Parameter-free quantitative simulation of high-dose microstructure and hydrogen retention in ion-irradiated tungsten
Daniel R. Mason, Fredric Granberg, Max Boleininger, T. Schwarz‐Selinger, K. Nordlund, S. L. Dudarev
Abstract
Hydrogen isotopes are retained in plasma-facing fusion materials, triggering hydrogen embrittlement and changing tritium inventory as a function of exposure to neutron irradiation. But modeling highly damaged materials---exposed to over 0.1 displacements per atom (dpa)---where saturation of damage is often observed, is difficult because a microstructure containing high density of defects evolves nonlinearly as a function of dose. In this study we show how to determine the defect and hydrogen isotope content in tungsten exposed to high irradiation dose, using no adjustable or fitting parameters. First, we generate converged high dose ($>1$ dpa) microstructures, using a combination of the creation-relaxation algorithm and collision cascade simulations. Then we make robust estimates of vacancy and void regions using a modified Wigner-Seitz decomposition. The resulting estimates of the void surface area enable predicting the deuterium retention capacity of tungsten as a function of radiation exposure. The predictions are compared to $^{3}\mathrm{He}$ nuclear reaction analysis measurements of tungsten samples, self-irradiated at 290 K to different damage doses and exposed to low-energy deuterium plasma at 370 K. The theory gives an excellent match to the experimental data, with both model and experiment showing that 1.5--2.0 at.% deuterium is retained in irradiated tungsten in the limit of high dose.