Theoretical design and parametric sensitivity analysis of a passive containment cooling system based on separated heat pipes

A design-oriented inverse methodology is developed for a separated heat pipe passive containment cooling system (SHP-PCS) to determine feasible system configurations from prescribed accident heat removal requirements. A steady thermal-hydraulic sizing model is established by coupling heat transfer characteristics, two-phase flow pressure losses, natural circulation constraints, and engineering design limitations. The resulting configuration is further evaluated using a one-dimensional steady-state analysis model to investigate the effects of working fluid inventory, heat exchanger geometry, and riser dimensions on system performance. Two system-level heat removal requirements are considered, including a 50 MW high-pressure and high-temperature accident condition and a 12 MW long-term cooling condition. The designed separated heat pipe module is analyzed as the basic heat removal unit, and multiple modules can be integrated to satisfy the overall system requirements. The results show that the optimized configuration demonstrates the capability of passive heat removal under a relatively small source-sink elevation difference. The working fluid inventory exhibits a significant influence on system performance, with an optimal range of approximately 30–40%. The heat exchanger diameter shows an optimum due to the competition between hydraulic resistance reduction and heat transfer degradation, while riser diameter mainly affects system performance by changing vapor-side flow resistance. The proposed inverse-design framework provides a systematic approach for determining SHP-PCS configurations from required heat removal duties and provides engineering guidance for the optimization and application of separated heat pipe passive containment cooling systems.