ML17325B600

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LER 99-012-00:on 990420,concluded That Auxiliary Bldg ESF Ventilation Sys Not Capable of Maintaining ESF Room Temps post-accident.Caused by Inadequate Control of Sys Design Inputs.Comprehensive Action Plan Being Developed
ML17325B600
Person / Time
Site: Cook American Electric Power icon.png
Issue date: 05/20/1999
From: OROURKE B W
INDIANA MICHIGAN POWER CO.
To:
Shared Package
ML17325B598 List:
References
LER-99-012, LER-99-12, NUDOCS 9905260279
Download: ML17325B600 (4)


Text

NRCForm366U.S.NUCLEARREGULATORYCOMMISSION(6-1998)LICENSEEEVENTREPORT(LER)(Seereverseforrequirednumberofdigits/charactersforeachblock)APPROVEDBYOMBNo.3150.0104EXPIRES06/30/2001ESTIMATEDBURDENPERRESPONSETOCOMPLYWITHTHISMANDATORYINFORMATIONCOLLECTIONREOVESD50.0HRS.REPORTEDLESSONSLEARNEDAREINCORPORATEDBJTOTHEUCEJISINGPROCESSANDFEDBACKTOINDUSTRY.FORWARDCOMMENTSREGARDUIGBURDENESTSJATETOTHEII&ORMATIONANORECORDSMANAGEMENTBRANCHIT4AS),V.S.NVCLEARRFGUIATORYCOMMISSION.WASHBJGTON.OC205S54XI.ANOTOTHEPAPERWORKREDUCTIONPROJECTtst50410l),OFFICEOFMANAGEMENTANDBUCGEf,WASIeNGTceLDC2050$FACILITYNAMEI1)CookNuclearPlantUnit1DOCKETNUMBERr2)05000-315PAGEI5)1of3TITLEI4)AuxiliaryBuildingESFVentilationSystemMayNotbeCapableofMaintainingESFRoomTemperaturesPost-AccidentMONTH04DAYYEAR201999EVENTDATE(5)YEAR1999LERNUMBER(8)SEQUENTIALNUMBER012REVISIONNUMBER00REPORTDATE(7)MONTHDAYYEAR05201999ILID.C.Cook,Unit2AILINAM05000-316DCNUMBEROTHERFACILITIESINVOLVED(8)OPERATINGMODE(9)POWERLEVEL(10)0%20.2201(b)20.2203(a)(1)20.2203(a)(2)(i)20.2203(a)(2)(v)20.2203(a)(3)(i)20.2203(a)(3)(ii)50.73(a)(2)(l)50.73(a)(2)(ii)50.73(a)(2)(iii)50.73(a)(2)(viii)50.73(a)(2)(x)73.71THISREPORTISSUBMITTEDPURSUANTTOTHEREQUIREMENTSOF10CFRII:(Checkoneormore)(11)20.2203(a)(2)(ii)20.2203(a)(2)(iii)20.2203(a)(2)(iv)20.2203(a)(4)50.36(c)(1)50.36(c)(2)LICENSEECONTACTFORTHISLER(12)50.73(a)(2)(iv)50.73(a)(2)(v)50.73(a)(2)(vii)OTHERSpecii/yInAbstractbekrrrornNRCForm366ANAMEMs.BrendaW.O'ourke,ComplianceEngineerTELEPHONENUMBER(IIK5udeAreaCode)(616)465-5901x2604COMPLETEONELINEFOREACHCOMPONENTFAILUREDESCRIBEDINTHISREPORT(13).CAUSESYSTEMCOMPONENTMANUFACTURERREPORTABLETOEPIXCAUSESYSTEMCOMPONENTMANUFACTURERREPORTABLETOEPIXSUPPLEMENTALREPORTEXPECTED(14XYES(IfYes,completeEXPECTEDSUBMISSIONDATE)NOEXPECTEDSUBMISSIONDATE15MONTH10DAY311999Abstract(Limitto1400spaces,I.e.,approximately15singie-spacedtypewrittenlines)(16)OnApril20,1999,duringperformanceoftheExpandedSystemReadinessReview(ESRR)fortheAuxiliaryBuildingVentilationSystems,itwasconcludedthatthereisinsufficientassurancethattheEngineeredSafetyFeaturesVentilation(AES)systemiscapableofperformingitssafetyandaccidentmitigationfunction.Thisconclusionwasbasedonapreliminaryevaluationofnumerousidentifiedsystemdeficienciestakenintheaggregate.Specifically,significanterrorsincalculationsforauxiliarybuildingEngineeredSafetyFeaturescubicletemperaturesexpectedduringpostulatedaccidentscenarios,vulnerabilityofAESdampercontrolairsystemmodificationtosinglefailure;andlackofmissileprotectionfortheComponentCoolingWaterpumpareasupplyfans.Basedonthecombinedeffectsofthesedeficiencies,theabilityoftheAESsystemtomaintainauxiliarybuildingtemperaturestowithinsafety-relatedequipmentdesigntemperaturesunderaccidentconditionscannotbeassured.Thepreliminarycausesforidentifiedconditionsare:inadequatecontrolofsystemdesigninputs;failuretoadequatelyimplementsinglefailuredesigncriteriaduringthemodificationprocess;andlackofacleardefinitionindesignandlicensingdocumentsregardingdesignrequirementsforsystemprotectionagainstmissileeffects.AcomprehensiveactionplanisbeingdevelopedtodeterminetheauxiliarybuildingdesigntemperaturesrequiredtobemaintainedbytheAESventilationsystem.Inaddition,asinglefailureanalysisfortheAESventilationsystemwillbeperformedtoidentifyfailuresthatcouldpreventthesystemfromperformingitsdesignandsafetyfunction.Basedontheresultsofthecompletedevaluation,informationregardingthesafetysignificance,andcorrectiveandpreventiveactionswillbeprovidedinanupdatetothisLER.9905260279990520PDRADOCK050003'l5SPDR

NRCFORM366AU.S.NUCLEARREGULATORYCOMMISSION(6-1998)LICENSEEEVENTREPORT(LER)TEXTCONTINUATIONFACILITYNAME(1)CookNuclearPlantUnit1DOCKETNUMBER(2)05000-315YEARLERNUMBER(6)SEQUENTIALNUMBERREVISIONNUMBERPAGE(3)2of3TEXT(Ifmorespaceisrequired,useadditionalcopiesofNRCForm(366A)(17)ConditionsPriortoEventUnit1wasinMode5,ColdShutdownUnit2wasinMode5,ColdShutdown199901200DescritionofEventOnApril20,1999,duringperformanceoftheExpandedSystemReadinessReview(ESRR)fortheAuxiliaryBuildingVentilationSystems,itwasconcludedthatthereisinsufficientassurancethattheEngineeredSafetyFeaturesVentilation(AES)systemiscapableofperformingitssafetyandaccidentmitigationfunction.Thisconclusionwasbasedonapreliminaryevaluationofnumerousidentifiedsystemdeficienciestakenintheaggregate.Specifically,significanterrorsincalculationsforauxiliarybuildingEngineeredSafetyFeatures(ESF)cubicletemperaturesexpectedduringpostulatedaccidentscenarios,combinedwithsmalldesignmarginsthatexistedbetweencalculatedroomtemperaturesanddesignrequirements;vulnerabilityofAESdampercontrolairsystemmodificationtosinglefailure;andlackofmissileprotectionfortheComponentCoolingWater(CCW)pumpareasupplyfanswhichcouldresultinasinglecatastrophicfailure-generatedmissileimpactingbothtrainsofAES.Basedonthecombinedaffectsofthesedeficiencies,theabilityoftheUnit1and2AESsystemstomaintainauxiliarybuildingtemperaturestowithinsafety-relatedequipmentdesigntemperaturesunderallaccidentconditionscannotbeassured.Inaccordancewiththerequirementsof10CFR50.72(b)(2)(iii)(D),a4hournotificationwasmadetotheNRConApril20,1999,at1645hours,foranyeventorconditionthatalonecouldhavepreventedthefulfillmentofthesafetyfunctionofstructuresorsystemsthatareneededtomitigatetheconsequencesofanaccident.CauseofEventThepreliminarycausefortheuseofnon-conservativeandincorrectassumptionsinauxiliarybuildingheatloadcalculationsisduetoinadequatecontrolofsystemdesigninputs.ThisissuewaspreviouslyidentifiedinAEP:NRC:1260GH,datedMarch19,1999,"EnforcementActions98-150,98-151,98-152and98-186,ReplytoNoticeofViolationDatedOctober13,1998."ThepreliminarycauseforAESdamperdesignsinglefailurevulnerabilityisfailureofthedesignchangeprocesstoidentifythepotentialadverseimpactontheAESsystemcreatedbythemodificationtothedampercontrolairsystemin1997.ThepreliminarycauseforCCWpumpareasupplyfansusceptibilitytomissileeffectsislackofacleardefinitionindesignandlicensingdocumentsregardingAESdesignrequirementsforprotectionagainstmissileeffects.AnalsisofEventThisLERissubmittedinaccordancewith10CFR50.73(a)(2)(v)(D)foraconditionthatcouldpreventthefulfillmentofthesafetyfunctionsoftheAESsystemthatareneededtomitigatetheconsequencesofanaccident:TheAESsystemsafetyandaccidentmitigationfunctionistoprovidesufficientcoolingtotheauxiliarybuildinggeneralareasandESFequipmentroomsrequiredtooperateduringaccidentconditions.ThisincludestheCCW,ContainmentSpray,ResidualHeatRemoval,ChargingandSafetyInjectionequipmentrooms.TheAESsystemalsomaintainstheauxiliarybuildingatanegativepressurerelativetotheoutsideenvironmenttoensureradioactivecontaminationreleasedduringanaccidentiscontainedwithintheauxiliarybuilding,filteredandexhaustedtotheenvironmentviaamonitored,releasepath.Inaddition,TechnicalSpecification3.7.6.1requiresthattwoindependentAESventilationsystemfan/filterexhausttrainsbeoperableinModes1through4.Calculationsweredevelopedtoestablishtheauxiliarybuildingheatloads,ESFcubicleroomandgeneralareatemperaturesduringnormal,shutdownandaccidentconditions.DuringtheESRRreviewofthesecalculations,numerousdiscrepancieswereidentified.Forexample,calculationofauxiliarybuildingareatemperatureduringaccidentconditionsNRCFORM366A(6-1996)

NRCFORM366AU.S.NUCLEARREGULATORYCOMMISSION(6-1998)LICENSEEEVENTREPORT(LER)TEXTCONTINUATIONFACILITYNAME(1)CookNuclearPlantUnit1DOCKETNUMBER(2)05000-315YEARLERNUMBER(6)SEQUENTIALNUMBERREVISIONNUMBERPAGE(3)3of3199901200TEXT(ifmorespaceisrequired,useadditionalcopiesofNRCForm(366A)(17)didnotincludetheheatloadfortheCCWsystempiping.Thisequipmentisconsideredasignificantheatloadintheauxiliarybuildingandexcludingitfromthecalculationcouldresultinnon-conservativeauxiliarybuildingareatemperaturevalues.Inaddition,thesevaluesserveasinputassumptionstootherauxiliarybuildingventilationcalculations.Asaresult,actualauxiliarybuildingareaandESFcubicleroomtemperaturescouldimpactthequalificationoftheESFequipmentlocatedintheareasservedbytheAESandCCWpumpareaventilationsystems.TheAESventilationsystemconsistsoftwofan/filterexhausttrains(oneinstandby)whichdrawsairfromtheauxiliarybuildingthroughtheequipmentcubiclesfromacommonventduct,anddischargestheexhausttotheoutsideatmosphereviatheventstack.Eachtrainconsistsofaroughingfilter,highefficiencyparticulateair(HEPA)filters,andanormallyclosedpneumaticallyoperatedfacedamper.Inaddition,eachtraincontainsabypassductwithanormallyopenpneumaticallyoperatedbypassdamperwhichdirectsairflowaroundthecharcoaladsorbers.Duringnormaloperation,onefan/filterunitoperatescontinuously,directingtheexhaustairthroughtheroughingandHEPAfilters,bypassingthecharcoalfilters,anddischargingtotheunitvent.Thisoperationaidsinairdistributionwithintheauxiliarybuilding,isolatestheatmosphereinthecubiciesbyinducingadraftthroughtheenteringportalsandremovesanyheatgeneratedwithintheenclosures.In1997,amodificationtothedampercontrolairsystemincludedtheinstallationofsolenoidvalvesintheairlinestothefaceandbypassdampers.Duringtheperformanceofsurveillancetest12OHP4030STP.25A/8,ontwoseparateoccasions,thefacedampersolenoidvalvefailed,resultinginthefacedamperfailingtoopenwhilethebypassdampersremainedclosed.Fornon-Slinitiatedevents,afailureofthefacedampersolenoidtoopenthe'facedamperorthebypassdampersolenoidtoopenthebypassdamperinresponsetoacontrolsignalcouldresultinboththefaceandbypass.dampersbeingintheclosedposition,blockingallairflowthroughtheaffectedtrain.IntheeventofaPhaseBIsolationsignal,thestandbytrainisenergizedandthebypassdampersautomaticallycloseandthefacedampersopentoexhaustairdirectlythroughthecharcoalfilters,roughingandHEPAfilters.AlthoughthesinglefailureofeitherthebypassorfacedampersolenoidvalvewouldrenderonetrainofAESinoperable,itwouldnotimpactthecapabilityofthestandbyfan/filtertrainfromperformingitssafetyandaccidentmitigationfunction.TheAESsystemdesignincludesthreevaneaxialsupplyfanslocatedintheCCWequipmentroomwhicharelocatedsidebyside,andconnectedtoacommonintakeplenumanddischargeduct.Becausevaneaxialfansaresusceptibletofanbladefailures,thefanbladesareapotentialmissilesourcewhichcouldimpactthefunctionofadjacentsafetyrelatedcomponents.Asaresult,failureoftheCCWpumpareasupplyfanscouldimpacttheabilityoftheAESsystemtomaintainESFcubicletemperaturestowithinequipmentdesigntemperatures,impactingthequalificationoftheESFequipment.BecauseofthenumeroussystemdeficienciesidentifiedduringtheESRR,acomprehensiveactionplanisbeingdevelopedtoevaluatetheidentifiedconditions.UntiltheaggregateeffectoftheseconditionsonAESsystemperformanceisevaluated,theoverallsafetyimpactcannotbedetermined.CorrectiveActionsAcomprehensiveactionplanisbeingdevelopedtodeterminetheauxiliarybuildingdesigntemperaturesrequiredtobemaintainedbytheauxiliarybuildingventilationsystems:Inaddition,asinglefailureanalysisfortheAESventilationsystemwillbeperformedtoidentifyfailureswhichcouldpreventthesystemfromperformingitsdesignandsafetyfunction.Basedontheresultsofthecompletedevaluation,additionalinformationregardingsafetysignificance,includingcorrectiveandpreventiveactionswillbeprovidedinanupdatetothisLER.PreviousSimilarEventsLER315/97-023-00NRCFORM366A(6-1998)