Atomistic simulations and experimental measurements of helium nano-bubbles in nickel

Deterioration of nickel-based alloy components in fission reactors is associated with the generation of helium from neutron-induced nuclear reactions. In tests at the macroscopic scale, deleterious effects of helium on the mechanical properties of nickel alloys are observed upon the formation and growth of helium bubbles. In order to enhance the understanding of helium effects in nickel, the properties of helium bubbles can be investigated by atomistic scale simulations. In the present work, we have studied helium bubbles in pure nickel, with diameters from 1.0 to 5.0 nm, using molecular dynamics (MD) simulations. The properties of nano-sized helium bubbles as a function of the helium-to-vacancy ratio are calculated at 600 K. The conditions for helium bubbles in mechanical equilibrium with the nickel matrix are determined. The results from simulations are found to be in good agreement with experimental data.