Correlation between tritium release and thermal annealing of irradiation damage in neutron-irradiated Li2SiO3

Annihilation of irradiation defects and tritium release processes in the neutron-irradiated Li2SiO3 and Li4SiO4 were investigated by means of electron spin resonance and thermal desorption spectroscopy, respectively. The experimental results indicated that tritium release from both samples began just before the irradiation defects were completely annihilated. The isothermal annealing experiments for both samples showed that there were fast and slow annihilation processes of the defects with activation energies of 0.12 and 0.63 eV for Li2SiO3, and 0.12 and 0.56 eV for Li4SiO4. The fast annihilation process could result mainly from diffusion of trapped electrons into the defects, whereas the slow annihilation process could be attributed to the annihilation of E′-center by recovering oxygen ions (O−). Therefore, the annihilation of E′-center would trigger the tritium release. A model of annihilation of E′-center and tritium behavior in neutron-irradiated ceramic tritium breeding materials is also proposed.