ML17331A089
| ML17331A089 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 03/10/1993 |
| From: | FITZPATRICK E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | MURLEY T E NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17331A090 | List: |
| References | |
| AEP:NRC:1166C, NUDOCS 9303160107 | |
| Download: ML17331A089 (22) | |
Text
SUBJECT:
ApplicationforamendtoLicense.DPR-58;changingTStoallow'-Iinterimpluggingcriteriaof1.0voltforCycle14.,Technicalsummarysupportingvalidity6'continueduse.ofWestinghouseReptWCAP-13187encl.DISTRIBUTIONCODE:0001DCOPIESRECEIVED:LTR/~ENCL/'IZE:ig+~+$TITLE:ORSubmittal:GeneralDistribution/DNOTES:-+-=;ACCEZ,ERXV@~OOCVMENTDISVagVTION.SYSTEMACCESSIONN]9R:9303160107DOC.DATE:93/03/10'OTARIZED:YES"DOCKETFACIL:50-315DonaldC.CookNuclearPower'lant,Unit1,IndianaM05000315AUTH.NAMEAUTHORAFFILIATIONFITZPATRICK,E.IndianaMichiganPowerCo.-(formerly'Indiana&MichiganEleRECIP.NAMERECIPIENTAFFILIATIONMURLEY,T.E.DocumentControlBranch(Document'-ControlDesk)RECIPIENTIDCODE/NAMEPD3-1LADEAN,WINTERNAL:NRR/DE/EELBNRR/DRCH/HICBNRR/DSSA/SPLBNUDOCS-ABSTRACTOGC/HDS2EXTERNAL:NRCPDRCOPIESLTTRENCL221111111110.11k"RECIPIENTIDCODE/NAMEPD3-1PDNRR/DORS/OTSBNRR/DSSA/SCSBNRR/DSSA/SRXBREGFILE'1-NSIC-COPIESLTTRENCL1.111111110'1.11".1ADDANOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE!CONTACI'IIEDOCUMENTCOi!'I'ROLDIMK,ROOMPl-37(EXT.504-2065)TOELIMINATEYOURNAMEFROMDISTR!BUTIONLISTSFORDOCUMENTSYOUDON'TNEED!DTOTALNUMBEROFCOPIESREQUIRED:LTTR16ENCL14
\~~o'i indianaMichiganPowerCompanyP.O.Box16631t:olumbus,OH43216AEP:NRC:1166GDonaldC.CookNuclearPlantUnit1DocketNo.50-315LicenseNo.DPR-58TECHNICALSPECIFICATIONSCHANGETOALLOWINTERIMPLUGGINGCRITERIAOF1.0VOLTFORCYCLE14U.S.NuclearRegulatoryCommissionDocumentControlDeskWashington,D.C.20555Attn:T.E.MurleyMarch10,1993
DearDr.Murley:
ThisletteranditsattachmentsconstituteanapplicationforanamendmenttotheTechnicalSpecifications(T/Ss)ofDonaldC.CookNuclearPlantUnit1inaccordancewith10CFR50.90.ItisrequestedthattheamendmenttotheT/Ssforsteamgeneratorinterimpluggingcriteria,asoutlinedintheNRCletterofJuly29,1992forlicenseAmendmentNo.166forfuelcycle13,beextendedtofuelcycle14oftheCookNuclearPlantUnit1.ThisextensionisessentialwhileourT/SammendmenttoallowalternatepluggingcriteriaisbeingreviewedbytheNRC(AEP:NRC:1166,March20,1992).Attachment1providesatechnicalsummaryoftherecentsteamgeneratortubeinterimpluggingcriteriavoltageevaluationsandtubesampleanalysisresults.TheseevaluationsandresultssupportthevalidityandcontinueduseoftheWestinghouseReportWCAP-13187insupportofthe1volt.interimpluggingcriteriaforfuelcycle14.NotechnicalchangesweremadetotheinterimpluggingcriteriaT/Ssrequirementsusedforfuelcycle13.T/Schangesweremadeonlytoreferencefuelcycle14intheappropriateT/Sparagraphswherefuelcycle13waspreviouslyreferenced.AdetaileddescriptionoftheproposedchangesandouranalysesconcerningsignificanthazardsconsiderationsarerepeatedfromourprevioussubmittalandareincludedinAttachment2tothisletterforyourconvenience.Attachment3containstheproposed3f'te19303i60i079303i0PDRADOCK050003i5PPGRoor l1ia~
