ML17325B015

Provides Info Re Degradation of A-193 Grade B6 Type 410 Stainless Steel Retaining Block Studs in Darling Valve & Mfg Co Clear Waterway Check Valves Installed at Plant

ML17325B015
Person / Time
Site:	Cook
Issue date:	10/28/1988
From:	ALEXICH M P INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
AEP:NRC:1054, NUDOCS 8811080073
Download: ML17325B015 (16)

Text

ACCEISRATEDDISTRIBUTIONDEMONSTRATIONSYSTEMREGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR:8811080073DOC.DATE:88/10/28NOTARIZED:NODOCKETFACIL:50-315DonaldC.CookNuclearPowerPlant,Unit1,Indiana60500031550-316DonaldC.CookNuclearPowerPlant,Unit2,Indiana&05000316~;~AUTH.NAMEAUTHORAFFILIATIONALEXXCH,M.P.IndianaMichiganPowerCo.(formerlyIndiana&MichiganElef(RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)

SUBJECT:

ProvidesinforedegradationofA-193GradeB6Type410stainlesssteelretainingblockstudsincheckvalves.DISTRIBUTIONCODE:A001DCOPIESRECEIVED:LTRENCLSIZE:TITLE:ORSubmittal:GeneralDistributionNOTESRlID'8RECIPIENTIDCODE/NAMEPD3-1LASCOTT,WINTERNAL:ARM/DAF/LFMBNRR/DEST/CEB8HNRR/DEST/MTB9HNRR/DOEA/TSB11U9~8~~CTREGFILE-01EXTERNAL:LPDRNSIC]COPIESLTTRENCL10111011111111111111RECIPIENTIDCODE/NAMEPD3-1PDNRR/DEST/ADS7ENRR/DEST/ESB8DNRR/DEST/RSB8ENRR/PMAS/ILRB12OGC/HDS1RES/DSIR/EIBNRCPDRCOPIESLTTRENCL2211111111101111D'8,RNCJXEK)ALL"RIDS"RECZPZEPlS:PLEASEHELPUSTOREMJCEWASTE.'XRGACTTHEDOCGMEÃZCONTROLDESK,ROCMP1-37(EXT.20079)TOELIMINATEYOURNAMEHKEDISTEKBUTIGNLISTSH)RDOCUKNTSY0UDON~TNEEDfDD8~TOTALNUMBEROFCOPIESREQUIRED:LTTR19'NCL'16 IndianaMichiganPowerCompany~P.O.Box16631Columbus,OH43216AEP:NRC:1054DonaldC.CookNuclearPlantUnitNos.1and2DocketNos.50-315and50-316LicenseNos.DPR-58andDPR-74VOLUNTARYREPORT:DEGRADATIONOFRETAININGBLOCKSTUDSINDARLINGVALVEANDMANUFACTURINGCOMPANYCLEARWATERWAYCHECKVALVESU.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C'.20555Attn:A.B.DavisOctober28,1988

DearMr.Davis:

ThepurposeofthisletteristoprovideyouwithinformationconcerningrecentlyobserveddegradationofA-193GradeB6Type410stainless,steelretainingblock,.studsinDarlingValveandManufacturingCompanyClearWaterwaycheckvalves,installedattheCookNuclearPlant.The'bservedconditiondid,not.resultin'anycheckvalvefailures,,'andwehavedetermined.that,thecondition"wasnotreportableunderTitle'0CFRorourtechnicalspecifications(T/Ss).However,becausedegradationofthetypeobservedattheCookNuclearPlanthasbeenofgeneralindustryinterestinthepast(e.g.,INPOSignificantOperatingExperienceReport[SOER]86-03),wehaveelectedtosubmitthisvoluntaryreport.Asummaryoftheobservedconditionandactionswehavetakenisprovidedbelow.Inconjunctionwiththeperformanceofothermaintenanceon8"DarlingClearWaterwayswingcheckvalve(2-SI-151W)installedinthelowpressureemergencycorecoolingsyst:em(ECCS),aninspectionofthevalveinternalswasperformedinaccordancewiththemaintenanceprogramthatweestablishedinresponsetoINPOSOER86-03.Duringthisinspection,oneofthetworetainingblockstudswas,foundbrokenandtheothercracked.AdiagramofthevalvetypeinquestionisprovidedinFigure1.The"retainingblockstuds(PartNo.11542-61-5)retaintheblocks(PartNos.1'1542-60/60-1),thatholdthevalvediscassemblyinplace.Asaresultofthisfinding,the"correspondingcheck*valve(2-SI-151E)intheredundantlowpressure-ECCStrainwas(8311080073S81028PDRADQCK05000315PPDC

