ML17332A751

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Application for Amend to License DPR-58,incorporating 2.0 Volt Interim SG Tube Support Plate Plugging Criterion for Fuel Cycle 15
ML17332A751
Person / Time
Site: Cook American Electric Power icon.png
Issue date: 04/25/1995
From: FITZPATRICK E
INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17332A752 List:
References
AEP:NRC:1166R, NUDOCS 9505010273
Download: ML17332A751 (27)
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Text

RIORITY1CCELERATED RIDSPROCI'.SSIi G)REGULATORY INFORMATION DISTRIBUTION SYSTEM(RIDS)ACCESSION NBR:9505010273 DOC.DATE:

95/04/25NOTARIZED:

NODOCKETFACIL:50-315 DonaldC.CookNuclearPowerPlant,Unit1,IndianaM05000315AUTH.NAMEAUTHORAFFILIATION FITZPATRICK,E.

IndianaMichiganPowerCo.(formerly Indiana&MichiganEleRECIP.NAME RECIPIENT AFFILIATION DocumentControlBranch(Document ControlDesk)

SUBJECT:

Application foramendtolicenseDPR-58,incorporating 2.0voltinterimSGtubesupportplatepluggingcriterion forfuelcycle15.DISTRIBUTION CODE:AOOIDCOPIESRECEIVED:LTR JENCLLSIZE:I++8-TITLE:ORSubmittal:

GeneralDistribution NOTESRECIPIENT IDCODE/NAME PD3-1LAHICKMAN,J INTERNA~@IL~ENPEI NRR/DE/EMCB NRR/DSSA/SPLB NUDOCS-ABSTRACT EXTERNAL:

NOACCOPIESLTTRENCL11111111111111RECIPIENT IDCODE/NAME PD3-1PDNMSS/DWM/LLDP NRR/DRCH/HICB NRR/DSSA/SRXBOGC/HDS2NRCPDRCOPIESLTTRENCL112211111011ENVOTETOALL"RIDS"RECIPIEV'TS:

PLEASEHELPUSTOREDUCEO'KSTE!COVTACT'I'IIEDOC!:KIEV.

I'OVTROLDESK,ROOKIPI-37(EXT.504-OS3)TOELDIIiATE YOURNAi!L'ROil DISI'RIBUTION LIS'ISI:ORDOCUh,IEi'I'S YOUDOi"I'L'I'.D!

TOTALNUMBEROFCOPIESREQUIRED:

LTTR14ENCL13 itjC IndianaMichiganPowerCompanyP.O.Box16631Columbus, OH432168April25,i995DocketNos'0-315AEP:NRC:1166R U.S.NuclearRegulatory Commission ATTN:DocumentControlDeskWashington, D.C.20555Gentlemen:

DonaldC.CookNuclearPlantUnit1TECHNICAL SPECIFICATION CHANGESTOINCORPORATE

2.0 VOLTINTERIMSTEAMGENERATOR

TUBESUPPORTPLATEPLUGGINGCRITERION FORFUELCYCLE15Thisletteranditsattachments providesupplemental information inresponsetotheMarch15,1995,telephone discussions withyourstaffregarding ourFebruary3,1995,letter,AEP:NRC:1166Q, concerning application foramendment tothetechnical specifications (T/Ss)ofDonaldC.CookNuclearPlantUnitl.Specifically, thissupplemental information addresses theapplicable requirements ofdraftNRCGenericLetter(GL)94-XX,"Voltage-BasedRepairCriteriafortheRepairofWestinghouse SteamGenerator TubesAffectedbyOutsideDiameterStressCorrosion Cracking."

Foryourconvenience, allattachments previously submitted withAEP:NRC:1166Q arebeingre-submitted andsupersede thosecontained inthatsubmittal.

Attachment 1providesatechnical summaryofthespecificinspection practices andcalculational methodologies outlinedinGL94-XXthatwillbeappliedtotheUni.t1interimpluggingcriteriaprogramandthe10CFR50.92nosignificant hazardsevaluation.

Theevaluation andresultssupportcontinued useof2voltinterimpluggingcriteriaforfuelcycle15.Attachment 2containsexistingT/Spagesmarkedtoreflecttherequested changes.Attachment 3providestheproposedrevisedT/Spages./95050i0273 950425PDRADOCK05000315PDR J45 U.S.NuclearRegulatory Commission Page2AEP:NRC:1166R Webelievetheproposedchangeswillnotresultin(1)asignificant changeinthetypesofanyeffluentthatmaybereleasedoffsite,or(2)asignificant increaseinindividual orcumulative occupational radiation exposure.

TheseproposedchangeshavebeenreviewedbythePlantNuclearSafetyReviewCommittee andwillbereviewedbytheNuclearSafetyandDesignReviewCommittee atthenextregularly scheduled meeting.Incompliance withtherequirements of10CFR50.91(b)(1),

copiesofthisletteranditsattachments havebeentransmitted totheMichiganPublicServiceCommission andtotheMichiganDepartment ofPublicHealth.TheT/SpagesaffectedbythoseproposedchangesarealsoimpactedbytheT/Spagessubmitted withourApril13,1995,letterAEP:NRC:1129D, UseofLaserWeldedSleevesforSteamGenerator Tubes.Sincerely, E.E,Fitzpatrick VicePresident SWORNTOANDSUBSCRIBED BEFOREMETHIS4~DAYOF1995NoryPublicehAttachments cc:A.A.BlindG.CharnoffJ.B.MartinNFEMSectionChiefNRCResidentInspector