Dr.T.E.Murley-2-AEP:NRC:1166GrevisedT/Spages.Attachment4containsthemarked-upcopiesoftheexistingT/Ss.Webelievethattheproposedchangeswillnotresultin(1)asignificantchangeinthetypesofeffluentsorasignificantincreaseintheamountofanyeffluentsthatmaybereleasedoffsite,or(2)asignificantincreaseinindividualorcumulativeoccupationalradiationexposure.TheseproposedchangeshavebeenreviewedbythePlantNuclearSafetyReviewCommitteeandthecorporateNuclearSafetyandDesignReviewCommittee.IncompliancewiththerequirementsoflOCFR50.91(b)(1),copiesofthisletteranditsattachmentshavebeentransmittedtoMr.J.R.PadgettoftheMichiganPublicServiceCommissionandtotheMichiganDepartmentofPublicHealth.Pleasecontactusifyouhaveanyquestionsconcerningthislicenseamendmentrequest.Thisletterissubmittedpursuantto10CFR50.54(f)and,assuch,anoathstatementisenclosed.Sincerely,pg+p~jVicePresidentehAttachmentsEnclosurecc:A.A.Blind-BridgmanJ.R.PadgettG.CharnoffA.B.Davis-RegionIIINRCResidentInspector-BridgmanNFEMSectionChief Dr.T.E.Murley-3-AEP:NRC:1166Gbc:S.J.BrewerD.H.Malin/K.J.TothJ.D.Benes/J.R.JensenM.L.Horvath-BridgmanJ.B.ShinnockW.G.Smith,Jr.W.M.Dean,NRC-Washington,D.C.AEP:NRC:1166GDC-N-6015.1 aCOUNTYOFFRANKLINE.E.Fitzpatrick,beingdulysworn,deposesandsaysthatheistheVicePresidentoflicenseeIndianaMichiganPowerCompany,thathehasreadtheforgoingresponsetoAEP:NRC:1166G-TechnicalSpecificationChangeToAllowInterimPluggingCriteriaOf1.0VoltForCycle14andknowsthecontentsthereof;andthatsaidcontentsaretruetothebestofhisknowledgeandbelief.Subscribedandsworntobeforemethis~~dayof199H40TARYPUBLICRlTAD.HILLNOTARYPUBLIC.STATEOFOIUO l'4*h4r.~
ATTACHMENT1TOAEPNRC'1166GTECHNICALSUMMARYOFTHERECENTSTEAMGENERATORTUBEINTERIMPLUGGINGCRITERIAVOLTAGEEVALUATIONSTUBESAMPLEANALYSISRESULTS ATTACHMENT1TOAEP:NRC:1166GPage1Thetechnicalbasisforimplementingtheinterimpluggingcriteriaforfuelcycle13wasbasedonsubmittaldocumentsAEP:NRC:1166,1166A,1166B,1166C,and1166D.IncludedasanattachmentwasWestinghouseReport,WCAP-13187titled"D.C.CookUnit1SteamGeneratorTubePluggingCriteriaforIndicationsatTubeSupportPlates"datedMarch1992.TheWCAPcontainsthetechnicalapproachforachievingassuranceoftubestructuralintegritybasedoneddycurrentbobbincoilvoltagerepaircriteria.ApplicationoftheWCAPtuberepairvoltagecriteriaisbasedonvoltagegrowthratesfromthepriortwooperatingcyclesof0.8and0.7volts.Analysisofvoltagegrowth"ratedoneforfuelcycle13,attheendoffuelcycle12in1992,showedthelargestvoltagegrowthwas0.49volts.ThisiswellbelowtheprojectedgrowthratesreferencedbytheWCAP.Analysisforthemaximumendofcyclevoltageprojectedforindicationsleftinservicebelow1.0voltwas1.40volts.ThisindicationvoltageiswellwithinthestructurallimitsproposedbytheWCAPstructuralvoltagelimitsforpotentialtubeleakageandburst.NRCsubmittalletterAEP:NRC:1166FcontainsthefullreportonevaluationsperformedtoestimatetheprojectedEOCvoltagegrowthrateaswellasleakrateandburstprobabi.lity.Inaddition,tubesampleswereremovedfromsteamgeneratorNo.12aspartoftheT/Ssalternatepluggingcriteriaformetallographicevaluation,leaktesting,andbursttesting.Thefollowingtablesummarizestheresultsonthosetubesamplesleakandbursttestedatthefirstandsecondsupportplate(SP)elevati.ons.SuamaryTableTubeLeakandBurstTestDataLocationFieldE/C~XDDPCttRll-C60/SPI1.1Volt,BCSAI,RPCLeak~lt.PINotDoneBursttPI9,100SEHFractography~DthX~ADttI5432Rll-C60/SP21.4Volt,BCHAI,RPCRlg-C16/SP11.4Volt,BCSAI,RPCNotDone>2,650(ET)*NoLeakage9,35010P725523828Rlg-C21/SPl2.0Volt,BCSAI,RPC>2,650(ET)*NoLeakage10,200Rlg-C21/SP2NDD,BCNDD,RPC*ET~TestdoneatelevatedNotDonetemperature.11,20038NoData