Analysisoflarge-scaletestsforAP-600passivecontainmentcoolingsystemOriginalResearchArticle

Allnext-generationlightwaterreactorsutilizepassivesystemstoremoveheatvianaturalcirculationandaresignificantlydifferentfrompastandcurrentnuclearplantdesigns.OneuniquefeatureoftheAP-600isitspassivecontainmentcoolingsystem(PCCS),whichisdesignedtomaintaincontainmentpressurebelowthedesignlimitfor72hwithoutactionbythereactoroperator.Duringadesign-basisaccident(DBA),i.e.,eitheraloss-of-coolantoramain-steam-linebreakaccident,steamescapesandcomesincontactwiththemuchcoolercontainmentvesselwall.Heatistransferredtotheinsidesurfaceofthesteelcontainmentwallbyconvectionandcondensationofsteamandthroughthecontainmentsteelwallbyconduction.Heatisthentransferredfromtheoutsideofthecontainmentsurfacebyheatingandevaporationofathinliquidfilmthatisformedbyapplyingwateratthetopofthecontainmentvesseldome.Airintheannularspaceisheatedbybothconvectionandinjectionofsteamfromtheevaporatingliquidfilm.Theheatedairandvaporriseasaresultofnaturalcirculationandexittheshieldbuildingthroughtheoutletsabovethecontainmentshell.AlloftheanalyticalmodelsthataredevelopedforandusedintheCOMMIX-1DcodeforpredictingperformanceofthePCCSwillbedescribed.Thesemodelscovergoverningconservationequationsformulticomponentssingle-phaseflow,transportequationsforthek−ɛtwo-equationturbulencemodel,auxiliaryequations,liquid-filmtrackingmodelforbothinside(condensate)andoutside(evaporatingliquidfilm)surfacesofthecontainmentvesselwall,thermalcouplingbetweenflowdomainsinsideandoutsidethecontainmentvessel,andheatandmasstransfermodels.VariouskeyparametersoftheCOMMIX-1DresultsandcorrespondingAP-600PCCSexperimentaldataarecomparedandtheagreementisgood.Significantfindingsfromthisstudyaresummarized.