludesthesamedesignfeaturesastheoriginalhardware.Allpartsarelockedinplaceorcapturedbymechanicaldevices.ThestressesinthestabilizerdonotchangeandPage2of17 0h~'If4 remainlessthantheallowestresses.Therepairhardwareisfabricatedfromintergranularstresscorrosionresistantmaterial.Thereisnoweldingintheconstructionorinstallationoftheshroudrepairhardware.Thefastfluxlevelsatthestabilizersarewellbelowthedamagethresholdwhichcouldresultinthedegradationofmaterialproperties.After25yearsofoperation,themaximumfastfluenceattheshroudrepaircomponentswillbewellbelowthevaluetocausedamage.Therefore,itisveryunlikelythatacomponentwillfail.A>LAXCEThedesignofthenewimprovedshroudrepairlowersupportlatcheshavebeenanalyzedindetailinReference30.Thedesignofthenewlatchesmaintainstheoriginaldesignfunction.Thefunctionoftheoriginallatchwastosecurethewedgetothelowerspring.Thisis'primarilyneededwhenthewedgeloosescontactwiththereactorvesselwall.Thisisanimportantfunctionsincethewedgewillotherwiseslidedownandcreateexcessivegaps.Thenewlatchdesignmaintainsthewedgesupportcapabilityandcanreadilysupportthedeadweightandflowforceswhichcouldacttopushthewedgedown.Thenewlatchdesignincorporatesanotherspringwhichcantolerateverticaldisplacements.Therefore,theoriginalfunctionalrequirementisaccomplishedwhileaddingmoreflexibilityintheverticaldirectiontoaccommodateverticaldisplacements.Underthemostprobableoperatingandslidingconditionsthenewlatchdesignisexpectedtoperformsatisfactorilyfortheremaininglifeoftheplant.Evenforworstcasepostulatedconditions,thelatchiscapableofoperatingwithoutfailurethroughoutthenextoperatingcycle.ThenewlatchescantolerateadifFerentialverticaldisplacementfortheworstcasethermaltransientevent(lossoffeedwaterevent)withoutexperiencinganoverstresscondition.Alsofornormalplantoperation,themaximumverticaldifFerentialdisplacementunderprobablewedgeinteractionconditions(assumingnoslippagebetweentheRPVandthewedge)is0.10inches.UnderthisdeflectionthestressesinthenewlatcheswillbelessthanthestresslimitestablishedtopreventstresscorrosioninX-750materialfora40yearlifetime.Acomparisonoftheoriginallatchdesigntothenewdesignhasbeenperformedusingcommonfiniteelementmodelingmethods.Theresultsshowthatthenewlatchis8to12timesmorecapableoftoleratingverticaldisplacementsthantheoriginaldesign.Thisorderofmagnitudeimprovementinthedesignprovidesassurancethatthenewlatchwillperformsatisfactorilyinthenextoperatingcycle.The'removaloftheclearancebetweenthetoggleboltsandtheshroudsupportconewillassurethatthetierodverticalforceswillbeasintendedintheoriginaldesign.TheverticalclearancesinthestabilizerassemblieswereeliminatedusingtheprocedureincludedinReference28.Eachofthefourstabilizerassemblieswerethentorquedtotheoriginalrequiredinstallationvalue.Withthetierodinatightconditionatstartup,theproperverticalthermalexpansionloads.canbeaccomplishedduringtheheatupofthereactor,andmaintaintheholddownforcesontheshroudthroughsubsequentheatupsandcooldowns.A.4Theinstalledstabilizerstierodsarefabricatedentirelyfromthetype316,316Lstainlesssteel(bothwithacarboncontentlessthan0.02%)oralloyX-750.TheaddedcontactextensionandmodifiedlatchesarefabricatedfromalloyX-750.Thereplacementcomponentsforthe270'ierodmodificationwillbefabricatedusingthesamematerialsasthecurrentlyinstalledstabilizers.ThefabricationrequirementsforthetwoproposedtierodmodificationswillbeinaccordancewiththepreviouslyapprovedfabricationrequirementsfortheNMP-1coreshroudstabilizers.Thereisnoweldingrequiredduringfabricationorinstallation.Fage3of17

BhKLLYSIS:Theapplicablecriteriaandconformanceforthisanalysisisasfollows.ThecriteriaisthesamecriteriathatwasusedfortheoriginalShroudRepairDesignSafetyEvaluation,Reference23.Theconformancesectionsspecificallyaddressthethreeproposedmodifications.B.1IhsigaLifeKritaig:Thedesignlifeofallrepairhardwarewillbefortwenty-fiveyears(theremaininglifeoftheplant,pluslifeextensionbeyondthecurrentoperatinglicense),toinclude20EffectiveFullPowerYears.B.1.1RgmizIhsignLiRThehardwareforthethreemodificationsisfabricatedtothesamedesignbasis,includingmaterialrequirements,astheoriginalshroudrepairhardware.Allrepairhardwarehasbeendesignedforadesignlifeoftwenty-fiveyears(theremaininglifeoftheplant,pluslifeextensionbeyondthecurrentoperatinglicense),toinclude20EffectiveFullPowerYears.Thisrequirementisdocumentedinreferencel.Assuringanadequatedesignlifeismainlyamaterialselectionandprocesscontroleffort,forthisequipment.Theselectionoflowcarbonstainlesssteelsandhighnickelalloysassures'thebestavailablematerialsforthenuclearreactorenvironment.Solutionannealingandsensitizationtestingareimposedtoguardagainstintergranularstresscorrosioncracking(IGSCC).Processchemicalcontrolsareimposedtoassurethatcontaminationbyheavymetalandchlorineorsulfurcompoundswillnotoccur.Thisisthesamedesignselectionsandcontrolsimposedforastandardfortyyearphntlife.Thereisnothingintheequipmentorinstallationthatputsaspecificlimitonhowlongitcanbeused,suchascreeporradiationdegradation.ThestressesinthelatcharewithinASMEcodelimitsandthelatchisanalyzedtoberesistanttostresscorrosionforaminimumof2yearsassumingconservativeworstcasedisplacementsintheretainer.Itisfullyexpectedthattheretainerwilllastforasignificantlylongertimebasedonthefactorofimprovementwhichhasbeendemonstratedfromtheoriginaldesign.Fortheexpectedslidingcasewherethemovementisalwaysalongthewedgdspringinterface,theretainerwilllastforaleasttheremaininglifeoftheplant.Theretainerswillbeinspectedatthenextoutagetodeterminewhichtypeofslidingisoccurringinordertovalidatetheservicelifetimeoftheretainers.B2Saki'eHguBmh{Crhczig:IToassurethesafetydesignbasisissatisfiedandthatthesafeshutdownoftheplantandremovalofdecayheatarenotimpaired,therepairhardwareshallassurethatthecoreshroudwillmaintainthefollowingbasicsafetyfunctions:TolimitdeflectionsanddeformationtoassurethattheEmergencyCoreCoolingSystems(ECCS)canperformtheirsafetyfunctionsduringanticipatedoperationaloccurrencesandaccidents.Maintainpartitionsbetweenregionswithinthereactorvesseltoprovidecorrectcoolantdistribution,forallnormalplantoperatingmodes..Providepositioningandsupportforthefuelassemblies,controlrods,incorefluxmonitors,andothervesselinternalsandtoensurethatnormalcontrolrodmovementisnotimpaired.Page4of17

