CFD analysis for optimization of aerodynamic barriers for severe accident consequence mitigation at a nuclear power plant

Abstract

One of the key post-Fukushima developments in nuclear safety is consideration of post-accident consequence mitigation to minimize the radiological consequences of a nuclear power plant severe accident. In our previous study, a conceptual approach based on aerodynamic barriers was successfully examined to confine and control the dispersion of fission products following a containment breach during a severe accident. This approach used a vortex-like air circulation within a defined boundary around the reactor containment with the induced flow directing the released radioactive aerosols toward strategically placed sanction intakes. To support practical implementation of the proposed aerodynamic barriers approach, this study investigated optimal configuration of the aerodynamic barriers using CFD analysis with respect to variations in environmental and accident conditions, and provide robust performance in capturing radioactive aerosols. The CFD analyses were based on coupled Euler–Lagrange method using OpenFOAM and simulated the release and transport of CsI as representative form of fission products under the influence of aerodynamic barriers. The results showed that controlling aerodynamic barrier installation distance and momentum ratio is very important to ensure radioactive aerosols capture. The results indicated that dynamic adjustment of aerodynamic barrier discharge speed and angle is important to handle changes in wind speeds. The results also indicated that successful air flow confinement and radioactive aerosol capture can be achieved with proper control of these key variables (e.g., maintaining the momentum ratio between 1 and 15) while showing minor impact of wind direction variations on the barrier performance.