Effect of containment spray system on fission product release during large break loss of coolant accident in two-loop small PWR.

• Modeling and analysis of the entire small pressurized water reactor nuclear power plant were conducted using the MELCOR code. • This paper analyzed the total release quantity and distribution patterns of radioactive aerosols and inert gases. • This paper analyzed the impact of the activation of the containment spray system on the release and distribution of radioactive aerosols and inert gases. The small-sized pressurized water reactor (PWR) characterized by its high inherent safety and wide applicability, has become a promising type of reactor with broad prospects for development. Currently, there is a limited amount of research dedicated to the analysis of accident source terms specific to small-sized pressurized water reactors, this study adopts the ACP100 as a reference to establish a model of a small-sized pressurized water reactor power plant using the severe accident analysis code MELCOR. This study investigated the release and distribution characteristics of radioactive materials under the scenario of a large break loss of coolant accident in the heat pipe section. Specifically, it analyzed the impact of opening and shutting down the containment spray system on the release and distribution of radioactive materials. The results indicate that in the absence of the containment spray system, the majority of radioactive aerosols are primarily distributed in liquid form within the containment, with a small portion depositing on other components and dispersing in the gas phase; inert gases are primarily distributed in the gaseous phase within the containment. With the containment spray system engaged, there is an increase in the total quantity of radioactive aerosols and the concentration of radioactive aerosols in the gaseous phase significantly decreases, while the concentration of liquid-phase radioactive aerosols dramatically increases. The containment spray system exhibits strong capabilities for the removal and retention of radioactive aerosols. While the total release quantity remains largely unchanged, the time to reach the peak release of inert gases is significantly shortened The containment spray system significantly affects the release rate of inert gases. [ABSTRACT FROM AUTHOR]