Geometrical structure effect on entry-tube flow characteristic of fast reactor control assembly

The control assembly is an important safety component of sodium-cooled fast reactor. The entry-tube geometrical structure has a significant effect on flow characteristics. The flow characteristics of plate-throttle entry-tube were investigated by hydraulic experiment, and the fluid-structure coupling numerical simulation was verified by experiment data. The results show that reducing the thickness of throttle plate and increasing the diameter of connecting rod can effectively improve the entry-tube throttling capacity. Considering the limitation of flow velocity, the dimensionless thickness-diameter ratio of 0.5 and connecting rod diameter of 20 mm are regarded as the optimum structure parameters of entry-tube. Due to the shortage of plate-throttle entry-tube in experiment, an alternative project of square-groove entry-tube was proposed. It is verified that this project is feasible with the similar flow velocity and pressure distribution in two types of entry-tubes. (authors)