Optimization and performance analysis of a looped separate heat pipe-based passive residual heat removal system for HTR-PM

• A looped separate heat pipe-based PRHRs design for HTR-PM is proposed. • Heat removal capacity is satisfied under accident conditions with one set of failures. • Optimized design reduces air-cooling tower volume to 30% of the original size. • The required height difference between the tower and the reactor is eliminated. The high-temperature gas-cooled reactor pebble-bed module (HTR-PM) is a promising advanced nuclear reactor. The passive residual heat removal system is an indispensable safety system guaranteeing the inherent safety of HTR-PM. This study presents a novel design of a looped separate heat pipe-based passive residual heat removal system for HTR-PM. The effects of the inlet air temperature, condensation length, air cooling tower height, and height difference between the evaporator and the condenser are systematically investigated. Due to the sufficient length of the evaporator, the driving force inside the looped separate heat pipe is significantly greater than the total pressure drop of the system, allowing the height difference between the condenser and the evaporator to be eliminated. The study explores the feasibility of condenser miniaturization, revealing that a 70% reduction in size is achievable. The optimal design scheme recommends reducing the condensation length of the air cooler to 70% of its original size and lowering the height of the air cooler tower to 40% of its original height. The operation in the steady state is further calculated based on the optimal design scheme. The outcome indicates that it is possible and advantageous to miniaturize the condenser to prepare and operate the separate heat pipe-based passive residual heat removal system. These findings present new opportunities for miniaturization and mobilization of the passive residual heat removal system for the high-temperature gas-cooled reactor. Further experiments should focus on implementing this strategy on small-scale separate heat pipe heat removal systems.