Characterization of Thermo‐Mechanical Coupling and Heat Pipe Failure Analysis in the SAIRS Space Reactor

This study establishes a three‐dimensional “SAIRS” heat pipe reactor model with integration of a sodium heat pipe model to investigate the heat transfer and mechanical performance of the core under steady‐state conditions. An irradiation swelling model for uranium nitride is incorporated into the heat pipe reactor to analyze the thermo‐mechanical behavior of the core at various burnup levels, as well as the impact of heat pipe failures at varying locations and quantities on the core's thermo‐mechanical performance is examined. The computational results indicate that, under steady‐state conditions, the core temperature gradually decreases radially, with a temperature difference of 216 K, while stress distribution is influenced by multiple factors. The hexagonal core design may lead to local thermal stress concentration at peripheral sharp corners of the core. As burnup increases, core temperature, deformation, and stress all rise, with the maximum stress increase reaching 54.6 MPa. Fuel experiences the most significant temperature and deformation increases, yet exhibits the smallest stress variation due to its elastic modulus. Changes in core temperature and stress depend on the location and spacing of failed heat pipes. When two central heat pipes fail, the localized temperature can reach 1812 K, whereas failures in peripheral heat pipes lead to higher system temperature rises. Wider spacing between failed heat pipes can mitigate localized overheating and stress concentration. The reactor can maintain fuel rod thermal stress below the yield limit through heat redistribution and regulation capabilities of adjacent functional heat pipes.