Computational Modelling of Spray System Deployment to a Scaled-Down Model of NPP for Severe Accident Mitigation

The objective of this study is to develop a numerical model for spray analysis and to investigate the impact of wind (freestream) on the effectiveness of the spray, using a laboratory scale (1/50^th) model. In this study, a numerical method was developed to analyze the performance of spray to capture particles. To construct the numerical method the following models and techniques were used: ANSYS CFX was selected to perform CFD analysis, the ICEM CFD was used to define meshes, the Eulerian and the Lagrangian approaches were coupled to solve for the behaviors of fluid flow and water particles, TAB model was applied for the breakup of fluid particles, and mathematical models for a spray scrubber were used to analyze the removal of solid particles by sprayed water particles. In summary: 1) If the number of mesh elements is more than 1.5 million, the removal efficiency of TiO₂ dust and the collection efficiency of water particles are independent from the number of the elements. 2) When the spray position is 60 cm from the containment wall, the removal efficiency decreases a little following an increase in the freestream velocity. This is true up to 1.5 m/s, until the removal efficiency increases when the freestream velocity rises above 1.5 m/s.