MELCOR Application to LOCA Studies Effect of Safety 該應(yīng)用程序的安全分析研究的影響

MELCORApplicationtoPlantAccidentAnalysesatPSI

Y.Liao,S.Guentay,J.Birchley,T.HastePaulScherrerInstitute,SwitzerlandOutlineIntroductiontorecentMELCORapplicationsatPSILossofRHRaccidentsduringmid-loopoperationLOCAsduringhotshutdownoperationLOCAsduringfullpoweroperationSensitivitystudytotheprimarysidenodalizationConclusionsIntroductiontorecentMELCORapplicationsatPSIBeznaupowerplant:TwoloopWestinghousePWR1130MWcorethermalpowerSafetyinjectionpumps:JSI1-A,B,C,DLossofRHRduringmid-loopoperation(22hafterreactortrip)Initialconditionswithcorepowerat0.57%FP,lowprimarypressureLOCAsduringhotshutdownoperation(4hafterreactortrip)Initialconditionswithcorepowerat0.92%FP,intermediateprimarypressureLOCAsduringfullpoweroperationInitialconditionswithcorepowerat100%FP,highprimarypressureThistalkfocusesoneffectofsafetyinjectiontime,injectionrateandsteamgeneratorrefluxcondensationoncorerecoveryMELCORnodalizationfor2-loopWestinghousePWR

LossofRHRduringmid-loopoperationObjectiveDeterminelatestinjectiontimetorecoverthecorewithoutdamageAssumptionsUpperheadinplaceandboltsdetensionedNoaccumulatoravailableOneinjectionpumpavailableforrecoverywithlimitedflowrate(3.5kg/sforbasecase,3.0kg/sforsensitivitystudy)delayedsometimeaftercoreuncovery(2840sforthereferencecase,2640sand3040sforsensitivitystudies)Comparisonofeventsequences

Parameter(unit)Injectiontime(s)150001520015400Startofcoreuncovery(s)123601236012360Startofinjection,ti(s)+2640+2840+3040Levelincoreatti(m)1.261.251.25Max.coretemperatureatti(K)99211001185Startofoxidation(s)++35--165--365Peakcoretemperature(K)118512402369Timetofinalquench(s)++3920++4010++3040*MassofH2generated(kg)2320+relativetostartofcoreuncovery*forintactrods--/++relativetostartofinjectionComparisonofcoreliquidlevels

Comparisonofmaximumfuelrodtemperatures

LossofRHRduringmid-loopoperationSummaryCorecanberecoveredwithjust3.5kg/sinjected(onechargingpump)beforeoxidationexcursionInsensitivetoinjectionrateaslowas3.0kg/sInjectioncanbedelayeduntilcoreisabout50%uncoveredcorrespondstomax.coretemperatureofabout1000KinreferencecasehighlikelihoodofoxidationexcursionifinjectionisdelayedfurtherDetailsappearinAccidentManagementfollowingLossofResidualHeatRemovalduringMid-LoopOperationinaWestinghouseTwo-LoopPWR(J.Birchley,T.Haste,M.Richner,NuclearEngineeringandDesign)LOCAsduringshutdownoperationObjectiveExaminethemarginagainstcoredamagewhenactuationofsafetyinjectionisdelayedLargebreakLOCANoaccumulatoravailableBasecaseassuming30sdelayforJSI1-DsafetyinjectionshowscorerecoverywithoutcoredamageThreesensitivitycasesassuming930sdelaytostudysafetymarginagainstsafetyinjectionavailabilityCaseI:FullinjectionratewithonlyJSI1-DCaseII:FullinjectionratewithonlyJSI1-ACaseIII:FullinjectionrateswithJSI1-A,BandDComparisonofcladdingtemperatures(EffectofJSIavailabilityandinjectionpoint)

LOCAsduringshutdownoperationSmallbreakLOCA(3cm)NoaccumulatoravailableFullinjectionofonlyonepump(JSI1-D)at1500saftercoreuncoverySecondarysideatconstantpressure(37bar)Claddingtemperaturesincentralring

