Heat pipe failure accident analysis of the multipurpose dual-mode heat pipe nuclear reactor power system

This study conducts a comprehensive analysis of heat pipe failure accidents in the Multipurpose Dual-Mode Heat Pipe Nuclear Reactor power system to validate its thermal safety characteristics. Considering the importance of heat pipe reliability in reactor operations, the research focuses on three primary failure modes—heat transfer failure, condensation failure, and detachment failure—under scenarios where up to 5 % of heat pipes fail simultaneously. Utilizing a hybrid methodology integrating nuclear-thermal coupling simulations via OpenMC and finite element analysis (FEA) in COMSOL, the power distribution of fuel assemblies and full-power operational characteristics were quantified. A three-dimensional thermal–hydraulic model incorporating thermal resistance networks was developed to simulate heat pipe performance. Results demonstrate that under reference operating conditions, all core components, including fuel rods (peak temperature 1038.6 K), cladding (1017.5 K), and heat pipe walls (979.2 K), remain significantly below safety thresholds. In the event of simultaneous failure of the three highest-power heat pipes (6.67 % of total), the most severe temperature increments (up to 26.65 % rise in peak fuel temperature) occur during detachment failure, yet all components sustain temperatures within prescribed limits. Notably, cascading failures are mitigated as residual heat pipes maintain operational integrity, with maximum heat transfer capacities remaining below design limits (8241.7 W). The study confirms the robustness of the reactor's thermal redundancy and heat pipe layout, ensuring safe operation even under worst-case failure scenarios. These findings provide critical insights for the advancement of heat pipe-cooled nuclear reactor (HPR) designs.