Information Notice 2001-06, Centrifugal Charging Pump Thrust Bearing Damage Not Detected Due to Inadequate Assessment of Oil Analysis Results and Selection of Pump Surveillance Points: Difference between revisions
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| issue date = 05/11/2001 | | issue date = 05/11/2001 | ||
| title = Centrifugal Charging Pump Thrust Bearing Damage Not Detected Due to Inadequate Assessment of Oil Analysis Results and Selection of Pump Surveillance Points | | title = Centrifugal Charging Pump Thrust Bearing Damage Not Detected Due to Inadequate Assessment of Oil Analysis Results and Selection of Pump Surveillance Points | ||
| author name = Marsh L | | author name = Marsh L | ||
| author affiliation = NRC/NRR/DRIP/REXB | | author affiliation = NRC/NRR/DRIP/REXB | ||
| addressee name = | | addressee name = |
Revision as of 08:51, 14 July 2019
ML011070643 | |
Person / Time | |
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Issue date: | 05/11/2001 |
From: | Marsh L Operational Experience and Non-Power Reactors Branch |
To: | |
References | |
IN-01-006 | |
Download: ML011070643 (7) | |
UNITEDSTATESNUCLEARREGULATORYCOMMISSIONOFFICEOFNUCLEARREACTORREGULATIONWASHINGTON,D.C.20555-0001May11,2001NRCINFORMATIONNOTICE2001-06:CENTRIFUGALCHARGINGPUMPTHRUSTBEARINGDAMAGENOTDETECTEDDUETO
INADEQUATEASSESSMENTOFOILANALYSIS
RESULTSANDSELECTIONOFPUMP
SURVEILLANCEPOINTS
Addressees
Allholdersofoperatinglicensesfornuclearpowerreactors,exceptthosewhohavepermanentlyceasedoperationsandhavecertifiedthatfuelhasbeenpermanentlyremoved
fromthereactor.
Purpose
TheU.S.NuclearRegulatoryCommission(NRC)isissuingthisinformationnoticetoalertaddresseesthatinadequateassessmentofpumpoilanalysisresults,combinedwith
surveillancetestingwhichdoesnotmonitorallrelevantpumpoperatingconditions,mayallow
severepumpdegradationtogoundetected.Itisexpectedthatrecipientswillreviewthe
informationforapplicabilitytotheirfacilitiesandconsideractions,asappropriate,toavoid
problems.However,thesuggestionscontainedinthisinformationnoticearenotNRC
requirements;therefore,nospecificactionorwrittenresponseisrequired.DescriptionofCircumstancesOnJune19,2000,whiledisassemblingtheCcharging/safetyinjectionpump(CSIP)toreplaceamechanicalseal,ShearonHarrisNuclearPlant(SHNP)personneldiscoveredsignificant
damagetotheoutboardthrustbearing.Furtherexaminationrevealedthatthebabbittmaterial
onthebearingshoesofthismulti-padthrustbearinghadmeltedandre-solidifiedwithinthe
thrustbearingcagearea.Onboththeshoesandthesleeveofthethrustbearing,radialwearin
thedirectionofnormalpumprotationwasindicativeofmetal-to-metalcontactbetweenthetwo
surfaces.Theinboardradialbearingandshaftalsohadminorwear.SHNPstatedina
licenseeeventreport(Reference1)thatthemostprobablecauseofthedamagewasa
momentarylossoflubricationflowtotheoutboardthrustbearing.Aninadequatefill-and-ventof
thepump,whichmayhavecausedamomentaryincreaseintheaxialthrustontheoutboard
thrustbearing,wasalsogivenasapotentialrootcause.ElementalanalysisofaroutinepumpbearingoilsampletakenonSeptember19,1999,usingadirectcurrentplasma(DCP)spectrometer,revealeda40-foldincreaseintheparticlecountin
therangeof5to10micronsovertheprevioussampletakenonMay11,1999.(Theparticle
countincreasedfrom15,800to660,000countsper100millilitersample.)AllothertestedML011070643 IN2001-06Page2of5parameterswerenormal.SHNPreviewedtheElectricPowerResearchInstitute(EPRI)LubricationGuide(Reference2)andconcludedthatthesizerangeofthesewearparticleswas
consistentwithbenignwear.ThebearingoilintheCSIPwasreplacedonDecember21,1999, andSHNPcontinuedsamplingat6-monthintervals.Thenextoilsample,takenon
February23,2000,alsoshowedahighparticlecountinthe5to10micronrange.Trace
amountsofironandtinwerealsodetectedforthefirsttime.Theanalysisofanotheroilsample
takenonJune18,2000,foundthatthelevelsofallparametersweresimilartothelevelsinthe
February23,2000,sample.EachCSIPatSHNPisaPacificModel21/2RLIJ,11-stage,centrifugalpumpmanufacturedbyFlowserveCorporation,formerlyIngersoll-DresserPumpCompany.TheCCSIPisthestandby
pump.Duringtheperiodinwhichhighparticlecountsinthethreeoilsamplesweredetected, theCpumpwasintermittentlyinservicetosupportplantoperations.Surveillancetesting,as
requiredbytheSHNPinservicetestingprogramandtheSHNPTechnicalSpecifications,was
performedontheCpumpduringthisperiod.Inservicetests,includingvibrationmeasurement, wereconductedduringplantoperationonNovember13,1999,andJanuary3,2000,withthe
pumpoperatingatthenormalchargingflowrateofapproximately90gallonsperminute(gpm).
PerformancedatafrombothtestsindicatedtheCCSIPmettheestablishedpumphydraulic
andmechanicalacceptancecriteriaintheAmericanSocietyofMechanicalEngineers(ASME)
CodeforOperationandMaintenanceofNuclearPowerPlants(OMCode),andnoadverse
trendswerenoted.OnApril23,2000,arefuelingoutagetesttosatisfytheSHNPtechnical
specificationswasperformedsuccessfully,withthepumpachievingaflowrateof609gpm.Subsequenttothediscoveryoftheseverelydegradedoutboardpumpthrustbearing,discussionswiththepumpmanufacturerrevealedthatatflowratesbetweenapproximately250
and600gpm,thenetaxialthrustofeachSHNPCSIPpumpisinthedirectionoftheoutboard
thrustbearing.Therefore,SHNPconcludedthatduringnormalplantoperationandsurveillance
testing,theoutboardthrustbearinghadbeeneithernotloadedoronlylightlyloaded.In
addition,SHNPcouldnotassessthecapabilityoftheCCSIPtoperformitsfunctionduringa
small-break,loss-of-coolantaccident,inwhichthepumpaxialthrustwouldhavefullyloadedthe
outboardthrustbearing.InresponsetoanNRCnoticeofviolation(Reference3),SHNPdescribedcorrectivestepseithercompletedorinprogresstoaddressthisissue.Theseincluded(1)counselingoperators
onconsequencesofimproperpumpfill-and-ventoftheCSIP,(2)establishingoilanalysis
criteriaforincreasedlubricantparticlecounts,(3)reinforcingexpectationsfordispositionof
abnormalindications,(4)samplingCSIPlubricatingoilquarterlyinsteadofsemi-annually,
(5)revisingthemaintenanceproceduretoensurethattheCSIPlubricatingoilsystemwill
functionasexpected,and(6)implementingadesignmodificationtoinstalltemperatureand
vibrationproximityprobesoneachCSIP.
IN2001-06Page3of5NRCRequirementsandIndustryGuidanceandPracticesonPumpConditionMonitoringThecurrentrequirementsforinservicetestingofsafety-relatedpumpsarespecifiedinSection50.55aofTitle10oftheCodeofFederalRegulations(10CFR50.55a),"Codesand
Standards."Forplantswhicharerequiredtoupdatetheirinservicetesting(IST)programsafter
September22,2000,whichisoneyearaftertherecentchangeto10CFR50.55a(Reference
4),Subsection(b)(3)requiresthatsafety-relatedpumpsbetestedtothe1995Editionandthe
1996AddendaoftheASMEOMCode.TheCoderequiresthatsafety-relatedpumpsbetested
bienniallyat+/-20%oftheirdesignflowrate,andeverythreemonthsatspecificreferencepoints.
OverallvibrationmeasurementsofeachpumpbearingaretakenasspecifiedbytheCode.The
SHNPISTprogramisinaccordancewithanearlierversionoftheCode,whichrequirespump
testingtobeconductedeverythreemonthsatreferencepointsofoperationreadilyduplicated
duringsubsequenttests.Pumphydraulicperformanceisassessedbycomparingcurrent
performancewithreferencevaluesestablishedwhenthepumpisknowntobeoperating
acceptably.Pumpmechanicalperformanceisassessedlikehydraulicperformance,unlessthe
specifiedmultipleofthemeasuredoverallvibrationreferencevalueexceedstheabsolute
vibrationacceptancecriterion.NeithertheCodenortheregulationsrequireanyspecificpumpconditionmonitoringactivitiestobeperformedonsafety-relatedpumps.However,theNRChasobservedduringinspection
activitiesthatmanyUScommercialnuclearpowerplantshavesometypeofcondition
monitoringprogramfortheirrotatingmachinery.Theseprogramsusuallyincludebothsafety- relatedandnon-safety-relatedequipment.Becausenoregulationscovertheseprograms,the
testingperformed,theexaminationscompleted,andtheacceptancecriteriausedforeach
conditionmonitoringactivityvarywidely.TheEPRILubricationGuideincludesinformationonthetestingandanalysisoflubricants.Theguideidentifiesparticlesizeandwear-metalcontentaskeypropertiestoanalyze.Theguide
alsoprovides"classic"warninglimitsforcertainmeasuredproperties.Theguidedoesnot
recommendaspecificwarninglimitforparticlecount.However,theguideemphasizestrending
criticalpropertiesofaspecificapplicationandestablishingappropriatewarninglimits.When
theselimitsareexceededandtheresultsareverified,theguiderecommendsoilreplacement
andfurtherstudyifnecessary.TheNRChasauthorizedalternativestotheCodevibrationrequirementsbasedontheperformanceofpumpconditionmonitoringactivities.Forexample,aspartofanalternativeto
theCodevibrationacceptancecriterion,onefacilitycommittedtoimplementaplant-specific
pumpconditionmonitoringprogramforcertainsafety-relatedpumps.TheNRChasdetermined
thatthisproposedalternativedemonstratesanacceptablelevelofqualityandsafety.
IN2001-06Page4of5 DiscussionAkeyfactorinthefailuretodiscoverthedamagedbearingbeforedisassemblywasnotactivelypursuingtherootcauseoftheabnormallyhighparticlecountintheSeptember19,1999,oil
sample.TheEPRIguideimpliesthatparticleslessthan10micronsinsizearegeneratedfrom
"benignwear."Theguidedoesnotdiscussthesignificanceofchangesinwearparticle
concentration.However,theguidedoesdiscusstrendingofparameters.SHNPperformed
spectroscopicanalysisofeachsampleandtrendedtheresultsofthesetests.Thelowweight
percentofthewearparticleswasapparentlythereasonwhytheelementalanalysisdidnot
detectthepresenceofbearingmaterial.Ferrographyandelectronmicroscopicscan
examinationwereconductedafterthediscoveryofthebearingdegradationandthereforewere
notafactorindiagnosingtheelevatedparticlecount.SHNPelectedtocontinuewitharoutine
oilsamplingscheduledespitethehighparticlecountandthelackofaplausiblerootcausefor
thiscondition.Amoreaggressiveoilsamplingschedule(e.g.,weekly)wouldlikelyhave
revealedtheseverelydegradedoutboardthrustbearingseveralmonthsbeforethepumpwas
disassembled.Inserviceandtechnicalspecificationsurveillancetestingdidnotindicatethattheoutboardthrustbearingwasseverelydamaged.Thepurposeofpumpinservicetestingistoidentify
degradationbeforethepump'sperformanceofitssafety-relatedfunctionisimpaired.Forthe
chargingpumpsattheSHNP,thepurposeoftechnicalspecificationtestingistoverifythatthe
pumpwilldeliveraspecificflowattherequiredtotaldevelopedhead.Thefailureofbothtests
toindicatebearingdegradationappearstohavebiasedthedecisiontonotinvestigatethe
elevatedparticlecount.Informationprovidedbythevendorrevealedareversalinthedirectionofthepumpaxialforceasafunctionofthepumpflowrate.ThispumpdesigncharacteristicwasunknowntoSHNP
personnelbeforetheydiscoveredtheseverelydegradedbearingandthentalkedwiththe
vendor.TheCodedoesnotrequireSHNPtoaccountforthisdesignconditionthroughtesting.
Thetechnicalspecificationfullflowtestafterthefirstdetectionofthehighparticlecountneither
detectedthisconditionnorcausedacatastrophicfailureofthepump.Thisissueillustratesthat
theassessmentofsafety-relatedpumpperformanceisdependentnotonlyonverifying
successfulsurveillancetesting,butalsoonunderstanding(1)pumpandsystemdesignand
performancecharacteristics,(2)performancetestingresults,and(3)theresultsofcondition
monitoringactivitiesandtheircorrelationwithknownpumpdesigncharacteristicsand
performancetestresults.
IN2001-06Page5of5GenericImplicationsIftrendsofconditionmonitoringdataarenotactivelyinvestigatedwhentheydeviatefromanestablishedbaseline,alicenseemayoverlooksignificantpumpdegradationthatisnotdetected
byperformancetesting.Thisinformationnoticerequiresnospecificactionorwrittenresponse.Ifyouhaveanyquestionsaboutthisnotice,pleasecontactoneofthetechnicalcontactslistedbeloworthe
appropriateOfficeofNuclearReactorRegulation(NRR)projectmanager./RA/LedyardB.Marsh,Chief
EventsAssessment,GenericCommunicationsandNon-PowerReactorsBranchDivisionofRegulatoryImprovementPrograms
OfficeofNuclearReactorRegulationTechnicalcontacts:J.Colaccino,NRRBobHagar,RegionII301-415-2753919-362-0601 E-mail:jxc1@nrc.govE-mail:rch2@nrc.gov
- Attachments:1.ListofReferences
2.ListofRecentlyIssuedInformationNotices
IN2001-06Page5of5GenericImplicationsIftrendsofconditionmonitoringdataarenotactivelyinvestigatedwhentheydeviatefromanestablishedbaseline,alicenseemayoverlooksignificantpumpdegradationthatisnotdetected
byperformancetesting.Thisinformationnoticerequiresnospecificactionorwrittenresponse.Ifyouhaveanyquestionsaboutthisnotice,pleasecontactoneofthetechnicalcontactslistedbeloworthe
appropriateOfficeofNuclearReactorRegulation(NRR)projectmanager./RA/LedyardB.Marsh,Chief
EventsAssessment,GenericCommunicationsandNon-PowerReactorsBranchDivisionofRegulatoryImprovementPrograms
OfficeofNuclearReactorRegulationTechnicalcontacts:J.Colaccino,NRRBobHagar,RegionII301-415-2753919-362-0601 E-mail:jxc1@nrc.govE-mail:rch2@nrc.gov
Attachments:1.ListofReferences
2.ListofRecentlyIssuedInformationNoticesDistribution:INReadingFilePUBLICADAMSACCESSIONNUMBER:ML011070643Template#=NRR-052
ÿPubliclyAvailableNon-PubliclyAvailableSensitiveÿNon-SensitiveOFFICETechEditor)REXB:DRIPEMEB:DEEMEB:DENAMEPKleene*RHagar*JColaccino*DTerao*DATE04/09/200104/09/200104/10/200104/18/2001OFFICEEMEB:DEREXB:DRIPD:DEREXB:DRIPNAMEGImbro*JTappert/txkfor*JStrosnider*LDATE04/18/200104/24/200105/03/2001OFFICIALRECORDCOPY
Attachment1Page1of1References1.ShearonHarrisNuclearPowerPlantUnit1,DocketNumber50-400,LicenseeEventReport2000-007-01,"TechnicalSpecificationsViolationDuetoInoperableCharging
SafetyInjectionPump,"datedMarch12,2001.2.NP-4916-R2,ElectricPowerResearchInstitute/NuclearMaintenanceApplicationsCenterLubricationGuide,Revision2,publishedFebruary1995.3.ShearonHarrisNuclearPowerPlantUnit1,DocketNumber05000-400,ReplytoNoticeofViolation(NRCInspectionReportNumbers50-400/00-03,50-400/00-10)dated
March2,2001.4.FederalRegister,Volume64,Number183,"IndustryCodesandStandards;AmendedRequirements,"(10CFRPart50),issuedSeptember22,1999.
______________________________________________________________________________________OL=OperatingLicense
CP=ConstructionPermitAttachment2IN2001-06
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