He atoms diffusion and aggregation in Li2TiO3: A molecular dynamics study

LF Zhou and L He and DY Yang and YH Li, NUCLEAR ENGINEERING AND DESIGN, 413, 112567 (2023).

DOI: 10.1016/j.nucengdes.2023.112567

Advanced reactor projects will consider the utilization of Li2TiO3 as a potential material for neutron moderation and certain radiation shielding applications in fission reactors, as well as for tritium breeder blanket material in fusion reactors. He is one of the particles produced by the reaction of Li with neutrons during the service of Li2TiO3. The diffusion and aggregation of He in Li2TiO3 can cause embrittlement failure of Li2TiO3. Understanding the diffusion and aggregation behavior of helium in Li2TiO3 is crucial for evaluating service life, as well as for the selection and design of advanced nuclear reactor components. In this paper, the diffusion of He in Li2TiO3 and the nucleation behavior of a He cluster were studied by molecular dynamics simulations. The following results were mainly obtained: (1) The long-range diffusion activation energy of He atoms in Li2TiO3 is about 0.5 eV, and it varies significantly with the change of Li vacancy content. (2) He atoms tend to be distributed in the Li layers after sufficient diffusion in Li2TiO3, so the best nucleation site for He clusters in Li2TiO3 may be located in the Li layers. (3) After a He cluster reaches a certain size, it can trigger defects by extruding an O-LiTi2-O layer in its immediate vicinity on one side and migrating with the extruded O-LiTi2-O layer. (4) A He cluster can promote their own growth by releasing pressure.

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