Effect of γ-ray irradiation on thermal conductivity of tritium breeding material Li2TiO3

Thermal performance is one of the important parameters for tritium breeders in D-T fusion reactor. It has a certain significance to study the effect of irradiation damages on the thermal conductivity for enriching the database. gamma-ray irradiation has been adopted due to its presence in the reactor and uniform defect distribution similar to neutron irradiation. The results of XRD and Raman indicate that the samples are damaged by irradiation. The irradiation defects have been studied by Electron Paramagnetic Resonance (EPR or ESR). E'-center and Ti3+ are determined as the main defects introduced in irradiated Li2TiO3. The spatial distribution of defects introduced in Li2TiO3 by gamma-ray irradiation is uniform calculated by Fluka. The relative concentrations of E'-center, A-centers and Ti3+ have been obtained by EasySpin simulation. The thermal diffusivity at room temperature decreases as irradiation dose increases. However, there is no obvious change in trends for thermal conductivity. For isochronal annealing experiments, it can be found that the thermal conductivity changes by the effects of E'-center and Ti3+. E'-center gradually decreases with the increase of the annealing temperature. The comprehensive analysis of experimental results and EasySpin fitting results has been performed. According to analysis and comparison with other reports, it is indicated that E'-center has negative effects on thermal conductivity, while the presence of Ti3+ plays a major role in enhancing the thermal conductivity. Based on the work, the suggestion for improving thermal conductivity by adopting additional Ti3+ has been proposed.