-BridgmanJ.R.Padgett f't4V'tr~va4 ATTACHMENT 1TOAEP:NRC:1166R DESCRIPTION OFCHANGESTOTHEDONALDC.COOKNUCLEARPLANTUNIT1TECHNICAL SPECIFICATIONS 10CFR50.92EVALUATION

/~J,~II~&~I~-n~

PsAttachment 1toAEP:NRC:1166R Page1I.INTRODUCTION Thisamendment requestproposesachangetoCookNuclearPlantUnit1steamgenerators (SG)T/Ss4.4.5.2,4.4.5.3,4.4.5.4,4.4.5.5,3.4.6.2andBases3/4.4.5and3/4.6.2toallowcontinued useofSGtubesupportplateinterimpluggingcriteria(IPC)forfuelcycle15.Becauseofthechanges,textshiftandrepagenation arerequired.

ThechangeallowsSGtubeswithbobbincoileddycurrentindications lessthanorequalto2voltsattubesupportplateintersections toremaininservice,regardless ofapparentdepthoftubewallpenetration, ifasaresult,theprojected end-of-cycle (EOC)distribution ofcrackindications isshowntoresultinprimary-to-secondary leakagelessthan12.6gpminthefaultedloopduringapostulated steamlinebreakevent.Indications greaterthan2voltsbutlessthanorequalto5.6voltsmayremaininserviceifamotorized rotatingpancakecoil(MRPC)probeinspection doesnotdetectdegradation.

Thisamendment, specifictofuelcycle15,wouldreducethenumberofSGtubespluggedduetoindications atsupportplateintersections.

ReducingthenumberofpluggedtubesprovidesAD@Abenefitsandmaintains reactorcoolantsystem(RCS)flowmargin.Anassessment reportaddressing theeffectiveness oftheIPCmethodology described inWCAP-13187, Revision0,wascompleted following fuelcycle13andreportedinsubmittal documentAEP:NRC:1166J.

Thereportconcluded thatthevoltagedistribution foundbyinspection atEOC13in1994isingoodagreement withtheprojections madeatEOC12in1992.Thevoltagegrowthratescontinuetobeverysmall,withamaximumgrowthof0.4voltsforfuelcycle13comparedto0.49voltsforfuelcycle12.Notubeswerefoundforwhichthebobbincoilvoltageexceededthe2voltIPCrepairlimitatEOC13.Themaximumprojected EOC14voltagebasedonEOC13voltagedistribution is2.0voltsusingtheNRCmodeland1.9voltsusingtheindustrymodel.Considering theresultsofthisreport,continuation of2voltIPCisjustified forfuelcycle15.Similarassessment andprojection reportswillbepreparedatEOC14basedonGL94-XXreporting requirements.

II'PPLICATION OFDRAFTGL94-XXREUIREMENTS TOTHCOOKNUCLARPLANTUNIT1SGIPCLICENSEAMENDMENT REVESTFORCYCLE15TheCookNuclearPlantUnit1,2voltIPCwillbeimplemented pertheguidanceofGL94-XXalongwiththelatestindustrydataforburstandleakagedatabases.NRCGL94-XXwillbefactoredintotheCookNuclearPlantUnit1IPCasfollows:

Attachment 1toAEP:NRC:1166R Page2Analystswillbebriefedregarding thepossibility ofprimarywaterstresscorrosion cracking(PWSCC)attubesupportplateintersections.

IfPWSCCisfoundatthesupportplateintersections itwillbereportedtotheNRCstaffpriortostartup.2)Thesupporting datasetsforcalculation ofburstprobability andestimation ofprimarytosecondary leakageduringapostulated mainsteamlinebreakwillbethoselistedinSections2.a.land2.b.3(1),

respectively, oftheGL.3)Mainsteamlineburstprobability andleakagecalculations willbeperformed following theguidanceofGL94-XX,Section2,"TubeIntegrity Evaluation."

Calculations performed insupportofthevoltage-based repaircriteriawillfollowthemethodology described inWCAP-14277, "SteamLineBreakLeakRateandTubeBurstProbability AnalysisMethodsforOutsideDiameterStressCorrosion CrackingatTubeSupportPlateIntersections,"

datedJanuary1995'hecalculations willbeperformed priortoreturning theSGstoserviceusingtheas-foundEOC14voltagedistribution.

Theprojected EOC15voltagedistribution resultswillbereportedinthe90dayreport.Nodistribution cutoffwillbeappliedtothevoltagemeasurement variability distribution forcalculation oftheprojected EOCvoltagedistribution.

4)Inspection scope,dataacquisition, anddataanalysiswillbeperformed following theguidanceofGL94-XX,Section3,"Inspection Criteria" andAppendixA,"NDEDataAcquisition andAnalysisGuidelines" submitted byourletterAEP:NRC:1166H forthecycle14IPC.Motorized rotatingpancakecoilinspection willbedoneonallindications exceeding 1.5volts.Motorized rotatingpancakecoilinspection willalsobedoneonallintersections wherecoppersignals,largemixedresiduals, ordentslargerthan5voltsinterfere withdetection offlaws.Probewearinspections andre-inspections willbeperformed usingtheguidelines ofAppendixA,SectionA.2.3,assubmitted byourletterAEP:NRC:1166H.

