Collaborative motion of helium and self-interstitial atoms enhanced self-healing efficiency of irradiation-induced defects in tungsten

Abstract

Helium (He) is a typical impurity element and plays a crucial role in the microstructural evolution in nuclear materials under irradiation. Here, we systematically investigate the interactions between He and self-interstitial atoms (SIAs) as well as their influences on the kinetic behaviors of SIAs in tungsten (W), using both first-principles and object kinetic Monte Carlo methods. It is found that there are attractive interactions between He and SIAs, which become stronger with the increasing of SIA numbers. Specifically, the He-SIA1 and He-SIA2 complexes adopt a three-dimensional (3D) migration pattern with an effective energy barrier of 0.38 and 0.61 eV, respectively, which is completely different from the 1D migration of SIAs in W (⩽0.033 eV) without He. Such an unexpected collaborative 3D motion of He-SIA complexes increases the probability of vacancy-interstitial recombination and reduces the number of surviving defects. Consequently, our calculations reveal the enhanced effect of He on the self-healing efficiency in W, which is originated from the collaborative 3D motion of He-SIA complexes. The current results can improve our fundamental understanding of the influence of He on the evolution of irradiation defects and have great implications to estimate the performance of W-PFMs in fusion environment.

Modeling tungsten response under helium plasma irradiation: a review

“…There are several other OKMC simulations reported in the literature that investigate the effects of certain physical processes on bubble evolution. For instance, Ma et al [90] and Hou et al [91] studied the collaborative motion of helium and SIAs and found that a helium atom changes the motion pattern of an SIA from one-dimensional (1D) migration to three-dimensional (3D) migration. As a result, the annihilation rates between vacancies and SIAs are increased.…”