ML17335A223

Submits Addl Info Re Relief Request for Third 10-yr Interval Pump in-service Test Plan.Proposed Alternative Is Being Submitted Because Code Requirements for Vibration Cannot Be Met Due to Containment Spray Pumps Being Tested

ML17335A223
Person / Time
Site:	Cook
Issue date:	09/04/1998
From:	POWERS R P INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AEP:NRC:0969BM, AEP:NRC:969BM, NUDOCS 9809160029
Download: ML17335A223 (20)

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CATEGORY1.REGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)r'CCESSIONNBR:9809160029DOC.DATE:98/09/04NOTARIZED:NODOCKETFACIL:50-315DonaldC.CookNuclearPowerPlant,Unit1,IndianaM0500031550-316DonaldC.CookNuclearPower.Plant,Unit2,XndianaM05000316AUTH.NAMEAUTHORAFFILIATIONPOWERS,R.P.IndianaMichiganPowerCo.(formerlyIndiana&.MichiganEleRECIP.NAMERECIPIENTAFFILIATIONRecordsManagementBranch(DocumentControlDesk)

SUBJECT:

Submitsaddiinforereliefrequestforthird10-Yrintervalpumpin-servicetestplan.Proposedalternativebeingsubmittedbecausecoderequirementsforvibrationcannotbemetduetocontainmentspraypumpsbeingtested.DISTRIBUTIONCODE:A047DCOPIESRECEIVED:LTRENCL'SIZE:TITLE:ORSubmittal:Inservice/Testing/RelieffromASMECode-GL-89-04NOTES:ATRECIPIENTIDCODE/NAMEPD3-3LASTANG,JINTERNAL:AEOD/SPD/RABNRR/DE/ECGBOGC/HDS3'ES/DET/EMMEBCOPIESLTTRENCL111111111011RECIPIENTIDCODE/NAMEPD3-3PDFIECENUDOCS-ABSTRACTRES/DET/EIBCOPIESLTTRENCL11111111EXTERNAL:LITCOANDERSONNRCPDR1111NOAC11DNNOTETOALLnRIDSnRECIPIENTSPLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083TOTALNUMBEROFCOPIESREQUIRED:LTTR13ENCL12 IndianaMichigan~PowerCompany500CircleDriveBuchanan,Ml491071373INOIAiMNICHIGAHIrWMSeptember4,1998AEP:NRC:0969BM10CFR50.55aDocketNos.:50-31550-316U.S.NuclearRegulatoryCommissionATTN:DocumentControlDeskMailStop0-Pl-17Washington,D.C.20555-0001Gentlemen:DonaldC.CookNuclearPlantUnits1and2RELIEFREQUESTFORTHETHIRDTENYEARINTERVALPUMPIN-SERVICETESTPLANADDITIONALINFORMATIONThepurposeofthisletteristoproposeanalternativetotherequirementsofASMESectionXI,OMa-1988,Part6,paragraph5.2,Table34forthecontainmentspray(CTS)pumps.This~alternativeisbeingsubmittedundertheprovisionsof10CFR50.55a(a)(3)(ii),"compliancewiththespecifiedrequirementsofthissectionwouldresultinhardshiporunusualdifficultywithoutacompensatingincreaseinthelevelofqualityorsafety".TheproposedalternativeisbeingsubmittedbecausethecoderequirementsforvibrationcannotbemetduetotheCTSpumpsbeingtestedatlowflowconditionsandbecauseofthepumps'esign.OuroriginalreliefrequestsforthethirdtenyearintervalweresubmittedbyletterAEP:NRC:0969AM,datedJune12,1996.ByletterdatedMay27,1997,theNRCdeniedthereliefrequestforthecontainmentspraypumps,statingthatinsufficientinformationwasprovidedintheoriginalrequest.OnJanuary13,1998,andFebruary9,1998,discussionswereheldwithmembersofyourstaffregardingtestingoftheseCTSpumps,andarequestforinterimreliefwassubmittedviaAEP:NRC:0969BJ,datedMarch3,1998.Theinterimreliefwasrequestedwhileamodificationwasmadetooursparepumpatthemanufacturer'sservicecenter.Themodificationtothepumpwasmadeinanattempttoreducethepump'svibrationlevelsatlowflowsatwhichthevibrationdataaretaken.Themodifications,however,didnotsignificantlyreducethevibrationlevelsatlowflow,andpermanentreliefisbeingrequested.Thepermanentreliefrequestiscontainedintheattachmenttothisletter.ThereliefrequestcontainstheadditionalinformationtheNRCrequestedintheMay27,1997,denial.9809160029',980904PDRADOCK05000315P'DR