ML17329A420

Application for Amend to License DPR-58,revising TSs to Allow Alternate Plugging Criteria to Establish Operability of SG Tubes.Westinghouse Nonproprietary Rept WCAP-13188 & Proprietary Rept WCAP-13187 Encl.Proprietary Rept Withheld

ML17329A420
Person / Time
Site:	Cook
Issue date:	03/20/1992
From:	FITZPATRICK E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	MURLEY T E NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17329A421	List: ML17329A420 ML17329A422 ML17329A423 ML17334B415
References
AEP:NRC:1166, NUDOCS 9203260124
Download: ML17329A420 (15)

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ACCEK,ERATEDDISTMBUTIONDEMONSTPWTIONSYSTEM"f.~..p,REGULATOOINFORMATIONDISTRIBUTIONSTEM(RIDE)rkiqi"'ACCESSIONNBR:9203260124DOC.DATE:92/03/20NOTARIZED:YESDOCKETFACIL:50-315Donald,C.CookNuclearPowerPlant,Unit1,IndianaM05000315AUTH.NAMEAUTHORAFFILIATIONFITZPATRICK,E.IndianaMichiganPowerCo.(formerlyIndiana&MichiganEleRECIP.NAMERECIPIENTAFFILIATIONMURLEY,T.E.DocumentControlBra@eh(DocumentControlDesk)

SUBJECT:

ApplicationforamendtoLicenseDPR-58,revisingTSstoallowalternatepluggingcriteriatoestablishoperabilityofSGtubes.WestinghousenonproprietaryreptWCAP-131886proprietaryreptWCAP-13187encl.Proprietaryreptwithheld.DISTRIBUTIONCODE:A001DCOPIESRECEZVD:LTRIENCL+SIZERECIPIENTIDCODE/NAMEPD3-1LASTANG,JINTERNAL:NRR/DET/ECMB7DNRR/DOEA/OTSB11NRR/DST/SELB7ENRR/DST/SRXB8ECOPIESLTTRENCL1122111111111011RECIPIENTIDCODE/NAMEPD3-1PDNRR/DET/ESGBNRR/DST8E2NRR/DST/SICB8H7NUDOCS-ABSTRACTOGC/HDS2RES/DSIR/EIBCOPIESLTTRENCL1111111'111011EXTERNAL:NRCPDR1lj(jDNSIC11~NOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWAS'ONTACTTHEDOCUMENTCONTROLDESK,ROOMPI-37(EXT.20079)TOELIMINATEYOURNAMEFROMDISTRIBUTIONLISISFORDOCUMENTSYOUDON'TNEED(TOTALNUMBEROFCOPIESREQUIRED:LTTR18ENCL16 sp't~'~}

indianaMichiganPowerCompanyP.O.Box1663$Columbus,OH43216AEP:NRC:1166DonaldC.CookNuclearPlantUnit1DocketNo.50-315LicenseNo.DPR-58TECHNICALSPECIFICATIONSCHANGETOALLOWALTERNATEPLUGGINGCRITERIAU.S.NuclearRegulatoryCommissionDocumentControlDeskWashington,D.C.'20555Attn:T.E.MurleyMarch20,3.992

DearDr.Murley:

ThisletteranditsattachmentsconstituteanapplicationforamendmenttotheTechnicalSpecifications(T/Ss)forDonaldC.CookNuclearPlantUnit1inaccordancewith10CFR50.90.ThepurposeofthislicenseamendmentrequestistoobtainauthorizationtouseanalternatepluggingcriteriatoestablishoperabilityofCookNuclearPlantUnit1steamgeneratortubes.TheT/Ssnowrequiresteamgeneratortubestobepluggedorrepairedwhenthedegradationexceeds40%tubewallpenetrationasdeterminedbynon-destructiveexamination.'ebelievethatflawindicationswithintheboundsofthetubesupportplatewithabobbinvoltagelessthanorequalto1.5voltsmayremaininservice.Flawindicationsgreaterthan1.5voltsbutlessthanorequalto4.0voltsmayremaininserviceifarotatingpancakecoil(RPC)probeinspectionverifiesthataxialouterdiameterstresscorrosioncracking(ODSCC)isthedegradationmechanism.Flawindicationswithavoltagegreaterthan4.0voltswillbepluggedorrepaired.Wealsobelievethatatubecanremaininserviceifthesignalamplitudeislessthanorequalto4.0volts,regardlessofthedepthofpenetration,iftheprojectedend-of-cycledistributionofcrackindicationsisverifiedtoresultinprimary-to-secondaryleakagelessthan120gpminonesteamgeneratorduringapostulatedsteamlinebreak.WestinghouseWCAP-13187,"D.C.CookUnit1SteamGeneratorTubePluggingCriteriaforIndicationsatTubeSupportPlates,"providesthedevelopmentofthe4.0voltalternatepluggingcriteria.92032b0124920320PDRADOCK05000315FDR(g))~g~/QZrip'ease/foal&/inP Dr.T~E.Murley-2-AEP:NRC;1166AdetaileddescriptionoftheproposedchangesandouranalysesconcerningsignificanthazardsconsiderationsareincludedinAttachment1tothisletter.Attachment2containstheproposedrevisedT/Sspages.Attachment3containsthemarked-upcopiesoftheexi.stingT/Ss.TheWestinghousereports,WCAP-13187,"D.C,CookUnit1SteamGeneratorTubePluggingCriteriaforIndicationsatTubeSupportPlates"(Proprietary),andWCAP-13188,"D.C.CookUnit1SteamGeneratorTubePluggingCriteriaforIndicationsatTubeSupportPlates"(Non-Proprietary),areinAttachment4.EnclosedinAttachment5areaWestinghouseauthorizationletter,CAW-92-282,accompanyingaffidavit,ProprietaryInformationNotice,andCopyrightNotice.BecauseWCAP-13187containsinformationproprietarytoWestinghouseElectricCorporation,itissupportedbyanaffidavitsignedbyWestinghouse,the.owneroftheinformation.TheaffidavitsetsforththebasisonwhichtheinformationmaybewithheldfrompublicdisclosurebytheCommissionandaddresseswithspecificitytheconsiderationslistedinparagraph(b)(4)ofSection2790oftheCommission'sregulations.Accordingly,itisrespectfullyrequestedthattheinformationwhichisproprietarytoWestinghousebewithheldfrompublicdisclosureinaccordancewith10CFRSection2790oftheCommission'sregulations.CorrespondencewithrespecttothecopyrightorproprietaryaspectsoftheitemslistedaboveorthesupportingWestinghouseaffidavitshouldreferenceCAW-92-282andshouldbeaddressedtoN.Liparulo,ManagerofNuclearSafetyandRegulatoryActivities,WestinghouseElectricCorporation,P.0.Box355,Pittsburgh,Pennsylvania15230-0355.Webelievethattheproposedchangeswillnotresultin(1)asignificantchangeinthetypesofeffluentsorasignificantincreaseintheamountofanyeffluentsthatmaybereleasedoffsite,or(2)asignificantincreaseinindividualorcumulativeoccupationalradiationexposure.TheseproposedchangeshavebeenreviewedbythePlantNuclearSafetyReviewCommitteeandwillbereviewedbytheNuclearSafetyandDesignReviewCommitteeattheirnextregularlyscheduledmeeting.Incompliancewiththerequirementsof10CFR50.91(b)(1),copiesofthisletteranditsattachmentshavebeentransmittedtotheMichiganPublicServiceCommissionandtheNFEMSectionChief.Pleasecontactusifyouhaveanyquestionsconcerningthislicenseamendmentrequest.NuclearRegulatoryCommissionstaffreviewand