ML102140195

Day Report of Emergency Core Cooling System Model Changes Pursuant to the Requirements of 10 CFR 50.46

ML102140195
Person / Time
Site:	North Anna
Issue date:	07/29/2010
From:	Price A J Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
10-440
Download: ML102140195 (7)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, V I RGINIA 23261 July 29,2010U.S.Nuclear Regulatory Commission Attention:

DocumentControlDeskWashington,DC20555 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATIONUNIT230DAYREPORTOF EMERGENCY CORECOOLINGSYSTEM (ECCS)MODEL CHANGES PURSUANTTOTHE REQUIREMENTSOF10CFR50.46SerialNo.NL&OS/ETSDocketNo.LicenseNo.10-440 RO 50-339 NPF-7Inaccordancewith10CFR50.46(a)(3)(ii),Dominionherebysubmitsinformationregard ingcumulativeerrorsinAREVA'slargebreaklossofcoolantaccident(LBLOCA)EmergencyCoreCoolingSystem(ECCS)EvaluationModelandtheimpactoftheMeasurementUncertaintyRecapture(MUR)forNorthAnnaPowerStationUnit2(NAPS2)onPeakCladdingTemperature(PCT).Attachment1providesareportdescribingthechangesassociatedwiththeArevaLBLOCAECCS EvaluationModelandimpactoftheMURforNAPS2.InformationregardingtheeffectofthePCTchangestothereportedLBLOCArack-upisprovidedforNAPS2in Attachment 2.Tosummarizethe information inAttachment2, the calculatedPCTfortheLBLOCAanalysesischangedbyanabsolutevalueof53

°Ftoanewvalueof1874

°FforNAPS2.The current accumulationofchangesfortheseitems(sumofabsolutemagnitudes)sincethelast30-dayreportorreanalysisisgreaterthan50°Fandis significantasdefinedin10CFR 50.46(a)(3)(i).10CFR50.46(a)(3)(ii)requiresthelicenseetoprovideareportwithin30days,whichincludesaproposedscheduleforprovidingareanalysisortakingotheractionasmaybeneededtoshowcompliancewith10CFR50.46.Dominionhasreviewedtheinformation prov idedbyArevaanddeterminedthattheadjustedLBLOCAPCTvaluesandthemannerinwhichtheywerederivedcontinuetoconformtotherequirementsof10CFR50.46

.The identifiederrorsintheLOCAanalysisreducetheoverallPCTandthepositivechangeinPCTassociatedwiththemeasurementuncertaintyupratewasderivedbyperformingareanalysisataboundingpowerlevel.Thus

,Dominionhasnoimmediateplanstore-performtheLBLOCAanalysissinceasubstantialmarginremainsbetweentheadjustedPCT(1874 0F)andthe2200 0Flimitof10CFR50.46.DominionroutinelytracksadjustmentstotheLBLOCAcalculatedPCTvaluestoensurethatreasonablemarginstotheacceptancevaluesetby10CFR50.46aremaintained.

Th is informat ion satisfiesthe30dayreportingrequi rementsof10CFR 50.46(a)(3)(ii)

.

SerialNumber10-440DocketNo.50-339 30-DayECCSReportPage2of2Ifyouhaveanyfurtherquestionsregardingthissubmittal

,pleasecontactMr.ThomasShaubat(804)273-2763.Verytrulyyours, J.anriceViPesident-NuclearEngineeringCommitmentsmadeinthisletter:NoneAttachments:(2)1)ReportofChangesinArevaLargeBreakLOCAECCSEvaluationModel-NorthAnnaPowerStationUnit2.2)30-DayReportingof10CFR50.46MarginUtilization-NorthAnnaPowerStationUnit2.cc:U.S.NuclearRegulatoryCommissionRegionIIMarquisOneTower245PeachtreeCenterAvenue

, NE ,Suite1200 Atlanta ,Georgia30303-1257 NRC SeniorResidentInspectorNorthAnnaPowerStationMr.J.E.Reasor

