Self-irradiation effects in plutonium alloys

The plutonium α-decay leads to the formation of numerous defects, which affect physical properties. This work presents swelling measured both at the macroscopic and microscopic scales on δ-Pu alloys, together with a characterization of defects by positron annihilation spectroscopy (PAS). Swelling seems to depend on deltagen element and/or on α-decay rate, and differences are observed between macroscopic and microscopic swelling. PAS results suggest that the concentration of vacancy clusters increases at the early stages of aging. Simulation of displacement cascades performed by molecular dynamics revealed a very long time (a couple of nanoseconds) to reach thermalization, contrary to what is observed in other fcc metals.