Ifanyofthelastprobewearstandardsignalamplitudes priortoprobereplacement exceedthe+/-15$limit,byavalueof"X%",thenanyindications measuredsincethelastacceptable probewearmeasurement thatarewithin"XS"oftheplugginglimitwillbereinspected withthenewprobe.Forexample,ifanyofthelastprobewearsignalamplitudes priortoprobereplacement were17%aboveorbelowtheinitialamplitude, thentheindications thatarewithin2%(17%-15%)

oftheplugginglimitmustbereinspected withthenewprobe.Alternatively, thevoltagecriterion maybeloweredtocompensate fortheexcessvariation; forthecaseabove,amplitudes z0.98timesthevoltagecriterion couldbesubjecttorepair.

Attachment 1toAEP:NRC:1166R Page3Bobbincoilprobecalibration willbeperformed usingfour20%holesintheASMEcalibration standardinsteadofthe100%throughwallholes.Thisapproachwasconcurred withbytheNRCstaffattheJanuary18,1995,NRC/Industry meeting.5)GL94-ZX,Section5,"Operational LeakageRequirements,"

willbecontinued.

TheSGtubeleakagelimitof150gallonsperdaythrougheachSGwillbemaintained aspreviously approvedbytheNRCforourlastfuelcycle.CookNuclearPlantleakagemonitoring methodsprovidetimelyleakdetection,

trending, andresponsetorapidlyincreasing leaks.6)GL94-XX,Section6,"Reporting Requirements,"

willbeimplemented.

Itshouldbenoted,asstatedpreviously forSection2,thatthecalculation ofleakageandburstprobability requiredpriortoreturning theSGstoservicewillbeperformed byuseoftheas-foundEOCvoltagedistribution.

AEPSCCOMMENTSEXCEPTIONS TOGL94-XXANDASSOCIATED MPACTTOEPSCLICENSEAMENDMENT REVESTFORSGPCFORCYCLE15GL94-ZX,Sectionl,b:Analysesperformed byWestinghouse haveshownthatnotubesintheCookNuclearPlantUnit1SGswouldbesubjecttocollapseduringalossofcoolantaccident(LOCA)+safeshutdownearthquake (SSE)event.Therefore, notubesareexcludedbasedonthiscriteria.

Itemsl.b.2andl.b.3arenotapplicable sincetheseconditions donotexistintheCookNuclearPlantUnit1'SGs.Series51SGsdesignedbyWestinghouse donothaveflowdistribution baffleplates.2)GL94-ZX,Section3.b.2:BasedontubepullresultsfromCookNuclearPlantUnit1,copperdepositsarenotpresentonthetubeoutsidediameter(OD)surfacesorinthetubesupportplate(TSP)crevicecorrosion product.Similarly, CookNuclearPlantUnit1doesnothaveevidenceof"largemixedresidualsignals."

CookNuclearPlantUnit1doesnothaveahistoryofeddycurrentdatawhichisdifficult tointerpret.

3)GL94-ZX,Section3.c.2:Bobbincoilprobeswillcontinuetobecalibrated againstthe20%holesintheASMEcalibration standardtoremainconsistent withthemethodology usedtodevelopthecriteria.

GL94-ZX,Section3.c.4:Therequirement toreinspect alltubespriortothelastprobechangeout ifthewearmeasurement exceeds15%isunnecessary.

As'acknowledged intheGL,a5.6voltrepaircriterion isjustified, however,therepaircriterion iscurrently limitedto2.0volts.Suchindications areexpectedtobewell Attachment 1toAEP:NRC:1166R Page4withinstructural limitsatEOC15conditions, particularly whenUnit1growthratesareconsidered.

Reinspection ofindications necessitated byoutofspecification probewearwillbeconducted according toItem4ofpage2ofthisattachment.

5)GL94-XX,Section4,addresses theneedtoperformtubepulls.Tubepullscausesignificant outageextension, occupational radiation

exposure, andsignificant directcost.(Asanexample,removalofthreetubesamplesduringtheupcomingCookNuclearPlantUnit1refueling outageisestimated toaddtwotothreedaystotheoutagecriticalpath,havedirectcostsintherangeof$0.8-$1.3million,andincurfrom2-5manremexposure.)

Therefore, tubesselectedforpullingshouldbejudiciously chosenandshouldjustifythemonetaryexpenseandradiological exposure.

Tubesshouldnotbepulledmerelytosatisfyachronological requirement.

AEPSCbelievesthattheimposition ofthisrequirement duringthenextscheduled refueling outagewillnotenhancethecurrentburstandleakagedatabases sufficiently towarranttheaddedcost.Justification fornotperforming atubepullduringthenextoutageatCookNuclearPlantUnit1issuppliedbelow.A)In1992,nineCookNuclearPlantUnit1TSPintersections wereremovedformetallographic examination, bursttestingandleaktesting.Fieldbobbincoilvoltagesrangedfrom1.0to2.0volts,including fourintersections reportedasNDD.Burstpressures rangedfrom9,100to11,200psig.forthereportedindications andnointersections leakedduringtestingat2560psid.Examination oftubesafterbursttestingshowedcombinations ofaxiallyorientedintergranular stresscorrosion crackingandintergranular cellularcorrosion originating fromthetubeOD.Degradation morphology wasdominated bytheaxiallyorienteddegradation.

InadditiontotheUnit1tubepullssupporting SGIPC,significant numbersofintersections wereremovedfromUnit2in1984and1986.Inallcases,circumferentially orienteddegradation wasnotdetected.

