ComparisonoftwomodelsforapebblebedmodularreactorcorecoupledtoaBraytoncycleOriginalResearchArticle

Thepebblebedmodularreactor(PBMR)plantisapromisingconceptforinherentlysafenuclearpowergeneration.Thispaperpresentstwodynamicmodelsforthecoreofahightemperaturereactor(HTR)powerplantwithaheliumgasturbine.BoththePBMRanditspowerconversionunit(PCU)basedonathree-shaft,closedcycle,recuperative,inter-cooledBraytoncyclehavebeenmodeledwiththenetworksimulationcodeFlownex. OnemodelutilizesacoresimulationalreadyincorporatedintheFlownexsoftwarepackage,andtheotheracoresimulationbasedonmulti-dimensionalneutronicsandthermal-hydraulics.ThereactorcoremodeledinFlownexisasimplifiedmodel,basedonazero-dimensionalpoint-kineticsapproach,whereastheothermodelrepresentsastate-of-the-artapproachforthesolutionoftheneutrondiffusionequationscoupledtoathermal-hydraulicpartdescribingrealisticfueltemperaturesduringfasttransients.Bothreactormodelswereintegratedintoacompletecycle,whichincludesaPCUmodeledinFlownex. Flownexisathermal-hydraulicnetworkanalysiscodethatcancalculatebothsteady-stateandtransientflows.AninterestingfeatureofthecodeisitsabilitytoallowtheintegrationofanexternalprogramintoFlownexbymeansofasocalledmemorymapfile. Thetotalplantmodelsarecomparedwitheachotherbycalculatingrepresentativetransientcasesdemonstratingthatthecouplingwithexternalmodelsworkssufficiently.Todemonstratethefeaturesoftheexternalprogramahypotheticalfastincreaseofreactivitywassimulated.