~~e~pe*a Mr.A.B.Davis-2-AEP:NRC:1054inspected.Again,oneofthetworetainingblockstudswasfoundbrokenandtheothercracked.DiscoveryofthissecondinstancepromptedtheexpansionoftheinspectiontoallUnit2Darlingcheckvalvesofthesamedesignasthoseinwhichthedegradedstudswerefound.Thereare12valvesofthisdesigninstalledintheECCSandRHRsystemsineachunitatCookNuclearPlant.Allofthesevalvesareclassifiedaspressureisolationvalves'PIVs)andleaktestedinaccordancewithourISTvalveprogram.Theyare:o(4)10"checkvalvesattheaccumulatoroutlet(SI-166L1,L2,L3,L4)o(4)10"checkvalvesECCSinjectiontocoldlegs(SI-170L1,L2,L3,L4)o(2)8"checkvalveslowpressureECCS(SI-151E&W)o(2)8"checkvalvesnormalRHR(RH-133,-134)Figure2providesasimplifiedflowdiagramwhichidentifiesthelocationsofthesecheckvalvesineitherunitatCookNuclearPlant.SoonafterthedecisionwasmadetoinitiatetheinspectionofUnit2checkvalveshowever,Unit1wentfrompoweroperationtohotshutdown(Mode4)duetoanunrelatedevent.Asaresult,adecisionwasmadetoimmediatelyinspectallUnit1checkvalvesofthisdesignaccessibleinMode4.InUnit1,theonlycheckvalvesaccessibleforinspectionduringtheMode4forcedoutagewere1-SI-151E,1-SI-151W,1-SI-166L1,and1-SI-166L4.TheUnit1inspectionsfoundonebrokenstudineachofthecheckvalvesinstalledinthelowpressureECCS(1-SI-151E&W)andstudmaterialwithanappearancenottypicalofType410stainlesssteelineachofthetwoaccessibleaccumulatoroutletvalves(1-SI-166L1,&L4).ThecontinuingUnit2inspectionsidentifiedoneadditionalcheckvalvewithonecrackedstud(2-SI-166L4),andonevalve(2-SI-166Ll)inwhich,althoughthestudswereintact,thestudmaterialdidnothavetheappearancetypicalofType410stainlesssteel,thematerialspecifiedonthevalvedrawingfortheretainingblockstuds.Bothvalvesarelocatedontheaccumulatoroutlet.AsummaryofinspectionresultsforthevalvesinspectedinbothUnit1andUnit2isprovidedinTablel.ActionsResultinfromCheckValveInsectionsIneachofthecasesdiscussedabove,thecrackedorbrokenstuds,orstudsofamaterialhavinganappearancenottypicalof l4IIf!~"I"f~.%PI/'lI~

