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:00216 i'r.DamesG.Keppler,RegionalDirectorOfficeofInspection andEnforcement U.S.tluclearRegulatory Commission RegionIll799Roosevelt RoadGlenEllyn,Illinois60137

DearI'1r.Keppler:

Thisletterandtheaccompanying reportintheormofsixattachments supplement fir.D.V.Shaller's letterofflay26,1979concerning thesmallcracksidentified inthemainfeedwater elbowsattheDonaldC.CookPlantUnits1and2.Thereport,submitted inaccordance withTechnical Specification 6.9.1.8.i,detailstheresultsofAEP'sinvestigation intothismatter,thecorrective actionstaker,thetestprogramtobeimplemented onthefeedwater system,andasafetyevaluation ofthisevent.Onttay19,1979Unitt<o.2wasbroughttocoldshutdowncondition todetermine thesourceofnon-radioactive waterthatwasbuildingupinthecontainment sump.Investigation onNay20,1979revealedsmallcracksinelbowsofthemainfeedwater linestosteamgenerators 1and4.f1r.Shallerinformedi1r.K.R.Baker,NRCRegionIIIInspector, ofthesefindingsthatsameday.Ineachofthefoursteamgenerator secondary lines,avertical14-inchcarbonsteelfeedwater pipeisweldedtoa14-inchby16-inchreducer,whichinturnisweldedtoa16-inchcarbonsteelelbow.This16-inchelbovisweldeddirectlytoa16-inchlowalloynozzleonthesteamgenerator.

Thecrackswerefoundinthe16-inchfeedwater elbowsadjacenttothefeedwate1 elbow,'.tean gererator nozzlewelds.Thesecracksinitiated outsideoftheheataffectedzonesofthewelds.6'ry Yir.'ames G.KepplerRegionalDirector-2-June7,1979AEP:NRC:00216 IExamination oftheelbowshasindicated thecracksinitiated atthetop'of'theinnersurfaceoftheelbowatamachineddiscontinuity requiredfortheweld-endpreparation.

'IRadiographic examinations ofthenozzle/feedwater lineweldregionsforUnit2steamgenerators Nos.2and3showedindication ofcracksinthesameareaoftheelbows.ThesameareasinUnitIweresubsequently radiographed andindications werefoundinthe16-inchelbowsofthe,eedwater linestosteamgenerators No.2,3and4.Thisdiscovery ofcrackindications waspromptlyreportedtoRegionIII.Wewerenotabletodetectthepresenceofindications inthe16-inchelbowtosteamgenerator No.IinUnitIusingradiographic techniques becauseof theuniqueconditions ofthebackingring.Subsequent liquidpenetrant examination indicated crackinginthiselbow.Thewallthickness ofthe16-inchelbowisapproximately 50percent.greaterthanthatofthesteamgenerator nozzle.Tocompensate forthisdiffernceinwallthickness, theweldpreparation includedmachining andbevelingastepontheinsideoftheelbowtomatchthethickness ofthesteamgenerator nozzleatthepointoftheweld.Stressesconcentrated inthisthinnersectionadjacenttotheweldandweremagnified atthepointofdiscontinuity.

Thehighestdesignstresspointinthefeedwater lineinsidethecontainment isatthe90'4-inch elbowsatthebottomoftheverticalriser.The14-inchelbowsareinthesameverticalplaneastheaffected16-inchelbows.Fiveofthe14-inchelbowswereradiographed.

Noindications werefound.Samplesofthecrackedareasofthe16-inchelbowsweresenttotwolaboratories forretallurgical examination.

Reportsfromthemetal-lurgicalexaminations showedthatthecrackpropagaion.wascausedbyhigh-cyclefatigueassistedbycorrosion.

Furtherdetailsof'themetallurgical examination aredescribed inAttachment 2.Afterremvalofthe16-inchelbows,theinsideoftheUnit2steamgenerator nozzleswereexaminedbytheliquidpenetrant method.Light,pittingandintermittent linearindications werenotedonthenozzlecounter-bores.Subsequent visualinspection oftheUnitInozzlesshowedsimilarpittinginthenozzlecounterbore region.Wearereplacing the16-inchelbowstoallsteamgenerators inUnitsIand2.Thesenewelbowsdonothavethesharpdiscontinuities onthepipeinnersurface,andthestrengthoftheelbowintheweldareahasbeenincreased.

Thepitsandindications onthesteamgenerator nozzles Hr.JamesG.KepplerRegionalOirector-3-June7,1979AEP:NRC:00216arebeingblendedout.Thestressconcentration atthenozzlecounter-boreisbeingreducedwiththeadditionofa1/2-inchradiusfillet.Meareimplementing aprogramtodetermine thecharacteristics ofthehighcyclefatigue.Thisprogramincludestheinstallation ofstrain,temperature, pressureandvibration instrumentation atsignificant pointsonthepipingsystemoftwofeedvater linesinUnit2.Oetailsofthenew16-inchelbow,thenozzlerepairsandinstrumentation.

areinAttachment 5.Thesafetyimplications ofthiseventatCookNuclearPlanthavebeencarefully analyzedbyoursafetyreviewcommittees.

Itwasconcluded thatthecondition identified didnotadversely affectthehealthandsafetyofthegeneralpublic.Itdivas.concluded thatthereturnof-theunitstopowerwiththenewlydesignedelbowswillhavenoadverseeffectonthegeneralpublic.Operation ofUnit2withtheinstrumentation programwillindicatewhetherthereisanyneedforfurthercorrective action.Asafetyevaluation isgiveninAttachment 6.MeexpecttobeginstartupofUnit2byJune13,1979andUnit1byJune20,1979.Verytrulyyours,JEDkbAttachrrints ohnE.DolanVicePresident cc:R.C.CallenG.CharnoffR.S.HunterR.M.Jurgensen N.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)