ATTACHMENT1TOAEP'NRC'1166GPage2Thecorrosionwasconfinedtothesupportplateregionandhadcombinationsofaxiallyorientedintergranularstresscorrosion'crackingandintergranularcellularcorrosion.ThecorrosionwasofODorigin,anditoccurredineither360'andsorisolatedpatches.TheSP2regionoftubeR18-C21hadtheshallowestmaximumcrackdepth(38%throughwall)found.Itseddycurrentsignalwouldnotbeexpectedtobedetectedwithahighprobability.ThefirstsupportplatecreviceregionsoftubesR18-C16andR18-C21wereleaktestedatelevatedtemperatureandpressure.Neithertubeleakedthroughexistingcorrosionnetworksatnormaloperatingconditions(1500psi.differentialpr~ssurewithprimarysideat2250psiandsecondarysideat750psi)oratsteamlinebreakconditions(2650psidifferentialpressurewiththeprimarysideat3000psiandthesecondarysideat350psi).Roomtemperaturebursttestswer'econductedatahigherpressurizationrateof1000psi/seconSP1oftubesRll-C60,R18-C16andR18-C21andSP2oftubesRll-C60andR18-C21.Allburstathighburstpressures(9,100;10,725;10,200;9,350and11,200psig,respectively)andhadaxialburstopenings.Virgintubingburst,typicallybetween11,500and12,000psig.Inconclusion,theresultsofthevoltagegrowthrateevaluationsandtubesampleleakandburstwerewellwithintheguidelinesestablishedintheWCAP.Also,thevoltagegrowthrateisalmosthalfofwhatwasfoundforthetwopriorfuelcycles.Therefore,basedonalowvoltagegrowthrate,andleakandbursttestresults,theWCAPisstillconsideredatechnicallyappropriateandboundingdocumentapplicabletothenextfuelcycle,cycle14.Furthermore,theeddycurrentinspection,reporting,andleakagerequirementsaspreviousilystatedintheT/Ssforfuelcycle13,willbemaintainedforfuelcycle14.
ATTACHMENT2toAEP:NRC:1166GNOSIGNIFICANTHAZARDSCONSIDERATIONEVALUATIONINSUPPORTOFTHEINTERIMPLUGGINGCRITERIA Attachment2toAEP:NRC:1166GINTRODUCTIONPage1Alicenseamendmentisproposedtoprecludeunnecessarilypluggingsteamgeneratortubesduetotheoccurrenceofouterdiameterinitiatedstresscorrosioncracking(ODSCC)atthetubesupportplatesintheCookNuclearPlantUnit1steamgenerators.UsingtheexistingTechnicalSpecifications(T/Ss)steamgeneratortubepluggingcriteriaof40$tubewallpenetrationasdeterminedbynon-destructiveexamination(NDE),manyofthetubeswithcrackindicationswouldneedlesslyhavetoberemovedfromservice.TheinterimpluggingcriteriafortubesupportplateelevationODSCCoccurringintheCookNuclearPlantUnit1steamgeneratorsmayresultintubeswithbothpartialandthrough-wallcracksreturningtoservice.Inthelimitingcase,itisdemonstratedthatthepresenceofthrough-wallcracksaloneisnotreasonenoughtoremoveatubefromservice.DESCRIPTIONOFTHEAMENDMENTREQUESTAsrequired'by10CFR50.91(a)(1),ananalysisisprovidedtodemonstratethattheproposedlicenseamendmenttoimplementaninterimsteamgeneratortubepluggingcriteriaforthetubesupportplateelevationsatCookNuclearPlantUnit1involvesnosignificanthazardsconsiderations.Theinterimpluggingcriteriainvolveacorrelationbetweeneddycurrentbobbincoilsignalamplitude(voltage)andtubeburstandleakagecapability.Thepluggingcriteriaisbasedontestingoflaboratory-inducedODSCCspecimens,extensiveexaminationofpulledtubesfromoperatingsteamgenerators(industrywide),andfieldexperiencewithleakageduetoindicationsat,thetubesupportplates(worldwide).Specifically,crackindicationswithbobbincoilvoltageslessthanorequalto1.0volt,regardlessofindicateddepth,donotrequireremedialactionifpostulatedsteamlinebreakleakagecanbeshowntobeacceptable.Crackindicationswithbobbincoilsignalamplitudesexceeding1.0voltmustbeeitherpluggedorrepaired.OTheproposedamendmentwouldmaintainthepreviouslymodifiedT/Ss"3.4.5"SteamGenerators,"3.4.6,"ReactorCoolantSystemLeakage,"andtheassociatedbasesincorporatedforthe1voltinterimpluggingcriteria.TheseprovidetubeinspectionrequirementsandacceptancecriteriatodeterminethelevelofdegradationforwhichatubeexperiencingODSCCatthetubesupport'lateelevations.may'emaininserviceintheCookNuclearPlantUnit1steamgenerators.
