A Kinetic Monte Carlo Model for Helium Diffusion and Clustering in Fusion Environments

B.D. WIRTH; E. M. BRINGA

PHYSICA SCRIPTA - (Print)

IOP PUBLISHING LTD

Año: 2004 vol. T108 p. 80 - 84

0031-8949

Structural materials in fusion reactors will operate in harsh radiation conditions including high displacement rates from 14 MeV neutrons with accompanying high levels of hydrogen and helium production and will experience severe property degradation. Predicting their in-service performance requires a detailed understanding of the mechanisms of defect accumulation and microstructure evolution. The physical processes involved in radiation damage are inherently multiscale, spanning more than 15 orders of magnitude in length and 24 orders of magnitude in time. Here, we describe a kinetic Monte Carlo (KMC) model to simulate the migration and clustering of transmutant helium gas atoms and ultimately determine 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 illustrate the mechanisms responsible for the formation of vacancy-He clusters, in particular the high mobility of small vacancy-He clusters, which often lead to cluster growth through cluster–cluster coalescence events.