ML17331A089
| ML17331A089 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 03/10/1993 |
| From: | FITZPATRICK E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | MURLEY T E NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17331A090 | List: |
| References | |
| AEP:NRC:1166C, NUDOCS 9303160107 | |
| Download: ML17331A089 (22) | |
Text
SUBJECT:
Application foramendtoLicense.DPR-58;changing TStoallow'-Iinterimpluggingcriteriaof1.0voltforCycle14.,Technical summarysupporting validity6'continued use.ofWestinghouse ReptWCAP-13187 encl.DISTRIBUTION CODE:0001DCOPIESRECEIVED:LTR
/~ENCL/'IZE:ig+~+$TITLE:ORSubmittal:
GeneralDistribution
/DNOTES:-+-=;ACCEZ,ERXV@~
OOCVMENTDISVagVTION.SYSTEM ACCESSION N]9R:9303160107 DOC.DATE:
93/03/10'OTARIZED:
YES"DOCKETFACIL:50-315 DonaldC.CookNuclearPower'lant, Unit1,IndianaM05000315AUTH.NAMEAUTHORAFFILIATION FITZPATRICK,E.
IndianaMichiganPowerCo.-(formerly'Indiana
&MichiganEleRECIP.NAME RECIPIENT AFFILIATION MURLEY,T.E.
DocumentControlBranch(Document'-Control Desk)RECIPIENT IDCODE/NAME PD3-1LADEAN,WINTERNAL:
NRR/DE/EELB NRR/DRCH/HICB NRR/DSSA/SPLB NUDOCS-ABSTRACT OGC/HDS2EXTERNAL:
NRCPDRCOPIESLTTRENCL221111111110.11k"RECIPIENT IDCODE/NAME PD3-1PDNRR/DORS/OTSB NRR/DSSA/SCSB NRR/DSSA/SRXB REGFILE'1-NSIC-COPIESLTTRENCL1.111111110'1.11".1ADDANOTETOALL"RIDS"RECIPIENTS:
PLEASEHELPUSTOREDUCEWASTE!CONTACI'IIE DOCUMENTCOi!'I'ROL DIMK,ROOMPl-37(EXT.504-2065)
TOELIMINATE YOURNAMEFROMDISTR!BUTION LISTSFORDOCUMENTS YOUDON'TNEED!DTOTALNUMBEROFCOPIESREQUIRED:
LTTR16ENCL14
\~~o'i indianaMichiganPowerCompanyP.O.Box16631t:olumbus, OH43216AEP:NRC:1166G DonaldC.CookNuclearPlantUnit1DocketNo.50-315LicenseNo.DPR-58TECHNICAL SPECIFICATIONS CHANGETOALLOWINTERIMPLUGGINGCRITERIAOF1.0VOLTFORCYCLE14U.S.NuclearRegulatory Commission DocumentControlDeskWashington, D.C.20555Attn:T.E.MurleyMarch10,1993
DearDr.Murley:
Thisletteranditsattachments constitute anapplication foranamendment totheTechnical Specifications (T/Ss)ofDonaldC.CookNuclearPlantUnit1inaccordance with10CFR50.90.Itisrequested thattheamendment totheT/Ssforsteamgenerator interimpluggingcriteria, asoutlinedintheNRCletterofJuly29,1992forlicenseAmendment No.166forfuelcycle13,beextendedtofuelcycle14oftheCookNuclearPlantUnit1.Thisextension isessential whileourT/Sammendment toallowalternate pluggingcriteriaisbeingreviewedbytheNRC(AEP:NRC:1166, March20,1992).Attachment 1providesatechnical summaryoftherecentsteamgenerator tubeinterimpluggingcriteriavoltageevaluations andtubesampleanalysisresults.Theseevaluations andresultssupportthevalidityandcontinued useoftheWestinghouse ReportWCAP-13187 insupportofthe1volt.interimpluggingcriteriaforfuelcycle14.Notechnical changesweremadetotheinterimpluggingcriteriaT/Ssrequirements usedforfuelcycle13.T/Schangesweremadeonlytoreference fuelcycle14intheappropriate T/Sparagraphs wherefuelcycle13waspreviously referenced.
Adetaileddescription oftheproposedchangesandouranalysesconcerning significant hazardsconsiderations arerepeatedfromourprevioussubmittal andareincludedinAttachment 2tothisletterforyourconvenience.
