Numerical Investigation of Boiling and Two-Phase Natural Circulation in a Full-Scale Core Catcher Using OpenFOAM

The core catcher system is designed to cool molten corium relocated outside the reactor pressure vessel during a severe accident in a nuclear power plant. The relocated corium imposes a heat load on the core catcher, which induces boiling and two-phase flow within the cooling channels. This process drives a natural circulation flow that facilitates the overall cooling process. Understanding these complex thermal-hydraulic phenomena, particularly the two-phase flow characteristics within the channels, is essential for ensuring the long-term cooling efficacy and structural safety of the core catcher system. The primary goal of this study is to conduct an in-depth numerical analysis of the thermal-hydraulic phenomena within a full-scale core catcher design using the OpenFOAM CFD framework. To ensure the credibility of the simulation, the selected physical models were validated against experimental datasets obtained from the VPEX facility. Based on the validated computational platform, the investigation was scaled up to a three-dimensional domain representing the complete geometry of the core catcher.