Aging of materials subjected to irradiation

Materials under irradiation are sustained in non equilibrium states by a st eady input of energy. The physics of particle matter interaction correctly describes the elementary damage processes: modifications of the electronic structure (as a result of transmutations and electronic excitations), produ ction of atomic disorder. Materials ageing depends on the slow annealing of the latter damage. We give a brief survey of simple and useful concepts. S ome recent advances in the modelling of plasticity under irradiation are al so presented. We stress that the state or kinetic pathway of a material und er irradiation depends on three parameters: the irradiation temperature, th e irradiation flux and the space-time correlations in the damaging process (e.g. size of the displacement cascades).