Study of thermo-mechanical failure mechanisms of fuel assemblies for gas-cooled space nuclear propulsion system

The space nuclear propulsion system, characterized by its compact architecture, high power density, and extended operational lifespan, is regarded as one of the most promising space energy systems. However, the baffle design for the gaseous working fluid within the fuel assemblies in the system can lead to significant local temperature gradients, potentially causing severe thermal stress concentrations and crack-induced failure risks, so it is essential to investigate the thermomechanical stress behavior of structures under high-temperature gas flow conditions. This study employs fluid-structure interaction simulations to analyze energy supply assemblies under full-power steady-state conditions, which reveals the gaseous coolant’s temperature and pressure distribution and their effects on the assembly’s thermal stress. Joint analysis of heat flux, temperature, and stress distributions reveals two key temperature-stress response mechanisms driven by the baffle design. These mechanisms lead to thermal stress concentrations near the fuel’s center channel in the anterior middle section and the edge wall at the coolant outlet due to non-uniform thermal expansion. The findings highlight unique thermo-mechanical behaviors within the assemblies and offer a preliminary structural safety analysis, which can provide a reference for the operational safety design of such typical space energy systems.