CAST3M/ARCTURUS:AcoupledheattransferCFDcodeforthermal–hydraulicanalyzesofgascooledreactorsOriginalResearchArticle

Thesafetyofgascooledreactors(HighTemperatureReactors(HTR),VeryHighTemperatureReactors(VHTR)orGasCooledFastReactors(GFR))mustbeensuredbysystems(activeorpassive)whichmaintainloadsoncomponent(fuel)andstructures(vessel,containment)withinacceptablelimitsunderaccidentalconditions.Toachievethisobjective,thermal–hydraulicscomputercodesarenecessarytoolstodesign,enhancetheperformanceandensureahighsafetylevelofthedifferentreactors.Somekeysafetyquestionsarerelatedtotheevaluationofdecayheatremovalandcontainmentpressureandthermalloads.Thisrequiresaccuratesimulationsofconduction,convection,thermalradiationtransfersandenergystorage.Couplingwithneutronicsisalsoanimportantmodelingaspectforthedeterminationofrepresentativeparameterssuchasneutronicscoefficient(Dopplercoefficient,Moderatorcoeffcient,…),criticalpositionofcontrolrods,reactivityinsertionaspects,….ForGFR,thehighpowerdensityofthecoreanditsnecessaryreduceddimensioncannotrelyonlyonpassivesystemsfordecayheatremoval.Therefore,forcedconvectionusingactivesafetysystems(gasblowers,heatexchangers,…)arehighlyrecommended.Nevertheless,incaseofstationblack-out,thesafetydemonstrationoftheconceptshouldbeguaranteedbynaturalcirculationheatremoval.Thiscouldbeperformedbykeepingarelativelyhighback-uppressureforpureheliumconvectionandalsobyheavygasinjection.So,itisalsonecessarytomodelmixingofdifferentgases,theon-setofnaturalconvectionandthepressureandthermalloadsontotheproximateorguardcontainment.Inthispaper,wereportonthedevelopmentsoftheCAST3M/ARCTURUSthermal–hydraulics(LumpedParameterandCFD)codedevelopedatCEA,includingitscouplingtotheneutronicscodeCRONOS2andthesystemcodeCATHARE.Elementaryvalidationcasesaredetailed,aswellasapplicationofthecodetobenchmarkproblemssuchastheHTR-10thermal–hydraulicexercise.Examplesofcontainmentthermal–hydraulicscalculationsforfastreactordesign(GFR)arealsodetailed.