ML17317B262

Forwards LER 79-019/01T-0

ML17317B262
Person / Time
Site:	Cook
Issue date:	06/07/1979
From:	DOLAN J E INDIANA MICHIGAN POWER CO.
To:	KEPPLER J G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17317B263	List: ML17317B262 ML17317B264
References
AEP-NRC:00216, AEP-NRC:216, NUDOCS 7906150329
Download: ML17317B262 (3)

Text

INDIANAFMICHIGANPOV/EP.COMPANYP.O.BOX1SBOWLINGGREENSTATIONNEWYORK,H.Y.1000aDonaldC.-CookNuclearPlantUnits1and2DocketHos.50-315and50-316LicenseNos.DPR-58andDPR-74June7,1979AEP:HRC:00216i'r.DamesG.Keppler,RegionalDirectorOfficeofInspectionandEnforcementU.S.tluclearRegulatoryCommissionRegionIll799RooseveltRoadGlenEllyn,Illinois60137

DearI'1r.Keppler:

Thisletterandtheaccompanyingreportintheormofsixattachmentssupplementfir.D.V.Shaller'sletterofflay26,1979concerningthesmallcracksidentifiedinthemainfeedwaterelbowsattheDonaldC.CookPlantUnits1and2.Thereport,submittedinaccordancewithTechnicalSpecification6.9.1.8.i,detailstheresultsofAEP'sinvestigationintothismatter,thecorrectiveactionstaker,thetestprogramtobeimplementedonthefeedwatersystem,andasafetyevaluationofthisevent.Onttay19,1979Unitt<o.2wasbroughttocoldshutdownconditiontodeterminethesourceofnon-radioactivewaterthatwasbuildingupinthecontainmentsump.InvestigationonNay20,1979revealedsmallcracksinelbowsofthemainfeedwaterlinestosteamgenerators1and4.f1r.Shallerinformedi1r.K.R.Baker,NRCRegionIIIInspector,ofthesefindingsthatsameday.Ineachofthefoursteamgeneratorsecondarylines,avertical14-inchcarbonsteelfeedwaterpipeisweldedtoa14-inchby16-inchreducer,whichinturnisweldedtoa16-inchcarbonsteelelbow.This16-inchelbovisweldeddirectlytoa16-inchlowalloynozzleonthesteamgenerator.Thecrackswerefoundinthe16-inchfeedwaterelbowsadjacenttothefeedwate1elbow,'.teangereratornozzlewelds.Thesecracksinitiatedoutsideoftheheataffectedzonesofthewelds.6'ry Yir.'amesG.KepplerRegionalDirector-2-June7,1979AEP:NRC:00216IExaminationoftheelbowshasindicatedthecracksinitiatedatthetop'of'theinnersurfaceoftheelbowatamachineddiscontinuityrequiredfortheweld-endpreparation.'IRadiographicexaminationsofthenozzle/feedwaterlineweldregionsforUnit2steamgeneratorsNos.2and3showedindicationofcracksinthesameareaoftheelbows.ThesameareasinUnitIweresubsequentlyradiographedandindicationswerefoundinthe16-inchelbowsofthe,eedwaterlinestosteamgeneratorsNo.2,3and4.ThisdiscoveryofcrackindicationswaspromptlyreportedtoRegionIII.Wewerenotabletodetectthepresenceofindicationsinthe16-inchelbowtosteamgeneratorNo.IinUnitIusingradiographictechniquesbecauseoftheuniqueconditionsofthebackingring.Subsequentliquidpenetrantexaminationindicatedcrackinginthiselbow.Thewallthicknessofthe16-inchelbowisapproximately50percent.greaterthanthatofthesteamgeneratornozzle.Tocompensateforthisdiffernceinwallthickness,theweldpreparationincludedmachiningandbevelingastepontheinsideoftheelbowtomatchthethicknessofthesteamgeneratornozzleatthepointoftheweld.Stressesconcentratedinthisthinnersectionadjacenttotheweldandweremagnifiedatthepointofdiscontinuity.Thehighestdesignstresspointinthefeedwaterlineinsidethecontainmentisatthe90'4-inchelbowsatthebottomoftheverticalriser.The14-inchelbowsareinthesameverticalplaneastheaffected16-inchelbows.Fiveofthe14-inchelbowswereradiographed.Noindicationswerefound.Samplesofthecrackedareasofthe16-inchelbowsweresenttotwolaboratoriesforretallurgicalexamination.Reportsfromthemetal-lurgicalexaminationsshowedthatthecrackpropagaion.wascausedbyhigh-cyclefatigueassistedbycorrosion.Furtherdetailsof'themetallurgicalexaminationaredescribedinAttachment2.Afterremvalofthe16-inchelbows,theinsideoftheUnit2steamgeneratornozzleswereexaminedbytheliquidpenetrantmethod.Light,pittingandintermittentlinearindicationswerenotedonthenozzlecounter-bores.SubsequentvisualinspectionoftheUnitInozzlesshowedsimilarpittinginthenozzlecounterboreregion.Wearereplacingthe16-inchelbowstoallsteamgeneratorsinUnitsIand2.Thesenewelbowsdonothavethesharpdiscontinuitiesonthepipeinnersurface,andthestrengthoftheelbowintheweldareahasbeenincreased.Thepitsandindicationsonthesteamgeneratornozzles Hr.JamesG.KepplerRegionalOirector-3-June7,1979AEP:NRC:00216arebeingblendedout.Thestressconcentrationatthenozzlecounter-boreisbeingreducedwiththeadditionofa1/2-inchradiusfillet.Meareimplementingaprogramtodeterminethecharacteristicsofthehighcyclefatigue.Thisprogramincludestheinstallationofstrain,temperature,pressureandvibrationinstrumentationatsignificantpointsonthepipingsystemoftwofeedvaterlinesinUnit2.Oetailsofthenew16-inchelbow,thenozzlerepairsandinstrumentation.areinAttachment5.ThesafetyimplicationsofthiseventatCookNuclearPlanthavebeencarefullyanalyzedbyoursafetyreviewcommittees.Itwasconcludedthattheconditionidentifieddidnotadverselyaffectthehealthandsafetyofthegeneralpublic.Itdivas.concludedthatthereturnof-theunitstopowerwiththenewlydesignedelbowswillhavenoadverseeffectonthegeneralpublic.OperationofUnit2withtheinstrumentationprogramwillindicatewhetherthereisanyneedforfurthercorrectiveaction.AsafetyevaluationisgiveninAttachment6.MeexpecttobeginstartupofUnit2byJune13,1979andUnit1byJune20,1979.Verytrulyyours,JEDkbAttachrrintsohnE.DolanVicePresidentcc:R.C.CallenG.CharnoffR.S.HunterR.M.JurgensenN.C.t1oseley,NRC0.V.Shaller,BridgmanR.E.MasseRO:ZZZP.W.Steketee,Esa..R.Walsh,Esp.G.Charnoff,Esa.R.C.,CallenMPSCJ.M.HenniganG.OlsonPNSRCJ.F.StietzelDir.,ZE(40copies)Diz.,MZPC(4copies)