Simulation study of evolution of helium bubbles in bulk tungsten

Molecular dynamics (MD) methods have been employed to study the formation and growth of helium (He) bubble in bulk tungsten (W) from the atomic-level perspective. The primary variables examined are: irradiation temperature up to 2100 K, He concentration up to 10000 appm in order to study the effects of temperature and He concentration on micro-structural evolution, especially the He evolution. He atoms whose number ranged from 40 to 160 are randomly added to the tetrahedral interstice or octahedral interstice in the W matrix. The results show that the average size of He-V clusters increases with increasing in the temperature and He concentration in general. It is found that the He/V ratios of He-V clusters are mainly ranged from 1.5 to 4 after their nucleation with high He/V ratio more than 6. And the He/V ratio may be influenced greatly by the nearby He-V clusters. This is to be studied in the further work to understand how the He-V clusters interact in bulk W. These results can also provide input parameters to larger scale simulations methods, such as in kinetic Monte Carlo methods and rate theory.