It was recalled that the physical processes involved in radiation damage were inherently multi-scale; spanning more than 15 orders of magnitude in length and 24 orders of magnitude in time. Here, a kinetic Monte Carlo model was described for simulating the migration and clustering of transmutation helium gas atoms and ultimately determined the role of helium in mediating the long term aging of primary defects (vacancies, self-interstitial atoms and their clusters) produced in displacement cascades. The results illustrated the mechanisms responsible for the formation of vacancy-He clusters, in particular the high mobility of small vacancy-He clusters, which often led to cluster growth through cluster-cluster coalescence events.

A Kinetic Monte Carlo Model for Helium Diffusion and Clustering in Fusion Environments. B.D.Wirth, E.M.Bringa: Physica Scripta T, 2004, 108, 80-4