Simulation of the key phenomena in nuclear reactor two-phase flow and severe accident with particle method

This study aims to address important and difficult problems in the thermal safety field, such as the boiling and two-phase flow of nuclear reactor coolant and the migration behavior of molten materials during severe accidents. A high-precision solution technique was proposed using the moving particle semi-implicit method. A two-phase flow particle model was established to capture the complex interface between phases with a large density ratio and simulate the vapor-liquid phase transition. Specifically, a particle method model was developed for analyzing the processes of oxidation eutectic, high-temperature creep, remelting-solidification, and the relocation of degraded nuclear reactor cores during severe accidents. To this end, a complex process analysis software platform PANDA was developed based on the particle method for investigating key thermal safety phenomena in nuclear reactors; thus, the accurate simulation of complex phenomena such as the two-phase flow bubble dynamics of nuclear reactor coolant and severe accidents was effectively realized. © 2024 Chinese Academy of Sciences. All rights reserved.