Developmentofathree-dimensionalCDAanalysiscode:SIMMER-IVanditsfirstapplicationtoreactorcaseOriginalResearchArticle

Forthetransitionphaseanalysisofcoredisruptiveaccidents,thedevelopmentofathree-dimensionalreactorsafetyanalysiscode,SIMMER-IV,hasbeencarriedoutbasedonthetechnologyofthetwo-dimensionalSIMMER-IIIcode.TheworldfirstapplicationofSIMMER-IVtoasmall-sizedsodium-cooledfastreactorhasalsobeenattemptedtoclarifyeventprogressionintheearlystageofthetransitionphase.ThisSIMMER-IVcalculationiscomparedtothetwo-dimensionalcasecalculatedbySIMMER-III,neglectingthepresenceofcontrolrodguidetubes.Thepresentanalysiswiththethree-dimensionalrepresentationsuggeststhattheconventionalscenarioleadingtoratherearlyhigh-mobilityfuelpoolformationisunrealisticandthedegradedcoretendstokeeplowmobilityintheearlystageoftransitionphase.