Attachment2toAEP:NRC:1166GEVALUATIONPage2SteamGeneratorTubeInteritDiscussionInthedevelopmentoftheinterimpluggingcriteria,RegulatoryGuides(RG)1.121,"BasesforPluggingDegradedPWRSteamGeneratorTubes,"and1.83"InserviceInspectionofPWRSteamGeneratorTubes,"areusedasthebasesfordeterminingthatsteamgeneratortubeintegrityconsiderationsaremaintainedwithinacceptablelimits.RegulatoryGuide1.121describesamethodacceptabletotheNRCstaffformeetingGeneralDesignCriteria(GDC)2,4,14,15,31,and32byreducingtheprobabilityandconsequencesofsteamgeneratortuberupturethroughdeterminingthelimitingsafeconditionsoftubewalldegradation.Tubeswithunacceptablecracking,asestablishedbyinserviceinspection,shouldberepairedorr'emovedfromservicebyplugging.ThisRGusessafetyfactorsonloadsfortubeburstthatareconsistentwiththerequirementsofSectionIIIoftheASMECode.ForthetubesupportplateelevationdegradationoccurringintheCookNuclearPlantUnit1steamgenerators,tubeburstcriteriaareinherentlysatisfiedduringnormaloperatingconditionsbythepresenceofthetubesupportplate.Thepresenceofthetubesupportplateenhancestheintegrityofthedegradedtubesinthatregionbyprecludingtubedeformationbeyondthediameterofthedrilledhole.Itisnotcertainwhetherthetubesupportplatewouldfunctiontoprovideasimilarconstrainingeffectduringaccidentconditionloadings.Therefore,nocreditistakeninthedevelopmentofthepluggingcriteriaforthepresenceofthetubesupportplateduringaccidentconditionloadings.Conservatively,basedontheexistingdatabase,bursttestingshowsthatthesafetyrequirementsfortubeburstmarginsduringbothnormalandaccidentconditionloadingscanbesatisfiedwithbobbincoilsignalamplitudeslessthan6.8volts,regardlessofthedepthoftubewallpenetrationcracking.RegulatoryGuide1.83describesamethodacceptabletotheNRCstaffforimplementingGDC14,15,31,and32throughperiodicinserviceinspectionforthedetectionofsignificanttubewalldegradation.Uponimplementationofthepluggingcriteria,tubeleakageconsiderationsmustalsobeaddressed.Itmustbedeterminedthatthecrackswillnotleakexcessivelyduringallplantconditions.FortheinterimtubepluggingcriteriadevelopedfortheCookNuclearPlantUnit1steamgeneratortubes,littleornoleakageisexpectedduringnormaloperatingconditionsevenwiththepresenceofthrough-wallcracks.Industrywide,thecrack'orphologyofSCCattubesupportplateintersectionsisbestdescribedasshort,tight,axiallyorientedmicrocracksseparated Attachment2toAEP:NRC:1166G.Page3byligamentsofnon-degradedmaterial.ThesamemorphologyisjudgedtobepresentintheCookNuclearPlantUnit.1steamgenerators.Tubepullexaminationresultsfrom1983indicatedaxialSCCinitsearlystages.Thedepthsoftheevidenceddegradation(determinedbydestructiveexam)showedthemaximumdepthofpenetrationtobeapproximately10%through-wall.Therotatingpancakecoil(RPC)testingperformedduringthe1989and1992outageshasconfirmedthataxiallyorientedSCCcracksexistatthetubesupportplateintersections.BasedontheRPCtestingresultsandrelativelysmallamplitudebobbinvoltagescoupledwithlowbobbinvoltagegrowthrates,itisconcludedthataxiallyorientedODSCCbestdefinesthedegradationmorphologyoccurringattheCookNuclearPlantUnit1tubesupportplateintersections.Tubepullsduringthesummer1992refuelingoutageweredestructivelyexaminedandconfirmthetubedegradationphenomenaoccurringatthetubesupportplates.Noleakageduringnormaloperatingconditionshasbeenobservedatthesupportplatesinthefieldatsimilarplantsforcrackindicationswithsignalamplitudeslessthan7.7volts.Additionally,noprimary-to-secondaryleakageatthetubesupportplatehasbeendetectedinU.S.plants.Relativetotheexpectedleakageduringaccidentconditionloadings,thelimitingeventwithrespecttoprimary-to-secondaryleakageisapostulatedsteamlinebreakevent.Laboratorydataforpulledtubesfromotherplantsandmodelboilerspecimensshowlimitedleakageforindicationsunder10.0voltsduringapostulatedsteamlinebreak(SLB)condition(seeSection9.0ofWCAP-13187).AdditionalConsiderationsTheproposedamendmentwouldprecludeapproximately10manremoccupationalradiationexposurethatwouldotherwisebeincurredbyplantworkersinvolvedintubepluggingorrepairoperations.TheproposedamendmentwouldminimizethelossofmargininreactorcoolantflowthroughthesteamgeneratorinLOCAanalyses.Theproposedamendmentwouldavoidlossofmargininreactorcoolantsystemflowandthereforeassistindemonstratingthatminimumflowratesaremaintainedinexcessofthoserequiredforoperationatfullpower.Reductionintheamountoftubepluggingrequiredcanreducethelengthofplantoutagesandreduc'ethetimethatthesteamgeneratorisopentothecontainmentenvironmentduringanoutage,therebyminimizingairbornecontaminationandexposure.Inaddition,wewillperform100$bobbincoilinspectionofthehotlegtubestoidentifynewareasofconcernthatmayarisebyprovidingalevelofinserviceinspectionthatisfarinexcessofthecurrentT/Ssrequirements.
Attachment2toAEP:NRC:1166GNOSIGNIFICANTHAZARDSANALYSISPage4WehaveevaluatedtheproposedT/Schangesandhavedeterminedthattheydonotrepresentasignificanthazardsconsiderationbasedonthecriteriaestablishedin10CFR50.92(c).OperationoftheCookNuclearPlantinaccordancewiththeproposedamendmentwillnot:1)InvolveasinificantincreaseintherobabilitorconseuencesofanaccidentreviouslevaluatedTestingofmodelboilerspecimensforfreestandingtubesatroomtemperatureconditionsshowburstpressuresinexcessof5,000psiforindicationsofODSCCwithvoltagemeasurementsashighas19volts.Bursttestingperformedonpulledtubesfromotherplantswithupto10voltindicationsshowburstpressuresinexcessof5,900psiatroomtemperaturesCorrectingfortheeffectsoftemperatureonmaterialpropertiesandminimumstrengthlevels(asthebursttestingwasdoneatroomtemperature),tubeburstcapabilitysignificantlyexceedstheRG1.121criteria,requiringthemaintenanceofamarginofthreetimesnormaloperatingpressuredifferentialontubeburstifthrough-wallcracksarepresent.Basedontheexistingdatabase,thiscriteriaissatisfiedwithbobbincoilindicationswithsignalamplitudeslessthan6.8volts,regardlessoftheindicateddepthmeasurement.Thisstructurallimitisbasedona-95%lowertolerancelimit(LTL)confidencelevelofthedata.The1.0voltpluggingcriteriacomparefavorablywiththestructurallimitconsideringexpectedgrowthratesofODSCCatCookNuclearPlantUnit1.Alternatecrackmorphologiescancorrespondto6.8voltssothatauniquecracklengthisnotdefinedbyaburst-pressure-to-voltagecorrelation.However,relativeto'xpectedleakageduringnormaloperatingconditions,nofieldleakagehasbeenreportedatotherplantsfromtubeswithindicationswithavoltagelevelofunder7.7volts.Also,aqualitativeassessmentismadebetweenthebeginning-of-cycle(BOC)1.0volttubeplu'ggingcriteriaandthecurrent40$allowabletubewallpenetrationpluggingcriteriaatCookNuclearPlantUnit1.AnODSCC-degradedtubesupportplateintersectionwitha4.0voltbobbincoilresponseisexpectedto.burstatapproximately7,400psi,usingthemeancurveofFigure9-2ofWCAP-13187.Whilethe-95%LTLcurveisusedintheapplicationofthepluggingcriteria,themeancurvemustbeusedfor