Tritium needed as a fuel for fusion reactors is produced via neutron capture by lithium-6 (⁶Li). However, natural Li contains only about 7.8% ⁶Li, and enrichment of ⁶Li up to 90% is required for adequate tritium breeding in fusion reactors. The mercury amalgam method is superior to some of the lithium isotope enrichment methods. In Japan, lithium isotope enrichment methods have been developed to avoid the environmental hazards of using mercury. However, the isotope separation coefficient and efficiency is too low to meet the practical need of large mass production of ⁶Li.

Therefore, new Li isotope separation technique using a Li ionic superconductor functioning as a Li isotope separation membrane (LISM) have been developed [1]. Li ions move by electrodialysis through LISM between the cathode and the anode in lithium solutions. Because the mobility of ⁶Li ions is higher than that of ⁷Li ions, ⁶Li can be enriched on the cathode side of a cell.

It has been reported that the difference in the mobility between ⁶Li and ⁷Li become large in ionic superconductor. The isotope effect in ionic superconductor is expected to be applicable to isotope separation membrane. In this research, we numerically investigated the ionic mobility of Li isotopes in ionic superconductor. Combing the first principle and the kinetics Monte Calro simulation, we calculate the diffusion constant of ⁶Li and ⁷Li. I show the two important effects for the difference in the mobility between isotope of Li. The first is the quantum effect, which decrease the diffusion barrier for Li ion and increase the ratio of the diffusion constant of Li isotopes. The second is the correlation effect between ⁶Li, ⁷Li and vacancy.

Using Li_0.29La_0.57TiO₃ (LLTO) as the Li ionic superconductor was prepared, and the relationship between the ⁶Li separation coefficient and the electrodialysis time was investigated. After electrodialysis, we obtained a maximum of 1.04 for the ⁶Li isotope separation coefficient. This result showed that the ⁶Li isotope separation coefficient of this method is the same as that of the amalgamation process using mercury (1.06). Thus, this method has the potential to be a superior ⁶Li enrichment method to produce 90% enriched tritium breeder for fusion reactors.