Effect of Different P/D Ratios on the Thermal-Hydraulic Performance of Fuel Assemblies in a Lead-Cooled Fast Reactor

Abstract The core is the area of the nuclear reactor where the fission reaction occurs, therefore, it is necessary for a complete thermal-hydraulic study to offer vital research data to assure the safe and stable functioning of the nuclear reactor. Due to the large number of fuel rods in each box and the high average heat flux density on the surface of the fuel rods, the ratio of the pitch to the diameter of the fuel rods (P/D) and the width of the side channels of the fuel assembly have a large influence on the uniformity of the coolant temperature at the outlet of the fuel tank in lead-cooled fast reactors. The thermal and hydraulic calculations of the fast reactor fuel assemblies are carried out in this paper based on the parameters of the fuel assemblies of the small and micro lead-cooled fast reactor SMILE, and the feasibility of the numerical calculation method is verified. Second, three models with P/D of 1.15, 1.20, and 1.24 were created, and sensitivity analysis was performed for the width of each model’s opposite side channel. The findings demonstrate that as P/D increases, the coolant temperature uniformity at the fuel box’s outlet improves significantly. Additionally, when P/D = 1.24 and the side channel’s width is 1.95 mm, the fuel assembly’s outlet temperature is effectively flattened, increasing the thermal safety margin.