Effect of low dose γ-ray pre-irradiation on the tritium desorption behavior of Li2TiO3 breeding pebbles

The tritium release behavior of Li 2 TiO 3 breeder pebbles is governed by irradiation-induced defects, microstructure, and thermal transport processes. In fusion blankets, these materials are exposed not only to neutrons but also to γ-rays generated during nuclear reactions. In this work, Li 2 TiO 3 pebbles were pre-irradiated with low-dose γ-rays (100 and 500 kGy), subsequently irradiated with thermal neutrons, and then examined by tritium thermal desorption spectroscopy (TDS) under heating and isothermal conditions. The dominant tritium desorption peak shifted non-monotonically with γ-ray dose, whereas the apparent activation energies obtained from peak-shift analysis changed only slightly, from 0.21 eV for the 0 kGy sample to 0.16 and 0.13 eV for the 100 and 500 kGy samples, respectively. These values represent effective kinetic parameters for the coupled release process rather than single diffusion or de-trapping barriers. Isothermal TDS showed that γ-pre-irradiation slightly increased the fraction of tritium released during the initial holding stage, while the overall effect remained limited. The release curves can be approximated by an effective diffusion model after the early transient stage; however, the initial deviation from the model indicates the contribution of trapping or de-trapping, defect recovery, and surface processes. The results suggest that, under the present low-dose γ-pre-irradiation conditions, the intrinsic defects and porous microstructure of Li 2 TiO 3 pebbles still dominate the overall tritium release behavior.