Artem Lunev

Abstract:

Plasticity of oxide fuel based on uranium dioxide not only determines the material susceptibility to cracking and fracture - processes closely related to the harmful fission gas release - but also determines the structural transformations of the grain structure such as polygonization at high burn-up. To achieve a higher degree of safety in nuclear reactors, dislocation plasticity in uranium dioxide, which is one of the less-covered topic in nuclear materials science, should be studied in detail first. This may be achieved by applying several computational methods, the most helpful of which are molecular dynamics(MD) and discrete dislocation dynamics(DD). The authors would like to present their latest findings in applying these computational methods to evaluate dislocation motion in uranium dioxide and its relation with the material mechanical properties. First, the mobility of isolated &frac12;<110>{001} edge and &frac12;<110> screw dislocations was evaluated at temperatures T=500-2000K using accurate analytical description of the different modes of thermally activated dislocation motion and data obtained directly from MD simulations performed at the Supercomputing Center of the Russian Academy of Sciences using LAMMPS software. Second, the interaction of dislocations with voids was analyzed, and the unpinning mechanisms are discussed. Third, we present our latest version of our in-house two-dimensional dislocation dynamics code capable of connecting the atomic input with mechanical properties of the solid. This study was supported by the Russian Foundation for Basic Research (RFBR), research project No. 16-38-60016 (mol_a_dk).