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{{#Wiki_filter: | {{#Wiki_filter: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:== | ==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~ | /~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", | |||
~~4*1~~1t | 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.}} | |||
Revision as of 08:02, 29 June 2018
| ML17332A751 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| 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) | |
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.