Li mass loss and structure change due to long time heating in hydrogen atmosphere from Li₂TiO₃ with excess Li

Solid tritium breeding materials are used in a high temperature condition for a long time in a fusion reactor blanket. It is expected that a certain amount of Li will be evaporated and the pebble structure will be changed. Understanding of Li mass transfer behavior in the blanket is an important issue from viewpoints of establishment of tritium cycle and tritium safety. In this work the pebbles of Li₂TiO₃ with excess Li were heated at 900 °C in 1000 Pa H₂/Ar flow for a long time (72, 240, 720, 1200 h). The amount of Li mass loss under the hydrogen atmosphere was 0.665 wt% which was less than that under the water vapor atmosphere observed in the previous study. No significant Li mass loss was observed after 240 h. By heating for 240 h, the grain diameter increased from 1.8 to 3.1 μm and the specific surface area decreased from 0.72 to 0.20 m²/g. After 240 h, no significant grain growth and no significant decrease in the specific surface area were observed. From these results, it seems that there is a relation between Li mass loss and grain growth.