ML17241A339

Forwards Notification of Change to Small Break LOCA ECCS Evaluation Model Used for St Lucie Unit 1.Anomaly Was Discovered & Corrected That Resulted in Reducing Calculated PCT for Limiting SBLOCA by More than 50 F

ML17241A339
Person / Time
Site:	Saint Lucie
Issue date:	05/20/1999
From:	STALL J A FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-99-112, NUDOCS 9905270115
Download: ML17241A339 (4)

Text

CATEGORY'EGULAT.INFORMATIONDISTRIBUTIOSYSTEM(RIDS)$~~eACCESSIONNBR:9905270115DOC.DATE:99/05/20NOTARIZED:NOFACIL:50-335gt.LuciePlant,Unit1,FloridaPower&.LightCo.AUTK.NAPE.AUTHORAFFILIATIONSTALL,u.A.FloridaPower8LightCo.RECIP.NAMERECIPIENTAFFILIATIONRecordsManagementBranch(DocumentControlDesk)

SUBJECT:

ForwardsnotificationofchangetosmallbreakLOCAECCSevaluationmodelusedforSTLucieUnit1.AnomalywasdiscoveredEcorrected.LimitingPCTiswellwithin10CFR50.46acceptancecriteria.DISTRIBUTIONCODE:A001DCOPIESRECEIVED:LTRENCLSIZE:TITLE:ORSubmittal:GeneralDistributionDOCKET05000335NOTES:RECIPIENTIDCODE/NAMELPD2-2LAGLEAVES,WCOPIESLTTRENCL1111RECIPIENTIDCODE/NAMELPD2-2PDCOPIESLTTRENCL110RINTERNAL:ACRSNRR/DE/EEIBNRR/DE/EMEBNRR/DSSA/SRXBNUDOCS-ABSTRACTEXTERNAL:NOAC11'111.111111FPLECENTER~011NRR/DE%EMCB1NRR/DSSA/SPLB1NRR/SPSBJUNG,I1OGC/RP1NRCPDR11110D'ENOTETOALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATIONREMOVEDFROMDISTRIBUTIONLISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION,CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION415-2083TOTALNUMBEROFCOPIESREQUIRED:LTTR15ENCL14 FioridaPower&LightCompany,6351S.OceanDrive,JensenBeach,FL34957May20,1999L-99-11210CFR50A6U.S.NuclearRegulatoryCommissionATTN:DocumentControlDeskWashington,DC20555Re:St.LucieUnit1Docket50-335SBLOCAEvaluationModel30-Da10CFR50A6ReortTheattachedreportissubmittedpursuantto10CFR50A6(a)(3)(ii)toprovidenotificationofachangetothesmallbreaklossofcoolantaccident(SBLOCA)emergencycorecoolingsystemevaluationmodelusedforSt.LucieUnit1.Ananomalywasdiscoveredandcorrectedthatresultedinreducingthecalculatedpeakcladdingtemperature(PCT)forthelimitingSBLOCAbymorethan50'F,andmeetsthecriteriaforreportingwithin30days.ThelimitingPCTiswellwithinthe10CFR50A6acceptancecriteria.Pleasecontactusifyouhaveanyquestionsaboutthismatter.Verytrulyyours,J.A.StallVicePresidentSt.LuciePlantJAS/RLDAttachmentCC:RegionalAdministrator,RegionII,USNRCSeniorResidentInspector,USNRC,St.LuciePlant99052701i5990520PDRADQCK05000335iPPDRanFPLGroupcompany 4.frsllIIII St.LucieUnit1DocketNo.50-335SBLOCAEvaluationModel30-Da10CFR50.46ReortL-99-112AttachmentSiemensPowerCorporation(SPC)analyzestheSt.LucieUnit1emergencycorecoolingsystem(ECCS)performanceinpostulatedlossofcoolantaccidentspursuanttotherequirementsof10CFR50.46.SPCidentifiedandresolvedadeviationfromthe10CFR50,AppendixK,requirementsinthatthespecificationsfornodesinthecoremodelforthesmallbreaklossofcoolantaccident(SBLOCA)evaluationdidnotprovideaconvergedsolution.Correctionoftheanomalyresultedinasignificantdecreaseinthecalculatedpeakcladdingtemperature(PCT)forthelimitingsmallbreak.ItshouldbenotedthatthelargebreakLOCAcontinuestobethelimitinglossofcoolantaccidentanalyzedforSt.LucieUnit1.NatureofDeviation:SpecificationsfornodesintheSBLOCAcoremodeldidnotprovideaconvergedsolutionforthehotassemblyPCT.DescritionofErrorandCorrectiveAction:AconcerninvolvingproperdemonstrationofsolutionconvergenceforcorehotassemblycalculationswasidentifiedinSPCConditionReport(CR)6272.TheconcernledtothedeterminationthatthenodalrepresentationusedintheSBLOCAmethodologydidnotresultinaconvergedsolutionwithrespecttocorenodelength.Twomodelswereidentifiedasprinciplecontributorstotheanomaly:thetwo-velocitycross-flowmodelandthelevelmodel.Thetwo-velocitycross-flowmodellackssophisticatedtreatmentforthetwo-phasemomentumequationsthatareused,andcausessevereoscillationsduringtwo-phaseflowconditions.Inaddition,thelevelmodel,whichsharpenstheliquid-vaporinterface,canhavespuriousbehaviorundersomeconditions.Whenthesetwomodelsareusedinconjunction,solutionconvergenceisnotdemonstratedforthehotassemblyPCT.Theanomalywascorrectedbyspecifyinghomogeneousflow(single-velocity)atthecross-flowjunctionsandbyusingsmallequal-sizednodesinthecoremodel.TheserevisionstotheapplicationoftheSBLOCAmodelresultinconsistentandconvergedcoresolutionsinbothsteadystateandtransientcalculations.Calculationswiththecorrectedmodelincludedabreak-sizespectrumanalysis,whichdeterminedthatthelimitingsmallbreakchangedfrom.05ftto0.1ft.Thefinalresultisasignificantreductioninthecalculatedpeakcladdingtemperature.Thecorrectiveactioneliminatestheoscillatorybehaviorandresolvestheissueofsolutionconvergence.SPCreviewedthebenchmarkcalculationsforthecurrentSBLOCAmodelandconcludedthatthebenchmarkswerenotsensitivetothemodelchanges.ImactoftheError/Deviation:FortheSt.LucieUnit1SBLOCAanalysis,theimpactofthemodelchangeonthecalculatedPCTis-188'F.TherevisedPCTforthelimitingSBLOCAis1765'F.