U.S.NuclearRegulatoryCommissionPage2AEP:NRC:0969BMExpeditedreviewofthisreliefrequestisrequestedbecausethisreliefisnecessaryforrestartofourunits.Sincerely,REPEPowersVicePresident/jmcAttachmentsceJ.A.AbramsonJ.L.Caldwell,w/attachmentsMDEQ-DW&RPDNRCResidentInspector,w/attachmentsJ.R.Sampson,w/attachments U.S.NuclearRegulatoryCommissionPage3AEP:NRC:0969BMbc:T.P.Beilman,w/attachmentsE.R.Eckstein/D.R.Hafer/K.R.BakerJ.J.EutoFOLIO,w/attachmentsE.HinesJ.B.Kingseed/M.S.Ackerman/G.P.Arent/M.J.GumnsF.R.Pisarsky/B.B.BradleyJ.F.Stang,Jr.,NRC-Washington,DC,w/attachments ATTACHMENTTOAEP:NRC:0969BMCONTAINMENTSPRAYPUMPRELIEFREQUEST AttachmenttoAEP:NRC:0969BMPage1~Summa'heCookNuclearPlanthasfourcontainmentspray(CTS)pumpsofanoldervintagethatmetthe1983codeedition,butareunabletoconformwiththevibrationrequirementsimposedbythecodeupgradeforthethirdten-yearin-servicetestinterval.Theirinabilitytoconformisnotduetodegradedperformance,butratheraconsequenceoftheiroriginaldesignandtheirbeingtestedatlowflowconditions.Amodificationwasperformedtothespareassemblyinanefforttoreducelowflowvibrationstowithinlimitsspecified,bythecode.Extensivetestingofthepre-andpost-modificationdesignwasperformedonthespareCTSpumpwiththeassistanceofthepump'smanufacturer.Theseeffortsrevealedthatvibrationsencounteredonpumpsinstalledinthefieldhavesimilarvibrationsignaturestothesparepumpwhichhadnopreviousruntimeandwasthoroughlyinspectedpriortotesting.Thevibrationsexperiencedweredeterminedtobearesultofimpellervanepassduringlowflowconditions.Thisvibrationwasinverselyproportionaltoflowrate,withvibrationsdecreasingtoacceptablelimitsatthepump'sdesignflowrating.Althoughsomereductioninpumpvibrationswasachieved,therevisedacceptancelimitswerenotmet.Basedontestingperformeditwasconcludedthatfullcompliancewiththecodewouldrequireeitheracompletenewtestcircuitcapableofaccommodatingfullflow,oraredesignedrotatingelement(e.g.fivevaneimpeller),whichwouldreducethevanepassfrequencyvibration.Timetoimplementeitheroneoftheseoptionshasbeenestimatedatsixtotenmonths.Consequently,theirinstallationwouldresultinasignificanthardshipwithoutacompensatingincreasein,safety.Therefore,analternatemonitoringmethodisproposedtomeettheintentofthecode,detectionofpumpdegradation,andtoprovidereasonableassuranceofanacceptablelevelofqualityandsafety.Thealternatesurveillancespecifiedtomonitorthesafeoperationofthisequipmentadoptsanapproachtoanalyzeavibrationsignature,orspectrum.Insteadofanoverallaccumulativeapproach,thevibrationsignaturewillbedividedintonarrowbandsoffrequencysuchthatspecificformsofincipientdegradationcanbedetected.DiscussionswiththedirectoroftheVibrationInstitute,membersofASME/ANSI0&Mworkinggroupforin-servicetesting,thepumpmanufacturer,andpersonnelfromothernuclearutilitiesconfirmthatspectralanalysisisanacceptableindustrypracticeforpredictivemaintenanceonrotatingmachinery.

AttachmenttoAEP:NRC:0969BMPage2lnadditiontothealternatetestingspecifiedintheattachedreliefrequest,predictivemaintenance,suchasinfraredthermographyofmotorbearingsandspectralmonitoringonthepumpcasings,willbeemployed.Althoughnotpartofthereliefrequest,theseadditionaleffortswillfurtherenhancemonitoringoftheCTSpumps.REQUESTNO.1RELIEFREQUESTTHIRDTEN-YEARINTERVALPUMPZN-SERVICETESTPLANTITLE:ContainmentSprayPumpVibrationLimitsUNITAPPLICABILITY:Units1and2PUMPNAME:ContainmentSprayPUMPNUMBER(S):PP-009SYSTEM:ContainmentSpray(CTS)FLOWDIAGRAM:5144ASMECLASS:2PUMPFUNCTION:ProvidecoolingwaterflowtocontainmentatmosphereinaLOCAorsteamlinebreak.RELIEFTYPE:ProposedAlternativespraytheASMECODETESTREQUIREMENTS

