CONTENTS 

Chapter1 Introduction ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 1 

1.1 Generation-¢ô NuclearReactorSystems ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 1 

1.2 Sodium-CooledFastReactors ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 4 

1.2.1 Developmenthistoryandcur entsituation ofSFRs ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 4 

1.2.2 SystemcharacteristicsofSFRs ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 7 

1.3 SFRSafetyAnalysisandSevereAc idents¡­¡­¡­¡­¡­¡­¡­¡­ 11 

1.4 Particle-Bed-RelatedPhenomenaDuringSFRSevere Acident ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 14 

1.4.1 Molten-poolmobility ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 14 

1.4.2 Molten-poolsloshingmotion ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 15 

1.4.3 Debris-bedformationbehavior ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 15 

1.4.4 Debris-bedself-levelingbehavior ¡­¡­¡­¡­¡­¡­¡­¡­ 17 

1.5 Summar¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 18

References ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 19 

Chapter2 Molten-PolMobility ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 22 

2.1 Introduction ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 22 

2.2 TheoreticalModelsandMethodsforMolten-Pool Mobilit¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 23

2.2.1 Multiphaseflow model¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 23 

2.2.2 Particleviscositymodel ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 25 

2.2.3 Particlejammingmodel ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 26 

2.3 Molten-PoolMobilityinaLiquid-Dominant Particle-RichPool ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 28 

2.3.1 Experimentalconditionsinaliquid-dominant particle-richpool ¡­¡­¡­¡­¡­¡­ 28 

2.3.2 Simulationconditionfortheliquid-dominant particle-richpoolexperiments¡­ 30 

2.3.3 Analysesoftheliquid-dominantparticle-rich poolexperimentsandsimulations  31 

2.4 Molten-PoolMobilityinaParticle-DominantBubble-VisualizationPool ¡­¡­¡­¡­ 44 

2.4.1 Experimentalconditioninaparticle-dominant bubble-visualizationpool ¡­¡­ 45 

2.4.2 Simulationconditionfortheparticle-dominant bubble-visualizationpoolexperiments ¡­ 46 

2.4.3 Analysesoftheparticle-dominantbubble-visualization poolexperimentsandsimulations ¡­ 47 

2.5 Summary ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 57 References ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 58 

Chapter3 Molten-PolSloshingMotion ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 60 

3.1 Introduction ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 60 

3.2 SloshingMotioninaPureLiquidPool ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 65 

3.2.1 Symmetricdam-breakconditions ¡­¡­¡­¡­¡­¡­¡­¡­ 65 

3.2.2 Asymmetricdam-breakcondition ¡­¡­¡­¡­¡­¡­¡­¡­ 85 

3.2.3 Fluid-stepcondition ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 91 

3.2.4 Centralizedmolten-fuel-fragmentfaling condition ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 94 

3.2.5 Gas-injectionconditionwithhydraulic disturbances ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 100 

3.2.6 Gas-injectionconditionwithouthydraulic disturbances ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 105 

3.2.7 Gas-injectionconditionwithstratifiedliquids ¡­¡­ 112 

3.3 SloshingMotioninaLiquidPoolwithSolidPhase¡­¡­¡­¡­ 122 

3.3.1 Dam-breakandfluid-stepconditionwithring obstacles ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 123 

3.3.2 Dam-breakandfluid-stepconditionwithrod obstacles ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 127 

3.3.3 Dam-breakconditionwithsolidparticles ¡­¡­¡­¡­ 132 

3.3.4 Gas-injectionconditionwithsolidparticles ¡­¡­¡­ 138 

3.4 Summary ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 152 References ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 154 

Chapter4 DebrisBedFormationBehavior¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 158 

4.1 Introduction ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 158 

4.2 InvestigationsonDebrisBedFormationBehavior inJapan ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 164 

4.2.1 Single-sizesingle-shapesolidparticlecondition ¡­¡­ 164 

4.2.2 Mixedsolidparticlecondition ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 198 

4.3 InvestigationsonDebrisBedFormationBehavior inChina ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 216 

4.3.1 Single-sizesphericalsolidparticlecondition ¡­¡­¡­ 216 

4.3.2 Single-sizenon-sphericalsolidparticlecondition ¡­ 230 

4.3.3 Mixed-sizesphericalsolidparticlecondition ¡­¡­¡­ 233 

4.3.4 Gas-injectioncondition ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 240 

4.3.5 Botom-heatedcondition ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 247 

4.4 Summary ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 257 References ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 259 

Chapter5 DebrisBedSelf-LevelingBehavior¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 264 

5.1 Introduction ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 264 

5.2 ExperimentalStudiesonDebrisBedSelf-Leveling Behavior ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 269 

5.2.1 Microscopicflow-regimeexperiments ¡­¡­¡­¡­¡­¡­ 269 

5.2.2 Self-levelingexperimentsunderdepresurization andbotom-heatedboilingcondition ¡­ 281 

5.2.3 Self-levelingexperimentsundergas-injection condition ¡­¡­¡­¡­¡­¡­¡­¡­ 291 

5.3 ModelingStudiesonDebrisBedSelf-LevelingBehavior ¡­ 308 

5.3.1 Modelingforself-levelingonsetcriteria ¡­¡­¡­¡­¡­ 308 

5.3.2 Modelingforthevariationofinclinationangle ¡­¡­ 312 

5.3.3 Modelingforthevariationofmoundand bedheights ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 320 

5.4 NumericalStudiesonDebrisBedSelf-LevelingBehavior¡­¡­¡­ 331 

5.4.1 SIMMERsimulationwithdebris-fluidization andboiling-regulationmodels ¡­ 332 

5.4.2 SIMMERsimulationwithDEM model ¡­¡­¡­¡­¡­ 337 

5.4.3 SIMMERsimulationwithmodelsofinter-particle colisionsandcontacts ¡­¡­¡­ 347 

5.5 Summary ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 363 References ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 366 

Chapter6 ConclusionandFutureProspect¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 370 

6.1 ConclusionforPreviousInvestigations ¡­¡­¡­¡­¡­¡­¡­¡­¡­ 371 

6.2 FutureProspect ¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ 376