Release of tritium from boron carbide

Abstract

The release of tritium from B₄C powder and a single crystal has been investigated in the temperature range 400–800 °C. High-energy tritons, produced by bombarding a Cu target with 104 MeV α-particles, were used to prepare samples with a uniform tritium distribution. The release curves were analysed under the assumptions that (a) the diffusion within the B₄C is the rate-controlling step and (b) the effective average grain size can be deduced from the specific surface area of the powder. The obtained diffusion coefficients (in cm² s^–1) can be described with the following equation: D_(B4C)= 2.3 × 10^–4 exp(–96 ± 10 kJ mol^–1//_RT). The release of tritium from sintered material, with densities of 70–95% of the theoretical density, as well as from preoxidized samples has also been investigated. The diffusion coefficient D_(B2O3) for tritium in B₂O₃ is more than two orders of magnitude smaller than D_(B4C).