Uranium dioxide (UO2) is the primary fuel used in pressurized water reactors (PWRs). Under normal operating conditions and irradiation, the mechanical and microstructural behavior of UO2 evolves due to the accumulation of point defects (vacancies, interstitials, defect clusters) generated by nuclear fission events. These defects alter the thermo-mechanical behavior of the material, particularly through their interaction with dislocations, thereby influencing plasticity, stress relaxation, and ultimately, fuel integrity.
A detailed understanding of the elementary mechanisms governing these interactions is essential for improving the modeling of irradiated fuel mechanical behavior. In particular, the impact of point defects on dislocation mobility remains a key challenge in refining the constitutive laws used in the multi-scale simulation tools of the PLEIADES platform, which is dedicated to predicting fuel behavior under various operating conditions (nominal, transient, and accidental scenarios).
The objective of this study is therefore to analyze, at the atomic scale, the interactions between dislocations and point defects in UO2 in order to quantify their influence on the fundamental plasticity mechanisms. To this end, molecular dynamics calculations will be performed to investigate the effect of different types of point defects (e.g., Frenkel pairs) on dislocation mobility, considering key parameters such as temperature and applied stress. This work will enable the extraction of dislocation mobility laws in the presence of defects, which will serve as input data for micromechanical models used in larger-scale simulations, particularly those implemented in the PLEIADES platform.