Physical and Thermal Analysis of the Heat Pipe Cooled Micro Nuclear Reactor Core Based on Thorium-Plutonium Mixed Fuel

Power distribution inhomogeneity is a key issue in thorium-plutonium fueled heat pipe cooled micro nuclear reactor. In order to optimize the power distribution in the core, the reflector materials such as BeO, Be, Graphite, MgO and Al₂O₃, which have better neutronics properties, are selected in this study, and the effects of these materials on the power distribution and other physical properties of the core are analyzed and compared. The results show that the use of MgO as the reflector material can effectively improve the axial and radial power distribution of the core and reduce the structural mass; at the same time, the use of MgO softens the neutron energy spectrum, improves the initial reactivity of the core, and ensures a 5-year core lifetime. Thermal analysis based on single channel model shows that the bottom temperature of the core is significantly improved with the MgO material, although the thorium-plutonium fuel has a lower thermal conductivity than the UO₂ fuel, resulting in a slightly higher overall axial temperature. However, the thorium-plutonium fuel operates consistently below its melting point in the heat pipe cooled microreactor core, thereby meeting the thermal safety requirements. This study can provide design references and theoretical support for the application of thorium-plutonium fuel in heat pipe cooled micro nuclear reactor.