Synthesis of research on boiling pool thermalhydraulics at CEA and KfK

The accident phase following material melting and relocation is the so-called boiling pool phase. For reactor applications it is thought to be important to predict the location of the melt-through of the hexcan and the pressure inside the molten subassembly at that moment since these parameters are thought to govern the propagation of the molten materials in the neighbouring structures. The objectives of the Boiling Pool Thermal hydraulics investigations were: to investigate mixed UO2 and steel pools; to determine the heat flux distribution; and to validate analytical models. The general conclusion concerning the hexcan melt through in reactor does not depend on the detailed knowledge of the effect of the steel in the pool: this melt through occurs clearly without important pressurisation within the pool and high heat fluxes are rapidly established after fuel melting