Modeling of He-defect interactions in ferritic alloys for fusion

High concentrations of helium will be produced in fusion reactor structural materials due to neutron capture reactions. The creep-rupture and fracture properties may be severely degraded if helium aggregates at grain boundaries to a sufficiently high level. To design helium-resistant microstructures requires detailed knowledge of the transport and fate of helium to sinks. We utilize atomistic methods to study the fate of helium in the neighborhood of dislocations, grain boundaries and coherent nano-clusters in alpha-iron. The binding energies of helium to these defects are strongly correlated with excess atomic volume. Molecular dynamics and the dimer saddle point search method were employed to study the mobility of both interstitial helium atoms and helium-vacancy complexes in dislocations and grain boundaries. The migration energy of interstitial helium in these defects was found to range from about 0.4-0.5 eV. (C) 2008 Elsevier B.V. All rights reserved.