Attachment2toAEP:NRC:1166GPage5thisspecificcomparisoninordertoadequatelycomparethetwodatasetsused.PerVCAP-13187,acomparisonofthematerialpropertiesat650'Fandroomtemperatureconditionpropertiesshowedthattheelevatedtemperaturepropertiesareapproximately0.86oftheroomtemperatureproperties.Therefore,thetemperature-adjustedburstpressurefora4.0voltsbobbincoilindicationisexpectedtobeapproximately6,400psi.Figure11ofNUREG-0718plotstheburstpressuresofthinned0.875x0.050inchsteamgeneratortubes.At408actualuniformwallthinning,extending0.75inchinaxiallength,theburstpressureis6,800psi.TheNUREGtestdataisobtainedatatemperatureof600F,comparedtotheWestinghousedatanotedabove,whichisadjustedfor650'F.TheNUREGresultsat40$actualthinningarecomparabletothe4.0voltsBOCcriteriaexpectedburstpressure(6,800psiversus6,300psi).Theburstpressurefornon-thinnedtubeswithpartialdepthcracksupto0.75inchinlengthisslightlylowerthanforuniformthinninguptodepthsofabout60%.Also,NUREG-0718informationcanbeusedtoestimatetheburstpressureforatubewhichhasbeenslotted,simulatinganaxialcrack.Theexpectedburstpressurefora40$deep,0.75-inchlongEDMslotusingNUREG-0718isapproximately6,000psi.Therefore,itisjudgedthatthemarginofsafetycorrespondingtothecurrent40%byNDEdepthbasedpluggingcriteriaisnotsignificantlyreduceduponimplementationofa4.0voltsbobbincoilcriterion,whichishigherthanthisproposedinterimpluggingcriterionof1.0volt.Relativetotheexpectedleakageduringaccidentconditionloadings,theaccidentsthatareaffectedbyprimary-to-secondaryleakageandsteamreleasetotheenvironmentare:feedwatersystemmalfunction,lossofexternalelectricalloadand/orturbinetrip,lossofallACpowertostationauxiliaries,majorsecondarysystempipefailure,steamgeneratortuberupture,reactorcoolantpumplockedrotor,andruptureofacontrolroddrivemechanismhousing.Ofthese,themajorsecondarysystempipefailureisthemost'imitingforCookNuclearPlantUnit1inconsideringthepotentialforoff-sitedoses.Uponimplementationoftheinterimpluggingcriteria,itwillbeverifiedthatthedistributionofcrackingindicationsatthetubesupportplateintersectionsissuchthatprimary-to-secondaryleakagewouldresultinsiteboundarydoseswithinasmallfractionofthe10CFR100guideline,i.e.,30remthyroid,duringapostulatedSLBevent.Dataindicatesthata Attachment2toAEP:NRC:1166GPage6thresholdvoltageof2.8voltswouldresultinthrough-wallcrackswiththepotentialtoleakatSLBconditions.Applicationoftheproposedpluggingcriteriarequiresthatthecurrentdistributionofnumberofindicationsversusvoltagebeobtained.Theindicatedbobbincoilvoltageisthencombinedwiththerateofchangeinvoltagemeasurementtoestablishanend-of-cycle(EOC)voltagedistributionand,thus,leakrateduringSLBpressuredifferential.IfitisfoundthattheprojectedSLBleakagefordegradedintersectionsplannedtobeleftinserviceexceeds120gpm,thenadditionaltubeswillbepluggedtoreduceprojectedSLBleakagebelow120gpm.MonteCarloanalysesresultsbasedontheCookNuclearPlantUnit1growthrateandassumededdycurrentuncertaintiesindicatethatover4,000indications,allwitha(BOC)bobbincoilvoltageof2.0volts,wouldcontributelessthan1gpmleakageatSLBconditions.Basedontheinspectionresultsfromthelastoutage(1992),indicationsleftinserviceareexpectedtohaveatotalpredictedSLBleakrateof0.0gpmatEOCconditions.2)CreatetheossibilitofanewordifferentkindofaccidentfromanreviouslanalzedImplementationoftheproposedamendmentdoesnotintroduceanysignificantchangestotheplantdesignbasis.Useofthecriteriadoesnotprovideamechanismthatcouldresultinanaccidentoutsideoftheregionofthetubesupportplateelevations.Neitherasinglenormultipletuberuptureeventwouldbeexpectedinasteamgeneratorinwhichthepluggingcriteriahasbeenapplied(duringallplantconditions).ThebobbincoilsignalamplitudepluggingcriteriaisestablishedsuchthatneitheroperationalleakagenorexcessiveleakageduringapostulatedSLBconditionareanticipated.IndianaandMichiganPowerCompanywillimplementamaximumleakageratelimitof150gpd(0.1gpm)persteamgeneratortohelpprecludethepotentialforexcessiveleakageduringallplantconditionsuponapplicationoftheinterim'luggingcriteria.Thecurrenttechnicalspecificationlimitonprimary-to-secondaryleakageatoperatingconditionsisamaximumof1.0gpm"(1440gpd)forallsteamgeneratorsoramaximumof500gpdforanyonesteamgenerator.TheRG1.121criteriaforestablishingoperationalleakageratelimitsthatrequireplantshutdownarebaseduponleak-before-breakconsiderationstodetectafreespancrackbeforepotentialtuberupture,'he150 Attachment2toAEP:NRC:1166GPage7gpdlimitprovidesforleakagedetectionandplantshutdownintheeventoftheoccurrenceofanunexpectedsinglecrackresultinginleakagethatisassociatedwiththelongest:permissiblecracklength.RegulatoryGuide1.121acceptancecriteria(Item3ofSection3.2ofWCAP-13187)forestablishingoperatingleakagelimitsarebasedonleak-before-breakconsiderationssuchthatplaneshutdownisinitiatediftheleakageassociatedwiththelongestpermissiblecrackisexceeded.Thelongestpermissiblecrackisthelengththatprovidesafactorofsafetyofthreeagainstburstingatnormaloperatingpressuredifferential.Avoltageamplitudeof6.8voltsfortypicalODSCCcorrespondstomeetingthistubeburstrequirementatthe-95%LTLuncertaintylimitontheburstcorrelation.Alternatecrackmorphologiescancorrespondto6.8voltssothatauniquecracklengthisnotdefinedbytheburstpressureversusvoltagecorrelation.Consequently,typicalburstpressureversusthrough-wallcracklength'orrelationsareusedbelowtodefinethe"longestpermissiblecrack"forevaluatingoperatingleakagelimits.Thesinglethrough-wallcracklengthsthat,resultintubeburstatthreetimesnormaloperatingpressuredifferentialandSLBconditions,areabout0.44inchand0.84inch,xespectively.Nominalleakageforthesecracklengthswouldrangefrom0.1gpmto4gpm,respectively,whilelower95%confidencelevelleakrateswouldrangefromabout0.01gpmto0.5gpm,respectively.Anoperatingleakratelimitof150gpdwillbeimplementedinapplicationoftheinterimtubepluggingcriteria.Thisleakagelimitprovidesfordetectionof0.4inchlongcracksatnominalleakratesand0.6inchlongcracksatthe-95%LTLconfidencelevelleakrates.Thus,the150gpdlimitprovidesforplantshutdownpriortoreachingcriticalcracklengthsforSLBconditionsatleakrateslessthana-95$LTLconfidencelevelandforthreetimesnormaloperatingpressuredifferentialatlessthannominalleakrates.3)'nvolveasinificantreductioninamarinofsafetTheuseoftheintcrimpluggingcriteriafox'hetubesupportplateatCookNuclearPlantUnit1isdemonstratedtomaintainsteamgeneratortubeintegritycommensurate'withtherequirementsofRG1.121.RegulatoryGuide1.121describesamethodacceptabletotheNRCstaffformeetingGDC14,15,31,and32byreducingtheprobabilityofthe
~)'I~g~Attachment2toAEP;NRC;1166GPage8consequencesofsteamgeneratortuberupture.Thisisaccomplishedbydeterminingthelimitingconditionsofdegradationofsteamgeneratortubing,asestablishedbyinserviceinspection.Tubeswithunacceptablecrackingwillberemovedfromservice.Themost'imitingeffectwouldbeapossibleincreaseinleakageduringasteamlinebreakevent.Oncetheinterimpluggingcriteriaisapplied,excessiveleakageduringasteamlinebreakeventisprecludedbyverifyingthattheexpectedend-of-cycledistributionofcrackindications'tthetubesupportplateelevationswouldresultinminimalandacceptableprimary-to-secondaryleakageduringallplantconditions.Thishelpstodemonstratethatradiologicalconditionsarelessthanasmallfractionofthe10CFR100guideline