Pressure dependence of dryout in a heat-generating porous debris bed

Abstract

The primary objective of this work is to numerically study the effect of system pressure on the occurrence of dryout phenomena in heap-shaped, heat-generating porous debris beds. This is achieved using a multiphase computational fluid dynamics (CFD) model that is implemented in the framework of the commercial CFD platform ANSYS FLUENT. The model is extensively validated with available experimental data on two different aspects: pressure drop in two-phase flow through porous media and prediction of dryout in typical porous debris beds. A wide range of system pressure, relevant to severe accident conditions, is considered in this analysis in order to obtain a thorough understanding of its impact on multiphase flow and dryout occurrence in porous debris beds. This analysis is performed for different subcoolings of flooding water, which gives additional knowledge on the effects of coolant subcooling on dryout occurrence. Results indicate that dryout in debris beds occurs at progressively higher power densities as the system pressure is raised. Similar effects are observed with increase in liquid subcooling as well.