B)Outsidediameterstresscorrosion cracking(ODSCC)degradation growthrateforCookNuclearPlantUnit1hasdecreased overthelasttwocyclesandnointersections duringthelastoutagehadTSPintersection voltagesexceeding 2.0volts.Thishighlevelofperformance isattributed totheunitoperating atreducedtemperature andpressure, improvedsecondary sidechemistry controlandsludgeremoval,andaconservative inspection/repair program.BasedonthelowgrowthratesatUnit1andchemistry controlinitiatives, EOC14voltagesareexpectedtobewellbelow3.0volts,andmostlikelylessthan2.0volts.Recenttubepullsatotherplants Attachment 1toAEP:NRC:1166R Page5wheretheindication voltagewasgreaterthan2.0voltsandwherealargernumberofbeginning ofcycle(BOC)indications wereinthe2.0voltrangeindicated nounexpected degradation morphology.

TheexpectedEOC14voltagesatUnit1arewellbelowthethreshold forthroughwall degradation of2.8volts(determined fromatubepullatanotherplant)andwellbelowthethreshold forSLBleakageofapproximately 6.0volts.Duringthecurrentoperating cycle,Unit1hasnotexperienced anysecondary sidechemistry "excursions" whichmightsupportunexpected voltagegrowthorinitiation of"non-typical degradation morphologies.

C)Thecurrentrequirement toperformanMRPCinspection ofindications over1.5voltsissufficient toidentifynon-typicalmorphologies.

Forcasesofsignificant cellularcorrosion (identified atotherplants),metallographic

.examination hasshownthataxiallyorienteddegradation hasdominated themorphology andbursttestresults.Forsuch"caseswheresignificant circumferential components inacellularmorphology caninfluence burst,associated axialcomponents wouldyieldvoltagesfarinexcessofthe5to6voltrange,andsuchcircumferentially orienteddegradation wouldbeofsufficient depthtobedetectedbytheRPCprobe.IV,10CFR5092EVALUATION BACKGROUND CookNuclearPlantUnit1T/SAmendment 178permitted theimplementation ofa2.0voltSGtubeIPCforthe14thoperating cycleoftheCookNuclearPlantUnit1SGs.Thatlicenseamendment, applicable onlyforthecurrentoperating cycle(cycle14),requiredtherepairofflaw-like bobbinindications above2.0volts.Weareproposing useofasimilar2voltinterimrepaircriterion fortheupcomingcycle15.TheproposedIPCprogramfortheCookNuclearPlantUnit1SGsfollowstheguidanceandgeneralintentofGL94-XXtomaintaintubestructural andleakageintegrity.

DESCRIPTION OFTHEIPCREQUESTAsrequiredby10CFR50.91(a)(l),ananalysisisprovidedtodemonstrate thattheproposedlicenseamendment toimplement anIPCforthetubesupportplateelevation ODSCCoccurring intheCookNuclearPlantUnit1SGsinvolvesanosignificant hazardsconsideration.

TheIPCutilizes

Attachment 1toAEP:NRC:1166R Page6correlations betweeneddycurrentbobbinprobesignalamplitude (voltage) andtubeburstandleakagecapability.

Thepluggingcriterion isbasedontestingoflaboratory inducedODSCCspecimens andonextensive examination ofpulledtubesfromoperating SGs(industry wide-including threetubespulledin1992representing nineintersections fromCookNuclearPlantUnit1SGs.)CConsistent withGL94-ZX,theIPCprogramforCookNuclearPlantUnit1willincludethefollowing elementsaslistedunder"1.OverviewoftheVoltageRepairLimitApproach",

page3ofGL94-ZX.Performanenhancedinspection oftubes,particularly attheTSPintersections.

A100%bobbincoilinspection ofhotlegtubesupportplateintersections andcoldlegintersection downtothelowestcoldlegsupportplatewithknownODSCCindications willbeperformed.

Allflawindications withbobbinvoltagesgreaterthan1.5voltswillbeinspected byMRPC.UtilizeNDEdataacquisition andanalysisprocedures thatareconsistent withthemethodology usedtodevelopthevoltage-based repairlimits.TheCookNuclearPlantUnit1IPCprogramwillutilizeprocedures andtechniques consistent withthemethodologies usedtoestablish theIPCasdescribed inSection3ofEnclosure 1oftheGL,withtheexception that20%.throughwall holeswillbeusedinthestandard(Section3.c.2ofGL94-XX).Repairorplugtubesthatexceedthevoltagelimits.Flaw-like signalsadjacenttotheTSPwithbobbinvoltageslessthanorequalto2.0voltswillbeallowedtoremaininservice.Flaw-likeindications adjacenttotheTSPwithabobbinvoltageofgreaterthan2.0voltsbutlessthanorequalto5.6voltsmayremaininserviceifMRPCinspection doesnotdetectaflaw.'law indications withavoltageofgreaterthan5.6voltswillberepaired.

Determine theBOOvoltagedistribution.

Beginning ofCycle15voltagedistribution willbeestablished fromtheactualtubeinspections tobeperformed duringthenextoutageandwillbeestablished usingcurrentprogrammethodology.

ProjecttheEOC15distribution.

Attachment 1toAEP:NRC:1166R Page7AnEOCvoltagedistribution willbeestablished basedontheEOC14ECTdata.EOC15voltagedistribution willbeprojected usingMonteCarlotechniques asdescribed inWCAP-14277 andwillincludeallowance foreddycurrentuncertainty asdefinedintheGLandaconservative voltagegrowthrateallowance.