.0l'I ThechangesinthelowerspringspacingaQectsthesystemspringcharacteristicsforloadsactingbetweentwocontacts.Additionalseismicanalysis(Reference24)calculatedcoresupportdisplacementsfortheboundingconditions.Thesectionbelowisrevisedtoincludethemaximumdisplacementsbasedonmodifiedlowerspringspacingandincludesthegapbetweentheshroudandthecontactextension.Alldisplacementsremainacceptable.Thenewmodifiedlatchdesignonthelowerspringwedgedoesnote6ectthemaximumdisplacementsbelow.Thecorespraypipinganalysisperformedtosupporttheshroudrepairincludedashrouddisplacementof0.904in.horizontallyand0.65in.vertically,causedbyafaultcondition.ThisdisplacementwillnotcreateanunacceptableloadingconditionintheECCSpipingandthereforewillperformitsintendedsafetyfunction.Theproposedmodificationsdonotchangethemaximumdisplacementscalculatedfortheoriginalshroudrepairattheuppershroud.Thereforethereisnochangeinloadingofthecorespraypiping.Theproperdecayheatremovalrequiresthattheshroudtoremainasaflowboundarytoforcewaterthroughthefuelandnotallowalargeleakageintothedowncomerregion.ThemaximumpermanenthorizontalofFsetofadjacentshellsections,thatarenotdirectlysupportedbyeithertheupperorlowersprings,islimitedbystructuralstopsto0.75in.Sincethewall'oftheshroudis1.5in.thick,theshroudwillstillfunctionproperlyasaflowboundarywithinthereactor.ThesafeshutdownoftheplantisafunctionoftheSCRAMcapability.Thecoresupportplateandthetopguidemustbekeptalignedwithintestlimitssothatfrictionbetweenthecontrolrodsandfuelbundleswillnotimpairpropermotion.Theworstcaseconditionexistswhenthetopguidemovesonedirectionandthecoresupportmovestheopposite.Thiscreatesthemaximumanglebetweenthefuelbundlesandtheguidetubes.Themaximumtemporarycalculatedhorizontaldisplacementofthetopguideis0.904in.andthemaximumforthecoresupportis0.85in.Thecorrespondingallowabledisplacementare1.87in.and1.49in.Thereisnocalculatedpermanenthorizontaldisplacementofthetopguideandthemaximumpermanentdisplacementforthecoresupportis0.48inches.Thecorrespondingallowablecoresupportpermanentdisplacementsis0.67inches.B.3ZbmDr~iKCilain):Repairstothecoreshroudarenotrequiredtototallypreventleakagefromthecoreregionintothedowncomerannulus.However,thedesignshallensurethatcrackedweldsdonotseparateundernormaloperationsasaminimum.Designwillaccountforleakagefrom.theregioninsidetheshroudintotheannulusregionduringnormaloperation.Theleakageshouldnotexceedtheminimumsubcoolingrequiredforproperrecirculationpumpoperationandthecorebypassflowleakagerequirementsassumedinthereloadsafetyanalysisshallbemaintained.Thedesignwillalsoverifyacceptableleakagethroughtheflowpartitionresultingfromweldseparationduringaccidentandtransientevents.B31Elm2'ztithuTheoriginalshroudrepairdesignensuredthatcrackedweldswillnotseparateundernormaloperations.Theoriginalshroudrepairdesignaccountedforleakagefromtheregioninsidetheshroudintotheannulusregionduringnormaloperation.Theleakagedoesnotexceedtheminimumsubcoolingrequiredforproperrecirculationpumpoperationandthecorebypassflowleakagerequirementsassumedinreloadsafetyanalysesismaintained.Page5of17 05 TherearenorequiremenrallowableleakageduringtheaccidentOCAand/orseismic).Aftertheaccident,theleakageislimitedbytheallowabledeflectionssuchthattheshroudsectiondoesnotdisplacesuf5cientlytoopenanyverticalflowareas.Themaximumpermanenthorizontaldisplacementofashroudcylindricalsectionthatisnotdirectlysupportedbyeithertheupperorlowerspringsislessthan0.75inch,whichisequaltoonehalfofthethicknessoftheshroud.Thus,leakageafteranaccidentwillbelimitedtotheleakagethroughacrack.Sincethepressuredifferenceacrosstheshroudissmall,theleakagewillbesmall.Thethreeproposedmodificationshavenoaffectonthepotentialweldcrackseparationoranypotentialleakagepath.Thethreemodificationsdonotrequireanynewholesorpenetrationsthroughtheshroud/shroudsupport.ThereforetheleakagecalculationsandperformancepredictionsinReferences23and29remainvalid.TheaddedcontactextensionprovidesassurancethemaximumpermanentdisplacementoftheshroudcylinderbetweenweldHSandH6Aremainslessthan0.75inch.8.4ZhxImimaiXihzafhgCdbxig:Therepairshallbedesignedtoaddressthepotentialforvibration,andtokeepvibrationtoanacceptablelevel.Thenaturalfrequencyoftherepairedshroud,includingtherepairhardware,shallbedetermined.Thevibratorystressesshallbelessthantheallowablestressesoftherepairmaterials.Forcingfunctionstobeconsideredincludethecoolantflowandthevibratoryforcestransmittedviathe'endpointattachmentsfortherepair.Testingmaybeusedasanalternativeortosupplementthevibrationanalysis.UB4lBBSIYB~U'KEl{~Theoriginalshroudrepairwasdesignedtoaddressthepotentialforvibration,andtokeepvibrationtoaminimum.Thenaturalfrequencyoftherepairedshroud,includingtherepairhardware,hasbeendetermined.Theusagefactorduetocyclicstressescausedbyvibrationwillbelessthan1.0forthedesignlifeoftherepairhardware.Forcingfunctionsconsideredincludedthecoolantflowandthevibratoryforcestransmittedviatheendpointattachmentsfortherepair.DetailsoftheoriginalvibrationanalysisareprovidedinReference23.Thethreerepairmodificationshavenoaffectonthenatural&equencyofthestabilizerassemblyoronthevortexsheddingfrequency.ThereforetheoriginalvibrationevaluationinReference23remainsvalidforthestabilizerassemblies.Thepotentialforvibrationofthenewextensionpieceshasbeenconsidered.Forcingfunctionsconsidered,includedthevibratoryforcestransmittedfromthestabilizerassembliesandcoolantflow.Thestabilizervibratoryforcesarelow,asdemonstratedintheoriginalvibrationanalysis,thereforevibratoryforcesimposedontheextensionpiecesarelow.Thecoolantflowwillnotvibratethelowercontactextensionsbecausetheextensionsarecapturedinalldirectionsontheexistinglowerspringassembly.Thelowercontactextensionisa"U"shapedpartwhichfitsaroundtheexistinglowercontact.Stepsattheendsofitslegsextendunderthelowercontacttopreventaxialmovement.Atangtowardsthetopfitsinthegapbetweenthelowercontactandthelowerspringtopreventhorizontalmovement.Apositivespringforcefromthelegskeeptheparttightandpreventrandomvibrations.TheonlytimethatFIVisofinterestiswhenthelowerwedgelosescontactwiththevesselwall.Thiscanoccurduringhydrotest,maximumseismicconditions,andduringthelimitingupsetthermalfeedwaterevent.Theseeventshaveshortdurationwiththelongestpotentialdurationbeing8hoursforthehydrotestevent.Thelossofcontactatthelowerspringsupportisnotaconcernineitherthetierodassemblyor-thesubassemblyofthelatchandlowerwedgeforthefollowingreasons:Page6of17

.0' Thetimewhencontislostisarelativeshortdurationandteassociatednumberofcyclesislimited.Anindependentcalculationofthenewlatchandlowerwedgeassemblyshowsthatthenatural&equencyissuKcientlyhightoavoidflowinducedvibration.Theclearancewhichiscreatedbetweenthewedgeandthevesselwallislessthan0.050"whichwilllimitthemotionofthelowerwedgeinthelateraldirection.Thispreventsanysignificantcontactforcesfrombeingproduced,andcontactwoulddampenoutanyexcitationofthelowerwedge.Therelativeradialmovementsbetweenthevesselandtheshroudaresuchthatsurfacecontactislikelytoremainatoneofthetwosurfacesduringthepostulatedevents.Evenpostulatingthatnosupportispresentatthelowerspring,analysishasbeenperformedforthe'ierodassemblywhichdemonstratesthatflowinducedvibrationwillnotoccur.)Inconclusion,noneoftheshroudrepaircomponentsaresusceptibletoflowinducedvibrationwhencontactislostatthelowerspringcontact.B.SLmliugmExidiugIaimmlIncreasedstressonexistinginternalcomponents,usedintherepair,isacceptableaslongasthecurrentplantlicensingbasisaremet.Increasesinappliedloadshallbedemonstratedtobeacceptable.Therepairshallbedesigned'soastoproduceacceptableloadingontheoriginalstructureoftheshroud,consistentwiththecriteriaprovidedherein.Therepairshouldminimizestressesintroducedintotheshroudconsistentwiththecriteriaprovidedsoastonotaggravatefurthershroudcracking.Therepairshouldminimizetheloadingonthesupportingstructuresoftheshroud,suchastheshroudsupportconeandtheRPVwall,tostaywithintheoriginaldesignallowablestressesofthesestructures.~SupplementalseismicanalysisfortheproposedmodificationsshallconformtothesamemethodologyandcriteriausedintheoriginalshroudrepairseismicanalysisasdocumentedintheFSAR.~~ILQKIJHlg911EXhfhlgI1lfCKBBlStressesontheoriginalstructureoftheshroud,whicharedirectlyimpactedbytheshroudrepairhardware,havebeendemonstratedtobeacceptable.Theresultsofthisevaluationaredocumentedinreferences4,5and11forallofthepostulatedaccidents.Theoriginalshroudrepairwasdesignedtominimizestressesintroducedintotheshroudconsistentwiththecriteriaprovidedsoastonotaggravatefurthershroudcracking.Theadditionofthecontactextensions,themodificationtothe270'ierodandtheadditionofmodifiedlowerwedgelatcheshasaninsignificantafFectonthecomponentloadsandstresses.InadditionanalysesincludedinReference29havebeencompletedregardingthepotentialimpacttheshroudstabilizerassembliescouldhaveonverticalweldcracking.Theresultshaveshownthatanyhoopstressinducedattheverticalweldsduetoshroudstabilizerthermalpr'eloadisnegligible.TheoverallPage7of17 0e~I~