, Jr.OldDominionElectricCooperative InnsbrookCorporateCenter4201DominionBlvd

.Suite300GlenAllen,Virginia23060Dr.V.SreenivasNRCProject ManagerU.S.NuclearRegulatoryCommissionOneWhiteFlintNorth11555RockvillePike Ma il Stop 0-8 G9ARockville,MD20852-2738 Ms.K.R.CottonNRCProject ManagerU.S.NuclearRegulatoryCommissionOneWhiteFlintNorth11555RockvillePikeMailStop 0-8 G9A Rockville , MD 20852-2738 Serial NO.1 0-440 DocketNo.50-339 ATTACHMENT 1REPORTOF CHANGES INAREVALARGEBREAKLOCAECCS EVALUATION MODEL NORTH ANNA POWER STATIONUNIT2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

Serial Number 10-440 Docket No.50-339ReportofChangesinAREVALBLOCAECCSEvaluationModel

'NorthAnna Power StationUnit2 IdentificationofECCS Evaluation Model ChangeThecurrentlargebreaklossofcoolantaccident(LBLOCA)analysesforNorthAnnaPowerStationUnit 2 (NAPS 2)wereperformedusingtheAREVARealisticLBLOCAEvaluationModel(EM).AREVAidentifiedtwochangesandtheNAPSMURalsoimpactedthePCTrackup

.ThechangesaredescribedbelowandprovidetheresultsofanassessmenttodeterminetheimpactonPCT.Change:S-RELAP5KineticsandHeatConductionModelchanges(-29

°F)Previously,theIdahoNationalLaboratory(INL)announcedanerrorinthecodingofthepointkineticsmodel.The correctionswereprovidedbyINLandtheninstalledinto S-RELAP5.Recently ,INLannouncedthatthepreviouserror correctionswereincorrect.ThiswascapturedinaninternalAREVAcorrectiveactionsystemitem.TheAREVAcorrectiveactionitemwasdraftedduetoINLannouncingthattheheatconductionsolutionisincorrectlyprogrammed.Theerrorisassociatedwithusingtheincorrectheatcapacitywhenevaluatingtherightboundarymeshpoint.Insteadofusingthelast(adjacent)meshintervalheatcapacity,thecode incorrectlyusesthenexttolastmeshintervalheatcapacity.Theaffectoftheerrorismaximizedincylindricalandsphericalgeometrieswithfewmeshpoints,whichcanbeminim izedwithanincreasednumberofmeshpoints.TheeffectisfurtherminimizedbytheS-RELAP5RealisticLBLOCA,SBLOCAandNon-LOCAmethodologyguidelinesrequiringclosemeshspacingattheleftandrightboundaries.Thiserrorexists exclusivelyintheRELAP5seriesofcodes.ThecorrectionsforthesetwoerrorswereinstalledintoanewcodeversionofS-RELAP5and50.46 evaluationswereperformed.NorthAnnaUnit2hasaPCTimpactof-29°F.Change: Steam GeneratorEntrainmentbiasfactor(FIJ)change(-4

°F)AninternalAREVA correctiveactionitemwaswrittentoevaluatetheimpactofnotentrainingtheappropriateamountofliquidintothesteam generatortubesduringaLBLOCAevent.TheRealisticLBLOCAmethodologyusesabiasoninterphasefrictionatthesteam generatortubesheetentrancetoinsureanacceptableamountofliquidisentrainedintothesteam generatortubesduringalargebreak.ThebiasdeterminationwasperformedbycomparingcalculatedresultsfromS-RELAP5withmeasureddatafromtheUpperPlenumTestFacility(UPTF)tests.TheUPTFtestfacilityrepresentsafullscale ,fourloopPWRcompletewiththe necessaryhardwarethatcanbeusedtorepresentgeometryspecificphenomenathatoccursduringalargeorsmallbreakLOCA.TheS-RELAP5parameterthatcontrols entrainmentisinterphasefriction

.Therangeofinterphasefrictionspansseveralordersofmagnitudebetweentheflowregimesoccurringinthehotleg

,hotlegriser,steam generatorinletplenumandsteamgeneratortubesheet.

