RIS 2000-25, Potential Deficiency in Qualification of Okonite Single-Conductor Electrical Control Cables
| ML003749767 | |
| Person / Time | |
|---|---|
| Issue date: | 12/26/2000 |
| From: | Matthews D B Division of Regulatory Improvement Programs |
| To: | |
| Shapaker, J | |
| References | |
| RIS-00-025 | |
| Download: ML003749767 (6) | |
UNITEDSTATESNUCLEARREGULATORYCOMMISSIONOFFICEOFNUCLEARREACTORREGULATIONWASHINGTON,DC20555-0001December26,2000NRCREGULATORYISSUESUMMARY2000-25POTENTIALDEFICIENCYINQUALIFICATIONOFOKONITESINGLE-CONDUCTORELECTRICALCONTROLCABLES
ADDRESSEES
Allholdersofoperatinglicensesfornuclearpowerreactors,exceptthosewhohavepermanentlyceasedoperationsandhavecertifiedthatfuelhasbeenpermanentlyremoved fromthereactorvessel.
INTENT
TheU.S.NuclearRegulatoryCommission(NRC)isissuingthisregulatoryissuesummary(RIS)tonotifyaddresseesofapotentialdeficiencyintheenvironmentalqualification(EQ)ofcertain single-conductorOkoniteelectricalcablesusedforinstrumentationandcontrol(I&C)
applicationsinnuclearpowerplants.TheNRCiscontinuingtoworkwiththenuclearpower industrytoreachclosureinthismatter.Consequently,thisRISonlypresentsthecurrentstatus oftheNRC/industryeffort;asupplementtothisRISwillbeissuedwhenasatisfactorybasisfor closureisidentified.ThisRISdoesnottransmitanynewrequirementsorstaffpositions.No specificactionorwrittenresponseisrequired.
BACKGROUND
INFORMATIONTheBrookhavenNationalLaboratory(BNL),undercontracttotheNRC,hasbeenconductingresearchonlow-voltageI&CcablestosupporttheresolutionofGenericSafetyIssue(GSI)168,
"EnvironmentalQualificationofElectricEquipment."Aspartofthisresearch,inlate1999,a loss-of-coolant-accident(LOCA)test(Test#5)wasconductedonI&Ccableshavingethylene propylenerubber(EPR)insulationandcoveredwithabondedchlorosulfonatedpolyethylene (CSPE)outerjacket.Thepurposeofthetestwastodeterminewhethercableswithbonded jacketswouldexperienceafailuremechanismthatisunique,thatis,afailuremechanismother thanwhatunbondedjacketedcableshaveshownunderpostulatedLOCAconditions.The testingwasperformedattheWyleLaboratoriesinHuntsville,Alabama,usingcablesamples obtainedfromseveralmanufacturers,includingOkonite.TheOkonitesamplesweresingle conductor,#12Americanwiregauge(AWG)cable,withtheinsulationandbondedjacket coveringnotedabove.Forthetest,thecablesampleswerefirstsubjectedtoaccelerated thermalandradiationaging,andthenexposedtosimulatedLOCAconditions.Theacceleratedthermalandradiationagingparameterswereselectedonthebasisofeachvendor'soriginalEQtestreport.FortheOkonitecablesamples,preagingwasconductedto demonstrate20-yearand40-yearqualification.Theparametersfordemonstrating40-yearML003749767 RIS2000-25Page2of4qualificationofOkonitecableincludedelevatedtemperatureexposurefor504hoursat150C(302F),followedbyexposureto500kGy(50Mrads)ofgammaradiationatadoserateof6.5kGy/hr(0.65Mrad/hr).ThesimulatedLOCAtestconsistedofexposingthecablesamplesto1500kGy(150Mrads)ofgammaradiationatadoserateof7.5kGy/hr(0.75Mrad/hr),followedbyexposuretoadouble- peaksteamprofile,asdescribedinInstituteofElectricalandElectronicEngineers(IEEE)
Standard323-1974.Thepeaktemperatureandpressureconditionsofthesteamprofilewere, respectively,174C(346F)and779.1kPa(113psig).Aboric-acidbasedchemicalspraywasinitiatedwhenthetestchamberpressuredecreasedto220.6kPa(32psig),andwas continuedfortwenty-fourhours.Thedurationofthesteamexposurewas10days.FollowingtheexposureofthecablesamplestothesimulatedLOCAconditions,thespecimensweresubmergedinwaterandsubjectedtovoltage-withstandtestingatatestvoltageof
2400voltsac(equivalentto80v/milac),asdescribedinIEEEStandard383-1974.Allthree Okonitespecimensthatunderwent40-yearequivalentpreaging,andoneoftwoOkonite specimensthatunderwent20-yearequivalentpreaging,failedinstantaneously.Theartificial agingisbelievedtohavecontributedtothefailuremechanismsincecircumferentialcracks wereobservedfollowingcablepreaging.Longitudinalsplitswereobservedonthecablejackets followingexposuretothesimulatedLOCAconditions.Thedetailsofthistestarediscussedin aletterreportfromRobertLofaro,BNL,toSatishAggarwal,NRC,"ResultsofTest5onBonded