Attachment 3containstheproposed3f'te19303i60i07 9303i0PDRADOCK050003i5PPGRoor l1ia~
Dr.T.E.Murley-2-AEP:NRC:1166G revisedT/Spages.Attachment 4containsthemarked-up copiesoftheexistingT/Ss.Webelievethattheproposedchangeswillnotresultin(1)asignificant changeinthetypesofeffluents orasignificant increaseintheamountofanyeffluents thatmaybereleasedoffsite,or(2)asignificant increaseinindividual orcumulative occupational radiation exposure.
TheseproposedchangeshavebeenreviewedbythePlantNuclearSafetyReviewCommittee andthecorporate NuclearSafetyandDesignReviewCommittee.
Incompliance withtherequirements oflOCFR50.91(b)(1),
copiesofthisletteranditsattachments havebeentransmitted toMr.J.R.PadgettoftheMichiganPublicServiceCommission andtotheMichiganDepartment ofPublicHealth.Pleasecontactusifyouhaveanyquestions concerning thislicenseamendment request.Thisletterissubmitted pursuantto10CFR50.54(f)and,assuch,anoathstatement isenclosed.
Sincerely, pg+p~jVicePresident ehAttachments Enclosure cc:A.A.Blind-BridgmanJ.R.PadgettG.CharnoffA.B.Davis-RegionIIINRCResidentInspector
-BridgmanNFEMSectionChief Dr.T.E.Murley-3-AEP:NRC:1166G bc:S.J.BrewerD.H.Malin/K.J.TothJ.D.Benes/J.R.JensenM.L.Horvath-BridgmanJ.B.ShinnockW.G.Smith,Jr.W.M.Dean,NRC-Washington, D.C.AEP:NRC:1166G DC-N-6015.1 aCOUNTYOFFRANKLINE.E.Fitzpatrick, beingdulysworn,deposesandsaysthatheistheVicePresident oflicenseeIndianaMichiganPowerCompany,thathehasreadtheforgoingresponsetoAEP:NRC:1166G
-Technical Specification ChangeToAllowInterimPluggingCriteriaOf1.0VoltForCycle14andknowsthecontentsthereof;andthatsaidcontentsaretruetothebestofhisknowledge andbelief.Subscribed andsworntobeforemethis~~dayof199H40TARYPUBLICRlTAD.HILLNOTARYPUBLIC.STATEOFOIUO l'4*h4r.~
ATTACHMENT 1TOAEPNRC'1166G TECHNICAL SUMMARYOFTHERECENTSTEAMGENERATOR TUBEINTERIMPLUGGINGCRITERIAVOLTAGEEVALUATIONS TUBESAMPLEANALYSISRESULTS ATTACHMENT 1TOAEP:NRC:1166G Page1Thetechnical basisforimplementing theinterimpluggingcriteriaforfuelcycle13wasbasedonsubmittal documents AEP:NRC:1166, 1166A,1166B,1166C,and1166D.Includedasanattachment wasWestinghouse Report,WCAP-13187 titled"D.C.CookUnit1SteamGenerator TubePluggingCriteriaforIndications atTubeSupportPlates"datedMarch1992.TheWCAPcontainsthetechnical approachforachieving assurance oftubestructural integrity basedoneddycurrentbobbincoilvoltagerepaircriteria.
Application oftheWCAPtuberepairvoltagecriteriaisbasedonvoltagegrowthratesfromthepriortwooperating cyclesof0.8and0.7volts.Analysisofvoltagegrowth"ratedoneforfuelcycle13,attheendoffuelcycle12in1992,showedthelargestvoltagegrowthwas0.49volts.Thisiswellbelowtheprojected growthratesreferenced bytheWCAP.Analysisforthemaximumendofcyclevoltageprojectedforindications leftinservicebelow1.0voltwas1.40volts.Thisindication voltageiswellwithinthestructural limitsproposedbytheWCAPstructural voltagelimitsforpotential tubeleakageandburst.NRCsubmittal letterAEP:NRC:1166F containsthefullreportonevaluations performed toestimatetheprojected EOCvoltagegrowthrateaswellasleakrateandburstprobabi.lity.
Inaddition, tubesampleswereremovedfromsteamgenerator No.12aspartoftheT/Ssalternate pluggingcriteriaformetallographic evaluation, leaktesting,andbursttesting.Thefollowing tablesummarizes theresultsonthosetubesamplesleakandbursttestedatthefirstandsecondsupportplate(SP)elevati.ons.
