A molecular dynamics study on bubble growth in tungsten under helium irradiation

Molecular dynamics simulation has been performed to investigate the effects of irradiated helium atoms in tungsten on the bubble nucleation and the dislocation loop formation. Simulation results clearly show that helium atoms in tungsten tend to migrate as isolated interstitials at high temperatures and to be absorbed to existing tungsten-vacancies or defects such as bubbles or dislocations. Tungsten self-interstitial atoms pushed out from the helium bubble tend to stay in the vicinity of the bubble and, then form a dislocation loop when the number of the atoms exceed the threshold. Since the bubbles and dislocation loops cause further nucleation of bubbles, there appears a helium bubble array along (1 1 1) direction. The bubble growth rate within this self induced bubble growth mechanism will be much faster than that of existing growth model. The growth model needs to be reformulated by taking the self-induced effects into account. (C) 2014 Elsevier B.V. All rights reserved.