Improvement and validation of containment spray removal aerosol models based on single droplet collection particle mechanism

Abstract

Nuclear safety is the lifeline for the development and application of nuclear energy. In severe nuclear power plant accidents, aerosols are the major carriers of fission products, which may leak into the environment and cause potential radioactive contamination. Containment spray is an important mitigation measure for severe accidents in nuclear power plants. It can effectively reduce containment atmospheric pressure and radioactive aerosol concentration. This paper improves the containment spray removal models so as to address the low accuracy of the original models of the ISAA code. Based on single droplet collection particle mechanism, new inertial impaction and interception models were used to accurately calculate the collection efficiency of large particles. Additionally, a new correlation was used to explain the Brownian diffusion collection mechanism of small particles. Moreover, thermophoresis and diffusiophoresis models were introduced to consider the contribution of steam condensation in the containment to the collection efficiency. A rear capture model was introduced to incorporate the influence of recirculation within the wake of large droplets on the collection efficiency. Furthermore, THAI, TOSQAN and CSE experiments were selected to validate and evaluate the improved ISAA code. According to the calculation results, the improved models can simulate the attenuation trend of suspended aerosols with higher accuracies and significantly improves the calculation accuracy of the spray removal constants. This work contributes to understand of the scavenging mechanism of aerosol particle by containment spray droplets, and provides an analysis method with higher simulation accuracy. At the same time, it points out shortcomings in the simulation of aerosol behavior in the current ISAA code and discusses future improvements to the code.