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This research aims to investigate the application of the hot pressing (HP) sintering process in the fabrication of W-B-Fe-Cr-C advanced shielding materials and analyze the relationship between their microstructure and mechanical properties. The findings reveal that the HP sintering process can effectively produce reactive sintered boride (RSB) materials with high density and engineering application size. The results indicate that the residual stress in RSB-HP improves its bending strength to some extent. Residual stress and granular structure are both related to phase aggregation during sintering. Microstructural analysis has unveiled the granular organizational characteristics and the pathways of crack propagation within the RSB-HP. These discoveries hold significant importance for comprehending the potential of the HP sintering process in the context of nuclear fusion shielding material preparation and provide a scientific foundation for further optimizing the sintering process and performance of RSB materials.

Li2TiO3 and Li4SiO4 are considered as candidate tritium breeding materials due to its excellent physical, chemical and tritium release performance. Thermal conductivities of solid tritium breeding materials are determined by microstructure, sintering density and surface condition which will change during operation of fusion reactor. A comprehensive understanding of thermal performance of tritium breeding materials is essential due to the extreme operation condition in the fusion reactor. In this work, the microstructure and thermal conductivity was investigated for Li2TiO3 and Li4SiO4 annealed at the corresponding temperature of tritium breeding blanket. SEM (Scanning electron micrography) results presented the stable structure of Li2TiO3 and instability of Li4SiO4. XRD (X-ray diffraction) and Raman indicated the disorder of the crystal structure. It can be attributed to lithium loss during annealing process. EPR (Electron paramagnetic resonance) showed that there were almost no defects related unpaired electron. It is due to defect recovery at higher temperature, as well as tiny H2 amount in sweeping gas. There was no obvious change of thermal performance for Li2TiO3 during different annealing time. It is indicated that Li2TiO3 has a good thermal performance to resist heat load. But thermal performance of Li4SiO4 decreased largely after annealing. It is resulted from variation of the structure during annealing process. Based on the present work, it is illustrated that Li2TiO3 has stable thermal performance under annealing condition, however, the thermal performance of Li4SiO4 is not so stable for long service time at higher temperature.

For deuterium–tritium fusion reactor, the fuel of tritium is not available naturally. Tritium should be produced by the reaction of Li (n, ɑ) T. Li4SiO4 is one of promising candidates due to its high lithium density. In present work, effects of tritium release behavior from Li4SiO4 have been investigated and compared. The main release peak at lower temperature was attributed to tritium located on/near the grain surface and chemical adsorption on pore surface. The small peak at higher temperature was designated as tritium diffusion from grain including lattice and boundary. The tritium release behavior was simulated by diffusion model and surface reaction model. Tritium behavior is controlled by both diffusion and surface reaction for different stages. Based on the desorption theory, the kinetic parameters were obtained. The effects on tritium release behavior were studied. The porosity has significant effects on tritium release. Higher porosity has large specific surface providing more activation sites and fast channels for tritium release which results in lower temperature of tritium release. The main tritium release form was considered as tritium water. The release peak of deuterium moved towards lower temperature after adsorbing water vapor for 1800 h. It was demonstrated that adsorbing water was beneficial for tritium release due to isotope exchange. Compared the effects of porosity and water vapor, higher porosity has larger effects on tritium release in the present work. Based on the work, the tritium release is controlled by both diffusion and surface reaction at different stage and affected by comprehensive effects including porosity and adsorption water.

Lithium-based tritium breeding materials will be adopted to produce tritium in the D-T fusion reactor. Li2TiO3 and Li4SiO4 pebbles have been proposed as candidates in water-cooled ceramic breeder blanket (WCCB) and helium-cooled ceramic breeder blanket (HCCB) respectively. Biphasic ceramics of core–shell Li2TiO3-Li4SiO4 have been considered as advanced breeding materials due to combining the superiority of Li2TiO3 and Li4SiO4. The defects will be introduced into tritium breeders in the operation of fusion reactor. They have important effects on tritium release. It is necessary to carry out the experiment on irradiation defects evolution. The annihilation kinetics of defects induced by γ-ray irradiation were investigated. Fluka and Flair were used to calculate the DPA (displacement per atom) of these irradiated pebbles. EPR (Electron Paramagnetic Resonance) characterization and EasySpin simulation were adopted to analyze the evolution and annihilation kinetics processes of irradiation defects. The concentration of defects decreased as the annealing temperature increased. There were still a certain amount of defects in Li4SiO4 and Li2TiO3-Li4SiO4 when the defects in Li2TiO3 disappeared by annealing. Li2TiO3 pebbles have a better irradiation stability than that of Li4SiO4 pebbles. According to the results of EasySpin simulation, the defect concentration of E’-center and O-related was obtained respectively. The kinetics parameters for the defects of E’-center and O-related center in Li2TiO3 and Li4SiO4 were acquired. The evolution behavior of Ti3+ in core–shell Li2TiO3-Li4SiO4 contributes to the recovery of defects. The correlation between annihilation of irradiation defects and tritium release was discussed. The anti-irradiation damage stability of three kinds of ceramic breeders were evaluated. This work carries out the research on the defect kinetics of the new core–shell structure tritium breeder. Meanwhile, a comprehensive comparison of the annihilation properties of three promising breeders has been made. Li2TiO3 pebbles present excellent tritium release performance due to higher annihilation rate constant. Compared the performances of these breeder pebbles, Li2TiO3 plays a positive role in irradiation tolerance and tritium release performance, and Li4SiO4 has higher lithium density which benefit for tritium production.