conclusionisthattshroudstabilizershadnoaffectonthesoudverticalweldcrackingidentifiedatV9andV10.ThereforetheevaluationinReference23remainsvalid.~Theoriginalshroudrepairdesignminimizedtheloadingonthesupportingstructuresoftheshroud,suchastheshroudsupportconeandtheRPVwall,tostaywithintheoriginaldesignallowablestressesofthesestructures.Theresultsofthisevaluationaredocumentedinreferences4,5and11forallofthepostulatedaccidents.Relocatingthe270'owerspringassemblychangesthespacingbetweentheadjacentlowerspringassemblies.Thechangeinspacingaffectsthenetspringcharacteristicsandloaddistributionwhentwospringssharethehorizontalseismicload.Analysisshowtheloadonanyonespringdoesnotexceedtheloadsusedintheoriginalstressevaluation,Reference24.Thestressevaluationremainsvalidforthemodified270'tabilizermodification.B.5.1.1RimehaalzshThemodificationsaddingthecontactextensionsandmodifiedlowerwedgelatchesh'avenoaffectontheseismicanalysis.Relocatingthelowerspringaffectstheoriginalseismicanalysis.Supplementalseismicanalysiswasmadeusingthesamemethodologyandcriteriaaswasusedintheoriginalseismicanalysis.Thechangesinthespacingbetweenlowerspringsandaffectstheeffectivespringcharacteristicswhentwospringssharethehorizontalseismicloads.Springslessthan90'partincreasetheeffectivespringconstantandspringsgreaterthan90'endtolowerthespringconstant.Equivalentspringconstantsweredeterminedfortheboundingconditionsandadditionalseismiccalculationsweremadetodetermineloadsanddisplacements(Reference24).Theindividualspringloadsdonotexceedtheloadsusedintheoriginalstressevaluation(Reference25)andthecalculateddisplacementsremainacceptable(PartB.2.1).B6A4H~IGBThedesignshallnotadverselyaffectthenormalflowofwaterintheannulusregion,orthenormalbalanceofflowinthisregion.Thedesignshallnotadverselyrestricttheflowofwaterintotherecirculationsuctioninlet.B61AUHNoneofthethreemodificationsadverselyaffectthenormalflowofwaterintheannulusregion,orrestricttheflowinanywaythatwouldadverselyaffectnormalbalanceofflowinthisregion.Thedesigndoesnotadverselyrestricttheflowofwaterintotherecirculationsuctioninlet.B.7Bwzgazy.RwzatheZramluzeQZ2QIC81:InputstotheEOPcalculations,suchasbulksteelresidualheatcapacityandreductionofreactorwaterinventoryshallbeaddressedbasedonrepairhardwaremassandwaterdisplacement.IB.7.1Z~zgcmy.~m~ggZzm~ig~)nTheadditionofthespringcontactextensionsandnewlatcheshaveaninsignificantaffectontheEOPcalculations,suchasbulksteelresidualheatcapacityandreductionofreactorwaterinventorysincethequantityofsteeladdedisnegligibleascomparedtothemassandvolumeoftheexistingshroudrepairhardwareandreactorinternals.Page8of17 O.V0 Thedesignoftherepairshallaccountfortheaffectsofirradiationrelaxationutilizingend-of-lifefluenceonthematerials.B81RUWEIIRcoBTheoriginaldesignoftherepairaccountsfortheaffectsofirradiationrelaxationutilizingend-of-lifefluenceonthematerials.InaccordancewithReference1,thedesignconsidersanEnd-of-Lifepreloadrelaxationfortheupperandlowersprings.TheradiationlevelislessthanthelimitcontainedintheUFSAR.Thebasisforthisisdocumentedinreference11(designbasisforreference1).Thecontactextensionhasapositivespringloadedclampingforcearoundthelowercontact.Theinitialinstallationclampingforceisnotrequiredtokeepthepartcapturedorfortheparttoremainfunctional.Radiationrelaxationmayreduce,butwillnoteliminatethepositiveclampingload.ApostulatedreductionintheinitialclampingloadduetoradiationrelaxationisnotaconcernbecausetheextensionpiecesarecapturedinalldirectionsasdiscussedinPartB.4.1andanyamountofpositiveclampingloadwillpreventfreemovementorrandomvibrationsoftheextensionpieces.Apositivespringforceinthelatchisachievedbycompressingthelatchpriortoinsertionintotheholewithinthelowerwedge.Apostulatedreductionintheinitialcompressionloadduetoradiationrelaxationisalsonotaconcernforthelatchesastheyarecapturedbyrecessedareasinthewedgeandthelowerspring.B9TimbaltychoKdtcria):Therepairhardwareshallconsidertheeffectsofthermalcyclesfortheremaininglifeoftheplant.AnalysisshalluseoriginalplantRPVthermalcyclediagrams.ThedesignshallassumeanumberofthermalcyclesequaltoorgreaterthanthenumberassumedintheoriginalRPVdesign.Alternatively,thermalcyclesdefinedbyactualplantoperatingdatamaybeemployediftechnicallyjustified.Usingthisthermalcycleinformationrepaircomponentsandtherepairedshroudshallbeevaluatedforfatigueloadingalongwithanyotherdesignvibratoryloads.B91XhezmalCychzTheoriginalshroudrepairhardwareanalysisconsideredtheeffectsofthermalcyclesfortheremaininglifeoftheplantasdocumentedinReference5.Theanalysisconsideredthermalexpansionforthevaryingtemperaturesandmaterialcombinationsoftheshroud,shroudsupportcone,reactorvesselandtheshroudrepairstabilizersfornormalandupsetthermalconditions.Thestressesresultingfromthethermalcycleshavebeenevaluatedbyafatigueanalysis.Theresultsshowthatitseffectonfatiguelifeoftheplantisnegligible.Thethreemodificationshaveaninsignificanteffectonpreviousfatigueanalysis.TheanalysisprovidedinReference30hasevaluatedthemodifiedlowerwedgelatchesfortheircapabilitytowithstandloadingconditionsduetothermaldifferentialverticaldisplacementsbetweentheRPVandthestabilizerlowerspring.Theanalysisconcludedthatfornormalplantthermalcyclesaswellastransientthermalcycles(lossoffeedwaterevent),thenewlatcheswhenconsideringthemostprobableloadingconditionswillhandlethesethermalcyclessatisfactorilyforatleasttheremainingplantlife.TheremovaloftheclearancebetweenthetoggleboltsandtheshroudsupportconewillassurethatthedifFerentialverticaldisplacementsarelimitedtothedesignvaluesusedintheReference30analysis.Page9of17

