Radiation Effects in {UO}2

The term radiation effects refers to all macroscopic changes in physical and chemical properties of a solid exposed to radiation, preceded by microscopic modifications collectively defined as radiation damage. A comprehensive and up to date overview of research performed in this field is presented here. We mostly focus on UO2 based fuels, as they represent the overwhelming majority of nuclear fuels nowadays. In the first part, dedicated to understanding the physics behind radiation damage, we discuss the main processes involved as well as the damage caused by each source, including neutrons, α-, β- and γ-decays and Fission Products (FPs).In the second part, the corresponding lattice defects, of both the point and the extended type, are described together with the latest results in terms of modeling, carried out by both ab initio and Molecular Dynamics (MD) techniques. In the following sections, we analyze in details the modifications suffered by nuclear fuel during its life cycle, in terms of elastic, mechanical, and chemical properties. We then describe the resulting High Burnup Structure (HBS) and discuss the current theoretical approaches to explain its formation.