Numerical study on a 7-pin bundle fuel assembly with different wire arrangements

The sodium cooled fast reactor is a Gen-IV reactor with great development prospect. The thermal-hydraulic analysis of the fuel assembly is crucial to the safety and efficiency of the reactor operation. In this paper, four assemblies with different wire arrangements were established to study the influence of wire arrangement on the thermal-hydraulic characteristics of the fuel assembly using Computational Fluid Dynamics (CFD). The solver is steady state and flow convergence is taken into account when the residuals for all flow variables are less than 10⁻⁵. It is observed that among these four arrangements, the reverse arrangement exhibits the largest average transverse flow and global Nusselt number. Additionally, the temperature difference between different sub-channels is the smallest, resulting in the most uniform temperature field. Furthermore, the average temperature of the fuel cladding is notably decreased in comparison to other arrangements. To evaluate the pressure loss and heat transfer performance of the assembly, the performance evaluation criterion PEC is introduced. The findings reveal that the PEC of the reverse arrangement is superior; in other words, it simultaneously reduces pressure drop and enhances heat transfer.