LOCAsduringshutdownoperationSummaryLargebreakLOCAMELCORcalculationsindicatedthatwith930sdelay,onepumpalonemightnotbesufficient,asthetemperaturesatthestartofcorerefillingarealreadyhighenoughforcladoxidationtostartIfallthreeJSIpumpsavailableafter930sdelay,MELCORshowsthattheinjectiontakenmaybesufficienttorefillthecoreIntermediatebreakLOCA(20cm)Recoveryshownforinjectionofonepumpalone(JSI1-D)delayedby930sSmallbreakLOCA(3cm)Recoveryshownforinjectionofonepumpalone(JSI1-D)evenactuatedat1500saftercoreuncoveryMoredetailspresentedinMELCORANDSCDAPANALYSESOFLOSS-OF-COOLANTACCIDENTSDURINGCOOLDOWNINAWESTINGHOUSE2-LOOPPWR(J.Birchley,T.Haste,M.Richner,NENE2007Conference)LOCAsduringfullpoweroperationObjectiveExamineeffectofSGrefluxcondensationoncorerecoveryHelpthedetailedanalysisforthesuccesscriteriaoftherecirculationsafetyinjectionsystemoncetheinjectionrateislimitedbysumpcloggingAssumptionsSGsdepressurizedat50K/h,AFWavailableAccumulatorsavailableBeforeswitchingtosumprecirculationFullinjectionratesavailableforsafetyinjectionpumpsJSI1-A,B,DWhenswitchingtosumprecirculationOnerecirculationinjectionpumpavailableActuatedwhencoreisabout50%uncoveredWithlimitedinjectionratesvaryingfrom0.0to10.0kg/sMELCORcases

CaseNr.BreaksizeRecirculationinjectionpumpavailabilityandflowrateSGrefluxcondensation2in4in6inNo10.0kg/s8.0kg/s3.0kg/sYesNoNr.1xx-Nr.2xxNr.3xxNr.4xxxNr.5xxxNr.6xxxNr.7xxxNr.8xxxNr.9xxxCases1-3:NorecirculationinjectionpumpavailableComparisonofcorewaterlevels ComparisonofpressuresCases1-3:NorecirculationinjectionpumpavailableSummaryNocorerecoveryifnorecirculationinjectionpumpavailableSGheatsinkestablishedbeforecoreuncoveryforthe2inchcasewitha50K/hdepressurizationrateSGheatsinkmayalsobeestablishedforlargerbreaksizeLOCAswithagreaterdepressurizationrateSGrefluxcondensationismoreeffectiveforsmallerbreaksizeLOCAsNext,the2inchbreakLOCAanalysesinCases4to9studytheeffectofrefluxcondensationavailabilitycombinedwithlimitedrecirculationinjectionratesoncorerecoveryCases4,5:EffectofSGrefluxcondensationwiththerecirculationinjectionratelimitedto10.0kg/sComparisonofcorewaterlevels ComparisonofcladdingtemperaturesCases4,5:EffectofSGrefluxcondensationwiththerecirculationinjectionratelimitedto10.0kg/sSummaryforCases4and5WithSGrefluxcondensationtakingplace,corecanbecooledimmediatelyafterrecirculationinjectionWithoutSGrefluxcondensation,corecannotbecooledsoeffectivelyastoavoidcladdingfailure(>900C)Cases6,7:EffectofSGrefluxcondensationwiththerecirculationinjectionratelimitedto8.0kg/sComparisonofcorewaterlevels ComparisonofcladdingtemperaturesWithoutrefluxcondensation:coreisdamagedandrelocatedCases6,7:EffectofSGrefluxcondensationwiththerecirculationinjectionratelimitedto8.0kg/sWithrefluxcondensation:corecanberecoveredwithoutanycladdingfailureCases8,9:EffectofSGrefluxcondensationwiththerecirculationinjectionratelimitedto3.0kg/sComparisonofcorewaterlevels ComparisonofcladdingtemperaturesWithoutrefluxcondensation:coreisrelocatedtothelowerheadCases8,9:EffectofSGrefluxcondensationwiththerecirculationinjectionratelimitedto3.0kg/sWithrefluxcondensation:corecanberecoveredwithPCT<1204CSensitivitystudytotheprimarysidenodalization

SensitivitystudytotheSGandupperplenumnodalizationBasecase:2-nodeSG,1-nodeupperplenumSensitivitycase:8-nodeSG,4-nodeupperplenumComparisonofcorewaterlevels ComparisonofcladdingtemperaturesSensitivitystudytothecorenodalizationBasecase:2-nodeSG,1-nodeupperplenum,3-nodecoreSensitivitycase:8-nodeSG,4-nodeupperplenum,9-nodecoreComparisonofcorewaterlevels ComparisonofcladdingtemperaturesLOCAsduringfullpoweroperationSummarySGheatsinkcanbeestablishedbydepressurizationforsmallbreakLOCAsSGrefluxcondensationsignificantlyaidscorerecoveryWhenSGrefluxcondensationtakingplace,therecirculationinjectionsystemissuccessfultoavoidcoredamagewithinjectionratesaslowasabout3.0kg/sWithoutSGrefluxcondensation,therecirculationinjectionsystemaloneisnotsuccessfultoavoidcoredamagewithinjectionratesashigh