Speaker
Description
Kenji Morita, Kodai Ishii, Makiko Sekiya, Yumiko Tanaka, Tsuyoshi Hoshino
Rokkasho Institute for Fusion Energy, National Institutes for Quantum Science and Technology (QST), Rokkasho, Aomori 039-0212, Japan.
Keywords: Lithium-6 Enrichment, Ionic Conductor, Electrodialysis, Breeding blanket
In fusion power generation, achieving tritium self-sufficiency necessitates a sufficient ratio of lithium-6 (6Li) in the breeding blanket materials. While Lithium is abundant in nature, natural abundance of 6Li in lithium is only 7.6%. Therefore, isotope separation technology is crucial to meet the required 6Li ratio for fusion reactors. The practically applied lithium isotope separation method is the amalgam method using mercury, which raises environmental concerns, making the development of alternative technologies desirable.
At QST, research and development are underway for the extraction of high-purity lithium and the enrichment of 6Li using electrodialysis with a lithium-ion conducting solid electrolyte membrane (Lithium Separation Method by Ionic Conductor: LiSMIC). For the enrichment of 6Li, this technology exploits the mass-dependent difference in the diffusion rates of lithium ions within the solid electrolyte. According to the transition state theory, the ratio of the diffusion coefficients for 6Li and 7Li is given by the square root of the inverse mass ratio, approximately 1.08, which characterizes the separation and enrichment performance. By applying a voltage across the membrane, lithium ions migrate from the anode to the cathode under the influence of the electric field. Owing to its slightly higher mobility, 6Li is expected to migrate faster, leading to its enrichment on the cathode side. Consequently, the characteristics of the applied voltage can influence the separation performance of 6Li.
This presentation will discuss the impact of applied voltage characteristics on the separation factor and the migration rate of lithium, highlighting the trade-off relationship between these two parameters. Given that a 6Li enrichment level of 90% is required for the DEMO reactor, a multi-stage LiSMIC system will be essential for achieving this target. Therefore, cascade theory will be applied to the obtained experimental data to estimate the scale of a potential production facility.
