Molecular dynamics simulation of the hydrogen retention of faceted helium bubble in bcc iron

ZY Ming and Z Chen and ZF Wang and Z Liu and C Yin and SF Mao and MY Ye, FUSION ENGINEERING AND DESIGN, 212, 114842 (2025).

DOI: 10.1016/j.fusengdes.2025.114842

Reduced activation ferritic-martensitic (RAFM) steels are primary candidate structural materials for blanket in future fusion reactors. The helium (He) bubble is one of the typical irradiation-induced defects in RAFMs under serving environment, which could have a considerable influence on both mechanical properties and fuel retention. Recent irradiation experiments showed that faceted He bubbles will be produced within various of RAFMs under specific irradiation conditions. However, the hydrogen retention induced by faceted He bubbles remains unclear. In this work, molecular dynamics (MD) simulations were performed to evaluate the hydrogen (H) retention effects of faceted He bubbles with 100 and 110 planes in body-centered cubic (bcc) iron (Fe) at 973 K. The equilibrium H spatial distributions of four types of bubble system are analyzed and the trapping volumes and trapping energies of these bubbles are given. Simulations show that the stability of He bubble will influence the trapping ability: The faceted bubbles with more stable configurations would exhibit 10-20 % lower H retention amount than the spherical bubble with equal volume, although the surface areas of faceted bubbles are larger than the spherical bubble. Besides, the simulation results suggest that the polyhedron bubble with Wulff configurations is still the most stable configuration in bcc Fe at high temperature. In addition, the stress distribution on faceted He bubble surface leads to uneven distributions of trapped H atoms.

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