Transient performance evaluation of passive residual heat removal system in liquid molten salt reactor

• Proposes an evaluation framework for PRHRS in MSRs, defining key safety criteria including heat removal capacity. • Develops a RELAP5-TMSR simulation model and validates the system’s effectiveness under three severe accident scenarios. • Confirms robust safety performance across all accidents, with all key parameters maintained within safe limits. • Provides design insights for passive safety systems in advanced molten salt reactors based on systematic transient analysis. The passive residual heat removal system (PRHRS) enhances the inherent safety of molten salt reactors (MSRs) by enabling autonomous operation following an accident. However, its transient performance under accident scenarios requires further evaluation. This study applies a set of performance evaluation criteria for the PRHRS in a liquid-fueled MSR, focusing on key safety parameters such as temperature limits. Using the RELAP5-TMSR code, a transient system model was proposed to simulate design-basis accidents, including station blackout, primary pump seizure, and loss of flow in the secondary circuit. The results indicate that the PRHRS effectively maintains the fuel salt temperature below the 815 °C material limit while preventing solidification of the coolant salt. Furthermore, the system demonstrates a sufficient heat removal capacity to remove decay heat under extended accident conditions reliably. These findings demonstrate the effectiveness of the PRHRS for the studied reactor design and contribute to the safety assessment framework for liquid-fueled MSRs.