REFERENCE:

OMa-1988,Part6;paragraph5.2TestProcedureandtheRangesforVibrationTestParametersshowninTable3a.CODEREQUIREMENTDESCRIPTION:Forcentrifugalpumpsrunningat2600rpm,whereV,isthereferencedbroadbandunfilteredvibrationmeasurement;Acceptablerangeat52.5V,Alertrange>2.5V,to6V,or>0.325,in/secRequiredactionrange>6V,or>0.70in/secBASISFORCODEALTERNATIVE:TheCTSpumpsinstalledatCookNuclearPlantvibrateinexcessoftherequiredactionlevelspecifiedwithinTable3aofOMa-1988.Thisisnotduetodegradedperformance,butratherequipmentdesignandthelimitedflowachievableduringsurveillancetesting.Baselinetestingofasparepumpassemblyconfirmedthatthevibrationdecreaseswithincreasingflow,towithinacceptablelimits,asshowninfigure1.TheCTSpumpsareasinglestageunitmountedvertically.Thepumpshavedualsuctioninadoublevolutecasingequippedwithanimpellerwithanevennumber(4)ofvanes.Theradialclearance"GapB"betweentheimpeller'svanesandeachvolutelipissmall.Thepipingconfigurationonlyallowsthesepumpstobetestedatlowflow,about25%oftheirbestefficiencypoint.Theresultantflowvectors,whichrepresentfluidleavingthetipofeachvane,arenotinlinewitheithervolute.

AttachmenttoAEP:NRC:0969BMPage3Consequently,hydraulicshockwavesdevelopatthevanepassfrequencyof4timestherunningspeed,or119.38Hz(-7200CPM),asshowninbothfigures2and3.Inanefforttocomplywiththenewcodevibrationrequirements,amodificationwasmadetoourspareassemblyatthepumpmanufacturer'sservicecenter.Thisconsistedofmaximizingthe"GapB"clearancebycuttingbackeachcasingdischargevolute.Theobjectivewastoreducetheoverallvibrationatlowflowtoanacceptablelevelwithoutaffectingthehydraulicperformanceofthepump.Pre-andpost-modificationtestresultsareshowninfigures4and5.Figure4illustratesthatthepumphydraulicperformanceatthedesignflowwasnotaffected.However,figure5illustrateslessthan1/3ofthedesiredvibrationimprovementwasachievedataflowrateequivalenttotheplant'stestcircuit.Vibrationatthedesignflowof3200gpmwasessentiallyunchanged,remainingwithinacceptablelimits.Basedonasfoundtestingofthesparepumpassembly,modificationsandsubsequenttestingresults,itwasconcludedthatliteralcompliancewiththenewcodewouldrequireoneofthefollowingoptions:1)Acompletenewtestcircuittoaccommodateamuchhigherflowrate.2)Adifferentrotatingelementforthepump(e.g.fivevane),whichshouldreducethevanepassfrequencyandoverallvibration.Thefirstoptionmustprovideapproximately1500gpmadditionalflowcapacity,accountforpumpheatgeneratedduringthetest,andmeettheoriginaldesignbasisrequirementthattheCTSdischargeheaderbemaintaineddryfromthetopofbothCTSsprayheatexchangersallthewayintocontainment.Therearetwomethodstoaccomplishthisoption:A)ToprovidetheflowcapacityandheatremovalcapabilitywithoutfillingtheCTSheatexchangerwouldrequireapproximately500feetoflargeborepipeperunittorecirculatethewaterfromtherefuelingwaterstoragetank(RWST).TheroutingofthispipebetweentheRWSTlocatedoutsideintheyard,andeachpumplocatedinthebasementoftheauxiliarybuilding,wouldencounternumerousstructuralinterferences,orB)UseoftheCTSheatexchangerwouldsupportanalternateroutecontainedentirelywithintheauxiliarybuilding.However,thisroutewouldrequireadditionofseveralisolationvalves,approximately150feetoflargeborepipingperunit,andadditionalventingcapability.Itwouldlikelyalsorequireacoderelieftoperformthesurveillanceinmode5,becauseofapotentialforentrainingtheairpresentintheCTSdischargeheader, AttachmenttoAEP:NRC:0969BMPage4Thesecondoptionistodesignandmanufactureanewimpeller.Themanufacturerdoesnotcurrentlyhaveafivevaneimpellerdesignedforthisapplication,thus,thiswouldrequireextensivedevelopmentandtesting.Thiswouldaffectthehydraulicperformanceofthemachines,andcouldrequirefullflowtestingoftheinstalledpumpstovalidatethedesignchange.Timerequiredtoimplementanyofthepreviouslydescribedoptionshasbeenestimatedatsixtotenmonths.Consequently,theirinstallationwouldresultinasignificanthardshipwithoutacompensatingincreaseinsafety.Therefore,alternativemonitoringisproposedtomeettheintentofthecode,andtoassureanacceptablelevelofqualityandsafety.PROPOSEDALTERNATIVETESTING:TheproposedalternativetestingistoperformspectralmonitoringandanalysisoverthefrequencyrangespecifiedinASMEOMa-1988,Part6.Analysisistobeperformedonallfrequenciescontainedinthefrequencyrange,alarmingtobeperformedonthefrequenciesofdegradationidentifiedbelow:~FundamentalTrainFrequency(FTF)~BallSpinFrequency(BSF)~2TimesBallSpinFrequency(2XBSF)~BearingPassOuterRaceFrequency(BPOR)~BearingPassInnerRaceFrequency(BPIR)Thefrequenciesforestablishingthealarmsarecontainedwithinthefollowingtables,includingAlertandActionalarmlevels.Thealertandactionalarmlevelswillbebasedonthemaximumpeakvalueofdegradationfrequenciescontainedwithineachbandofthebaselinespectralmeasurement.Bandswhichcontainnodistinctdegradationfrequencyshallbealarmedusingtheproductof2.5timesand6timesthemaximumpeakvalueofthebaselinespectralmeasurementinaccordancewithtable3.aofASMEOMa-1988Part6.

