ML17229A115

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Informs That Util Agrees W/Nrc Staff Re Importance of Issues Surrounding Revised LBLOCA Evaluation Model.Final Analysis of Impact of Model Error on ECCS Acceptance Criteria Will Be Prepared
ML17229A115
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 10/25/1996
From: BOHLKE W H
FLORIDA POWER & LIGHT CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-96-283, NUDOCS 9611050179
Download: ML17229A115 (7)


Text

CATEGORY1REGULATINFORMATIONDISTRIBUTIONSTEM(RIDS)ACCESS3;0$.NBR:9611050179DOC.DATE:96/10/25NOTARIZED:NOFACIL:50-335St.LuciePlant,Unit1,FloridaPower6LightCo.AUTH.NAMEAUTHORAFFILIATIONBOHLKE,W.H.FloridaPoweraLightCo.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)DOCKET05000335

SUBJECT:

Informsthatutilagreesw/NRCstaffreimportanceofissuessurroundingrevisedLBLOCAevaluationmodel.FinalanalysisofimpactofmodelerroronECCSacceptancecriteriawillbeprepared.DISTRIBUTIONCODE:A001DCOPIESRECEIVED:LTRKENCLSIZE:TITLE:ORSubmittal:GeneralDistributionNOTES:AERECIPIENTIDCODE/NAMEPD2-3LAWIENSiL.COPIESRECIPIENTLTTRENCLIDCODE/NAME11'D2-3PD11COPIESLTTRENCL110INTERNAL:ACRSNRR/DE/EMCBNRR/DSSA/SPLBNUDOCS-ABSTRACTEXTERNAL:NOAC1111111111FILECENTERRR/DRCHHICBNRR/DSSA/SRXBOGC/HDS3NRCPDR1111111011DNOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083TOTALNUMBEROFCOPIESREQUIRED:LTTR13ENCL12 FloridaPower&LightCompany,P.O.Box14000,JunoBeach,FL33408-0420OgT251996L-96-28310CFR50.46U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555Re:St.LucieUnit1DocketNo.50-335RevisedLBLOCAEvaluationModel;PreliminaAssessmentofImactonPCTRef:(1)NRCletter:BrianW.SherontoT.F.Plunkett,10CFR50.46LARGEBREAKLOSS-OF-COOLANTACCIDENTEVALUATIONMODELFORST.LUCIEPLANT,UNIT1(TACNO.M96355);October11,1996.(2)Telecon10/24/96,4:00pm,J.A.Zwolinski(NRC),etal,toW.H.Bohlke(FPL),et.al.Reference(1)informedFloridaPowerandLightCompany(FPL)ofproblemsidentifiedbytheNRCconcerningchangestotheSiemensPowerCorporation(SPC)largebreakloss-of-coolant(LBLOCA)evaluationmodelusedbySPCforpressurizedwaterreactors.TheletterrequestedthatFPLevaluate,inaccordancewith10CFR50.46(a)(3)(ii),theimpactofidentifiedmodelerrorsandchanges,andtakewhateveractionsarerequiredtoassurecompliancewith10CFR50.46.FPLagreeswiththeNRCstaffregardingtheimportanceoftheissuessurroundingthesubjectLBLOCAevaluationmodel.AsdiscussedinReference(2),FPLhasagreedtodocumentthecurrentassessmentandtherationaleleadingtoFPL'sconclusionthatSt.LucieUnit1isoperatingincompliancewith10CFR50.46.Theattachmenttothislettercontainsthatassessmentwithsupportingrationale.Becausethecurrentassessment'scalculationalresultshavenotreceivedfinalverificationbySPC,FPLisalsopreparingafinalanalysisoftheimpactoftheLBLOCAmodelerroronemergencycorecoolingsystemacceptancecriteria.FPLwillsubmitthisanalysistotheNRCuponcompletionofitsreviewofSPCrevisedcalculationalmodelfinalresults.Pleasecontactusifthereareanyquestionsregardingthissubmittal.Verytrulyyours,W.H.BohlkeVicePresidentNuclearEngineeringWHB/RLD~~nnCid96ii050i79qhi025PDRADQCK05000335PPDR

Attachment:

LBLOCAAssessmentForSt.LucieUnit1QG(icc:StewartD.Ebneter,RegionalAdministrator,RegionII,USNRC.SeniorResidentInspector,USNRC,St.LuciePlant.anFPLGroupcompany 0I;'<<)'r ATTACHMENTLBLOCAAssessmentForSt.LucleUnit1FPLhasperformedanassessmentforSt.LucieUnit1inlightofNRC'sconcernwiththecalculationofpeakcladdingtemperature(PCT)resultingfromaLargeBreakLossofCoolantAccident(Reference1).TheNRCidentifiednon-physicalbehaviorintheheattransfercoefficientforrefloodratesbetween1.00in/secand1.77in/secintheNRCapproved1986ECCS/LBLOCAevaluationmodelforSiemensPowerCorporation(SPC).FPLhasdevelopedamodificationtotheheattransfercoefficientwithalinearfunctionbetween1.00in/secand1.77in/secwhichcorrectsthenon-physicalbehavioroftherefloodheattransfercorrelation.FPLconcludesthatthismodificationisappropriatebecause:i)Theendpointsforinterpolatingtheheattransfercoefficientaretherespectivevaluesatfloodingratesof1.00in/secand1.77in/sec.ii)Thelinearinterpolationoftheheattransfercoefficientbetweenthefloodingratesof1.00in/secand1.77in/secfollowsthetrendofincreasingheattransfercoefficientwithincreasingrefloodrateshownbytheFLECHTtestdata(Reference2).iii)Thevaluesoftheheattransfercoefficientthroughouttherangeofinterestareconservativeforpressurizedwaterreactorapplications.AnassessmentofPCTusingtheaboveinterpolationapproachhasshownaPCTof2027F(Reference3),whichisanincreaseof115FwithrespecttothecurrentanalysisofrecordPCTof1912F.TherecalculatedPCTremainswellbelowthe10CFR50.46criterionof2200F(margin)150F).However,themagnitudeoftheincreasemeetsthedefinitionofsignificantchangeper10CFR50.46.Inaddition,thepreliminaryresultsofthecalculationshowthatthemaximumlocalcladdingoxidationismuchlessthan17%andthecorewidemaximumoxidationismuchlessthan1%.Inconclusion,the10CFR50.46acceptancecriteriaremainsatisfied.TheinformationusedbyFPLtoreachitsconclusionisbaseduponcomputercodecalculationswhichhavenotreceivedaformalverificationunderSPC'sandFPL'squalityassuranceprograms.Aformalreviewofthisanalysisiscurrentlyinprogress.Meanwhile,FPLhasperformedareviewoftheaboveanalyticalresultswithrespecttothefollowingmajorparameters.ThereviewconcludesthattheoperationofSt.LucieUnit1willcontinuetoremainincompliancewith10CFR50.46:HeatTransferCoefficient:Theheattransfercoefficientinthecurrentanalysisislessthanthatseenwiththeuncorrected1986modelcorrelation.Thebehavioroftheheattransfercoefficientwithtimeatvariouselevationsisasexpected.FloodingRate:Thefloodingrateshowsadropfromavalueof-2in/secat75secondstoavalueof-1.2in/secat150secondsintothetransient.ThecalculatedincreaseinPCTisconsistentwiththereducedheattransfercoefficientinthisrangeoffloodingrates.

l1-PeakCladdingTemperature:ThePCThasincreasedandthecorrespondingtimetoreachthePCThasincreasedbymorethan30secondsunderthereducedheattransfercoefficientassumption.ThisbehaviorofPCTfollowingmodificationoftheheattransfercoefficientisasexpectedandthemagnitudeofthechangeappearsreasonable.

References:

1.LetterB.W.Sheron(NRR)'toT.F.Plunkett(FPL),"10CFR50.46LargeBreakLoss-Of-CoolantAccidentEvaluationModelForSt.LucieUnit1(TACNo.M96355),"datedOctober11,1996.2.N.Lee,"PWRFLECHTSEASETUnblockedBundle,ForcedandGravityRefloodTask,DataEvaluationandAnalysisReport,"EPRI-NP-2013NUREG/CR-2256WCAP-9891February1982.3.LetterTMH:96:223,T.M.Howe(SPC)toR.J.Rodriguez(FPL),"AssessmentofNon-PhysicalBehaviorinHeatTransferforSt.LucieUnit1LBLOCA,"October23,1996.

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