Consequently

,determiningthe uncertaintyininterphasefriction Page 1of2 Serial Number 10-440 Docket No.50-339isnotfeasiblesoaconservativebiasisusedinstead.ThemagnitudeofthebiasisdeterminedbyadjustingtheS-RELAP5RealisticLBLOCAMultiplier"FIJ"until S-RELAP5 over-predictstheentrainmentobservedinUPTFtestsbyanamountwhichisconservativealthougharbitrary.WiththeS-RELAP5KineticsandHeatConductionModelchangesmentionedpreviously,theFIJmultiplierof1.75isinvalidand under-predictsthemeasuredentrainment.There-evaluationoftheS-RELAP5entrainmentyieldedavalueof5

.0fortheFIJmultiplier,whichisappropriatewith amodelingchangetothesteamgeneratorriserangle,greaterthan30-degrees,andwiththehorizontalstratificationflagsettooffinthehotleg.ThecorrectionsforthiserrorwereimplementedandthePCTimpacttoNorthAnnaUnit2isassessedtobe-4 OF.Change:ImpactofMeasurementUncertaintyRecapture(MUR)(+20 OF)NorthAnnaevaluatedthePCTimpactofa1.7%increaseincorepowerfortheMURpoweruprateonUnit 2.FortheMURpoweruprate,anexplicitRealisticLBLOCAanalysiswasperformedbyAREVAbyperformingananalysiswith59casesbeingrunwithincreasednominalcorepowerfrom2893MWtto2942.2MWt,whichboundstheMURratedthermalpowerof2940MWt.TheresultingevaluationbyAREVAidentifieda+20°FchangetothePCTforNAPS 2.ConclusionDominionhasperformedanevaluationofPCTforcomparisonto10CFR50.46 requirements.TheAnalysisofRecordPCTforNAPS2is1789°F.ConsideringthecurrentPCTchangesaswellasallpreviously reportedchangesanderrors,the licensingbasisLBLOCAPCTis1874°FforNAPS2.TheLBLOCAresultshavesufficient margin tothe2200°Flimitspecifiedin10CFR50.46(b)(1).ThecurrentPCTassessmentof53°Fisgreaterthanthe50°Flimitforreportingasdefinedin10CFR50.46(a)(3)(i);hence,thechangeisconsideredsignificantandsubmittalofthis30dayreporttotheNRCis required.Page 2 of 2---------_._--------------------------

Serial Number 10-440 DocketNo.50-339 ATTACHMENT 230DAYREPORTINGOF10CFR50.46MARGIN UTILIZATIONNORTHANNAPOWER STATIONUNIT2 VIRGINIAELECTRICANDPOWER COMPANY (DOMINION)

SerialNumber10-440DocketNo.50-33910CFR50.46 MARGIN UTILIZATION

-AREVA LARGE BREAK LOCA Plant Name:NorthAnnaPowerStation,Unit2 Utility Name: Virginia ElectricandPower Company DEGB 1.65 12 SGTP (%): Limiting Break Size: Notes: Analysis Information EM: AREVA RLBLOCA EM Analysis Date: 2004 Vendor: AREVA FQ: 2.32 Fuel: Mixed: NAIF/Advanced Mark-BW Only AREVAFuelinPlant, Analysis Covers Both TypesLICENSINGBASISAnalysisofRecordPCT Clad Temp COF)Notes 1789 64 8 0 0 22 10-19-20 0 0-32 65 0 20{1}-29{1}0{1}-4{1}0 D.Other1.NonePCTASSESSMENTS (Delta PCT)A.Prior ECCS Model Assessments 1.Forslund-RohsenowCorrelationModeling2.RWSTTemperatureAssumption3.LBLOCA/Seism icSGTubeCollapseICECONCodeErrors4.RLBLOCAChokedFlowDisposition5.RLBLOCAChangesinUncertaintyParameters6.MixtureLevelModelLimitationintheS-RELAP5Code7.PointKineticsProgrammingIssuewithRELAP5-BasedComputerCodes8.ColdLegCondensationUnderPredictedbyS-RELAP5FollowingAccumulatorInjection9.Cross-FlowJunctionAreainS-RELAPModel10.RadiationtoFluidHeatTransferModelChange C.2009/2010 ECCS Model Assessments1.S-RELAP5KineticsandHeatConductionModel2.RODEX3A-ThermalConductivityDegradation3.SGentrainmentbiasfactor(FIJ)change B.Planned Plant Modification Evaluations1.AdvancedMark-BWTopNozzleModification2.GSI-191SumpStrainer3.MURImplementationLICENSINGBASISPCT

+PCTASSESSMENTS PCT=1874 NOTES:{1}Thecurrentaccumulationofchangesfortheseitems(sumofabsolutemagnitudes)sincethelast30-dayreportorreanalysisis greaterthan50°Fandissignificantasdefinedin10CFR50.46(a)(3)(i).Page1of1