Fortheprojected EOC'voltagedistribution, calculate leakageandconditional tubeburstprobability (andrepairtubesifnecessary).

Steamlinebreakleakagewillbecalculated, asdescribed inWCAP-14277,basedontheEOC15projected voltagedistribution.

Projected leakagemustremainbelow12.6gpminthefaultedloopforoffsitedoseestimates toremainwithin10$ofthe10CFR100guidelines.

Thisvaluewascalculated, usingStandardReviewPlanmethodology, priortotheCycle14licenseamendment requestandwillnotchangefortheupcomingcycle.Conditional tubeburstprobability willbecalculated according tothemethodology described inWCAP-14277.

Consistent withtheGL,ifburstprobability isfoundtobegreaterthan1x102,theNRCwillbeconsulted.

Asprescribed inGL94-XX,anevaluation ofprimarytosecondary leakage(andsubsequently offsitedose)isrequiredforallplantsimplementing theIPC.Allbobbinindications areincludedinthesteamlinebreakleakageanalyses, alongwithconsideration oftheprobability ofdetection.

Iftheprojected leakageexceeds12.6gpminthefaultedloopduringapostulated steamlinebreakevent,thenumberofindications inwhichtheIPCareappliedisreducedthroughtuberepairuntiltheprimary-to-secondary leakagelimitsaresatisfied.

EVALUATION TubeDegradation Characterization Ingeneral,thedegradation morphology occurring atthetubesupportplateintersections atplantsintheU.S.canbedescribed asaxiallyorientedODSCC.Thedegradation morphology atCookNuclearPlantUnit1isentirelycompatible withtheoverallindustrydatabase.SteamGenerator TubeIntegrity Inthedevelopment ofanIPCforCookNuclearPlantUnit1,Regulatory Guide(RG)1.121,"BasesforPluggingDegradedPWRSteamGenerator Tubes"andRG1.83,"Inservice Inspection ofPWRSteamGenerator Tubes"areusedasthebasesfordetermining thatSGtubeintegrity considerations aremaintained withinacceptable limits.Regulatory Guide1.121describes amethodacceptable totheNRCstaffformeetingGeneralDesignCriteria

~~4*1~~1t Attachment 1toAEP:NRC:1166R Page8(GDC)14,15,31,and32byreducingtheprobability andconsequences ofSGtuberupturethroughdetermining thelimitingsafeconditions oftubewalldegradation beyondwhichtubeswithunacceptable

cracking, asestablished byinservice inspection, shouldberemovedfromservicebyplugging.

Thisregulatory guideusessafetyfactorsonloadsfortubeburstthatareconsistent withtherequirements ofSectionIIIoftheASMECode.For-the.tubesupportplateelevation degradation occurring intheCookNuclearPlantUnit1SGs,tubeburstcriteriaareinherently satisfied duringnormaloperating conditions bythepresenceofthetubesupportplate.Thepresenceofthetubesupportplateenhancestheintegrity ofthedegradedtubesinthatregionbyprecluding tubedeformation beyondthediameterofthedrilledhole,thusprecluding tubeburst.Conservatively, nocreditistakeninthedevelopment ofthepluggingcriteriaforthepresenceofthetubesupportplateduringaccidentconditions.

Basedontheexistingdatabasefor7/8inchtubing,bursttestingshowsthatthesafetyrequirements fortubeburstmarginsduringaccidentcondition loadingscanbesatisfied withEOCbobbincoilsignalamplitudes lessthan9.6volts,regardless ofthedepthoftubewallpenetration ofthecracking.

Uponimplementation oftheseIPC,tubeleakageconsiderations mustalsobeaddressed.

Itmustbedetermined thatthecrackswillnotleakexcessively duringallplantconditions.

Forthe2voltinterimtubepluggingcriteriadeveloped fortheCookNuclearPlantUnit1SGtubes,noleakageisanticipated duringnormaloperating conditions evenwiththepresenceofpotential throughwall cracks.Theexpectedvoltagewhichwouldsupportprimary-to-secondary leakageatnormaloperating conditions isapproximately 10volts.Noprimary-to-secondary leakageattheTSPhasbeendetectedinU.S.plants.Relativetotheexpectedleakageduringaccidentcondition

loadings, thelimitingeventwithrespecttodifferential pressureexperienced acrosstheSGtubesisapostulated steamlinebreakevent.For7/8inchtubing,pulledtubedatasupportsnoleakageupto2.81voltsandlowprobability ofleakagebetween2.81and6.0volts,forbothpulledtubesandmodelboilerspecimens, attheboundingsteamlinebreakpressuredifferential of2560psi.Steamlinebreakprimarytosecondary leakagewillbecalculated asprescribed inGL94-XXandWCAP14277,usingEOC14eddycurrentdata.Thiscalculated leakagemustbeshowntobelessthan12.6gpminthefaultedloop.Additional Considerations Theproposedamendment wouldprecludeoccupational radiation exposurethatwouldotherwise beincurredbypersonnel involvedintubepluggingorrepairoperations'y reducingnon-essential tubeplugging, theproposedamendment wouldminimizethelossofmargininthereactorcoolantflowthroughtheSGinLOCAanalyses.

Theproposedamendment wouldavoidlossofmargininreactorcoolantsystemflowand,therefore, assistinmaintaining minimumflowratesinexcessofthatrequiredforoperation at Attachment 1toAEP:NRC:1166R Page9fullpower.Reduction intheamountoftuberepairrequiredcanreducethelengthofplantoutagesandreducethetimethattheSGisopentothecontainment environment duringanoutage.The100%eddycurrentbobbinprobeinspection associated withimplementation oftheIPCwillhelptoidentifynewareasofconcernwhichmayarisebyproviding alevelofinservice inspection whichisfarinexcessoftheT/Srequirements utilizing the.40%depth-based plugginglimitforacceptable tubewalldegradation.

SIGNIFICANT HAZARDSANALYSISInaccordance withthethreefactortestof10CFR50.92(c),

implementation oftheproposedlicenseamendment isanalyzedusingthefollowing standards andfoundnotto1)involveasignificant increaseintheprobability orconsequences ofanaccidentpreviously evaluated; 2)createthepossibility ofanewordifferent kindofaccidentfromanyaccidentpreviously evaluated; or3)involveasignificant reduction inmarginofsafety.Conformance oftheproposedamendment tothestandards foradetermination ofnosignificant hazardsasdefinedin10CFR50.92(threefactortest)isshowninthefollowing paragraphs.

1)Operation ofCookNuclearPlantUnit1inaccordance withtheproposedlicenseamendment doesnotinvolveasignificant increaseintheprobability orconsequences ofanaccidentpreviously evaluated.

Testingofmodelboilerspecimens forfreespantubing(notubesupportplaterestraint) atroomtemperature conditions showburstpressures inexcessof5000psiforindications ofouterdiameterstresscorrosion crackingwithvoltagemeasurements ashighas19volts.Bursttestingperformed onpulledtubesfromCookNuclearPlantUnit1withuptoa2.02voltindication shows.measured burstpressureinexcessof10,000psiatroomtemperature.

Bursttestingperformed onpulledtubesfromotherplantswithupto7.5voltindications showburstpressures inexcessof6,300psiatroomtemperatures.

Correcting fortheeffectsoftemperature onmaterialproperties andminimumstrengthlevels(asthebursttestingwasdoneatroomtemperature),

tubeburstcapability significantly exceedsthesafetyfactorrequirements ofRG1.121.Asstatedearlier,tubeburstcriteriaareinherently satisfied duringnormaloperating conditions duetotheproximity ofthetubesupportplate.Testdataindicates thattubeburstcannotoccurwithinthetubesupportplate,evenfortubeswhichhave100$throughwall electric-discharge machinednotches0.75inchlong,providedthetubesupportplateisadjacenttothenotchedarea.Sincetube-to-tube supportplateproximity precludes tubeburstduringnormaloperating conditions, useofthecriteriamust,therefore, retaintubeintegrity characteristics whichmaintaintheRG1121marginofsafetyof143timestheboundingfaultedcondition (steamlinebreak)pressuredifferential.

Attachment 1toAEP:NRC:1166R Page10Duringapostulated mainsteamlinebreak,theTSPhasthepotential todeflectduringblowdown, therebyuncovering theintersection.

Basedontheexistingdatabase,theRG1.121criterion requiring maintenance ofasafetyfactorof1.43timesthesteamlinebreakpressuredifferential ontubeburstissatisfied by7/8inchdiametertubingwithbobbincoilindications withsignalamplitudes lessthan9.6volts;-regardless oftheindicated depthmeasurement.

A2.0voltpluggingcriteriacomparesfavorably withthe9.6voltstructural limitconsidering thepreviously calculated growthratesforODSCCwithinCookNuclearPlantUnit1SGs.Considering avoltagegrowthcomponent of0,8volts(40%voltagegrowthbasedon2.0voltsBOC)andanondestructive examination uncertainty of0.40volts(208voltageuncertainty basedon2.0voltsBOC),whenaddedtotheBOCIPCof2.0volts,resultsinaboundingEOCvoltageofapproximately 3.2voltsforcycle15operation.

A6.4voltsafetymarginexists(9.6structural limit-3.2voltEOC-6.4voltmargin).Forthevoltage/burst correlation, theEOCstructural limitissupported byavoltageof9.6volts.Usingthisstructural limitof9.6volts,aBOCmaximumallowable repairlimitcanbeestablished usingtheguidanceofRG1.121.TheBOCmaximumallowable repairlimitshouldnotpermitasignificant numberofEOCindications toexceedthe9.6voltstructural limitandshouldassurethatacceptable tubeburstprobabilities areattained.

ByaddingNDEuncertainty allowances andanallowance forcrackgrowthtotherepairlimit,thestructural limitcanbevalidated.

ThepreviousIPCsubmittal established theconservative NDEuncertainty limitof20%oftheBOCrepairlimit.Forconsistency, a40$voltagegrowthallowance totheBOCrepairlimitisalsoincluded.

Thisallowance isextremely conservative forCookNuclearPlantUnit1.Therefore, themaximumallowable BOCrepairlimit(RL)basedonthestructural limitof9.6voltscanberepresented bytheexpression:

RL+(0.2xRL)+(0.4xRL)9.6volts,or,themaximumallowable BOCrepairlimitcanbeexpressed as,RL-9.6voltstructural limit/1.6

-6.0volts.Thisstructural repairlimitsupportsthisapplication forcycle15IPCimplementation torepairbobbinindications greaterthan2.0voltsbasedonRPCconfirmation oftheindication.

