Multi-scale modeling of creep behavior in U3Si2-Al composites and the impact on curved fuel elements’ irradiation performance

Abstract

U₃Si₂-Al dispersion fuel is a promising candidate for the conversion of high-performance research reactors due to its high burnup characteristics. As irradiation time increases, the in-pile creep performance of the composite fuel plays a crucial role in determining the mechanical integrity and safety of the fuel elements. To assess the creep behavior, a multi-scale representative volume element (RVE) model of U₃Si₂-Al composite fuel was developed in this study and the influence factors were investigated. Meanwhile, the developed model was used in a three-dimensional finite element model to analyze the mechanical deformation of the composite fuel plates under irradiation. The obtained results show that: (1) the macroscopic creep rate of U₃Si₂-Al composites was influenced by factors such as U₃Si₂ volume fraction, tensile stress, temperature, and fission rate; (2) the aluminum matrix is the primary contributor to overall creep deformation, with its thermal creep contribution being the dominant factor, exhibiting substantially higher creep rates than U₃Si₂ particles; and (3) using the aluminum matrix creep model in place of the creep model with a coefficient of 50 × 10⁻²²mm³/fission/MPa resulted in greater thickness increases and modifications in Mises stress distribution in curved fuel plates under irradiation conditions. This research provides a critical theoretical framework for understanding the creep behavior of U₃Si₂-Al composites, facilitating future mechanical stress analysis of fuel elements.