.Inaddressingthecombinedeffectsofaloss-of-coolantaccident(LOCA)andasafeshutdownearthquake(SSE)onthesteamgeneratorcomponent(asrequiredbyGDC2),ithasbeendeterminedthattubecollapsemayoccurinthesteamgeneratorsatsomeplants.Thisisthecaseasthetubesupportplatesmaybecomedeformedasaresultoflateralloadsatthewedgesuppo'rtsattheperipheryoftheplateduetothecombinedeffectsoftheLOCArarefactionwaveandSSEloadings.Theresultingpressuredifferentialonthedeformedtubesmaycausesomeofthetubestocollapse.Therearetwoissuesassociatedwithsteamgeneratortubecollapse.First,thecollapseofsteamgeneratortubingreduces'theRCSflowareathroughthetubes.Thereductioninflowareaincreasestheresistancetoflowofsteamfromthe.coreduringaLOCAwhich,inturn,maypotentiallyincreasepeakcladtemperature.Second,thereisapotentialthatpartialthrough-wallcracksintubescouldprogresstothrough-wallcracksduringtubedeformationorcollapse.Consequently,sincetheleak-before-breakmethodologyisapplicabletotheCookNuclearPlantUnit1reactorcoolantsystemprimaryloops,theprobabilityofbreaksintheprimarylooppipingissufficientlylowthattheyneednot'econsideredinthestructuraldesignbasisoftheplant.ExcludingbreaksintheRCSprimaryloops,theLOCAloadsfromthelargebranchlinebreakswereanalyzedforCookNuclearPlantUnit1andwerefoundtobeofinsufficientmagnitudetoresultinsteamgeneratortubecollapseorsignificantdeformation.
Attachment,2toAEP:NRC:1166GPage9Regardlessofwhetherornotleak-before-breakisappliedtotheprimarylooppipingatCookNuclearPlantUnit1,anyflowareareductionisexpectedtobeminimal(muchlessthan1%)andPCTmarginisavailabletoaccountforthispotentialeffect.Analysesresultsshowthatnotubesnearwedgelocationsareexpectedtocollapseordeformtothedegreethatsecondary-to-primaryin-leakagewouldbeincreasedovercurrentexpectedlevels.Forallothersteamgeneratortubes,thepossibilityofsecondary-to-primaryleakageintheeventofacombinedLOCAandSSEeventisnotsignificant.Inactuality,theamountofsecondary-to-primaryleakageintheeventofacombinedLOCAandSSEisexpectedtobelessthanthatcurrentlyallowed,i.e.,500gpdpersteamgenerator.Furthermore,secondary-to-primaryin-leakagewouldbelessthanprimary-to-secondaryleakageforthesamepressuredifferentialsincethecrackswouldtendtocloseunderasecondary-to-primarypressuredifferential..Also,thepresenceofthetubesupportplateisexpectedtoreducetheamountofin-leakage.AddressingRG1.83considerations,implementationoftheinterimpluggingcriteriaissupplementedby100$inspectionrequirementsatthetubesupportplateelevationshavingODSCCindications,reducedoperatingleakratelimits,andeddycurrentinspectionguidelinestoprovideconsistencyinvoltagenormalization.Asnotedpreviously,implementationoftheinterimpluggingcriteriawilldecreasethenumberoftubeswhichmustberepairedortakenoutofservicebyplugging.TheinstallationofsteamgeneratortubeplugsreducestheRCSflowmarginand,thus,implementationoftheinterimpluggingcriteriawillmaintainthemarginofflowthatwouldotherwisebereducedintheeventofincreasedtubeplugging.Basedontheabove,itisconcludedthattheproposedchangedoesnotresultinasignificantreductioninmarginwithrespecttoplantsafetyasdefinedintheFinalSafety-AnalysisReportoranybasesoftheplantTechnicalSpecifications.CONCLUSIONBased'ontheprecedinganalysis,itisconcludedthatusingthetubesupportplateelevationbobbincoilsignalamplitudeinterimsteamgeneratortubepluggingcriteriaforremovingtubesfrom Attachment2toAEP:NRC:1166GPage10serviceatCookNuclearPlantUnit1isacceptableandtheproposedlicenseamendmentdoesnotinvolveaSignificantHazardsConsiderationasdefinedin10CFR50.92.