Thermal-mechanical coupling characteristics and heat pipe failure analysis of heat pipe cooled space reactor

•Developed a multiphase model of high-temperature heat pipe with the capability of calculating compressible vapor flow.•Developed a thermal–mechanical coupling model for a heat pipe cooled reactor.•Analyzed the heat transfer performance of heat pipes at different locations.•Evaluated the impact of multiple heat pipes failure at different locations on the reactor core. Heat pipe cooled reactor has wide application prospects in space environment because of the advantages of high reliability and small mass. Heat Pipe-Segmented Thermoelectric Module Converters (HP–STMCs) is a typical design of space heat pipe cooled reactor. In this paper, a new thermal–mechanical coupling analysis method for the reactor was proposed. A two-dimensional heat pipe code for multiphase heat transfer was developed, with simplification of the wick as a purely conductive process and consideration of the flow of compressible vapor. A thermal stress computational model of the core was established using COMSOL Multiphysics, with the heat pipes divided into six channels. Based on various power distribution conditions, different heating powers were employed to simulate the heat pipe operation within each channel. Normal and accident operating characteristics were analyzed by the model. Under normal operation, the maximum temperature is 1641.9 K, located in the center of the core, and heat pipes in the fifth channel have the highest heat transfer power, reaching 13.674 kW. During accidents, thermal stress emerges as the main threat to the reactor's safety. A single heat pipe failure at any location poses no safety risk, but the thermal stress exceeds the safety limit if two heat pipes fail at the reactor core's edge, reaching 269.92Mpa. With three failed heat pipes, stress exceeds limits even at the well-cooled middle position and raises the local maximum temperature to 1959.8 K. This research provides valuable experience for local effects assessment and safety analysis of heat pipe cooled reactors.