SuamaryTableTubeLeakandBurstTestDataLocationFieldE/C~XDDPCttRll-C60/SPI 1.1Volt,BCSAI,RPCLeak~lt.PINotDoneBursttPI9,100SEHFractography
~DthX~ADttI5432Rll-C60/SP2 1.4Volt,BCHAI,RPCRlg-C16/SP1 1.4Volt,BCSAI,RPCNotDone>2,650(ET)*NoLeakage9,35010P725523828Rlg-C21/SPl 2.0Volt,BCSAI,RPC>2,650(ET)*NoLeakage10,200Rlg-C21/SP2 NDD,BCNDD,RPC*ET~TestdoneatelevatedNotDonetemperature.
11,20038NoData ATTACHMENT 1TOAEP'NRC'1166G Page2Thecorrosion wasconfinedtothesupportplateregionandhadcombinations ofaxiallyorientedintergranular stresscorrosion
'cracking andintergranular cellularcorrosion.
Thecorrosion wasofODorigin,anditoccurredineither360'andsorisolatedpatches.TheSP2regionoftubeR18-C21hadtheshallowest maximumcrackdepth(38%throughwall) found.Itseddycurrentsignalwouldnotbeexpectedtobedetectedwithahighprobability.
ThefirstsupportplatecreviceregionsoftubesR18-C16andR18-C21wereleaktestedatelevatedtemperature andpressure.
Neithertubeleakedthroughexistingcorrosion networksatnormaloperating conditions (1500psi.differential pr~ssurewithprimarysideat2250psiandsecondary sideat750psi)oratsteamlinebreakconditions (2650psidifferential pressurewiththeprimarysideat3000psiandthesecondary sideat350psi).Roomtemperature bursttestswer'econducted atahigherpressurization rateof1000psi/seconSP1oftubesRll-C60,R18-C16andR18-C21andSP2oftubesRll-C60andR18-C21.Allburstathighburstpressures (9,100;10,725;10,200;9,350and11,200psig,respectively) andhadaxialburstopenings.
Virgintubingburst,typically between11,500and12,000psig.Inconclusion, theresultsofthevoltagegrowthrateevaluations andtubesampleleakandburstwerewellwithintheguidelines established intheWCAP.Also,thevoltagegrowthrateisalmosthalfofwhatwasfoundforthetwopriorfuelcycles.Therefore, basedonalowvoltagegrowthrate,andleakandbursttestresults,theWCAPisstillconsidered atechnically appropriate andboundingdocumentapplicable tothenextfuelcycle,cycle14.Furthermore, theeddycurrentinspection, reporting, andleakagerequirements aspreviousily statedintheT/Ssforfuelcycle13,willbemaintained forfuelcycle14.
ATTACHMENT 2toAEP:NRC:1166G NOSIGNIFICANT HAZARDSCONSIDERATION EVALUATION INSUPPORTOFTHEINTERIMPLUGGINGCRITERIA Attachment 2toAEP:NRC:1166G INTRODUCTION Page1Alicenseamendment isproposedtoprecludeunnecessarily pluggingsteamgenerator tubesduetotheoccurrence ofouterdiameterinitiated stresscorrosion cracking(ODSCC)atthetubesupportplatesintheCookNuclearPlantUnit1steamgenerators.
UsingtheexistingTechnical Specifications (T/Ss)steamgenerator tubepluggingcriteriaof40$tubewallpenetration asdetermined bynon-destructive examination (NDE),manyofthetubeswithcrackindications wouldneedlessly havetoberemovedfromservice.Theinterimpluggingcriteriafortubesupportplateelevation ODSCCoccurring intheCookNuclearPlantUnit1steamgenerators mayresultintubeswithbothpartialandthrough-wall cracksreturning toservice.Inthelimitingcase,itisdemonstrated thatthepresenceofthrough-wall cracksaloneisnotreasonenoughtoremoveatubefromservice.DESCRIPTION OFTHEAMENDMENT REQUESTAsrequired'by10CFR50.91(a)(1),
ananalysisisprovidedtodemonstrate thattheproposedlicenseamendment toimplement aninterimsteamgenerator tubepluggingcriteriaforthetubesupportplateelevations atCookNuclearPlantUnit1involvesnosignificant hazardsconsiderations.
