The effects of irradiation and high temperature on chemical states in Li2TiO3

For the development of deuterium-tritium fusion reactors, Tritium will be bred mainly by nuclear reactions of 6Li (n, α) T, as well as 7Li (n, n’ α) T. Some work on tritium recovery has been reported. In tritium breeding blanket, solid-state breeding materials will suffer irradiation by neutron and energetic particles such as tritium (2.7 MeV) and helium (2.1 MeV) produced by breeding reaction. Many researchers have reported that defects will be introduced by irradiation and affect tritium recovery. Tritium could be trapped by irradiation defects and bonded with the atoms in lithium ceramic, such as [≡Si-OT], [≡Si-OOT] and [≡Si-T] in Li4SiO4. Tritium would be also stabilized in the chemical states as LiOT and LiT in Li2O. The changes in bond could result in the changes of chemical states in lithium ceramics which will influence the tritium release processes. In addition, solid breeding materials will experience high temperature of maximum 1173 K and be swept by purge gas containing He+0.1% H2 in breeding zone of blanket. The microstructure and mechanical properties will change in such high temperature. The effects of hydrogen isotope from purge gas were also investigated. The chemical states were changed by forming new bond with deuterium. Some work on chemical states in solid breeding materials investigated by XPS and IR has been reported. LiOH on the surface of Li2TiO3 was readily formed by water exposure and the corresponding O-1s peak was indicated at 531.6 eV. O-D bonds were measured in deuterium-irradiated Li2O. The chemical states of Li, Si and O were changed on surface of Li4SiO4 irradiated by deuterium. In conclusion, the chemical states of tritium breeding materials will experience complex changes by both irradiation and high temperature in blanket conditions. The changes in chemical states will have effect on tritium recovery, resulting in lower tritium breeding ratio (TBR).Lithium-based ceramic of Li2TiO3 will be selected as one of the candidates due to its good tritium release, high chemical stability, low tritium inventory, and so on. However, few works on the effects of high temperature and irradiation conditions on the chemical states of Li2TiO3were combined and compared. The present work focuses on the change of chemical states in Li2TiO3 by deuterium irradiation and deuterium gas exposure at high temperature. XPS were performed to illustrate the chemical states in Li2TiO3. ESR has been applied to investigate the defects evolution in deuterium-irradiated samples.