Conservatively, anupperlimitof5.6voltswillbeusedtorepairbobbinindications whichareabove2.0voltsbutdonothaveconfirming RPCcalls.

Attachment 1toAEP:NRC:1166R PagellTheconservatism ofthisrepairlimitisshownbytheEOC13(Spring1994)eddycurrentdata.Theoverallaveragevoltagegrowthwasdetermined tobeonly1.48(oftheBOCvoltage).

Inaddition, theEOC13maximumobservedvoltageincreasewas0.40volts,andoccurredinatubewithaBOCindication of0.96volts.Theapplicability ofcycle14growthratesforcycle15operation willbeconfirmed priortoreturn.toserviceofCookNuclearPlantUnit1.Similarlargestructural marginsareanticipated.

Relativetotheexpectedleakageduringaccidentcondition

loadings, ithasbeenpreviously established thatapostulated mainsteamlinebreakoutsideofcontainment butupstreamofthemainsteamisolation valverepresents themostlimitingradiological condition relativetotheIPC.Insupportofimplementation oftheIPC,itwillbedetermined whetherthedistribution ofcrackindications atthetubesupportplateintersections attheendofcycle15areprojected tobesuchthatprimarytosecondary leakagewouldresultinsiteboundarydoseswithinasmallfractionofthe10CFR100guidelines.

Aseparatecalculation hasdetermined thisallowable steamlinebreakleakagelimittobe12.6gpm.AlthoughnotrequiredbytheCookNuclearPlantdesignbasis,thiscalculation usestherecommended Iodine-131 transient spikingvaluesconsistent withNUREG-0800, andtheT/Sreactorcoolantsystemactivitylimitof1.0microcuriepergramdoseequivalent Iodine-131.Theprojected steamlinebreakleakageratecalculation methodology prescribed inGL94-ZXandWCAP14277willbeusedtocalculate EOC15leakage,basedonactualEOC14distributions andEOC15projected distributions.

Duetotherelatively lowvoltagegrowthratesatCookNuclearPlantUnit1andtherelatively smallnumberofindications affectedbytheIPC,steamlinebreakleakageprediction perGL94-ZXisexpectedtobesignificantly lessthantheacceptance limitof12.6gpminthefaultedloop.PriortoissueofGL94-XX,projected EOC14leakrateswerecalculated, basedondraftNUREG-1477,foratotaloftwelvecases,thecombination ofsixprobability-of-leak correlations andtwoleakratecalculation methodologies.

Resultsofthecalculations showthattheprojected EOC14leakratesrangedfrom0.001gpmto1.360gpm.Theseresultsarewellbelowthe12.6gpmallowable; therefore, implementation ofthe2voltIPCduringcycle15wouldnotadversely affectSGtubeintegrity andresultsinacceptable doseconsequences.

CurrentGL94-ZXmethodology requiresonlythelog-logistic probability ofleakagecorrelation beused.Projected EOC14SLBleakageusingthisfunctionwascalculated tobeonly0.001gpm.Basedontherelatively fewnumbersofintersections atCookNuclearPlantUnit1towhichtheIPCareapplied.and extremely smallCook Attachment 1toAEP:NRC:1166R Page12NuclearPlantUnit1plant-specific growthrate,asimilarvaluewouldbeexpectedbasedontheEOC14eddycurrentdata.Theinclusion ofallIPCintersections intheleakagemodel,alongwithapplication ofaprobability ofdetection of0.6,willresultinextremely conservative leakageestimations, especially sosincecloseexamination oftheavailable datashowsthatindications oflessthan2.8voltswillnotbeexpectedtoleakduringSLBconditions.

AllUnit1IPCindications areexpectedtobebelow2.8voltsattheEOC15conditions.

Theproposedamendment doesnotresultinanyincreaseintheprobability orconsequences ofanaccident.previously evaluated withintheCookNuclearPlantUnit1FSAR.2)Theproposedlicenseamendment doesnotcreatethepossibility ofanewordifferent kindofaccidentfromanyaccidentpreviously evaluated.

Implementation oftheproposedSGtubeIPCdoesnotintroduce anysignificant changestotheplantdesignbasis.Useofthecriteriadoesnotprovideamechanism whichcouldresultinanaccidentoutsideoftheregionofthetubesupportplateelevations.

NeitherasingleormultipletuberuptureeventwouldbeexpectedinaSGinwhichthepluggingcriteriahasbeenapplied(duringallplantconditions).

Specifically, wewillcontinuetoimplement amaximumleakageratelimitof150gpd(0.1gpm)perSGtohelpprecludethepotential forexcessive leakageduringallplantconditions.

Thecycle15T/Slimitsimposedonprimarytosecondary leakageatoperating conditions are:amaximumof0.4gpm(600gpd)forallSGs'withamaximumof150gpdallowedforanyoneSG.TheRG1.121criteriaforestablishing operational leakageratelimitsthatrequireplantshutdownarebaseduponleak-before-break considerations todetectafreespancrackbeforepotential tuberuptureduringfaultedplantconditions.

The150gpdlimitshouldprovideforleakagedetection andplantshutdownintheeventoftheoccurrence ofanunexpected singlecrackresulting inleakagethatisassociated withthelongestpermissible cracklength.Regulatory Guide1.121acceptance criteriaforestablishing operating leakagelimitsarebasedonleak-before-break considerations suchthatplantshutdownisinitiated iftheleakageassociated withthelongestpermissible crackisexceeded.