AttachmenttoAEP:NRC:0969BMPage5DeradationItemFTFBSF2XBSFBPORBPIROutboardMotorBearingFreuenc(Hz)11.51362.475124.9592.106145.83InboardMotorBearingFreuenc(Hz)12.20980.146160.29122.09175.47Alertlevelsperalarmbandnottoexceed0.325ipswithaminimumalarmsettingof0.03ipseActionlevelsperalarmbandnottoexceed0.70ipswithaminimumalarmsettingof0.06ips.Alarmbandsaresettoincludethosefrequenciesofdegradationasfollows:BandMinimumFrequency(Hz)9.8214.8860.99121200600MaximumFrequency(Hz)14.5859.50116.032006001000Itisimportanttonotethattheabovealarmbandscoverallbut6.76Hzofthecoderequiredfrequencyrange.Those6.76Hznotalarmedincludeonlyvanepass'andlinefrequenciesnotrelatedtomechanicaldegradation.Although6.76Hzofthefrequencyrangeisnotalarmed,analysiswillbeperformedonfrequencieswithineachunalarmedband.Eachbandischosentoprovidealarmcapabilityforspecificdegradationfrequenciesasshownbelow.BandOutboardBearingFTFN/AFTFN/AInboardBearingN/ARPMMachineBSF,BPOR2xBSF,BPIRN/AN/ABSF2xBSF,BPOR,BPIRN/AN/AN/AN/AN/AN/ABands5and6aresettoindicatemultiplesofafundamentaldefectfrequency,andarenotsettolookforfrequenciesofdegradationthatonlyoccurwithinthosebands.