'k ThedesignshallrecognizetheuseofexistingandanticipatedwaterchemistrycontrolmeasuresforBWRsandshallconsidertheaffectsofneutronfluxonanymaterialsusedintherepair.B.10.1Sincethematerialsforthethreemodificationsarethesameaswasusedfortheinstalledshroudrepairhardware,existingandanticipatedwaterchemistrycontrolmeasuresandtheaffectsofneutronfluxonthematerialshavebeenaddressedandwillhavenoeffectontherepairhardware.B.11L~~KIhl:Repairhardwaremechanicalcomponentsshallbedesignedtominimizethepotentialforloosepartsinsidethevessel.Thedesignrepairshallusemechanicallockingmethodsforthreadedconnections.Allpartsshallbecapturedandheldinplacebyamethodthatwilllastforthedesignlifeoftherepair.B~IThemodifiedstabilizerassemblyhasbeendesignedtominimizethepotentialforloosepartsinsidethevessel.Thedesignrepairusesmechanicallockingmethods(suchascrimpedjamnuts)forthreadedconnections.Allpartsarecapturedandheldinplacebyamethodsuchaspinning,staking,springretainers,interferencefits,andcrimpingthatwilllastforthedesignlifeoftherepair.Thelowercontactextensioniscapturedinalldirectionsontheexistinglowerspringassembly.Thelowercontactextensionisa"U"shapedpartwhichfitsaroundtheexistinglowercontact.Stepsattheendsofitslegsextendunderthelowercontacttopreventaxialmovement.Atangtowardsthetopfitsinthegapbetweenthelowercontactandthelowerspringtopreventhorizontalmovement.Apositivespringforcefromthelegskeeptheparttightandpreventrandomvibrations.Thespringforceisnotrequiredtoensuretheextensionissecuredtotheexistinglowercontact.Apositivespringforceinthelatchisachievedbycompressingthelatchpriortoinsertionintotheholewithinthelowerwedge.Thelatchesarecapturedbyrecessedareasinthewedgeandthelowerspringsotheycannotbecomealoosepart.LmmEachGcauxbdhztheRepaizZxmzm:Specialtooling/equipmentisbeingprovidedthatwillbetestedandpersonnelwillbetrainedonfullscalemockupstoassureadequatecontrolsexisttominimizethepotentialforvesselinternalsdamageorlooseparts.ProtectiveshieldshavebeendesignedthatcanbeinstalledasneededtoprotecttheFeedwaterSparger,CoreSprayLineandtheRecirculationnozzles.NMPCandGEinstallationprocedures/travelerswillbeusedtoestablishForeignMaterialExclusion(FME)controls.AlltoolsandequipmentusedintheVesselandSpentFuelPoolwillbeproperlysecured.B.12IaquxthuhuemKdhzig:Therepairdesignshallbesuchthatinspectionofreactorinternals,reactorvessel,ECCScomponentsandrepairhardwareisfacilitated.Theinstalledrepairhardwareshallnotinterferewithrefuelingoperationsandshallpermitservicingofinternalcomponents.Allpartsshallbedesignedsothattheycanberemovedandreplaced.Thisistoprovidefullaccesstotheannulusareaforotherpossiblefutureinspectionsand/ormaintenance/repairactivitiesthatmayprovenecessaryinthefuture.Page10of17

Noneofthethreemodificationsaffecttheaccessforinspections.Allpartshavebeendesignedsothattheycanberemovedandreplaced.CuximKdtezia):Therepairdesignshallbereviewedforcrevicestoassurethatcriteriaforcrevicesimmunetostresscorrosioncrackingaccelerationaresatisfied.B.13.1Qyg~Theselectionofthematerialsforthemodificationhardwareisthesameastheoriginalhardwareandassuresthatcriteriaforcrevicesshowntobeimmunetostresscorrosioncrackingaccelerationaresatisfied.B14M&xinhKribxe}:AllmaterialsusedshallbeinconformancewiththeBWRVIPrequirements.B14.1IHatcriahMaterialsforthethreemodificationshavethesamerequirementsastheoriginalshroudrepairhardwareandareinconformancewiththeBWRVIPrequirements.B.15{Cribxig:Thedesignedrepairshallminimizetheneedforfutureinspectionsandmaintenanceoftherepaircomponents.Thedesignedrepairshallminimizetherequirementforfutureinspectionsoftheaffectedshroudjoints.B.15.1ThestabilizerassembliesincludingthethreemodificationsarecurrentlyinspectedundertheNMP1AugmentedInserviceInspectionProgram(LDCRNo.1-94-ISI-009,Rev.3).B16ImtaE&III.JmmKdbxig:Tooling/equipmentusedforinstallationofrepaircomponentsshallbeevaluatedinaccordancewithReference9andshallconsiderthefollowing:HeavyloadsShutdownSystemStatus(N+1)RiggingHoleCuttingMethodB.16.1gi~~iI11~i~Themodifiedstabilizerassemblieshavethesameinstallationrequirementsastheoriginalstabilizerassemblywiththeexceptionthataspecialprocedure(Reference28)wasdevelopedandperformedtoPageIIof17 0

lensuretheclearanceswerVFemovedbetweenthetoggleboltsandtheholesontheshroudsideofthesupportcone.Thisprocedureensuresthatthetierodsremaintightandarerestoredtotheiroriginaldesignmechanicalpreload.Noholecuttingisrequiredforeithermodification.Theinstallationactivitiesassociatedwiththeproposedmodificationswereevaluatedinaseparatesafetyevaluation(Ref.26).8.17ExhfingReaderInhraah(Czitezi;9:Thedesignshallnotrelyonexistingreactorinternalsorcomponentstocarryloadsthathaveexperiencedcrackingintheindustry(e.g.shroudheadboltlugs,stubtubes).B.17.lExhiiagRuat'abnmhNoneofthethreemodificationrelyonexistingreactorinternalsorcomponentstocarryloadsthathaveexperiencedcrackingintheindustry(e.g.shroudheadboltlugs,stubtubes).Page12of17

'N~e C.CouldtheproposedchangeoractivityincreasetheprobabilityofoccurrenceofanaccidentpreviouslyevaluatedintheSAR?No.Theaffectedplantsystemsandcomponentswillbecapableofperformingtheirintendedfunctionswiththethreecoreshroudstabilizermodificationsinstalled.Thesemodificationsrestoretheshroudrepairstabilizerstotheirintendeddesigncondition.Asthemodificationsarebeingprovidedtotheplant'ssafety-relateddesignrequirements,theprobabilityofacomponentfailureisnotincreased.Thethreemodificationsimposeanegligiblechangetotheplantoperatingconditions.NeithermodificationwillinteractwithanycomponentassumedtoinitiateanaccidentintheUFSAR.NorwillthefailureorpresenceofthemodificationsinitiateanaccidentevaluatedintheUFSAR.2.CouldtheproposedchangeoractivityincreasetheconsequencesofanaccidentevaluatedpreviouslyintheSAR?No.ThecalculatedPeakCladTemperature(PCT)willremainbelow2200'F,andallstructures,systemsandcomponents(SSC)usedtomitigatethe(radiological)consequencesoftheaccidentsintheSARareindependentofthethreeproposedmodifications,andthus,theconsequencesoftheaccidentswillnotbeaffected.TheabnormaleventsintheUFSARthatpotentiallycouldbeaffectedbytheinstallationofthestabilizerswereevaluated,andtheyremainunchanged.Thethreeproposedmodificationsimposenochangetotheplantoperatingconditions,andthus,thereisnoaffectonanyLOCAandtransientanalyses.LOCA-Radiologicalanalysisisbasedontheplant'sengineeredsafetyfeatures(ESF)functioningwithindesignparameters,andtheradioactivematerialsourceterms.ThethreemodificationswillnotadverselyaffectanyESF,andthus,theESFfunctionswillnotbeaffected.TheradioactivematerialsourcetermsarebasedontheregulatorylimitPCTof2200'F.AsthePCTforNineMilePointIwillremainbelowthisregulatorylimit,thesourcetermswillnotbeaffected.Therefore,theconsequencesoftheLOCA-Radiologicalanalysiswillnotchange.TheMSLBanalysisreleaseislimitedbythecapacityoftheMSLFlowRestrictors,andusesUFSARallowablesforsourceterms.Asthethreemodificationswillnotaffecteitherofthese,theconsequencesoftheMSLBanalysiswillnotchange.Seismicanalyses(Ref.6)showthatthestabilizerswillremainfunctionalfollowinganearthquake3.CouldtheproposedchangeoractivityincreasetheprobabilityofoccurrenceofamalfunctionofequipmentimportanttosafetyevaluatedpreviouslyintheSAR?No.Thethreemodificationsaredesignedandconstructedassafetyrelatedcomponents.Noadverseequipmentinteractionswillbecreatedbyinstallingthethreemodifications.TheInstallationProcessesandToolingwillnotadverselyeffectanyinternalcomponentsimportanttosafetydiscussedintheSAR.Therefore,theprobabilityofequipmentmalfunctionsisnotincreased.4.CouldtheproposedactivityincreasetheconsequencesofamalfunctionofequipmentimportanttosafetyevaluatedpreviouslyintheSAR?No.Theinstallationofthethreemodificationsensuresthattheshroudstabilizerassemblieswillperformtheirintendedfunctions.Thus,consequencesofamalfunctionofequipmentimportanttosafetyisnotincreased.ThethreemodificationsandtheshroudstabilizersperformapassivefunctionthatdoesnotinterfacewithanyPage13of17 0

