Computational Fluid Dynamics Investigation of Fuel Rod Bowing Effects on Thermal-Hydraulic Instability in SFR Core

In this study, three-dimensional simulations were conducted using computational fluid dynamics software to investigate subchannel flow in a sodium-cooled fast reactor (SFR) fuel rod bundle. The investigation focused on partial blockage in subchannels resulting from the bending deformation of fuel rods and examined its impact on coolant flow and heat transfer characteristics. Simulations were performed for both central and corner rods under three distinct levels of bending deformation, with maximum deviations of 0.25, 0.5, and 0.75 mm, respectively, and the resulting flow and heat transfer performance were compared with those under normal operating conditions. This methodology comprehensively evaluated the effects of fuel rod bending on liquid sodium flow and heat transfer within the subchannels. The results demonstrate that bending not only causes local deterioration in heat transfer performance, uneven temperature distribution, and flow redistribution but also alters the secondary flow field structure. Notably, the effect of central rod bending is particularly significant. Overall, the study elucidates the influence of fuel rod bending on core safety in SFRs, thereby providing a theoretical basis for accident analysis and serving as a critical reference for the safe design of fuel assemblies.