Tritium release from thermal neutron-irradiated Li4SiO4 is initiated with the annihilation of E'-centers by recovering O- with diffusion of O-. Electron Spin Resonance (ESR) shows that differences in the formation of irradiation damage between 14 MeV and thermal neutrons in Li4SiO4 result in different tritium release behaviors. The kinetics for the annihilation of irradiation defects has been determined. The contribution of elastic collisions by 14 MeV neutrons was much higher than that of thermal neutrons. Isothermal annealing experiments show that annihilation of irradiation defects consisted of two processes: namely, the fast and slow annihilation processes. Their activation energies were determined to be 0.13 and 0.39 eV, respectively. Comparing the experimental results for the thermal and 14 MeV neutronirradiated Li4SiO4 shows that the activation energies of the slow annihilation process were significantly different. These results relate to the density of irradiation defects, which in turn depend on the contribution of the recoil particles produced by nuclear reactions to form irradiation damaged sites.