equipmentthatisutomitigatetheradiologicalconsequencesofamalfunctionintheUFSAR.Theeffectsoftheshroudrepairstabilizerassembliesontheconsequencesofpotentiallyaffectedtransientsarenegligible.Asthestabilizerassemblies,includingthethreemodifications,donotadverselyaffectequipment"ImportanttoSafety,"theconsequencesofalltransientswillnotchange.TheInstallationProcessesandToolingwillnotadverselyeFectanyequipmentimportanttosafety,asdiscussedpreviously.Therefore,thereisnoincreasetotheconsequencesofcomponentmalfunctions.5.CouldtheproposedactivitycreatethepossibilityofanaccidentofadifferenttypethananyevaluatedpreviouslyintheSAR.No.Thestabilizers,includingthethreemodifications,aredesignedtothestructuralcriteriaspecified'intheNineMilePoint1UFSAR.AlloftheloadsandloadcombinationsspecifiedintheUFSAR,thatarerelevant'tothecoreshroud,havebeenevaluated,andarewithindesignallowables.Thestabilizers,includingThethreemodifications,donotaddanynewoperational/failuremodeorcreateanynewchallengetosafety-relatedequipmentorotherequipmentwhosefailurecouldcauseanewtypeofaccident.Inaddition,thestabilizersorthethreemodificationsdonotcreateanynewcomponent/systeminteractionsorsequenceofeventsthatleadtoanewtypeofaccident.Ithasbeenpostulatedthatifacoreshroudhada360'rackandaMSLBaccidentoccurred,theuppershroudandthetopfuelsupportcouldlift.Ifthetopfuelsupportlifteds'ufficiently,thetopsofthefuelbundlescouldmove(shift),whichmightpreventthecontrolbladesfromcompletelyinserting(partialscram).Thiseventwouldbeanaccidentofadifferent'type.However,thecoreshroudstabilizerswouldlimittheshroudfrommoving,andthus,preventthetopfuelsupportfromlifting.Theproposedchangestothelowerspring,theadditionofthelowerextensionsandnewmodifiedlatcheshavenoaffectontheabilityofthestabilizertoperformthisfunction.ThethreemodificationsalsoensurethatthebarrelsectionoftheshroudbetweenweldsH5andH6AandthecoresupportdisplacementsarelimitedduringaMSLBorrecirculationLOCAwhencombinedwithanearthquake.Therefore,themodificationsdonotincreasetheprobabilityofoccurrenceofanaccidentofadiFerenttypethananyevaluatedpreviouslyintheSAR.6.CouldtheproposedactivitycreatethepossibilityofamalfunctionofequipmentimportanttosafetyofadifferenttypethananyevaluatedpreviouslyintheSAR.No.Thestabilizers,includingthethreemodifications,structurallyreplacetheshroudhorizontalwelds.Thethreemodificationsincludethesamedesignfeaturesastheas-installedstabilizers.Allequipmentassumedtooperateinthetransientanalyses,andthesafety-relatedstructures,systemsandcomponentswillnotbeadverselyaffectedbythestabilizers,includingthethreemodifications.Allcomponentsinteractingwiththestabilizerswillperformtheirintendedfunctions.Thestabilizers,includingthethreemodifications,donotincreasechallengestoorcreateanynewchallengetoequipment.Thestabilizers,includingthethreemodifications,donotcreateanynewsequenceofeventsthatleadtoanewtypeofmalfunction.Therefore,thepossibilityofadiFerenttypeofcomponentmalfunctionthanevaluatedintheSARisnotcreated.7.DoestheproposedactivityreducethemarginofsafetyasdefinedinthebasisforanyTechnicalSpecification.No.TheTechnicalSpecificationsBases,theUFSAR(includingtheshroudrepairdesignbasisdocumentslistedintheUFSAR)andtheNRCsafetyevaluation(SE)oftheNMP1shroudrepairwerereviewed.TheUSFARandtheNRCSEdefinetheacceptancelimitsforcalculateddisplacements/stressesasthe"designallowable"displacement/stresses.Thatis,neithertheUSFARnortheNRCSEdefinethesafetymarginasthedifferencebetweenthePage14of17 00 previouslycalculat&edisplacements/stressesandthedesignaiiowables.Therefore,increasesindisplacements/stressesasaresultoftheproposedmodificationswillnotreducethemarginofsafetyasdefinedbytheUSFARandtheNRCSE,providedthecalculateddisplacements/stressesremainlessthantheoriginaldesignallowables.Theanalysiscompletedforthe270'ierodmodification,thelowerspringcontactmodificationandthelowerwedgelatchmodificationdemonstratedthattheoriginalshroudrepaircalculatedreactorinternalsandrepairhardwarestressesarebounding,thereforethemarginofsafetyisnotreduced.Theanalysisfortheproposedmodificationsalsoindicatethatthecalculatedmaximumcoresupporttemporary(0.85")andpermanent(0.48")horizontaldisplacementsincreased.Theseincreasesdonotreducethemarginofsafetyasdefinedabove,becausethedisplacementsremainbelowthedesignallowabletemporary(1.49")andpermanent(0.67")displacements.ThisevaluationhasinvestigatedmodificationstotheshroudrepairstabilizersatNineMilePoint1whichwillrestorethemtotheirintendeddesignfunction.ThemodificationsincluderelocatingalowerspringassemblytoproperlybearagainsttheRPV,addingextensionstoassurethespringcontactsontheshroudextendbeyondweldH6Aandinstallingnewlatcheswhicharemoretolerantofdifferentialverticaldisplacement.Additionallynewinstallationrequirementswereimplementedtoensure'thetightnessofthestabilizerassemblies.Theplantlicensingbaseshavebeenreviewed.Thisreviewdemonstratesthatthesemodificationscanbeinstalled(1)withoutanincreaseintheprobabilityorcons'equencesofanaccidentormalfunctionpreviouslyevaluated,(2)withoutcreatingthepossibilityofanaccidentormalfunctionofanewordifferentkindfromanypreviouslyevaluated,(3)andwithoutreducingthemarginofsafetyinthebasesofaTechnicalSpecification.Therefore,installationofthesethreemodificationsdonotinvolveanunreviewedsafetyquestion.1.GE-NESpecification:25A5583,Rev.2,"ShroudRepairHardware,DesignSpecification"2.GE-NESpecification:25A5586,Rev.1,"ShroudRepairCode,DesignSpecification"3.UFSAR,Rev.12,NineMilePoint14.GE-NEDocument:24A6426,Rev.1,"ReactorPressureVesselStressReport"5.GE-NE-B13-01739-04,Rev.0,"ShroudRepairHardwareStressAnalysis"6.GE-NE-B13-01739-03,Rev.0,"SeismicDesignReportofShroudRepairforNineMilePoint1NuclearPowerPlant"7.NRCGenericLetter94-03,July25,1994,"IntergranularStressCorrosionCrackingofCoreShroudsinBoilingWaterReactors"8.NiagaraMohawkProcedure:Nl-MMP-GEN-914,"LiRingofMiscellaneousHeavyLoads"9.GE-NESpecification:386HA852,"ReactorServicingTools"Pagel5of17

10.GE-NEDocument:~DO-10909,Rev.7,"SAPG07,StaticDynamicAnalysisofMechanicalandPipingComponentsbyFiniteElementMethod"GE-NEDocument:DRFB13-01739,"NineMilePoint1ShroudStabilization"12.GE-NEProcedure:NM-SM-TP&P-04,"EDMActuators"13.NiagaraMohawkProcedure:Nl-ODG-11,"OutageSafetyAssessment"14.NiagaraMohawkProcedure:NIP-OUT-01,"ShutdownSafety"15.16.GE-NE"PostInspectionPlan"GE-NESpecification:21A1104,Rev.0,"SpecificationforReactorPressureVessel"17.18.BWROGVIPCoreShroudRepairDesignCriteria,Rev.1,September12,1994GE-NESpecification:25A5584,Rev.1,"FabricationofShroudRepairComponents"19.20.GE-NEDrawing:237E434,Rev.5,"ReactorVesselLoadings"GEDrawingGE-NESpecification:383HA718,ThermalCycles,ReactorVesselandNozzle,DescriptionBasisandAssumptions21.GE-NE-A0003981-1-13,Rev.1,"PerformanceImpactofShroudRepairLeakageforNMPI",I2/15/9422.NiagaraMohawkDocument:SO-EOP-M018,23.GE-NE-B13-01739-05,Rev.1,SAFETYEVALUATION,GECoreShroudRepairDesign24.Supplement1,GENE-B13-01739-03,Rev.0,NineMilePoint1,SeismicAnalysis,CoreShroudRepairModification25.Supplement4,GENE-B13-01739-04,NineMilePoint1,ShroudRepairHardwareStressAnalysis26.27.28.NMPCSafetyEvaluationNo.95-007Rev.1,NineMilePoint'1,CoreShroudRepairInstallation.GENE-B13-0173940,ShroudRepairAnomalies,NineMilePointUnit1,RFO14.NMP-SHD-003,LowerWedgeLatchReplacementandTieRodTorqueChecks.29.GENE-523-B13-01869-043,AssessmentoftheVerticalWeldCrackingontheNMP1Shroud,April1997.30.GENEB13-01739-22,DesignReportforImprovedShroudRepairLowerSupportLatches.31.NRCSafetyEvaluationoftheNMP1CoreShroudRepairDated3/31/95.Page16of17

.00 32.NRCSafetyEvaluateRelatedtoModificationstoCorrectShroudRepairDeviations,Dated3/3/97.Page17of17 ENCLOSURE5.--DESIGNREPORTFORIMPROVEDSHROUDREPAIRLOWERSUPPORTLATCHES~..9704100242.

