Evaluation of tritium release properties of advanced tritium breeders

Demonstration power plant (DEMO) fusion reactors require advanced tritium breeders with high thermal stability. Lithium titanate (Li₂TiO₃) advanced tritium breeders with excess Li (Li_2+xTiO_3+y) are stable in a reducing atmosphere at high temperatures. Although the tritium release properties of tritium breeders are documented in databases for DEMO blanket design, no in situ examination under fusion neutron (DT neutron) irradiation has been performed. In this study, a preliminary examination of the tritium release properties of advanced tritium breeders was performed, and DT neutron irradiation experiments were performed at the fusion neutronics source (FNS) facility in JAEA. Considering the tritium release characteristics, the optimum grain size after sintering is <5 μm. From the results of the optimization of granulation conditions, prototype Li_2+xTiO_3+y pebbles with optimum grain size (<5 μm) were successfully fabricated. The Li_2+xTiO_3+y pebbles exhibited good tritium release properties similar to the Li₂TiO₃ pebbles. In particular, the released amount of HT gas for easier tritium handling was higher than that of HTO water. (authors)