Thelongestpermissible crackisthelengththatprovidesafactorofsafetyof1.43againstburstingatfaultedconditions maximumpressuredifferential.

Avoltageamplitude of9.6voltsfortypicalODSCCcorresponds tomeetingthistubeburstrequirement atalower95%prediction limitontheburst

)

Attachment 1toAEP:NRC:1166R Page13correlation coupledwith95/95lowertolerance limitmaterialproperties.

Alternate crackmorphologies cancorrespond to9.6voltssothatauniquecracklengthisnotdefinedbytheburstpressureversusvoltagecorrelation.

Consequently, typicalburstpressureversusthrough-wall cracklengthcorrelations areusedbelowtodefinethe"longestpermissible crack"forevaluating operating leakagelimits.Consistent withtheCycle13andCycle14licenseamendment requestsforIPCandSection5ofEnclosure 1oftheGL,operational leakagelimitswillremainat150gpdperSG.Axialcracksleakingatthislevelareexpectedtoprovideleakbeforebreak(LBB)protection atboththeSLBpressuredifferential of2560psiand,whilenotpartofanyestablished LBBmethodology, LBBprotection willalsobeprovidedatavalueof1.43timestheSLBpressuredifferential.

Thus,the150gpdlimitprovidesforplantshutdownpriortoreachingcriticalcracklengthsforsteamlinebreakconditions.

Additionally, thisleak-before-break evaluation assumesthattheentirecreviceareaisuncovered duringblowdown.

'Partialuncoverywillprovidebenefittotheburstcapacityoftheintersection.

3)Theproposedlicenseamendment doesnotinvolveasignificant reduction inmarginofsafety.Theuseofthevoltagebasedbobbinprobeinterimtubesupportplateelevation pluggingcriteriaatCookNuclearPlantUnit1isdemonstrated tomaintainSGtubeintegrity commensurate withthecriteriaofRG1.121.Regulatory Guide1.121describes amethodacceptable totheNRCstaffformeetingGDC14,15,31,and32byreducingtheprobability ortheconsequences ofSGtuberupture.Thisisaccomplished bydetermining thelimitingconditions ofdegradation ofSGtubing,asestablished byinservice inspection, forwhichtubeswithunacceptable crackingshouldberemovedfromservice.Uponimplementation ofthecriteria, evenundertheworstcaseconditions, theoccurrence ofODSCCatthetubesupportplateelevations isnotexpectedtoleadtoaSGtuberuptureeventduringnormalorfaultedplantconditions.

TheEOC15distribution ofcrackindications atthetubesupportplateelevations willbeconfirmed byanalysisandcalculation toresultinacceptable primarytosecondary leakageduringallplantconditions andthatradiological consequences arenotadversely impacted.

Inaddressing thecombinedeffectsofaLOCAandSSEontheSGcomponent (asrequiredbyGDC2),ithasbeendetermined thattubecollapsemayoccurintheSGsatsomeplants.Thisisthecaseasthetubesupportplatesmaybecomedeformedasaresultoflateral l

Attachment 1toAEP:NRC:1166R Page14loadsatthewedgesupportsattheperiphery oftheplateduetothecombinedeffectsoftheLOCArarefaction waveandSSEloadings.

Then,theresulting pressuredifferential onthedeformedtubesmaycausesomeofthetubestocollapse.'here aretwoissuesassociated withSGtubecollapse.

First,thecollapseofSGtubingreducestheRCSflowareathroughthetubes.Thereduction inflowareaincreases theresistance toflowofsteamfromthecoreduringaLOCAwhich,inturn,maypotentially increasepeakcladtemperature.

Second,thereisapotential thatpartialthrough-wall cracksintubescouldprogresstothrough-wall cracksduringtubedeformation orcollapse.

Consequently, sincetheleak-before-break methodology isapplicable totheCookNuclearPlantUnit1reactorcoolantlooppiping,theprobability ofbreaksintheprimarylooppipingissufficiently lowthattheyneednotbeconsidered inthestructural designoftheplant.ThelimitingLOCAeventbecomeseithertheaccumulator linebreakorthepressurizer surgelinebreak.LossofcoolantaccidentloadsfortheprimarypipebreakswereusedtoboundtheCookNuclearPlantUnit1smallerbreaks.TheresultsoftheanalysisusingthelargerbreakinputsshowthattheLOCAloadswerefoundtobeofinsufficient magnitude toresultinSGtubecollapseorsignificant deformation.

Addressing RG1.83considerations, implementation ofthebobbinprobevoltagebasedinterimtubepluggingcriteriaof2.0voltsissupplemented byenhancededdycurrentinspection guidelines toprovideconsistency involtagenormalization, a100$eddycurrentinspection samplesizeatthetubesupportplateelevations perT/S,andMRPCinspection requirements forthelargerindications leftinservicetocharacterize theprincipal degradation asODSCC.Asnotedpreviously, implementation ofthetubesupportplateelevation pluggingcriteriawilldecreasethenumberoftubeswhichmustberepaired.

Theinstallation ofSGtubeplugsreducestheRCSflowmargin.Thus,implementation oftheIPCwillmaintainthemarginofflowthatwouldotherwise bereducedintheeventofincreased tubeplugging.

Basedontheabove,itisconcluded thattheproposedlicenseamendment requestdoesnotresultinasignificant reduction inmarginwithrespecttoplantsafetyasdefinedintheFinalSafetyAnalysisReportoranyBasesoftheplantT/Ss.

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