Institute of Solid State Physics

With respect to the first activity, we are working in International group of experts on development of advanced nuclear fuels for future, so-called Generation-IV fast reactors. Unlike present oxide fuels (e.g. UO₂), new fuels are supposed to be based on UN and UC. These materials have important advantages over standard fuels (higher metal densities, higher thermal conductivity) but also certain disadvantages. One of disadvantages is nitride and carbide easy oxidation in air. To reduce this effect, we are working on atomistic understanding of oxygen interaction with UN surfaces (perfect and containing defects). In particular, by means of the first principles computer simulations we demonstrated that O₂ molecule adsorbed on UN surface (Fig. 1a) can spontaneously dissociate into two O atoms (Fig. 1b) which become chemisorbed at the surface (which is typical for metals). Incorporation of oxygen ions into surface and subsurface N vacancies is also energetically favourable. One of our goals is multi-scale approach combining first principles calculations with thermodynamics, kinetic Monte Carlo and phenomenological analysis of fuel performance.