Mr.A.B.Davis-3-AEP:NRC:1054Type410stainlesssteelwerereplacedwithA-193GradeB8studmaterial.Thisnewstudmaterialisrecommendedbythevalvemanufacturerforthisapplication.Inaddition,maintenancejoborderswereinitiatedtoreplaceallA-193GradeB6Type410stainlesssteelstudswiththenewA-193GradeB8materialregardlessofwhetheranydegradationiscurrentlyevident.Thisactionisalsoinaccoidancewiththevalvemanufacturer'srecommendation.Todate,retainingblockstudsin10ofthe12Unit2checkvalvesand4ofthe12Unit1checkvalveshavebeenreplacedwiththenewA-193GradeB8studmaterial.ThestudsintheremainingUnit2checkvalveswillbereplacedduringthecurrentsteamgeneratorrepairprojectoutage.ThestudsintheremainingUnit1checkvalvesaretobereplacedduringthenextscheduledoutage,withthepossibleexceptionofthoseinstalledinthelowpressureinjectionlinestothecoldlegs(1-SI-170Ll,L2,L3andL4).Serviceconditionsforthesevalvesmaynotbeconducivetothetypeofstuddegradationobservedintheothersystemsinspected.Westinghouse,whosuppliedthecheckvalvesundertheoriginalNSSScontract,andDarling,thevalvemanufacturer,wereadvisedoftheinspectionfindingsdiscussedabove.Westinghouseisconductingmetallurgicalevaluationstodeterminetherootcauseofthestuddegradation.EvaluationofSafetSinificanceWithregardtotheevaluationofthesafetysignificanceofourvalveinspectionfindings,thefollowingkeyfactorswereconsidered:1)Thecheckvalvesintheiras-foundconditionhadnotfailed,norwasvalveoperabilityimpaired.2)InadvertentpressurizationofalowpressureECCSsystemisprecludedsinceineachcasewhereacheckvalvewithpotentiallydegradedstudswasfound,at.leasttwovalveswereavailabletopreventbackleakagefromthereactorcoolantsyst:em.3)'Thecheckvalveswouldhaveperformedtheirintendedfunction(i.e.,opened)intheeventofaLOCAregardlessofwhethertheretainingblockstudshadcompletelyfailed.4)Ofthe10valvesinspectedonUnit2,threeshoweddegradationoftheretainingblockstudsandonewasfoundtohavequestionablestudmaterial.ThecorrespondingUnit1valveswhichseethesameserviceconditionsasUnit2wereinspectedandstudsreplacedwiththenewstudmaterial.NoanomalieswereobservedintheremainingUnit2checkvalvesinspected.

)>~V4h'yI Mr;A.B.Davis-4-AEP:NRC:10545)TheUnit2valvesinthedegradedconditionhadfunctionedsuccessfullyinpassingtherequiredflowduringMode5or6operationatthebeginningofthesteamgeneratorrepairoutage.Successfuloperationofthesevalvesduringthisevolutionisequivalenttopassingthefullflowtestnormallyperformedtoconfirmvalveoperability.Unit1wasreturnedtoserviceonSeptember15,1988,andtheactionsdiscussedabovetoreplaceretainingblockstudsonbothunitshavecommenced.ThisdocumenthasbeenpreparedfollowingCorporateprocedureswhichincorporateareasonablesetofcontrolstoensureitsaccuracyandcompletenesspriortosignaturebytheundersigned.Sincerely,M.P.AlxichVicePresidentldpcc:D.H.Williams,Jr.W.G.Smith,Jr.-BridgmanR.C.CallenG.CharnoffA.B.DavisNRCResidentInspector-BridgmanG.Bruchmann f

TABLE1SUMMARYOFANCHOR/DARLINGCHECKVALVEINSPECTIONSValveSizeServiceLocationRetainingBlockStudConditionUnit11-SI-151E8IISafetyInjection(SI)ToHotLegsOneBrokenStud11-SI-151W81I1-SI-166L110"SIToHotLegsAccumulatorOutletOneBrokenStudQuestionybleStudMaterialUnit21-SI-166L410"AccumulatorOutletQuestionableStudMaterial2-RH-1332-RH-1342-SI-151E8II8II8IIResidualHeatRemoval(RHR)ToColdLegRHRToColdLegSIToHotLegsOKOKOneBrokenStud3OneCrackedStud2-SI-151W8IISIToHotLegsOneBrokenStudOneCrackedStud2-SI-166L110"2-SI-166L210"2-SI-166L310"2-SI-166L410"2-SI-170L110"2-SI-170L410"AccumulatorOutletAccumulatorOutletAccumulatorOutletAccumulatorOutletLowPressureInjectionToColdLegLowPressureInjectionToColdLegQuestionableStudMaterialOKOKOneCrackedStudOKOK Table1Notes:1)Abrokenstudisastudthathascompletelyshearedintotwoparts.Ineachcasewhereabrokenstudisreported,thebreakoccurredatorneartheplaneoftheinterfacebetweenthevalvebodyandtheretainingblock.2)QuestionablestudmaterialreferstostudsthatlookedshinyinsteadofhavingtheblackappearancetypicalofType410stainlesssteel,themateriallistedonthevalvedrawingsfortheretainingblockstuds.Itappearsthatthe"as-found"materialiseitherType304or316stainlesssteel.3)Acrackedstudisastudthathaspartiallyshearedbuthasnotpartedintotwopieces.

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