ENCLOSURE6INSPECTIONHISTORY I

KineMilePointUnit1InvesselVisualInspectionSummaryofInspectionsPerformedRefuelingOutage'97Thefollowingidentifiestheinvesselvisualinspectionsduringthe1997refuelingoutage:"A"corespraypiping,welds,andbrackets(attachmentwelds)"B"corespraypiping,welds,andbrackets(attachmentwelds)Therewerenorelevantindicationsnoted:Upperspargers"A"and"C"lookingatthespargers,spargerwelds,includingtheteeboxwelds,nozzles,nozzleweldsandbrackets(attachment)welds.Lowerspargers"B"and"D"lookingatthespargers,spargerwelds,includingtheteewelds,nozzles,nozzleweldsandbrackets(attachment)welds.Twoindicationswererecorded(1)crackatnozzle23Aandoneonnozzle26Abothindicationswereobservedonpreviousdat'a.ThereisnoapparentdifferenceinthecracklengthRom1995until1997.Allofthesteamdryer,banksandskirts,liftinglugs.Closeattentiontoclips,lowerstiffener,andareaswithpreviousindicationsasnotedbelow:Bank2,Clip5Bank2,Clip2LockingChannelat225'ank2,LowerStiffener,1"HoleBank4,Clip5Thepreviouslyidentifiedindicationwasnotedwithnogrowthorchange.Thepreviouslyidentifiedindicationwasnotedwithnogrowthorchange.Thepreviouslyidentifiedindicationwasnotedwithnogrowthorchange.Thepreviouslyidentifiedindicationwasnotedwithnogrowthorchange.Thepreviouslyidentifiedindicationwasnotedwithnogrowthorchange.

J Examinationofthemoistureseparatorshowednonewindicationsandnogrowthorchangeinindicationslocatedonthe102standpipebracket.Examinedbolting,wedgesandverifiedgeneralcleanliness.SIIA09-IDTC1245norecordableindicationsnotedSIIA09-IDTC3645oneindicationwasnotedandrecordedonthedrytubeshaftjustbelowthecollar.Evaluatedvariousareasduringexaminationofallcomponentswithinthevesselthisoutage.Allfeedwaterspargers,endbrackets,pins,wedgeblocksandQowholeswereexaminedwithnoindicationsnoted.Inaddition,theblendradiusofallfourfeedwaternozzleswereexaminedandfoundacceptable.ChuL2aiahLocatedat180degrees,77"downthevesselwall.Severalaccessiblecorelocationswereinspectedfordebris,erosioncorrosionandseatingsurfaces.(wXivirfo97.v~

ENCLOSURE7AFFIDAVIT(GE)

P1 GeneralElectricCompanyI,GeorgeB.Stramba~beingdulysworn,deposeandstateasfollows:(1)IamProjectManager,RegulatoryServices,GeneralElectricCompany("GE")andhavebeendelegatedthefunctionofreviewingtheinformationdescribedinparagraph(2)whichissoughttobewithheld,andhavebeenauthorizedtoapplyforitswithholding.(2)TheinformationsoughttobewithheldiscontainedintheGEproprietaryreportsGE-NE523-B13-01869-043,AssessmentoftheVertical8'eldCraclangontheNMPIShroud,Revision0,ClassIII(GENuclearEnergyProprietaryInformation),datedApril1997,GENEB13-01739-40,ShroudRepairAnomaliesNineMilePointUnitI,RFOI4,Revision0,ClassIII(GENuclearEnergyProprietaryInformation),datedApril1997,andGENEB13-01739-22,DesignReportforImprovedShroudRepairLowerSupportRetainers,Revision0,ClassIII(GENuclearEnergyProprietaryInformation),datedApril1997.Theproprietaryinformationisdelineatedbybarsmarkedinthemarginadjacenttothespecificmaterial.(3)Inmakingthisapplicationforwithholdingofproprietaryinformationofwhichitistheowner,GEreliesupontheexemption&omdisclosuresetforthintheFreedomofInformationAct("FOIA"),5USCSec.552(b)(4),andtheTradeSecretsAct,18USCSec.1905,andNRCregulations10CFR9.17(a)(4),2.790(a)(4),and2.790(d)(1)for"tradesecretsandcommercialorfinancialinformationobtainedRomapersonandprivilegedorconfidential"(Exemption4).Thematerialforwhich'xemptionfromdisclosureisheresoughtisall"confidentialcommercialinformation",andsomeportionsalsoqualifyunderthenarrowerdefinitionof"tradesecret",withinthemeaningsassignedtothosefermsforpurposesofFOIAExemption4in,respectively,ecvC'2171QCC'.9~v~,704F2d1280(DCCir.1983).(4)'omeexamplesofcategoriesofinformationwhichfitintothedefinitionofproprietaryinformationare:aInformationthatdisclosesaprocess,method,orapparatus,includingsupportingdataandanalyses,wherepreventionofitsusebyGeneralElectric'scompetitorswithoutlicenseRomGeneralElectricconstitutesacompetitiveeconomicadvantageoverothercompanies;GBS-97-3-ahunp1l.docAffidavitPagoI

v'14'vVv~>i+los~y~svIe1v+VV~b.Informationwinch,ifusedbyacompetitor,wouldreducehisexpenditureofresourcesorimprovehiscompetitivepositioninthedesign,manufacture,shipment,installation,assuranceofquality,orlicensingofasimilarproduct;c.Informationwhichrevealscostorpriceinformation,productioncapacities,budgetlevels,orcommercialstrategiesofGeneralElectric,itscustomers,oritssuppliers;d.Informationwhichrevealsaspectsofpast,present,orfutureGeneralElectriccustomer-fundeddevelopmentplansandprograms,ofpotentialcommercialvaluetoGeneralElectxic;e.Informationwhichdisclosespatentablesubjectmatterforwhichitmaybedesirabletoobtainpatentprotection.Theinformationsoughttobewithheldisconsideredtobeproprietaryforthereasonssetforthinbothparagraphs(4)a.aud(4)b.,above.(S)TheinfozmationsoughttobewithheldisbeingsubmittedtoNRCinconfidence.TheinformationisofasortcustomazilyheldinconfidencebyGE,andisinfactsoheld.Theinformationsoughttobewithheldhas,tothebestofmyknowledgeandbelief,consistentlybeenheldinconfidencebyGE,nopublicdisclosuxehasbeenmade,anditisnotavailableinpublicsources.AlldisclosurestothirdpartiesincludinganyrequiredtraxisxxiittalstoNRC,havebeenmade,ormustbemade,pursuanttoregulatoryprovisionsor'roprietaxyagreementswhichprovideformaintenanceoftheinfozxnationinconfidence.Itsinitialdesignationaspropzietazyinformation,andthesubsequentstepstakentopreventitsunauthorizeddisclosure,areassetforthinparagraphs(6)and(7)following.(6)Initialapprovalofproprietarytreatmentofadocumentismadebythemanageroftheoriginatingcomponent,thepersonmostlikelytobeacquaintedwiththevalueandsensitivityoftheinformationinrelationtoindustryknowledge,AccesstosuchdocumentswithinGEislimitedona"needtoknow"basis.(7)Theprocedureforapprovalofexternalreleaseofsuchadocumenttypicallyrequiresreviewbythestaffmanager,projectmanager,principalscientistorotherequivalentauthority,bythemanagerofthecognizantmarketingfunction(orhisdelegate),andbytheLegalOperation,fortechnicalcontent,competitiveeffect,anddeterminationoftheaccuracyoftheproprietarydesignation.DisclosuresoutsideGEarelnnitedtoregulatorybodies,customers,andpotentialcustomers,andtheiragents,suppliers,andlicensees,andotherswithalegitimateneedfortheinformation,andthenonlyinaccordancewithappropriateregulatoryprovisionsorproprietaxyagreements.(8)Theinformationidentifiedinparagraph(2),above,isclassifiedasproprietarybecauseitcontainsdetailedresultsofanalyticalmodels,methodsandprocesses,GBS-97-3-ahmpll.doc~AffidavitPage2