Dr.T.E.Murley-3-AEP:NRC:1166approvalofthesechangesarerequestedpriortoMay22,1992.ThisistheminimumamountoftimenecessarytoprepareforimplementationofthealternatepluggingcriteriaduringtheUnit1refuelingoutagebeginningapproximatelyJune23,1992.ThisdocumenthasbeenpreparedfollowingCorporateproceduresthatincorporateareasonablesetofcontrolstoensureitsaccuracyandcompletenesspriortosignaturebytheundersigned.Sincerely,VicePresidentehAttachmentscc:D.H.Williams,Jr.A.A.Blind-BridgmanJ.R.PadgettG.CharnoffA.B.Davis-RegionIIINRCResidentInspector-BridgmanNFEMSectionChief ATTACHMENT1toAEP:NRC:1166NOSIGNIFICANTHAZARDSCONSIDERATIONEVALUATIONINSUPPORTOPTHEALTERNATEPLUGGINGCRITERIA Attachment1toAEP:NRC:1166INTRODUCTIONPage1Alicenseamendmentisproposedtoprecludeunnecessarilypluggingsteamgeneratortubesduetotheoccurrenceofouterdiameterinitiatedstresscorrosioncracking(ODSCC)atthetubesupportplatesintheCookNuclearPlantUnit1steamgenerators.UsingtheexistingTechnicalSpecifications(T/Ss)steamgeneratortubepluggingcriteriaof40%tubewallpenetrationasdeterminedbynon-destructiveexamination(NDE),manyofthetubeswithcrackindicationswouldneedlesslyhavetoberemovedfromservice.ThealternatepluggingcriteriafortubesupportplateelevationODSCCoccurringintheCookNuclearPlantUnit1steamgeneratorsmayresultintubeswithbothpartialandthrough-wallcracksreturningtoservice.Inthelimitingcase,itisdemonstratedthatthepresenceofthrough-wallcracksaloneisnotreasonenoughtoremoveatubefromservice.DESCRIPTIONOFTHEAMENDMENTREQUESTAsrequiredby10CFR50.91(a)(1),ananalysisis,providedtodemonstratethattheproposedlicenseamendmenttoimplementanalternatesteamgeneratortubepluggingcriteriaforthetubesupportplateelevationsatCookNuclearPlantUnit1involvesnosignificanthazardsconsiderations.Thealternatepluggingcriteriainvolvesacorrelationbetweeneddycurrentbobbincoilsignalamplitude(voltage)andtubeburst.andleakagecapability.Thepluggingcriteriaisbasedontestingoflaboratory-inducedODSCCspecimens,extensiveexaminationofpulledtubesfromoperatingsteamgenerators(industryvide),andfieldexperiencefromleakageduetoindicationsatthetubesupportplates(worldvide).Specifically,crackindicationswithbobbincoilvoltageslessthanorequalto4.0volts,regardlessofindicateddepth,donotrequireremedialactionifpostulatedsteamlinebreakleakagecanbeshowntobeacceptable.Crackindicationswithbobbincoilsignalamplitudesexceeding4.0voltsmustbeeitherpluggedorrepaired.Bobbincoilsignalamplitudesgreaterthan1.5volts,ifleftinserviceatthediscretionoftheowner,mustbeinspectedusingamotorizedrotatingpancakecoil(RPC).TheproposedamendmentwouldmodifyT/Ss3.4.5"SteamGenerators,"3.4.6,"ReactorCoolantSystemLeakage,"andtheassociatedbases.TheseproposedchangesprovidetubeinspectionrequirementsandacceptancecriteriatodeterminethelevelofdegradationforwhichatubeexperiencingODSCCatthetubesupportplateelevationsmayremaininserviceintheCookNuclearPlantUnit1steamgenerators.

Attachment1toAEP:NRC:1166EVALUATIONSteamGeneratorTubeInteritDiscussioPage2Inthe.developmentofthealternatepluggingcriteria,RegulatoryGuides(RG)1.121,"BasesforPluggingDegradedPWRSteamGeneratorTubes,"and1.83"InserviceInspectionofPWRSteamGeneratorTubes,"areusedasthebasesfordeterminingthatsteamgeneratortubeintegrityconsiderationsaremaintainedwithinacceptablelimits.RegulatoryGuide1.121describesamethodacceptabletotheNRCstaffformeetingGeneralDesignCriteria2,4,14,15,31,and32byreducingtheprobabilityandconsequencesofsteamgeneratortuberupturethroughdeterminingthelimitingsafeconditionsoftubewalldegradation.Tubeswithunacceptablecracking,asestablishedbyinserviceinspection,shouldberepairedorremovedfromservicebyplugging.ThisRGusessafetyfactorsonloadsfortubeburstthatareconsistentwiththerequirementsofSectionIIIoftheASMECode.ForthetubesupportplateelevationdegradationoccurringintheCookNuclearPlantUnit1steamgenerators,tubeburstcriteriaareinherentlysatisfiedduringnormaloperatingconditionsbythepresenceofthetubesupportplate.Thepresenceofthetubesupportplateenhancestheintegrityofthedegradedtubesinthatregionbyprecludingtubedeformationbeyondthediameterofthedrilledhole.Itisnotcertainwhetherthetubesupportplatewouldfunctiontoprovideasimilarconstrainingeffectduringaccidentconditionloadings.Therefore,nocreditistakeninthedevelopmentofthepluggingcriteriaforthepresenceofthetubesupportplateduringaccidentconditionloadings.Conservatively,basedontheexistingdatabase,bursttestingshowsthatthesafetyrequirementsfortubeburstmarginsduringbothnormalandaccidentconditionloadingscanbesatisfiedwithbobbincoilsignalamplitudeslessthan6.8volts,regardlessofthedepthoftubewallpenetrationofthecracking.RegulatoryGuide1.83describesamethodacceptabletotheNRCstaffforimplementingGDC14,15,31,and32throughperiodicinserviceinspectionforthedetectionofsignificanttubewalldegradation.Uponimplementationofthepluggingcriteria,tubeleakageconsiderationsmustalsobeaddressed.Itmustbedeterminedthatthecrackswillnotleakexcessivelyduringallplantconditions.ForthealternatetubepluggingcriteriadevelopedfortheCookNuclearPlantUnit1steamgeneratortubes,littleornoleakageisexpectedduringnormaloperatingconditionsevenwiththepresenceofthrough-wallcracks.Industrywide,thecrackmorphologyofSCCattubesupportplateintersectionsisbestdescribedasashort,tight,axiallyorientedmicrocrackseparatedbyligamentsofnon-degradedmaterial.Thesamemorphologyisjudgedtobepresent Attachment1toAEP:NRC:1166Page3intheCookNuclearPlantUnit1steamgenerators.Tubepullexaminationresultsfrom1983indicatedaxialSCCinitsearlystages.Thedepthsoftheevidenceddegradation(determinedbydestructiveexam)showedthemaximumdepthofpenetrationtobeapproximately10%through-wall.TheRPCtestingperformedduringthe1989outagehasconfirmedthataxiallyorientedSCCcracksexistatthetubesupportplateintersections.BasedontheRPCtestingresultsandrelativelysmallamplitudebobbinvoltagescoupledwithlowbobbinvoltagegrowthrates,itisconcludedthataxiallyorientedODSCCbestdefinesthedegradationmorphologyoccurringattheCookNuclearPlantUnit1tubesupportplateintersections.Additionaltubeswill'epulledduringthenextrefuelingoutage(summer1992)fordestructiveexaminationtoconfirmthetubedegradationphenomenaoccurringatthetubesupportplates.Noleakageduringnormaloperatingconditionshasbeenobservedinthefieldatsimilarplantsforcrackindicationswithsignalamplitudeslessthan7.7volts.Additionally,noprimary-to-secondaryleakageatthetubesupportplatehasbeendetectedinU.S.plants.Relative.totheexpectedleakageduringaccidentconditionloadings,thelimitingeventwithrespecttoprimary-to-secondaryleakageisapostulatedsteamlinebreakevent.Laboratorydataforpulledtubesfromotherplantsandmodelboilerspecimensshowlimitedleakageforindicationsunder10.0voltsduringapostulatedSLBcondition(SeeSection9,0ofWCAP-13187).AdditionalConsiderationsTheproposedamendmentwouldprecludeapproximately10manremoccupationalradiationexposurethatwouldotherwisebeincurredbyplantworkersinvolvedintubepluggingorrepairoperations.TheproposedamendmentwouldminimizethelossofmargininreactorcoolantflowthroughthesteamgeneratorinLOCAanalyses.Theproposedamendmentwouldavoidlossofmargininreactorcoolantsystemflowandthereforeassistindemonstratingthatminimumflowratesaremaintainedinexcessofthoserequiredforoperationatfullpower.Reductionintheamountoftubepluggingrequiredcanreducethelengthofplantoutagesandreducethetimethatthesteamgeneratorisopentothecontainmentenvironmentduringanoutage,therebyminimizingairbornecontaminationandexposure.Inaddition,therequired100%bobbincoilinspectiontobeperformedateachoutageasoutlinedinWCAP-13187willhelptoidentifynewareasofconcernwhichmayariseby.providingalevelofinserviceinspectionthatisfarinexcessofthecurrentT/Ssrequirements.

Attachment1toAEP:NRC:1166NOSIGNIFICANT1ULEARDSANALYSISPage4VehaveevaluatedtheproposedT/Sschangeandhavedeterminedthatitdoesnotrepresentasignificanthazardsconsiderationbasedonthecriteriaestablishedin10CFR50.92(c).OperationoftheCookNuclearplantinaccordancewiththeproposedamendmentwillnot:InvolveasinificantincreaseitherobabilitorconseuencesofanaccidetrevousevauatedTestingofmodelboilerspecimensforfreestandingtubesatroomtemperatureconditionsshowburstpressuresinexcessof5000psiforindicationsofODSCCwithvoltagemeasurementsashighas19volts.Bursttestingperformedonpulledtubesfromotherplantswithupto10voltindicationsshowburstpressuresinexcessof5900psiatroomtemperature.Correctingfortheeffectsoftemperatureonmaterialpropertiesandminimumstrengthlevels(asthebursttestingwasdone,atroomtemperature),tubeburstcapabilitysignificantlyexceedstheRG1.121criteria,requiringthemaintenanceofamarginofthreetimesnormaloperatingpressuredifferentialontubeburstifthrough-wallcracksarepresent.Basedontheexistingdatabase,thiscriteriaissatisfiedwithbobbincoilindicationswithsignalamplitudeslessthan6.8volts,regardlessoftheindicateddepthmeasurement.Thisstructurallimitisbasedona-95%lowertolerancelimit(LTL)confidencelevelofthedata.The4.0voltpluggingcriteriacomparesfavorablywiththestructurallimitconsideringexpectedgrowthratesofODSCCatCookNuclearPlantUnitl.Alternatecrackmorphologies'ancorrespondto6.8voltssothatauniquecracklengthisnotdefinedbyaburst-pressure-to-voltagecorrelation.However,relativetoexpectedleakageduringnormaloperatingconditions,nofieldleakagehasbeenreportedatotherplantsfromtubeswithindicationswithavoltagelevelofunder7.7volts(ascomparedtothe4.0voltproposedalternatetubepluggingcriteriaproposedinthissubmittal).Also,aqualitativeassessmentismadebetweenthebeginning-of-cycle(BOC)4.0volttubepluggingcriteriaandthecurrent40%allowabletubewallpenetrationpluggingcriteriaatCookNuclearPlantUnit1.AnODSCC-degradedtubesupportplateintersectionwitha4.0voltbobbincoilresponseisexpectedtoburstatapproximately7400psi,usingthemeancurveofFigure9-2ofWCAP-13187.Whilethe-95'tLTLcurveisusedintheapplicationofthepluggingcriteria,themeancurvemustbeusedforthisspecificcomparisoninordertoadequatelycomparethetwodatasetsused.PerWCAP-13187, Attachment1toAEP:NRC:1166Page5acomparisonofthematerialpropertiesat650Pandroomtemperatureconditionpropertiesshowedthattheelevatedtemperaturepropertiesareapproximately0.86oftheroomtemperatureproperties.Therefore,thetemperature-adjustedburstpressurefora4.0voltbobbincoilindicationisexpectedtobeapproximately6400psi.FigurellofNUREG-0718plotstheburstpressuresofthinned0.875x0,050inchsteamgeneratortubes.At40%actualuniformwallthinning,extending0.75inchinaxiallength,theburstpressureis6800psi.TheNUREQtestdataisobtainedatatemperatureof600P,comparedtotheWestinghousedatanotedabove,whichisadjustedfor650F.TheNUREGresultsat40%actualthinningarecomparabletothe4.0voltBOCcriteriaexpectedburstpressure(6800psiversus6300ps+.Theburstpressurefornon-thinnedtubeswithpartialdepthcracksupto0.75inchinlengthisslightlylowerthanforuniformthinninguptodepthsofabout