3. 9  Demonstration of the Effectiveness of a New Method of Lithium Isotope Separation
- Success in Lithium Isotope Separation and Enrichment without Environmental Pollution
 

Fig. 3-20 The principle of Li isotope separation and enrichment using ion conductors [anode] LiHSO4 6Li+ & 7Li+ + HSO4-(1) (in ion conductor) moving velocity of 6Li+ > moving velocity of 7Li+ [cathode] 6Li+ & 7Li+ enriched 6Li (2) From equations (1) and (2) 6Li is separated and enriched during the moving process of Li ions from anode to cathode in Li ion conductors owing to the difference of moving velocities caused by the difference of the masses of 6Li and 7Li

Fig. 3-21 Measuring result of Li ion conductivity in ion conductors(frequency: 5 Hz-13 MHz, temperature: room temperature ~ 8 degrees cent.) The electric conductivities of Li ion conductors are measured by a complex impedance method. It is shown that the high Li ion conductivity, which means high moving velocity of Li ions, is related to the amount of Li isotope separation per hour.

Fig. 3-22 Li isotope separation factors of ion conductors(for the case of 0.01 S/cm of ion conductivity) The measurement of the Li isotope separation factor of ion conductors is carried out by an electrolytic method. A high Li isotope separation factor means the capability of the high enrichment of 6Li.

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The high concentration of 6Li in a fusion reactor blanket system is needed to effectively produce tritium, which is the fuel of fusion reactors. Until now, the mercury amalgamation process is used for Li isotope separation. However, to avoid environmental mercury pollution, it is desired that a new Li isotope separation technology is developed. Then, the isotope separation technology was worked out and demonstrated using Li ion conductors, in which the moving velocities of the isotope ions are different owing to the mass difference (Fig. 3-20). Three types of Li ionic conductors, which were a spinel Li4Ti5O12, a perovskite La0.55Li0.35TiO3 and ramsdellite Li2Ti3O7 from the Li2O-TiO2 system, were selected as the Li ion conductors. Electric conductivities of these three ion conductors were in the range from 10-7 to 10-1S/cm (room temperature to 800 degrees cent.). It was shown from the results that each ionic conductor has sufficient electric conductivity for isotope separation. The Li isotope separation factors of the three Li ionic conductors were 1.014 for the spinel, 1.010 for the perovskite and 1.058 for the ramsdellite. These are by no means inferior to those of the separation factors (1.02 to 1.07) obtained by the mercury amalgamation process. We are planning to develop practically, the Li isotope separation technology with ion conductors.

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Reference M. Umeda et al., Preliminary Characterization on Li Isotope Separation with Li Ionic Conductor, Fusion Technol., 39(2), 654 (2001).

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Persistent Quest - Research Activities 2001 Copyright(c) Japan Atomic Energy Research Institute