Diffusion of He interstitial and di-He cluster at grain boundaries in α-Fe

• Published in: Journal of nuclear materials 2007-08, Vol.367 (1), p.446-450
• Main Authors: Gao, F., Heinisch, H.L., Kurtz, R.J.
• Format: Article
• Language: English
• Subjects: Aplha-Fe; Applied sciences; Controled nuclear fusion plants; DIFFUSION; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; GRAIN BOUNDARIES; He interstitials; HELIUM; Installations for energy generation and conversion: thermal and electrical energy; Interfaces; INTERSTITIALS; IRON; MATERIALS SCIENCE; Migrations of Defects; MOLECULAR DYNAMICS METHOD; Nuclear fuels; NUCLEATION
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2007.03.021

A systematic molecular dynamics study of the diffusion mechanisms of He interstitial and di-He cluster at two representative interfaces has been carried out in α-Fe. The diffusion coefficient of a He interstitial and the effective migration energies were determined. The He atom diffuses along the Σ11 grain boundary one-dimensionally along specific directions, while it migrates two-dimensionally at low temperatures, and three-dimensionally at higher temperatures, in the Σ3 grain boundary. The di-He interstitial cluster can migrate rapidly along the Σ3 interface at low temperatures, but not at the Σ11 interface. It has been observed that a di-He interstitial cluster can kick out a self interstitial atom (SIA) at high temperatures, forming a He 2V complex. The SIA migrates rapidly near interfaces, whereas the He 2V complex is immobile at the temperatures considered. This small cluster may serve as the smallest nucleation for the formation of helium bubbles at interfaces.