Investigation of fission products distribution effected by spray system in PWR containment during severe accidents

Abstract

In addition to affecting the thermal and hydraulic response in containment, spray system also has a great impact on the dispersion of fission products in containment during severe accidents. In this work, the station-blackout (SBO) accident analysis model of CPR1000 nuclear power plant (NPP) is established based on the coupling model of spray and fission product removal. The calculation results show that the code degradation occurred under the SBO accident. Without the operation of the spray system, the containment is at risk of overpressure failure. The pressure and temperature in containment can be effectively maintained in a safe range by spray system. The analysis of hydrogen behavior shows that the operation of the spray system lead to the occurrence of early hydrogen deflagration, thus avoiding the later hydrogen deflagration after enrichment in containment. The spray system can effectively reduce the atmospheric aerosols and soluble vapors of fission products and make most of them remain in the pools. The sensitivity analysis indicates that the spray droplets diameter has the greatest influence on the aerosols removal, and the smaller the droplet size is, the more obvious the removal effect is. Overall, the research is greatly helpful to the design and optimization of the spray system in containment.