Conceptual Multi-Physic Coupling Simulation on Transient Operations Of a He-Xe Cooled Mobile Nuclear Power Plant

Abstract Mobile nuclear power plants (MNPP) with low-enriched fuel loading, compact structures, and flexible configurations significantly apply emergency power supply for remote locations. Due to good compressibility and heat-transfer performance, the He-Xe mixture is used as the working medium of the closed Brayton cycle (CBC) and the coolant of the graphite-based solid-state reactor (SSR). In the present work, multi-physics transient simulations are conducted based on the open-source software OpenFOAM. CFD methods solve the heat transfer between the solid matrix and the He-Xe channels, and the three-dimensional temperature distributions can be determined. Because of the large amounts of channels in the core, we employ a porous media model to decrease the mesh resolution near the channel-to-cladding interface. For simplification, the power transient is controlled by point kinetic equations. Doppler broadening effect is considered as the feedback between the neutronics and thermal-hydraulics. The rest components of the CBC, such as the pre-cooler, the compressor, the recuperator and the turbine, are represented as a one-dimensional model to update the boundary condition of the reactor core. The simulation results reveal dynamic features of the CBC system under several transient operations. The numerical analysis of this work could provide references to the further analysis of the MNPP.