A recent review published in Engineering offers an in-depth look at the Passive Containment Heat Removal System (PCS) for China’s third-generation advanced pressurized water reactor, Hua-long Pressurized Reactor (HPR1000). The study, conducted by Ji Xing, Li Gao, and their colleagues from China Nuclear Power Engineering Co. Ltd. and Harbin Engineering University, provides a detailed overview of the development, design, and validation of the PCS, highlighting its effectiveness in maintaining containment integrity under severe accident scenarios.

The containment vessel serves as the ultimate safety barrier in nuclear power plants, preventing radioactive leaks and protecting public health and the environment. During severe accidents, such as loss-of-coolant accidents (LOCAs), a large amount of high-temperature cooling water and steam is released into the containment vessel. If active safety systems fail, the heat inside the containment may not be effectively removed, risking overpressure failure. To address this, third-generation nuclear power plants like the HPR1000 adopt passive safety technology to cool the containment vessel without human intervention.

The HPR1000’s PCS is designed based on flashing-driven open natural circulation and efficient condensation heat transfer theory. It continuously removes heat generated inside the containment through condensation heat transfer on the outer surface of heat exchanger tubes. This system has been applied to several nuclear power units in China and Pakistan, including Fuqing No. 5 and No. 6 units, Zhangzhou No. 1 and No. 2 units, and K-2/K-3 units of the Karachi Nuclear Power Plant.

The study explores the PCS system layout for concrete containment, comparing closed and open natural circulation systems. The closed system consists of internal heat exchange, external heat exchangers, and water tanks, forming a closed loop with independent operating pressure. The open system, however, integrates the heat exchange tank into the natural circulation system, operating at atmospheric pressure. After extensive research, the open scheme was chosen for the HPR1000 due to its simpler structure and stronger heat removal capacity.

A key challenge in the PCS design is the presence of non-condensable gases like air, which inhibit steam condensation and reduce the heat transfer coefficient. To address this, the internal heat exchanger design was optimized with a dispersed tube bundle arrangement, allowing more direct contact between the heat transfer tubes and the steam–air mixture. This arrangement suppresses the air accumulation effect and enhances heat transfer efficiency.

The study also investigates the flow and heat transfer characteristics of the internal heat exchangers. Through a combination of numerical simulations and experiments, the researchers developed an empirical correlation for the condensation heat transfer coefficient, covering a wide range of parameters including pressure, air mass fraction, steam mass fraction, wall subcooling, tube length, tube diameter, and inclination angle. This correlation provides a robust basis for heat exchanger design.

The comprehensive performance of the PCS system was validated through a series of experiments. The results demonstrate that the PCS can achieve robust heat removal capabilities, with the system’s heat removal power exceeding 1.8 MW under design operating conditions. The system’s natural circulation flow rate and fluid temperature remain stable, ensuring effective containment pressure control.

Furthermore, the study examines the coupling characteristics between the PCS and the thermal–hydraulic behavior inside the containment. Using the PANGU experimental facility, researchers simulated various severe accident conditions, including large break loss-of-coolant accidents (LBLOCAs) and station blackouts (SBOs). The results show that the PCS can quickly start and automatically adjust its operating power according to the containment’s thermal conditions. The PCS’s continuous operation significantly affects the temperature distribution and hydrogen concentration within the containment, forming temperature stratification and altering gas migration patterns.

In conclusion, the HPR1000’s PCS system represents a significant advancement in passive safety technology for nuclear power plants. Its innovative design and comprehensive validation ensure effective containment heat removal and integrity under severe accident conditions. Future work will focus on further enhancing the system’s heat removal capabilities and optimizing its overall design to improve economy and performance.

The paper “Study on Key Technologies of Passive Containment Heat Removal System for HPR1000,” is authored by Ji Xing, Li Gao, Feng Liu, Zhongning Sun, Li Li, Xinli Yu, Yawei Mao, Haozhi Bian, Zhaoming Meng, Ming Ding. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.03.034. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.