Theinterimpluggingcriteriainvolveacorrelation betweeneddycurrentbobbincoilsignalamplitude (voltage) andtubeburstandleakagecapability.
Thepluggingcriteriaisbasedontestingoflaboratory-induced ODSCCspecimens, extensive examination ofpulledtubesfromoperating steamgenerators (industry wide),andfieldexperience withleakageduetoindications at,thetubesupportplates(worldwide).Specifically, crackindications withbobbincoilvoltageslessthanorequalto1.0volt,regardless ofindicated depth,donotrequireremedialactionifpostulated steamlinebreakleakagecanbeshowntobeacceptable.
Crackindications withbobbincoilsignalamplitudes exceeding 1.0voltmustbeeitherpluggedorrepaired.
OTheproposedamendment wouldmaintainthepreviously modifiedT/Ss"3.4.5"SteamGenerators,"
3.4.6,"ReactorCoolantSystemLeakage,"
andtheassociated basesincorporated forthe1voltinterimpluggingcriteria.
Theseprovidetubeinspection requirements andacceptance criteriatodetermine thelevelofdegradation forwhichatubeexperiencing ODSCCatthetubesupport'late elevations.
may'emain inserviceintheCookNuclearPlantUnit1steamgenerators.
Attachment 2toAEP:NRC:1166G EVALUATION Page2SteamGenerator TubeInteritDiscussion Inthedevelopment oftheinterimpluggingcriteria, Regulatory Guides(RG)1.121,"BasesforPluggingDegradedPWRSteamGenerator Tubes,"and1.83"Inservice Inspection ofPWRSteamGenerator Tubes,"areusedasthebasesfordetermining thatsteamgenerator tubeintegrity considerations aremaintained withinacceptable limits.Regulatory Guide1.121describes amethodacceptable totheNRCstaffformeetingGeneralDesignCriteria(GDC)2,4,14,15,31,and32byreducingtheprobability andconsequences ofsteamgenerator tuberupturethroughdetermining thelimitingsafeconditions oftubewalldegradation.
Tubeswithunacceptable
- cracking, asestablished byinservice inspection, shouldberepairedorr'emovedfromservicebyplugging.
ThisRGusessafetyfactorsonloadsfortubeburstthatareconsistent withtherequirements ofSectionIIIoftheASMECode.Forthetubesupportplateelevation degradation occurring intheCookNuclearPlantUnit1steamgenerators, tubeburstcriteriaareinherently satisfied duringnormaloperating conditions bythepresenceofthetubesupportplate.Thepresenceofthetubesupportplateenhancestheintegrity ofthedegradedtubesinthatregionbyprecluding tubedeformation beyondthediameterofthedrilledhole.Itisnotcertainwhetherthetubesupportplatewouldfunctiontoprovideasimilarconstraining effectduringaccidentcondition loadings.
Therefore, nocreditistakeninthedevelopment ofthepluggingcriteriaforthepresenceofthetubesupportplateduringaccidentcondition loadings.
Conservatively, basedontheexistingdatabase,bursttestingshowsthatthesafetyrequirements fortubeburstmarginsduringbothnormalandaccidentcondition loadingscanbesatisfied withbobbincoilsignalamplitudes lessthan6.8volts,regardless ofthedepthoftubewallpenetration cracking.
Regulatory Guide1.83describes amethodacceptable totheNRCstaffforimplementing GDC14,15,31,and32throughperiodicinservice inspection forthedetection ofsignificant tubewalldegradation.
Uponimplementation ofthepluggingcriteria, tubeleakageconsiderations mustalsobeaddressed.
Itmustbedetermined thatthecrackswillnotleakexcessively duringallplantconditions.
Fortheinterimtubepluggingcriteriadeveloped fortheCookNuclearPlantUnit1steamgenerator tubes,littleornoleakageisexpectedduringnormaloperating conditions evenwiththepresenceofthrough-wall cracks.Industrywide,thecrack'orphology ofSCCattubesupportplateintersections isbestdescribed asshort,tight,axiallyorientedmicrocracks separated Attachment 2toAEP:NRC:1166G
.Page3byligaments ofnon-degraded material.
Thesamemorphology isjudgedtobepresentintheCookNuclearPlantUnit.1steamgenerators.
Tubepullexamination resultsfrom1983indicated axialSCCinitsearlystages.Thedepthsoftheevidenced degradation (determined bydestructive exam)showedthemaximumdepthofpenetration tobeapproximately 10%through-wall.
Therotatingpancakecoil(RPC)testingperformed duringthe1989and1992outageshasconfirmed thataxiallyorientedSCCcracksexistatthetubesupportplateintersections.
BasedontheRPCtestingresultsandrelatively smallamplitude bobbinvoltagescoupledwithlowbobbinvoltagegrowthrates,itisconcluded thataxiallyorientedODSCCbestdefinesthedegradation morphology occurring attheCookNuclearPlantUnit1tubesupportplateintersections.
Tubepullsduringthesummer1992refueling outageweredestructively examinedandconfirmthetubedegradation phenomena occurring atthetubesupportplates.Noleakageduringnormaloperating conditions hasbeenobservedatthesupportplatesinthefieldatsimilarplantsforcrackindications withsignalamplitudes lessthan7.7volts.Additionally, noprimary-to-secondary leakageatthetubesupportplatehasbeendetectedinU.S.plants.Relativetotheexpectedleakageduringaccidentcondition
- loadings, thelimitingeventwithrespecttoprimary-to-secondary leakageisapostulated steamlinebreakevent.Laboratory dataforpulledtubesfromotherplantsandmodelboilerspecimens showlimitedleakageforindications under10.0voltsduringapostulated steamlinebreak(SLB)condition (seeSection9.0ofWCAP-13187).
Additional Considerations Theproposedamendment wouldprecludeapproximately 10manremoccupational radiation exposurethatwouldotherwise beincurredbyplantworkersinvolvedintubepluggingorrepairoperations.
Theproposedamendment wouldminimizethelossofmargininreactorcoolantflowthroughthesteamgenerator inLOCAanalyses.
Theproposedamendment wouldavoidlossofmargininreactorcoolantsystemflowandtherefore assistindemonstrating thatminimumflowratesaremaintained inexcessofthoserequiredforoperation atfullpower.Reduction intheamountoftubepluggingrequiredcanreducethelengthofplantoutagesandreduc'ethetimethatthesteamgenerator isopentothecontainment environment duringanoutage,therebyminimizing airbornecontamination andexposure.
Inaddition, wewillperform100$bobbincoilinspection ofthehotlegtubestoidentifynewareasofconcernthatmayarisebyproviding alevelofinservice inspection thatisfarinexcessofthecurrentT/Ssrequirements.
Attachment 2toAEP:NRC:1166G NOSIGNIFICANT HAZARDSANALYSISPage4Wehaveevaluated theproposedT/Schangesandhavedetermined thattheydonotrepresent asignificant hazardsconsideration basedonthecriteriaestablished in10CFR50.92(c).
Operation oftheCookNuclearPlantinaccordance withtheproposedamendment willnot:1)Involveasinificantincreaseintherobabilit orconseuencesofanaccidentreviouslevaluated Testingofmodelboilerspecimens forfreestandingtubesatroomtemperature conditions showburstpressures inexcessof5,000psiforindications ofODSCCwithvoltagemeasurements ashighas19volts.Bursttestingperformed onpulledtubesfromotherplantswithupto10voltindications showburstpressures inexcessof5,900psiatroomtemperatures Correcting fortheeffectsoftemperature onmaterialproperties andminimumstrengthlevels(asthebursttestingwasdoneatroomtemperature),
tubeburstcapability significantly exceedstheRG1.121criteria, requiring themaintenance ofamarginofthreetimesnormaloperating pressuredifferential ontubeburstifthrough-wall cracksarepresent.Basedontheexistingdatabase,thiscriteriaissatisfied withbobbincoilindications withsignalamplitudes lessthan6.8volts,regardless oftheindicated depthmeasurement.
Thisstructural limitisbasedona-95%lowertolerance limit(LTL)confidence levelofthedata.The1.0voltpluggingcriteriacomparefavorably withthestructural limitconsidering expectedgrowthratesofODSCCatCookNuclearPlantUnit1.Alternate crackmorphologies cancorrespond to6.8voltssothatauniquecracklengthisnotdefinedbyaburst-pressure-to-voltage correlation.
