Optimization of sintering conditions of advanced tritium breeder pebbles fabricated by the emulsion method

Highlights: • Li₂TiO₃ with excess Li (Li_2+xTiO_3+y) was developed as an advanced tritium breeder. • Li_2+xTiO_3+y pebbles fabrication by the emulsion method was carried out. • Optimum sintering conditions of the Li_2+xTiO_3+y pebbles were surveyed. • Sintering under vacuum and 1% H₂–He atmospheres was optimum condition. • The diameter of the sintered pebbles was 1.07 mm, and the grain size was <5 μm. - Abstract: Demonstration power plant (DEMO) reactors require advanced tritium breeders with high thermal stability. Li₂TiO₃ with excess Li (Li_2+xTiO_3+y) has been developed as a material for an advanced tritium breeder. Considering the tritium release characteristics and the packing factor of the blanket, the optimum pebble diameter and grain size after sintering were determined to be 1 mm and <5 μm, respectively. Therefore, optimum sintering conditions were surveyed in the present study to obtain these target values. The predominant factor affecting grain growth is assumed to be the presence of binder in the gel particles. This remaining binder reacts with the excess Li in the Li_2+xTiO_3+y and Li₂CO₃ is generated, which promotes grain growth. To inhibit the generation of Li₂CO₃, calcined Li_2+xTiO_3+y pebbles were sintered under vacuum and subsequent 1% H₂–He atmosphere conditions. The diameter of the sintered Li_2+xTiO_3+y pebbles was 1.07 mm, and the average grain size on the surfaces and cross sections was <5 μm. The results presented show that Li_2+xTiO_3+y pebbles with optimum characteristics were successfully fabricated using the emulsion method.