JacketElectricCables,"datedMarch6,2000(ADAMSaccessionnumberML003709449).SUMMARYOFISSUEFollowingreceiptofthetestresultsfromBNL,theNRCheldmeetingswithrepresentativesfromOkoniteandthenuclearindustryonFebruary8,and16,2000,respectively.Itwasdetermined thatthecompositeEPRwithCSPEjacketinOkonite'soriginalqualificationtestreportNQRN-1 isabondedjacketsystemthatisalmostidenticaltothespecimenstestedbyBNL.Okonite single-conductor,#12AWGcableswithEPRinsulationandbondedCSPEjacketareusedin electricalequipmentimportanttosafety,whicharelocatedinareasofnuclearpowerplantsthat areexposedtoharshenvironments.OkonitetestreportNQRN-1isthebasisforenvironmental qualificationofthiscableunder10CFR50.49,"EnvironmentalQualificationofElectric EquipmentImportanttoSafetyforNuclearPowerPlants."OnJune22,2000,theNRCstaffmetwithrepresentativesoftheNuclearEnergyInstitute(NEI),theOkoniteCompany(Okonite),andlicenseestodiscusstheBNLLOCAtest(Test#5)results.
TheindustrynotedthattheBNLtest,whichduplicatedtheoriginalOkonitequalificationtest, mayhavebeenconservative,andpresenteddatafromotherdocumentedEPRtestreportsto supportthiscontention.Thesereports,accordingtotheindustryrepresentative,showthatEPR
insulatedcablesconsistentlypassedLOCAtestswherethecableswerepreagedtoa40-year equivalentat60C(140F).NEIhassinceissuedasurveytolicenseesaskingthemtoidentifyanyOkonitesingleconductorcables(conductorsize8AWGandsmaller)in10CFR
50.49applicationsthatmaybeexposedtoaverageserviceconditionsmoreseverethan60C(140F)andtoprovidetheaveragetemperature,serviceduration,andsafetyfunction RIS2000-25Page3of4supportedbythecable.ByletterdatedJuly14,2000,OkoniteinformedtheNRCstaffthatitwilldeveloprevisedagingparametersthatarebasedontheresultsoftheNEIsurveyto requalifyOkonitesingle-conductorcable.OnOctober12,2000,NRCstaffmetwith representativesofNEIandtheOkoniteCompanytodiscussNEI'spreliminarysurveyresults.
ByletterdatedNovember9,2000(ADAMSaccessionnumberML003769561),NEItransmitted totheNRCitsreporttitled"NEISurveyResultsonOkoniteOkolonSingle-ConductorCables,"
datedNovember1,2000.Thestaffisconsideringfurtherevaluationstovalidatethe60C(140F)thresholdthatwasthefocusofthesurveyquestions.BasedontheNEIsurvey,30ofthe103operatingreactorsuseOkoniteOkolonsingle-conductorcablein10CFR50.49 applications.Fourunitshavethecableinstalledinenvironmentsthatare60C(140F)orgreater,whichmayaffecttheservicelifeofthecable.Oneunithasa0.76mm(30mil)Jacket onthecable,whichisthickerthanthatonthetestedcable.Oneunitwillreplacethecableand anotherunitmayreplaceitfollowinganinspectionin2001.Thefourthunitwilldeterminea courseofactionfollowingissuanceofthisRIS.Inaddressingthismatter,thestaffidentifiedconcernsregardingthecomprehensivenessoftheNEIsurveyrequestandthesummaryresults.Inparticular,theOkoniteOkoloncablesthatare routedinlocalizedadverseenvironments(hotspots)atreactorfacilitieswerenotidentifiedand thetechnicalbasisforthethresholdtemperatureof60C(140F)usedinthesurveyrequiresfurtherevaluation.ThestaffplanstoarticulateitsconcernsinalettertoNEIfollowingissuance ofthisRIS.Thestaffwilldeterminewhetherfurtherregulatoryactionisnecessaryafterithas receivedtheOkonitereportonthesubjectcable.ThebasisforallowingcontinuedoperationofnuclearpowerplantspendingtheNRC'seffortstoreachclosureinthismatterwasaddressedinanNRCmemorandumfromBrianW.Sheronto SamuelJ.Collins,"ActionPlantoAddressFailuresofBonded-JacketOkoniteSingle-Conductor CablesDuringLoss-of-Coolant-AccidentTestingbytheOfficeofNuclearRegulatory Research,"datedMay9,2000(ADAMSaccessionnumberML003711726).Inessence, continuedoperationofnuclearpowerplantsiswarrantedwhilethestaff,inconjunctionwiththe industry,continuestoevaluatethepotentialdeficiencyofthesubjectcables.Thisassessment isbasedonindustrystatementsregardingthelimitedapplicationofsingleconductor EPR/Hypalonbonded-jacketcablesinharshenvironmentsandstaffacknowledgmentthatmost ofthesecableswouldnotbeinanoperatingenvironmentassevereasthatsimulatedduring pre-testaging.Inaddition,thestaffisnotawareofanyinstalledcablesthatyetexperienced thesamethermalandradiationagingthatwasusedfortheLOCAqualificationtest.ThegenericimplicationsofsimilarOkonitecableofdifferentwiregagesize,similarcableofothermanufacturers,andsimilarmulti-conductorcableofallmanufacturersareoutsidethe scopeofthisRIS.Theyare,however,beingconsideredintheresolutionofGSI168.