60%.Also,NUREG-0718informationcanbeusedtoestimatetheburstpressureforatubewhichhasbeenslotted,simulatinganaxialcrack.Theexpectedburstpressurefora40%deep,0.75inchlongEDMslotusingNUREQ-0718isapproximately6000psi.Therefore,itisjudgedthatthemarginofsafetycorrespondingtothecurrent40'%yNDEdepthbasedpluggingcriteriaisnotsignificantlyreduceduponimplementationofthebobbincoilvoltagecriteriaat.CookHuclearPlantUnit1.Relativetotheexpectedleakageduringaccidentconditionloadings,theaccidentsthatareaffectedbyprimary-to-secondaryleakageandsteamreleasetotheenvironmentare:feedwatersystemmalfunction,lossofexternalelectricalloadand/orturbinetrip,lossofallACpowertostationauxiliaries,majorsecondarysystempipefailure,steamgeneratortuberupture,reactorcoolantpumplockedrotor,andruptureofacontrolroddrivemechanismhousing.Ofthese,themajorsecondarysystempipefailureisthemostlimitingforCookHuclearPlantUnit1inconsideringthepotentialforoff-sitedoses.Uponimplementationofthealternatepluggingcriteria,itwillbeverifiedonacycle-by-cyclebasisthatthedistributionofcrackingindicationsatthetubesupportplateintersectionsissuchthatprimary-to-secondaryleakagewouldresultinsiteboundarydoseswithinasmallfractionofthe10CFR100guideline,i.e.,30remthyroid,duringapostulatedsteamlinebreakevent.Dataindicatesthatathresholdvoltageof2.8voltswouldresultinthrough-wallcrackswiththepotentialtoleakatsteam'inebreak(SLB)conditions.Applicationofthe Attachment1toAEP:NRC:1166Page6proposedpluggingcriteriarequiresthatthecurrentdistributionofnumberofindicationsversusvoltagebeobtainedduringeachrefuelingoutage.Theindicatedbobbincoilvoltageisthencombinedwiththerateofchangeinvoltagemeasurementtoestablishanend-of-cycle(EOC)voltagedistributionand,thus,leakrateduringSLBpressuredifferential.IfitisfoundthattheprojectedSLBleakagefordegradedintersectionsplannedtobeleftinserviceexceeds120gpm,thenadditionaltubeswillbepluggedtoreduceprojectedSLBleakagebelow120gpm.MonteCarloanalysesresultsbasedontheCookNuclearPlantUnit1growthrateandassumededdycurrentuncertaintiesindicatethatover4000indications,allwitha(BOC)bobbincoilvoltageof2.0volts,'ouldcontributelessthan1gpmleakageatSLBconditions.Basedontheinspectionresultsfromthelastoutage(1990),indicationsleftinserviceareexpectedtohaveatotalpredictedSLBleakrateof0.1gpmatEOCconditions.2)Createtheossibilitoanewordifferentkindofaccidentfromanreviousanal@edImplementationoftheproposedamendmentdoesnotintroduceanysignificantchangestotheplantdesignbasis.Useofthecriteriadoesnotprovideamechanismthatcouldresultinanaccidentoutsideoftheregionofthetubesupportplateelevations.Neitherasinglenormultipletuberuptureeventwouldbeexpectedinasteamgeneratorinwhichthepluggingcriteriahasbeenapplied(duringallplantconditions).Thebobbincoilsignalamplitudepluggingcriteriaisestablishedsuchthatneitheroperationalleakagenorexcessiveleakageduringapostulatedsteamlinebreakconditionareanticipated.IndianaandMichiganPowerCompanywillimplementamaximumleakageratelimitof150gpd(0.1gpm)persteamgeneratortohelpprecludethepotentialforexcessiveleakageduringallplantconditionsuponapplicationofthealternatepluggingcriteria.Thecurrenttechnicalspecificationlimitonprimary-to-secondaryleakageatoperatingconditionsisamaximumof1.0gpm(1440gpd)forallsteamgeneratorsoramaximumof500gpdforanyonesteamgenerator.TheRG1.121criteriaforestablishingoperationalleakageratelimitsthatrequireplantshutdownarebaseduponleak-before-breakconsiderationstodetectafreespancrackbeforepotentialtuberupture.The150gpdlimitprovidesforleakagedetectionandplantshutdownintheeventoftheoccurrenceofanunexpectedsinglecrackresultinginleakagethatis Attachment1toAEP:NRC:1166Page7'egulatoryGuide1.121acceptancecriteria(Item3ofSection3.2ofWCAP-13187)forestablishingoperatingleakagelimitsarebasedonleak-before-breakconsiderationssuchthatplantshutdownisinitiatediftheleakageassociatedwiththelongestpermissiblecrackisexceeded.Thelongestpermissiblecrackisthelengththatprovidesafactorofsafetyofthreeagainstburstingatnormaloperatingpressuredifferential,Avoltageamplitudeof6.8voltsfortypicalODSCCcorrespondstomeetingthistubeburstrequirementatthe-95%LTLuncertaintylimitontheburstcorrelation.Alternatecrackmorphologiescancorrespondto6.8voltssothatauniquecracklengthisnotdefinedbytheburstpressureversusvoltagecorrelation.Consequently,typicalburstpressureversusthrough-wallcracklengthcorrelationsareusedbelowtodefinethe"longestpermissiblecrack"forevaluatingoperatingleakagelimits.Thesinglethrough-wallcracklengthsthatresultintubeburstatthreetimesnormaloperatingpressuredifferentialandSLBconditionsareabout0.44inchand0.84inch,respectively.Nominalleakageforthesecracklengthswouldrangefrom0.1gpmto4gpm,respectively,whilelower95'tconfidencelevelleakrateswouldrangefromabout0.01gpmto0.5gpm,respectively.Anoperatingleakratelimitof150gpdwi11beimplementedinapplicationofthealternatetubepluggingcriteria.Thisleakagelimitprovidesfordetectionof0.4inchlongcracksatnominalleakratesand0.6inchlongcracksatthe-95tLTLconfidencelevelleakrates.Thus,the150gpdlimitprovidesforplantshutdownpriortoreachingcriticalcracklengthsforSLBconditionsatleakrateslessthana-95tLTLconfidencelevelandforthreetimesnormaloperatingpressuredifferentialatlessthannominalleakrates.3)InvolveasinificantreductioninamarinofsafetTheuseofthealternatepluggingcriteriaatCookNuclearPlantUnit1isdemonstratedtomaintainsteamgeneratortubeintegritycommensuratewiththerequirementsofRG1.121.RegulatoryGuide1.121describesamethodacceptabletotheNRCstaffformeetingGDCs14,15,31,and32byreducingtheprobabilityoftheconsequencesofsteamgeneratortuberupture.Thisisaccomplishedbydeterminingthelimitingconditionsofdegradationofsteamgeneratortubing,asestablishedbyinserviceinspection.Tubeswithunacceptablecrackingshouldberemovedfromservice.Themostlimitingeffectwouldbeapossibleincreaseinleakageduringasteam Attachment1toAEP;NRC:1166Page8linebreakevent.Oncethealternatepluggingcriteriaisapplied,excessiveleakageduringasteamlinebreakeventisprecludedbyverifyingeachfuelcyclethattheexpectedend-of-cycledistributionofcrackindicationsatthetubesupportplateelevationswouldresultinminimalandacceptableprimary-to-secondaryleakageduringallplantconditions.Thishelpstodemonstrateradiologicalconditionsarelessthanasmallfractionofthe10CFR100guideline.Inaddressingthecombinedeffectsofaloss-of-coolantaccident(LOCA)andasafeshutdownearthquake(SSE)onthesteamgeneratorcomponent(asrequiredbyGDC2),ithasbeendeterminedthattubecollapsemayoccurinthesteamgeneratorsatsomeplants.ThisisthecaseasthetubesupportplatesmaybecomedeformedasaresultoflateralloadsatthewedgesupportsattheperipheryoftheplateduetothecombinedeffectsoftheLOCArarefactionwaveandSSEloadings.Theresultingpressuredifferentialonthedeformedtubesmaycausesomeofthetubestocollapse.Therearetwoissuesassociatedwithsteamgeneratortubecollapse.First,thecollapseofsteamgeneratortubingreducestheRCSflowareathroughthetubes.ThereductioninflowareaincreasestheresistancetoflowofsteamfromthecoreduringaLOCAwhich,inturn,maypotentiallyincreasepeakcladtemperature.Second,thereisapotentialthatpartialthrough-wallcracksintubescouldprogresstothrough-wallcracksduringtubedeformationorcollapse.Consequently,sincetheleak-before-breakmethodologyisapplicabletotheCookNuclearPlantUnit1reactorcoolantsystemprimaryloops,theprobabilityofbreaksintheprimarylooppipingissufficientlylowthattheyneednotbeconsideredinthestructuraldesignbasisoftheplant.ExcludingbreaksintheRCSprimaryloops,theLOCAloadsfromthelargebranchlinebreakswereanalyzedforCookNuclearPlantUnit1andwerefoundtobeofinsufficientmagnitudetoresultinsteamgeneratortubecollapseorsignificantdeformation.Regardlessofwhetherornotleak-before-breakisappliedtotheprimarylooppipingatCookNuclearPlantUnit1,anyflowareareductionisexpectedtobeminimal(muchlessthan1t)andPCTmarginisavailabletoaccountforthispotentialeffect.Analysesresultsshowthatnotubesnearwedgelocationsareexpectedtocollapseordeformtothedegree Attachment1toAEP:NRC:1166Page9thatsecondary-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,implementationofthealternatepluggingcriteriaissupplementedby100%inspectionrequirementsatthetubesupportplateelevationshavingODSCCindications,reducedoperatingleakratelimits,eddycurrentinspectionguidelinestoprovideconsistencyinvoltagenormalization,androtatingpancakecoilinspectionrequirementsforthelargerindicationsleftinservicetocharacterizetheprincipaldegradationmechanismasODSCC.Asnotedpreviously,implementationofthealternatepluggingcriteriawilldecreasethenumberoftubeswhichmustberepairedortakenoutofservicebyplugging.TheinstallationofsteamgeneratortubeplugsreducestheRCSflowmarginand,thus,implementationofthealternatepluggingcriteriawillmaintainthemarginofflowthatwouldotherwisebereducedintheeventofincreasedtubeplugging.Basedontheabove,itisconcludedthattheproposedchangedoesnotresultinasignificantreductioninmarginwithrespecttoplantsafetyasdefinedintheFinalSafetyAnalysisReportoranybasesoftheplantTechnicalSpecifications.CONCLUSIONBasedontheprecedinganalysis,itisconcludedthatusingthetubesupportplateelevationbobbincoilsignalamplitudealternatesteamgeneratortubepluggingcriteriaforremovtngtubesfromserviceatCookNuclearPlantUnit1isacceptableandtheproposedlicenseamendmentdoesnotinvolveaSignificantHazardsConsiderationasdefinedin10CFR50.92.