Multi-physical fuel performance modeling of U-50Zr helical cruciform fuel based on fluid-thermal-structure coupling methodology

Helical cruciform fuel (HCF) has the potential to improve the power density and safe margins of nuclear reactors. However, the four-petaled twisting profile of HCF contributes to completely different fuel performance against traditional rods, so the fluid-solid coupled analysis on HCF is significant. In this paper, one fluid-solid inter-action coupling code was developed for data communications and mesh mappings between the CFD and FEM solvers. The fluid-thermal-structure coupling simulation on HCF was carried out under in-pile conditions, and the multi-physical coupled fuel performance was analyzed. Under the non-irradiated condition, the maximum fuel temperature was predicted to be 598.8 K due to high heat transfer capacity, and the mechanical contact effect would lead to the stress concentration of 207.4 MPa at the blade zones. In the long-time irradiated stage, the swelling would result in fuel deformation and fluid channel compression, which could further affect the flow velocity and heat transfer behaviors. In addition, the principal plastic strain was estimated to be 0.086 at 4.83% FIMA burnup, which remains a tough challenge for the HCF application.