On the critical mechanisms for the embrittlement and strength degradation of post-irradiated U-10Mo fuels

Abstract

The four-point bending experimental findings clearly indicated that the post-irradiated U-10Mo fuels underwent noticeable macroscale embrittlement and strength degradation. During the irradiation process, fission gas bubbles (FGBs) are continuously formed and accumulated around the grain boundaries. Additionally, the irradiation-induced damage may lead to the degradation of mechanical properties of the U-10Mo skeleton. In this study, the representative volume element (RVE) models for post-irradiated U-10Mo fuels including the bubble-contained region and no-bubble region are established. Based on the Continuum Damage Mechanics (CDM) theory, the tensile test simulations are performed with the RVE models to obtain the macroscale stress–strain curves, using three assumed mechanical properties for the skeleton in the bubble-contained region. The research outcomes reveal that the strength degradation and fracture strain reduction of the U-10Mo fuel skeleton in the bubble-contained region are the dominant factors of the macroscale irradiation embrittlement and strength degradation of post-irradiated U-10Mo fuels. Furthermore, the FGBs enhanced local porosity aggravates this effect. This study sheds light on the mechanisms of irradiation-induced macroscale embrittlement and strength degradation in irradiated fuels, providing crucial insights for the safety assessment of fuel elements and components.