The primary moisture separator—a key component in the PWR nuclear power plant—determines the quality of supplied steam to a turbine. Investigating its characteristics is important because supplying steam with excessive droplet entrainment results in damages to pipes, valves, and turbines in power plant circuits. In this numerical study, the particle tracking method in the Eulerian–Lagrangian methodology is used to investigate the characteristics of a primary moisture separator. Various swirl vanes with different bending angles, vane quantities, and vane locations are chosen to investigate the effect of design parameters on characteristics of the primary moisture separator. Additionally, the water droplet size is considered to vary from 0.01 to 50 $\mathsf{\mu }$m in this study. The pressure drop between the inlet and outlet, the steam quality at the orifice outlet, and the particle collection ratio are discussed in this paper. The results show that steam quality increases as the bending angle decreases, and increasing the number of swirl vanes increases both the pressure drop and the steam quality.

The steam generator in a nuclear power plant should provide high quality steam to the turbine for better efficiency and stability. For this purpose, a steam separator is installed in the steam generator to manage the quality of the steam. In this study, computational fluid dynamics (CFD) technique was carried out to analyze the flow phenomenon of the swirl-vane type steam separator. When the steam enters the swirl-vane separator with droplets, it is affected by the centrifugal force. Some of the droplets are attached to the riser wall, some pass through the outlet (bypass and the downstream pipe) and the remaining droplets enter the next separator. A Lagrangian particle model was used to simulate the behaviors of steam and water droplets. The results show that the removal of the droplets depend on the size of the droplets. When the droplet size is small, it is removed by the outlet. In particular for the droplet size of 0.01 micron, over 75% of them are removed. When the droplet size is large, it is collected on the wall. In particular for the droplet size of 50 micron, over 95% of them are collected on the wall. Thus, the performance of the separator decreases as the droplet enters the next separator directly before being collected on the walls or on the outlet if the length of the riser above the swirl-vane is short.