Research on the long-term heat release and pressure relief system of HPR1000-based suppressive containment system under typical accident

Based on the suppressive containment design scheme for HPR1000 previously proposed, this study focuses on the Long-term Heat Release and Pressure Relief System (LHRPRS), investigating the impacts of structural parameters in the natural circulation loop and heat transfer coefficients of heat exchangers on the heat removal performance of the open natural circulation system. The results reveal that lowering the cooling water tank level significantly enhances the heat dissipation capacity and mass flow rate during two-phase flow in natural circulation while having minimal effects on single-phase flow, and increasing the height of the riser outlet within the tank improves heat removal efficiency and mass flow rate in both single-phase and two-phase stages. Based on these findings, parameter configurations for the LHRPRS were completed. For containment units with volumes of 70,000 m 3 and 86,000 m 3 without the Short-term Heat Release and Pressure Relief System (SHRPRS), even with comprehensive optimizations such as lowering the tank level and elevating the riser outlet height, the system still fails to meet the technical requirements for handling Large-Break Loss-of-Coolant Accidents (LBLOCA). For units equipped with SHRPRS, a containment volume of 49,000 m 3 achieves compliance with accident mitigation standards when the tank level is set to 2 m and the riser outlet height is configured at 1.5 m. Similarly, a containment volume of 60,000 m 3 meets the requirements under the same parameter configuration (2 m tank level and 1.5 m riser outlet height). These results provide critical insights for optimizing the functionalization of advanced PWR dual-concrete containment systems. • The reduction of the water tank liquid level has negligible impact on the heat removal power of natural circulation systems during the single-phase flow stage, • Increasing the riser outlet elevation enhances the driving force of the natural circulation loop • The influence of cold/hot pipe diameter on natural circulation systems is related to flow resistance and resistance distribution • Different configuration strategies for LHRPRS in DBA are proposed