First-principles study on the helium migration energies in B12X2 (X=O, Si, P, As) crystals for neutron absorber use

Abstract

Boron-carbide-based materials (B12X2) with two-atom instead of three-atom chains have better ductility, which indicates that they may be better alternatives to nuclear absorber materials than B4C. In this study, we investigated the migration energy of neutron-induced helium interstitials using density functional theory calculations. As a result, we discovered that the migration energy of helium in B12Si2 and B12O2 is lower than that in B4C, which suggests that these materials might be better in inhibiting the introduction of helium gas and subsequent volume expansion during the neutron irradiation. Moreover, we found that B12P2 and B12As2 have isotropic helium migration barriers, while B4C, B12Si2, and B12O2 exhibited a strong anisotropy in the helium migrations.

Keywords

• Helium
• migration
• FBR
• DFT
• neutron absorber