Isothermal release of tritium from neutron-irradiated Li 2O pellets

Abstract

Li 2O pellets irradiated with thermal neutrons were isothermally annealed to release tritium in a helium atmosphere at temperatures ranging from 673 to 1073 K. The release rates were found to significantly increase at elevated temperatures and to depend on the density of the Li 2O pellet. The overall diffusion coefficients of the release process were calculated using the cylindrical geometry model for the pellets as D (cm 2 s −1) = 1.02 × 10 −3 exp(−51.0 kJ mol −1/RT ) (90% theoretical density pellets), and D (cm 2 s −1) = 2.64 × 10 −3 exp(−46.5 kJ mol −1/RT ) (ca. 80% T.D. pellets) over the region 773≤ T ≤ 1073 K. The result of the release experiment at 673 K suggested that the diffusion rate was controlled by the decomposition of lithium hydroxide on the surface of Li 2O grains.