New helium bubble growth mode at a symmetric grain-boundary in tungsten: Accelerated molecular dynamics study

Abstract

This work, with an emphasis on helium irradiation rates appropriate for fusion-plasma conditions, advances the understanding of helium evolution at grain boundaries in W, an important consideration in the understanding of W as a plasma-facing component. Using accelerated molecular dynamics, helium bubble nucleation and growth at a symmetric ∑5[100](310) tilt grain-boundary in W is studied. The simulations reveal that the growth mode associated with bubble growth at the grain-boundary leads to a suppression of the helium supply to the bubble and hence to arrested growth. Such an unconventional bubble growth mode may dominate in materials with a high density of sinks.IMPACT STATEMENT Simulations of helium bubble nucleation and growth at a tungsten grain-boundary approaching helium-irradiation rates for fusion first-walls reveal a novel growth mode.