AttachmenttoAEP:NRC:0969BMPage6BASISFORCONCLUDINGALTERNATIVETESTINGYIELDSACCEPTABLELEVELSOFQUALITYANDSAFETY:Toconfirmthatvibrationatvanepassisnotanoperationalconcernforthesepumps,theplant'sspareassemblywassenttothemanufacturer'sfacilityforflowlooptesting.Thesparepumphasneverbeeninstalledortestedin-situ;therefore,itservedasabaselinetojudgehowthiskindofpumpperformswithnoelapsedruntime.CookNuclearPlantpersonnelandtheplant'svibrationequipmentwereusedduringtestingtoeliminatevariableswhencomparingtestresultstodatacollectedontheinstalledpumps.Xnaddition,aninternalpumpinspectionwasperformedverifyingallcriticaldimensionstobewithinacceptabletolerances.Figure2showsthevibrationspectrumforthesparemachineasreceivedbythemanufacturer,beforethevolutelipmodificationwasperformed.Thissignaturewastakenwhileoperatingat733gpm,whichcloselyapproximatesthetestconditionsattheplant.Thespectrumillustratesthedominancevanepassfrequencyhasovertheentirespectrum,withnoevidenceofdegradationatanyotherfrequency.Figure3isarecentvibrationspectrumfortheunit1eastCTSpumptakenduringanin-servicetest,performedafterroughly22yearsofservice.ThisspectralplotistypicalofthedataobtainedfortheotherCTSpumpsinstalledattheplant.Figures2and3arevirtuallyidentical,confirmingthatthevibrationcomponentoccurringatvanepassfrequencyisanexpectedconsequenceofpumpinternaldesignoperatingatthein-servicetestflowrate,andnotanindicationofpumpdegradation.Fullflowtestingofthesparepumpalsoverifiedthatasflowrateisincreasedclosertothepump'sbestefficiencypoint,overallvibrationandvanepassfrequencydecreasetolevelswellbelowthecodealertvalue.Therefore,overallvibrationatflowratesexpectedduringadesignbasisaccidentsatisfycoderequirements(Figure1).Thepumpmanufacturerhasindicatedthatvibrationoccurringatvanepassfrequencydoesnotrepresentdegradation,norwouldtherebeanymechanicaldefectsproducedbyoperatingatlowflowconditionsforshortperiodsoftime,suchasperiodicplantin-'ervicetests.Toconfirmthisassertion,thefourCTSpumpsinstalledattheplantwillbedisassembledandnondestructivelyexaminedforsignsofdegradationpriortorestart.Eachpumpmotorwillalsobedisassembledandinspectedto'nsureitsbearingshavenotdegraded.Theseinspectionswillprovidereasonableassurancethatquarterlytestsperformedatlowflowhavenotcauseddegradationandwillestablishanacceptablebaselinefortrendingfutureperformanceusingtheproposedalternativemethods.

AttachmenttoAEP:NRC:0969BMPage7Vibrationmonitoringisintendedtodetectchangesinamachine'smechanicalperformance.Thecodecurrentlyrequiresabroadbandunfilteredmeasurementfrom1/3minimumpumprunningspeeduptoatleast1000Hz.Thistypeofbroadbandmeasurementprovidesanoverallnumberindicativeofenergycontainedwithinfrequencyrange.Itdoesnotindicatethatadiscreetfrequencyresponsehaschangedand,therefore,cannotpreciselyidentifywhatformofdegradationmaybeincipient.Tobemoreeffective,vibrationmonitoringshoulddetectdeviationsatdiscreetfrequencies.Toprovideahigherdegreeofassurancethatnodegradationisoccurring,spectralmonitoringwillbeperformedtoidentifychangesindiscreetdegradationfrequencies.Spectralmonitoringiscapableofdeterminingwhichfrequency,-ifany,hasdeviatedfrombaseline.Analysisofspectralmeasurementsallowsforidentificationofdiscreetfrequenciesindicativeofmechanicaldegradation.Identificationofthosediscreetdegradationfrequenciesallowsmoreaccuratemechanicalperformanceanalysis,andadditionaldiagnosticsarenottypicallyrequiredtoidentifyrootcause.Basedontheabilityofthealternativetestingtoidentifyspecificdegradationtypes,andthatunalarmedfrequencieswillbeanalyzed,itisconcludedthattheproposedalternativetestingprovidesanacceptablelevelofqualityandsafety.

AttachmenttoAEP:NRC:0969BMPage8FigUre1:VibrationAffectedByFlow1.20.8~~>06-.O0I>0.4.Readingsatlowerbearingperpendiculartoshaffparallel:withpumpsuction/dischargenozzles(2V)0.20100015002000250030003500400045005000Flow(gpm)+OverallAsFoundHVanePassAsFound t

AttachmenttoAEP:NRC:0969BMPage9Figure2:Sparepumponminiflowbeforelipperpendiculartoshaftandparallelnozzles(2V).cutatlowerbearingwithsuction/dischargeVOTOP444g7200CDIRT~,III2xVohtPSIO>I~IIIFigure3:Unit1EastCTSonminiflowatlowerbearingperpendiculartoshaftandparallelwithsuction/dischargenozzles(2V)measuredon01/25/98.VOTOPOOLSIIJI2XVihOP4$4IizMz

AttachmenttoAEP:NRC:0969BMPage10Figure4:HydraulicsAffectedByLipCut600550-500-..=K450400500150025003500I45005500+AsFoundoPostLipCutFlow(gpm}

AttachmenttoAEP:NRC:0969BMPage11Figure5:VibrationAffectedByLipCut1.20.8VlCL0.6O0.Rea'din'gsatlower.bearihg':p'er'pendlculartoshaft:-:;.'aiallelwith'-pumpsuetionld1scharge'noziles(2V)--,0.4-'.2500100015002000250030003500400045005000Flow(gpm)+OverallAsFoundQVanePassAsFound40verallAfterLipCutXVanePassAfterLipCut