Numerical investigation of cooling ability in heat-generating porous debris bed after severe accident in PWR

A porous debris bed formed after a severe accident is structure composed of different sized particles. Due to the fission reaction in bed, decay heat continuously released. Therefore, cooling ability should be investigated determine safety bed. In this paper, two-phase conservation equations with closure correlations are proposed for boiling phenomenon inside pool. For flow resistance, drag force between gas and liquid continuous fluid considered as well resistance solid medium area. The transfer model takes into account phase phases mass liquid. All calculations conducted based on CFD method, related models written calculation program form User Defined Function (UDF). After necessary validation correlations, analysis discussion effect heating type, non-uniform distribution structural parameters, shape geometry. results show key natural convection boundary settings type. time series strong formation power factors that determined position crisis. addition, limited density by top half increase parameters operating pressure leads better ability. regular cylinder removal, while conical significantly reduces density, which dangerous long-term would improved if downcomer existed These three research parts conducive deepening understanding process serious accident.