However,relativeto'xpected leakageduringnormaloperating conditions, nofieldleakagehasbeenreportedatotherplantsfromtubeswithindications withavoltagelevelofunder7.7volts.Also,aqualitative assessment ismadebetweenthebeginning-of-cycle (BOC)1.0volttubeplu'gging criteriaandthecurrent40$allowable tubewallpenetration pluggingcriteriaatCookNuclearPlantUnit1.AnODSCC-degradedtubesupportplateintersection witha4.0voltbobbincoilresponseisexpectedto.burstatapproximately 7,400psi,usingthemeancurveofFigure9-2ofWCAP-13187.Whilethe-95%LTLcurveisusedintheapplication ofthepluggingcriteria, themeancurvemustbeusedfor Attachment 2toAEP:NRC:1166G Page5thisspecificcomparison inordertoadequately comparethetwodatasetsused.PerVCAP-13187, acomparison ofthematerialproperties at650'Fandroomtemperature condition properties showedthattheelevatedtemperature properties areapproximately 0.86oftheroomtemperature properties.
Therefore, thetemperature-adjusted burstpressurefora4.0voltsbobbincoilindication isexpectedtobeapproximately 6,400psi.Figure11ofNUREG-0718 plotstheburstpressures ofthinned0.875x0.050inchsteamgenerator tubes.At408actualuniformwallthinning, extending 0.75inchinaxiallength,theburstpressureis6,800psi.TheNUREGtestdataisobtainedatatemperature of600F,comparedtotheWestinghouse datanotedabove,whichisadjustedfor650'F.TheNUREGresultsat40$actualthinningarecomparable tothe4.0voltsBOCcriteriaexpectedburstpressure(6,800psiversus6,300psi).Theburstpressurefornon-thinned tubeswithpartialdepthcracksupto0.75inchinlengthisslightlylowerthanforuniformthinninguptodepthsofabout60%.Also,NUREG-0718 information canbeusedtoestimatetheburstpressureforatubewhichhasbeenslotted,simulating anaxialcrack.Theexpectedburstpressurefora40$deep,0.75-inch longEDMslotusingNUREG-0718 isapproximately 6,000psi.Therefore, itisjudgedthatthemarginofsafetycorresponding tothecurrent40%byNDEdepthbasedpluggingcriteriaisnotsignificantly reduceduponimplementation ofa4.0voltsbobbincoilcriterion, whichishigherthanthisproposedinterimpluggingcriterion of1.0volt.Relativetotheexpectedleakageduringaccidentcondition
- loadings, theaccidents thatareaffectedbyprimary-to-secondary leakageandsteamreleasetotheenvironment are:feedwater systemmalfunction, lossofexternalelectrical loadand/orturbinetrip,lossofallACpowertostationauxiliaries, majorsecondary systempipefailure,steamgenerator tuberupture,reactorcoolantpumplockedrotor,andruptureofacontrolroddrivemechanism housing.Ofthese,themajorsecondary systempipefailureisthemost'imitingforCookNuclearPlantUnit1inconsidering thepotential foroff-sitedoses.Uponimplementation oftheinterimpluggingcriteria, itwillbeverifiedthatthedistribution ofcrackingindications atthetubesupportplateintersections issuchthatprimary-to-secondary leakagewouldresultinsiteboundarydoseswithinasmallfractionofthe10CFR100guideline, i.e.,30remthyroid,duringapostulated SLBevent.Dataindicates thata Attachment 2toAEP:NRC:1166G Page6threshold voltageof2.8voltswouldresultinthrough-wall crackswiththepotential toleakatSLBconditions.
Application oftheproposedpluggingcriteriarequiresthatthecurrentdistribution ofnumberofindications versusvoltagebeobtained.
Theindicated bobbincoilvoltageisthencombinedwiththerateofchangeinvoltagemeasurement toestablish anend-of-cycle (EOC)voltagedistribution and,thus,leakrateduringSLBpressuredifferential.
IfitisfoundthattheprojectedSLBleakagefordegradedintersections plannedtobeleftinserviceexceeds120gpm,thenadditional tubeswillbepluggedtoreduceprojected SLBleakagebelow120gpm.MonteCarloanalysesresultsbasedontheCookNuclearPlantUnit1growthrateandassumededdycurrentuncertainties indicatethatover4,000indications, allwitha(BOC)bobbincoilvoltageof2.0volts,wouldcontribute lessthan1gpmleakageatSLBconditions.
Basedontheinspection resultsfromthelastoutage(1992),indications leftinserviceareexpectedtohaveatotalpredicted SLBleakrateof0.0gpmatEOCconditions.
