Speaker
Description
Minato Bannai1, Kiyoto Shin-mura1, Shido Kosuke1, Kazuya Sasaki1
1Hirosaki University
Fusion energy is expected to be the next generation energy source. For practical use, stable plasma confinement in a fusion reactor and efficient breeding of tritium, one of the fuels, are essential. Tritium is produced by the nuclear fission reaction between lithium (mass number 6), which is loaded as a tritium breeding material in a blanket surrounding the plasma, and neutrons. Tritium breeding materials must maintain a high tritium breeding ratio for several years, so they should be oxides with high lithium atom density and excellent stability under practical use conditions. Li2O is the oxide with the highest lithium atomic density, but its chemical stability is low and it is difficult to use it alone. We have therefore investigated the possibility of Li8ZrO6, which has the second highest lithium atom density after Li2O, as a tritium breeding material. As a result, we found that Li8ZrO6 maintains high lithium atom density and high mechanical strength over an expected use period of about three years at temperatures below 770 °C, which is the temperature range of most of the blanket space . In another study, we also showed that a two-phase coexisting sintered body, in which unstable phase crystal grains are surrounded by stable crystal grains has excellent stability. In this study, we investigate the possibility that the a two-phase sintered compact of Li2O and Li8ZrO6 has a higher lithium atom density and the same excellent stability as a single-phase sintered compact of Li8ZrO6. We fabricate this two-phase sintered compact and hold it for a long time in a high-temperature reducing atmosphere (320－900 °C in 0.1% H2-He) that simulates the environment inside the blanket, and clarify the changes in composition, crystal structure, and mechanical strength.