.41 includingcomputercodes,whichGEhasdevelopedandappliedtoperformevaluationsofindicationsinthecoreshroudfortheBWR.ThedevelopmentandapprovaloftheBWRShroudRepairProgramwasachicvcdatasignificantcost,ontheorderofonemilliondollars,toGE.ThedevelopmentoFtheevaluationprocesscontainedintheparagraph(2)documentalongwiththeinterpretationand,applicationoftheanalyticalresultsisderived&omthccxtcnsivccxpcricnccdatabasethatconstitutesamajorGEasset.(9)PublicdisclosureoftheinformationsoughttobewithheldislikelytocausesubstantialharmtoGE'scompetitivepositionandforecloseorreducetheavailabilityofprofit-makingopportunities.'IheinformationispartofGEscomprehensiveBWRsafetyand'technologybase,anditscommercialvalueextendsbeyondtheoriginaldevelopmentcost.Thevalueofthetechnologybasegoesbeyondtheextensivephysicaldatabaseandanalyticalmethodologyandincludesdevelopmentoftheexpntisetodetermineandapplytheappropriateevaluationprocess.Inaddition,thetechnology.baseincludesthevaluederived&omprovidinganalysesdonewithNRC-approvedmethods.Theresearch,development,engineering,analyticalandNRCreviewcostscompriseasubstantialinvestmentoftimeandmoneybyGE.TheprecisevalueoftheexpertisetodeviseanevaluationprocessandapplythecorrectanalyticalmethodologyisdifBculttoquantify,butitclearlyissubstantial.GE'scompetitiveadvantagewillbelostifitscompetitorsareabletousetheresultsoftheGEexperiencetonormalizeorverifytheirownprocessoriftheyareabletoclaimanequivalentunderstandingbydemonstratingthattheycanarriveatthesameorsimilarconclusions.ThevalueofthisinformationtoGEwouldbelostiftheinformationweredisclosedtothepublic.Makingsuchinformationavailabletocompetitorswithouttheirhavingbeenrequiredtoundertakeasimilarexpenditureofresourceswouldunfairlyprovidecompetitorswithawindfall,anddepriveGEoftheopportunitytoexerciseitscompetitiveadvantagetoseekanadequatereturnonitslargeinvestmentindevelopingtheseveryvaluableanalyticaltools.GBS-97-3-ahmp11.docAQidavitPage3

~0 tlt-r(tJ<4(PsaJC(aswfII'0ftV(tst(flltV(V(o~STATEOFCALIFORNIA))ss:COUNTYOFSANTACLARA)GeorgeB.Stramback,beingdulysworn,deposesandsays:Thathehasreadtheforegoinga6idavitapdthemattersstatedthereinaretrueandcorrecttothebestofhisknowledge,information,andbelief.ExecutedatSauJose,Cahfomia,this~dayof1991.orgeB.trambackGeneralElectricCompanySubscribedandswornbeforemethis7~~dayof1997.otaryPublic,StateofCQKACNOOomnMeP)it3RQg.SektCheCeely&COaaSISIIOet20,3MGBS-97-3-a&mp11.doeAfBfhvitPage4s

GeneralElectricCompanyAIFIDAVXX'GeorgeB.Stramback,beingdulysworn,deposeandstateasfollows:(1)IamProjectMazuzgcr,RegulatoryServices,GeneralElectricCompany("GE")andhavebeendelegatedthefunctionofreviewingtheinfozmauondescribedinpazagraph(2)whichissoughttobewithheld,andhavebeenauthonzedtoapplyforitswithholding.(2)ThcinformationsoughttobcwithheldiscontainedintheGEproprietarydrawingsReactorModification!InstallationDrawing,107E5679,Revision7,andthosedrawingslistedintheattachment.Thesedocuments,takenasawhole,constitutesaproprietarycompilationofinfozmation,someofitalsoindependentlyproprietary,preparedbyGeneralElectricCompany.Theindependentlyproprietazyelementsthataxcdrawingsaremarkedasproprietarinformation.(3)Inmakingthisapplicationforwithholdingofproprietazyinformationofwhichitistheowner,GEreliesupontheexemptionRomdisclosuresetforthintheFxeedomofInformationAct("FOIA"),5USCSec.552(b)(4),andtheTradeSecretsAct,18USCSec.1905,andNRCregulations10CFR9.17(a)(4),2.790(a)(4),and2.790(d)(l)for"tradesecretsandcommercialorfinancialinfozmationobtained&omapersonandpzivilcgedorconfidential"(Exemption4).Thematerialforwhichexemption&undisclosureisheresoughtisall"confidentialcommercialinformation",andsomepoztionsalsoqualifyunderthenarrowerdefinitionof"tradesecret",withinthemeaningsassignedtothosetermsforpurposesofFOIAExemption4in,respectively,VC'9dWCC'.199),z~Q704F2d1280(DCCir.1983).(4)SomeexamplesofcategoriesofiufozznationwhichQtintothcdefinitionofproprietaryinformationare:.a.Infozmationthatdisclosesaprocess,method,orapparatus,includingsuppoitingdataandanalyses,wherepreventionofitsusebyGeneralElectric'scompetitorswithoutlicenseRomGeneralElectricconstitutesacompetitiveeconomicadvantageoverothercompanies;b.Infozmationwhich,ifusedbyacompetitor,wouldzeducehisexpezuHtureofresourcesorimprovehiscompetitivepositioninthedesign,manufactuze,shipment,installation,assuranceofquality,orlicensingofasimilarproduct;GBS-97-3-afNMP12.docAf5davitPage1 NI c.Informationwhichrevealscostorpriceinformation,productioncapacities,budgetlevels,orcommercialstxategiesofGeneralEcctric,itscustomers,oritssuppliers;d.Informationwhichrevealsaspectsofpast,present,orfutureGeneralElectriccustomer-Sideddevelopmentplansandprograms,ofpotentialcommercialvaluetoGeneralHectric;e.Informationwhichdisclosespatentablesubjectmatterforwhichitmaybedesirabletoobtainpatentprotection.Theinformationsoughttobcwithheldisconsideredtobeproprietaryforthereasonssetforthinbothparagapbs(4)a.,(4)b.and(4)e.,above.TheinformationsoughttobcwithheldisbeingsubmittedtoNRCincon6dencc.Theinformationisofasortcustomarilyheld.incon6dcnccbyGE,andisinfactsoheld.Theinformationsoughttobewithheldhas,tothebestofmyknowledgeandbelief,consistentlybeenheldinconfidencebyGE,nopublicdisclosurehasbeenmade,anditisnotavaihbleinpublicsources.AlldisclosurestothirdpazticsincludinganyrequiredtraasmittalstoNRC,havebccnmade,ormustbomade,pursuanttoregulatorypzovisionsorpropzietaryagreementswhichprovideformaintenanceoftheinfozznationincon6dence.Itsinitialdesignationasproprietaryinformation,andthesubsequentstepstakentopreventitsunauthorizeddisclosure,azeassetfozthinparagraphs(6)and(7)following.hitialapprovalofpxopxzctazytreatxnentofadoemM:ntismadebythczmuugczoftheoriginatingcomponent,thepersonmostlikelytobeacquaintedwiththevalueandsensitivityoftheiafozxnaxioninrehtiontoindustryknowledge.AccesstosuchdocumentswithinGEishmitedona"needtoknow"basis.'Iheprocedureforapprovalofexternalreleaseofsuchadocumenttypicallyxectuircsreviewbythestaffmanager,projectmanager,pxincipalscicxxtistorotherequivalentauthority,bythemanagerofthccognizantmarketingRncnon(orhisdelegate),andbytheLegalOperation,fortechnicalcontent,competitiveeEcct,anddctemhetionofthcaccuracyofthepxopxictazydesignation.DisclosuresoutsideGEarelimitedtoregulatorybodies,custormm,andpotentialcustomers,andtheiragents,suppliers,andlicensees,andotherswithalegitimateneed.forthcinformation,andthenonlyinaccordancewithappzoyciateregulatoryprovisionsorproprietaryagrccmcxxts.Theinfozxnationidentifiedinparagraph(2),above,isclassiGcdaspxopxietaxybecauseitconstitutesacon6dentialcompilationofinformation,includingdetaileddesigndrawingresultsofahardwaredesignmodiGcatioa(stabilizerfortheshroudhorizontalwelds)intetMledtobeinstalledinareactortoresolvethereactorpressurevesselcoreshroudweMcrackingconcern.ThedevelopmentandapprovalofthisGBS-97-3wfNMp)2.docA6idavitPage2

designmodificationutilmxisystems,components,andmodelsandcomputercodesthatweredevelopedatasiyCificantcosttoGE,ontheorderofseveralhundredthousanddollars.Thedetailedresultsoftheanalyticalmodels,methods,andprocesses,includingcomputercodes,andconclusions&omtheseapplications,represent,asawhole,anintegratedprocessorapproachwhichGEhasdeveloped,andappliedtothisdesignmodification.ThedevelopmentofthesupportingprocesseswasatasignificantadditionalcosttoGE,inexcessofamilliondollars,overandabovethelargecostofdevelopingtheunderlyingindividualproprietaryrcportanddrawingsinformation.(9)PublicdisclosureoftheinfoanationsoughttobewithheldislikelytocausesubstantialharmtoGE'scompetitivepositionandforecloseorreducetheavailabiTityofprofit-mahngopportunities.TheinformationispartofGE'scomprehensiveBWRsafetyandtechnologybase,anditscommercialvalueextendsbeyondtheoriginaldevelopmentcost.Thevalueofthetechnologybasegoesbeyondtheextensivephysicaldatabaseandanalyticalmethodologyandincludesdevelopmentoftheexpertisetodetermineandapplytheappropriateevaluationprocess.Inaddition,thetechnologybaseincludesthevaluederivedRomprovidinganalysesdonewithNRC~vedmethods.tTheresearch,development,etgineering,analyticalandNRCreviewcostscompriseasubstantialinvestmentoftimeandmoneybyGE.'IheprecisevalueoftheLyeztisetodeviseanevaluationprocessandapplythecorrectanalyticalmethodologyisdiKculttoquantify,butitclearlyissubstantiaLGE'scompetitiveadvantagewillbelostifitscompetitorsareabletousetheresultsoftheGEexperiencetonormallizeorverifytheirownprocessoriftheyareabletoclaimanequivalentunderstandingbydemonstratingthattheycanarriveat.thesame,orsimilarconclusions.ThevalueofthisinformationtoGEwouldbelostiftheinformationweredisclosedtothepublic.MakingsuchinformationavailabIetocompetitorswithouttheirhavingbeenrequiredtoundertakeasimilarexpenditureofresourceswouldunSurlyprovidecompetitorswithawindfall,anddepriveGEoftheopportunitytoexerciseitscompetitiveadvantagetoseekanadequatereturn,on,itslargeinveshnentindevelopingtheseveryvaluableanalyticaltools.*GBS-97-3-aSMP12.docAfDdavitPago3

eeCIt,cJI2IuJD'WII'Ixsc.asxxt,IC.~~II~CD~CDSTATEOFCALIFORNIA))ss:CORIYOFSANTACUBA)Geog@B.Strarnback,beingduly~rn@Posesandsay:ThathchasreadtheforegoingaQbhvitandthemLttcrsstaredthcremaretrueandcorrecttothebestofhishnowIcdgc,inforrnationsandbelief.ExeurtcdatSanJose,California,this'~dayofl997.rgeB.backGeneralElectricCompanySubsenbexisutisexoxubefoxexutehis~XtbsfofI997:.otazyPublic,Stateo4l5hCoasgym~OIt~~NcCevPC~a~~~sgesnN3Caeet~amatpeeaOctm~GBS-97-3-aSMP12.docAf6davitPage4 t

nremvi'bi88:18i'plGEBNRTECHNOLOGY~~,'.j-P.26/26ATTACHMENT~Drawin112D6546,Rev.3,TieRod,SpringAssembly112D6573,Rcv.3,UpperSupportAssemblyGB&97-3wfNMP12.docA6idavitPagoS 1J CATEGORY1.REGULATINFORMATIONDISTRIBUTION.STEM(RIDS)ACCESSION'NBR:9704100242DOC.DATE:97/04/08NOTARIZED:YESDOCKETIFACIL:50-220NineMilePointNuclearStation,Unit1,NiagaraPowe05000220AUTH.NAMEAUTHORAFE'LIATIONMCCORMICK,M.J.NiagaraMohawkPowerCorp.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)

SUBJECT:

Forwardsproprietary&non-proprietaryreptsfromGEreGL94-03,"IntergranularStressCorrosionCrackinginBWRs."Listofrepts,encl.Enclswithheld,per10CFR2.790(b)(i).DISTRIBUTIONCODE:AP01DCOPIESRECEIVED:LTRENCLSIZE:TITLE:ProprietaryReviewDistribution-PreOperatingLicense&OperatingRENOTES:RECIPIENTIDCODE/NAMEPD1-1LAHOOD,DINTERNAL:ACRSOGC/HDS3EXTERNAL:NRCPDRCOPIESLTTRENCL11111110RECIPIENTIDCODE/NAMEPD1-1PDLECENTER01COPIESLTTRENCL11110DUENNOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083TOTALNUMBEROFCOPIESREQUIRED:LTTR7ENCLP

~~~W~I$'vCf,kII,f CATEGORY2REGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:9704100242DQC.DATE:9'7/04/08NOTARIZED:YES.DOCKETFACIL:50-220NineMilePointNuclearStationsUnitiiNiagaraPowe05000220AUTH.NAMEAUTHORAFFILIATION"MCCORMICK'.J.NiagaraMohawkPowerCorp.'-~RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)

SUBJECT:

Forwardsproprietary5non-proprietaryreptsfromGEreGL94-03'IntergranularStressCorrosionCrackinginBMRs."Listofrepts>encl.Enclswithheldiper1OCFR2.7'VO(b)(i).DISTRIBUTIONCODE:AP01DCOPIESRECEIVED:LTRENCLSIZE:TlTLE:ProprietaryReviewDistribution-PreOperatingLicense';cNOTES:l+38OperatingRRECIPIENTlDCODE/NAMEPDi-1LAHOQDiDINTERNAL:ACRSQGC/HDS3EXTERNAL:NRCPDRCOPIESLTTRENCL1111.111010RECIPIENTIDCODE/NAMEPDi-1PDFILECENTER01COPIESLTTRENCL110Y,DCENOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083TOTALNUMBERQFCOPIESREQUIRED:LTTR7ENCL5

\

NiAGARAMOHAWKGENERATI0NBUSiNESSCROUPMARTINJ.McCORMICKJR.P.E.VicePresidentNuciearEngineeringNINEMILEPOINTNUQI.EARBTATIONJLAKEROAD.P.O.BOX63.LYCOMING,NEWYORK13093/TELEPHONE(3I5)349.2660FAX(3(5)349-2605April8,1997NMPIL1200U.S.NuclearRegulatoryCommissionAttn:DocumentControlClerkWashington,DC20555RE:NineMilePointUnit1Docket50-220

Subject:

GenericLetter94-03"IntergranularStressConosionCracking(IGSCClinBoiling8'aterReactors"Gentlemen:BylettersdatedJanuary6,1995andJanuary23,1995,NiagaraMohawkPowerCorporation(NMPC)submittedanapplicationforrepairstotheNineMilePointUnit1(NMP1)coreshroud.Theshroudrepairsanduseofstabilizerassemblies(tierods)weresubmittedasanalternatetotherequirementsoftheASMECode,SectionXI,asallowedby10CFR50.55a(a)(3)(i).ThestaffprovidedapprovaloftheproposedalternaterepairbyletterdatedMarch31,1995.TheapprovalletterandattachedsafetyevaluationrequiredNMPCtosubmitre-inspectionplansfortheshroudandrepairassembliespriortothenextrefuelingoutageplannedfor1997.ByletterdatedFebruary7,1997,NMPCsubmittedplansforre-inspectionofthecoreshroudverticalweldsandrepairassembliesinaccordancewiththecriteriaprovidedbythe"BWRVesselandInternalsProgram"(BWRVIP)documentBWRVIP-07.Duringthe1997refuelingoutage,NMPCconductedcoreshroudverticalweldinspectionspertheapproveddocumentsandobservedverticalweldcrackingwhichexceededthescreeningcriteria.Additionally,inspectionsofthefourtierodassembliesfoundthetierodnutstohavelostsomepreloadandidentifieddamagetothelowerwedgeretainerclipsonthreetierods.FurtherdetailsoftheasfoundconditionsareprovidedinEnclosures1and2.ByphonecallsonMarch20,1997andApril2,1997,NMPCinformedthestaffoftheinspectionfindingsandindicatedthatanalysisoftheverticalweldcrackingandrestorationplanoftheshroudtierodassemblieswouldbesubmittedtotheNRCpriortorestartoftheunit.Thisletterandtheattachedenclosuresproviderootcause,correctiveactionsandthefinaldesigndocumentationwhichestablishestheacceptabilityoftheasfoundverticalweld9704100242970408PDRADOCK05000220P'DR

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