CAD analysis for molten pool experiment and assessment of CIF under subcooled boiling condition

In-vessel retention (IVR) of core melt is a key severe accident mitigation measure adopted by some advanced light water reactors. Decay heat removal for IVR is through the external reactor vessel cooling (ERVC) by flooding the reactor cavity during severe accident. As long as the heat flux on the vessel outer surface is lower than the critical heat flux (CHF), the reactor vessel can be sufficiently cooled to maintain the RPV integrity. Heat flux on the RPV outer surface is mainly determined by the core melt behavior, whereas CHF depends on the thermal-hydraulic parameters in the cooling channel outside the RPV. In the present studies, computational fluid dynamics (CFD) models for IVR experiments were carried out, to understand various phenomena related to molten pool and cooling channel. The UCLA experiment and SLUTAN experiment were simulated by using CFD method, the heat source driven natural convection heat transfer coefficient in UCLA experiment, and the two phase boiling phenomena in SLUTAN experiment were investigated in this paper. The CFD calculation results were compared with the experiments data