RIS2000-25Page4of4BACKFITDISCUSSIONThisRISrequestsnoactionorwrittenresponse.Consequently,thestaffdidnotperformabackfitanalysis.FEDERALREGISTERNOTIFICATIONAnoticeofopportunityforpubliccommentwasnotpublishedintheFederalRegister becausethisRISisinformational.PAPERWORKREDUCTIONACTSTATEMENTThisRISdoesnotrequestanyinformationcollection.
IfthereareanyquestionsconcerningthisRIS,pleasecontactthepersonlistedbelow./RA/D.B.MatthewsDavidB.Matthews,DirectorDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationTechnicalcontact:PaulC.Shemanski,NRR301-415-1377 E-Mail:pcs@nrc.govAttachment:ListofRecentlyIssuedNRCRegulatoryIssueSummaries RIS2000-25Page4of4BACKFITDISCUSSIONThisRISrequestsnoactionorwrittenresponse.Consequently,thestaffdidnotperformabackfitanalysis.FEDERALREGISTERNOTIFICATIONAnoticeofopportunityforpubliccommentwasnotpublishedintheFederalRegister becausethisRISisinformational.PAPERWORKREDUCTIONACTSTATEMENTThisRISdoesnotrequestanyinformationcollection.
IfthereareanyquestionsconcerningthisRIS,pleasecontactthepersonlistedbelow./RA/D.B.MatthewsDavidB.Matthews,DirectorDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationTechnicalcontact:PaulC.Shemanski,NRR301-415-1377 E-Mail:pcs@nrc.govAttachment:ListofRecentlyIssuedNRCRegulatoryIssueSummariesDISTRIBUTION
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CITF
______________________________________________________________________________________OL=OperatingLicense CP=ConstructionPermitAttachmentRIS2000-25 Page1of1LISTOFRECENTLYISSUEDNRCREGULATORYISSUESUMMARIES
_____________________________________________________________________________________RegulatoryIssueDateofSummaryNo.SubjectIssuanceIssuedto
_____________________________________________________________________________________2000-24ConcernsAboutOffsitePowerVoltageInadequaciesandGrid ReliabilityChallengesDueto IndustryDeregulation12/21/00AllholdersofOLsforpressurized-waterreactors(PWRs),except thosewhohavepermanently ceasedoperationsandhave certifiedthatfuelhavebeen permanentlyremovedfromthe reactorvessel2000-23RecentChangestoUraniumRecoveryPolicy11/30/00Allholdersofmaterialslicensesforuraniumandthoriumrecovery facilities2000-22IssuesStemmingfromNRCStaffReviewofRecentDifficulties ExperiencedinMaintainingSteam GeneratorTubeIntegrity11/03/00AllholdersofOLsforpressurized-waterreactors(PWRs),except thosewhohavepermanently ceasedoperationsandhave certifiedthatfuelhavebeen permanentlyremovedfromthe reactorvessel2000-21ChangestotheUnplannedScramandUnplannedScramWithLoss ofNormalHeatRemoval PerformanceIndicators10/31/00AllholdersofOLsfornuclearpowerreactors,exceptthosewho havepermanentlyceased operationsandhavecertifiedthat fuelhasbeenpermanently removedfromthereactorvessel2000-20AdvanceNoticeof
Intent
toPursueLicenseRenewal11/14/2000AllholdersofOLsfornuclearpowerreactors,exceptthose licenseeswhohavepermanently ceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel