Speaker
Description
Hiroki Isogawaa, Kazunari Katayamaa, Rin Ganahab, Hideaki Matsuurac
aDepartment of Advanced Energy Engineering Science, Kyushu University,
6-1 Kasugakouen Kasuga-shi Fukuoka, 816-0811, Japan
bSchool of Engineering, Kyushu University,
744 Motooka Nishi-ku Fukuoka-shi Fukuoka, 319-0395, Japan
bcDepartment of Applied Quantum Physics and Nuclear Engineering, Kyushu University,
744 Motooka Nishi-ku Fukuoka-shi Fukuoka, 319-0395, Japan
To ensure sufficient tritium inventory for the start-up phase of D-T fusion reactors, we have proposed a method of tritium production by the ⁶Li(n, α)T reaction in high-temperature gas-cooled reactors (HTGR). A key challenge is minimizing tritium loss under high-temperature conditions. While Li₂TiO₃ and Li₄SiO₄ are promising materials for blankets in fusion reactors, LiAlO₂—known for its excellent chemical stability at high temperatures—has been selected as a primary candidate for tritium production in HTGRs. A potential solution involves encapsulating LiAlO₂ with zirconium (Zr) in an Al₂O₃ container, but the tritium behavior in such composite systems is not yet fully understood.
In this study, we investigated tritium transfer behavior from LiAlO2 to Zr under heating conditions. LiAlO2 and Ni coated Zr were sealed in a quartz tube and irradiated by neutrons in the JRR-3 reactor. After irradiation, the following 3 experiments were conducted to evaluate the extent of tritium transfer from LiAlO2 to Zr.
・Run 1: LiAlO₂ powder + Ni-coated Zr spheres, heated to effectively 700 °C
・Run 2: LiAlO₂ pebble + Ni-coated Zr spheres, heated to 900 °C
・Run 3: LiAlO₂ powder + Ni-coated Zr spheres, heated to 1000 °C
The sealed samples were pre-heated to the target temperature at 30 °C/min and held for 60 minutes. In an Ar-filled glovebox, Zr spheres and LiAlO₂ were separated, and then individually reheated to either 900 °C or 1000 °C at 5 °C/min. Tritium release rates over time were quantified using sequential water bubblers: tritiated water vapor (HTO) was collected in the first bubbler, and gaseous tritium (HT), after oxidation, in the second. The tritium retention ratios in LiAlO₂, Zr, and other components were as follows:
・Run 1: LiAlO₂ powder: Ni-coated Zr : others = 94.0 : 4.3 : 1.7
・Run 2: LiAlO₂ pebble : Ni-coated Zr : others = 89.0 : 9.9 : 1.1
・Run 3: LiAlO₂ powder : Ni-coated Zr : others = 95.0 : 4.7 : 0.3
These results indicate that more than 90% of the tritium was retained within the LiAlO₂-Zr system after heating above 700 °C. The slightly lower retention in Run 2 may be attributed to the sintering of LiAlO₂ pebbles, which likely led to crystal grain growth and reduced tritium diffusivity. The "others" category represents tritium lost via permeation through the quartz tube during pre-heating and tritium released into the Ar atmosphere during the post-heating quartz breakage process.
