Thin Metallic Layer On The Top Of The Molten Corium Pool Study, Under Severe Accident Conditions With Its Impact On The Core Support Plate - Cfd Software Application

Under severe accident conditions with the core melt scenario, one of the safety issues is the thin metallic layer behaviour, which is believed to be created on the top of the corium pool. The thin layer properties are impacting directly the focussing effect and the magnitude of the heat flux transferred to the vessel walls. The heat transfer in the thin metallic layer is still a question, that computational fluid dynamics software is trying to answer. Analysis presented are the studies on this topic, with the sensitivity calculations on the key uncertain parameters in the thin metallic layer case - boundary conditions. The qualification of the turbulence models and Computational Fluid Dynamics (CFD) software set up is generated, for the low Prandtl metallic layer configurations, with established Rayilegh-Benard convections cells. The results from the analysis became important input values for the parallel CFD computations on the temperature distribution in the core support plate under severe accident conditions, which is crucial for the future thermal -mechanical study of the structure. A detailed analysis allows to determine the list of events with particular emphasis on the temperature gradient in the axial and radial directions. Numerical representation of temperature fields and phase changes under severe damage conditions, showing the temperature distribution on the core support plate and the degree of damage.All described above issues increase the further predictability of safety analyses and consequently will give a better estimation of the reactor pressure vessel rupture time and core support plate damage.