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Tritium breeders is required to have a high lithium atom density from the viewpoint of tritium breeding ratio. The first candidate material being studied in Japan at the present time is Li2+xTiO3 which is Li2TiO3 containing excess Lithium [1], however development of a material having even higher Lithium atom density is still under way. Li8ZrO6 has the highest lithium atom density except for Li2O which is a highly-reactive and unstable material. Although the lithium vaporization behavior from Li8ZrO6 at 900°C which is the maximum temperature which is assumed for Li2TiO3 and Li2+xTiO3 has been reported [2], research at lower temperatures where most tritium breeders are exposed has not been implemented yet. To elucidate the possibility of Li8ZrO6 as a tritium breeder, it is necessary to clarify the stability of its sintered body under actual use environment. In this study, Li8ZrO6 powder is synthesized in partial oxygen pressure controlled atmosphere by solid state reaction [3], and the lithium vaporization behavior and thermochemical stability of the Li8ZrO6 sintered body in a representative environment (320-900oC, 0.1% H2/He) to which the tritium breeders are exposed, lithium vaporization behavior and thermochemical stability are evaluated. Lithium vaporization rate was measured by gravimetric method and inductively coupled plasma, and crystal-phase change was analyzed by x-ray diffraction. In the relatively low temperature range, the sintered body of Li8ZrO6 maintained higher lithium atom density than the sintered body of Li2TiO3 and Li2+xTiO3 even after two years assumed as the actual use period. However, when the carrier gas contained water vapor as an impurity, LiOH was easily produced.
[1] T. Hoshino, et al., Fusion Engineering and Design, 82 (15-24), 2269-2273 (2007).
[2] K. Shin-mura, et al., Fusion Engineering and Design, 124, 762-766 (2017).
[3] K. Shin-mura, et al., Fusion Engineering and Design, 109-111, 1739-1743 (2016).