2)Createtheossibilit ofanewordifferent kindofaccidentfromanreviouslanalzedImplementation oftheproposedamendment doesnotintroduce anysignificant changestotheplantdesignbasis.Useofthecriteriadoesnotprovideamechanism thatcouldresultinanaccidentoutsideoftheregionofthetubesupportplateelevations.
Neitherasinglenormultipletuberuptureeventwouldbeexpectedinasteamgenerator inwhichthepluggingcriteriahasbeenapplied(duringallplantconditions).
Thebobbincoilsignalamplitude pluggingcriteriaisestablished suchthatneitheroperational leakagenorexcessive leakageduringapostulated SLBcondition areanticipated.
IndianaandMichiganPowerCompanywillimplement amaximumleakageratelimitof150gpd(0.1gpm)persteamgenerator tohelpprecludethepotential forexcessive leakageduringallplantconditions uponapplication oftheinterim'luggingcriteria.
Thecurrenttechnical specification limitonprimary-to-secondary leakageatoperating conditions isamaximumof1.0gpm"(1440 gpd)forallsteamgenerators oramaximumof500gpdforanyonesteamgenerator.
TheRG1.121criteriaforestablishing operational leakageratelimitsthatrequireplantshutdownarebaseduponleak-before-break considerations todetectafreespancrackbeforepotential tuberupture,'he 150 Attachment 2toAEP:NRC:1166G Page7gpdlimitprovidesforleakagedetection andplantshutdownintheeventoftheoccurrence ofanunexpected singlecrackresulting inleakagethatisassociated withthelongest:permissible cracklength.Regulatory Guide1.121acceptance criteria(Item3ofSection3.2ofWCAP-13187) forestablishing operating leakagelimitsarebasedonleak-before-break considerations suchthatplaneshutdownisinitiated iftheleakageassociated withthelongestpermissible crackisexceeded.
Thelongestpermissible crackisthelengththatprovidesafactorofsafetyofthreeagainstburstingatnormaloperating pressuredifferential.
Avoltageamplitude of6.8voltsfortypicalODSCCcorresponds tomeetingthistubeburstrequirement atthe-95%LTLuncertainty limitontheburstcorrelation.
Alternate crackmorphologies cancorrespond to6.8voltssothatauniquecracklengthisnotdefinedbytheburstpressureversusvoltagecorrelation.
Consequently, typicalburstpressureversusthrough-wall cracklength'orrelations areusedbelowtodefinethe"longestpermissible crack"forevaluating operating leakagelimits.Thesinglethrough-wall cracklengthsthat,resultintubeburstatthreetimesnormaloperating pressuredifferential andSLBconditions, areabout0.44inchand0.84inch,xespectively.
Nominalleakageforthesecracklengthswouldrangefrom0.1gpmto4gpm,respectively, whilelower95%confidence levelleakrateswouldrangefromabout0.01gpmto0.5gpm,respectively.
Anoperating leakratelimitof150gpdwillbeimplemented inapplication oftheinterimtubepluggingcriteria.
Thisleakagelimitprovidesfordetection of0.4inchlongcracksatnominalleakratesand0.6inchlongcracksatthe-95%LTLconfidence levelleakrates.Thus,the150gpdlimitprovidesforplantshutdownpriortoreachingcriticalcracklengthsforSLBconditions atleakrateslessthana-95$LTLconfidence levelandforthreetimesnormaloperating pressuredifferential atlessthannominalleakrates.3)'nvolveasinificantreduction inamarinofsafetTheuseoftheintcrimpluggingcriteriafox'hetubesupportplateatCookNuclearPlantUnit1isdemonstrated tomaintainsteamgenerator tubeintegrity commensurate
'withtherequirements ofRG1.121.Regulatory Guide1.121describes amethodacceptable totheNRCstaffformeetingGDC14,15,31,and32byreducingtheprobability ofthe
~)'I~g~Attachment 2toAEP;NRC;1166G Page8consequences ofsteamgenerator tuberupture.Thisisaccomplished bydetermining thelimitingconditions ofdegradation ofsteamgenerator tubing,asestablished byinservice inspection.
Tubeswithunacceptable crackingwillberemovedfromservice.Themost'imiting effectwouldbeapossibleincreaseinleakageduringasteamlinebreakevent.Oncetheinterimpluggingcriteriaisapplied,excessive leakageduringasteamlinebreakeventisprecluded byverifying thattheexpectedend-of-cycle distribution ofcrackindications't thetubesupportplateelevations wouldresultinminimalandacceptable primary-to-secondary leakageduringallplantconditions.
Thishelpstodemonstrate thatradiological conditions arelessthanasmallfractionofthe10CFR100guideline.
Inaddressing thecombinedeffectsofaloss-of-coolant accident(LOCA)andasafeshutdownearthquake (SSE)onthesteamgenerator component (asrequiredbyGDC2),ithasbeendetermined thattubecollapsemayoccurinthesteamgenerators atsomeplants.Thisisthecaseasthetubesupportplatesmaybecomedeformedasaresultoflateralloadsatthewedgesuppo'rts attheperiphery oftheplateduetothecombinedeffectsoftheLOCArarefaction waveandSSEloadings.
Theresulting pressuredifferential onthedeformedtubesmaycausesomeofthetubestocollapse.
Therearetwoissuesassociated withsteamgenerator tubecollapse.
First,thecollapseofsteamgenerator tubingreduces'theRCSflowareathroughthetubes.Thereduction inflowareaincreases theresistance toflowofsteamfromthe.coreduringaLOCAwhich,inturn,maypotentially increasepeakcladtemperature.
Second,thereisapotential thatpartialthrough-wall cracksintubescouldprogresstothrough-wall cracksduringtubedeformation orcollapse.
Consequently, sincetheleak-before-break methodology isapplicable totheCookNuclearPlantUnit1reactorcoolantsystemprimaryloops,theprobability ofbreaksintheprimarylooppipingissufficiently lowthattheyneednot'econsidered inthestructural designbasisoftheplant.Excluding breaksintheRCSprimaryloops,theLOCAloadsfromthelargebranchlinebreakswereanalyzedforCookNuclearPlantUnit1andwerefoundtobeofinsufficient magnitude toresultinsteamgenerator tubecollapseorsignificant deformation.
Attachment, 2toAEP:NRC:1166G Page9Regardless ofwhetherornotleak-before-break isappliedtotheprimarylooppipingatCookNuclearPlantUnit1,anyflowareareduction isexpectedtobeminimal(muchlessthan1%)andPCTmarginisavailable toaccountforthispotential effect.Analysesresultsshowthatnotubesnearwedgelocations areexpectedtocollapseordeformtothedegreethatsecondary-to-primary in-leakage wouldbeincreased overcurrentexpectedlevels.Forallothersteamgenerator tubes,thepossibility ofsecondary-to-primaryleakageintheeventofacombinedLOCAandSSEeventisnotsignificant.
Inactuality, theamountofsecondary-to-primary leakageintheeventofacombinedLOCAandSSEisexpectedtobelessthanthatcurrently allowed,i.e.,500gpdpersteamgenerator.
Furthermore, secondary-to-primary in-leakage wouldbelessthanprimary-to-secondary leakageforthesamepressuredifferential sincethecrackswouldtendtocloseunderasecondary-to-primarypressuredifferential..
Also,thepresenceofthetubesupportplateisexpectedtoreducetheamountofin-leakage.
Addressing RG1.83considerations, implementation oftheinterimpluggingcriteriaissupplemented by100$inspection requirements atthetubesupportplateelevations havingODSCCindications, reducedoperating leakratelimits,andeddycurrentinspection guidelines toprovideconsistency involtagenormalization.
Asnotedpreviously, implementation oftheinterimpluggingcriteriawilldecreasethenumberoftubeswhichmustberepairedortakenoutofservicebyplugging.
Theinstallation ofsteamgenerator tubeplugsreducestheRCSflowmarginand,thus,implementation oftheinterimpluggingcriteriawillmaintainthemarginofflowthatwouldotherwise bereducedintheeventofincreased tubeplugging.
Basedontheabove,itisconcluded thattheproposedchangedoesnotresultinasignificant reduction inmarginwithrespecttoplantsafetyasdefinedintheFinalSafety-AnalysisReportoranybasesoftheplantTechnical Specifications.
CONCLUSION Based'onthepreceding
- analysis, itisconcluded thatusingthetubesupportplateelevation bobbincoilsignalamplitude interimsteamgenerator tubepluggingcriteriaforremovingtubesfrom Attachment 2toAEP:NRC:1166G Page10serviceatCookNuclearPlantUnit1isacceptableandtheproposedlicenseamendment doesnotinvolveaSignificant HazardsConsideration asdefinedin10CFR50.92.