Tritium release behavior and application of a release model for the neutron-irradiated biphasic lithium ceramics

Abstract

In this study, neutron irradiation for the Li₂TiO₃-Li₄SiO₄ biphasic ceramics was conducted at Kyoto University Research Reactor (KUR). The tritium thermal desorption spectroscopy (tritium-TDS) and the electron spin resonance (ESR) were performed in the radiation-controlled area at Shizuoka University. It was confirmed that the tritium desorption peculiarities were dependent on the phase ratio of Li₂TiO₃ and Li₄SiO₄ in the ceramic and the neutron fluence. The tritium migration process in biphasic ceramics was intensively studied based on the diffusion and de-trapping kinetics. A tritium release model was established with the consideration of the tritium trapping by irradiation defects and diffusion/migration process from bulk to surface. The experimental data can be well reproduced by the proposed simulation code. The kinetic parameters obtained by the simulating process were almost consistent with the experimental results. The effects of grain size and phase ratio on the tritium release characteristics were also investigated. The simulation code can be also applied to pellets or pebbles. Besides, the simulation code was adapted to understand the tritium release behavior in the working condition of fusion reactors. It was found that the tritium release could reach a steady state when the blanket was operated at higher temperatures. The tritium retention in ceramics after the shutdown of the reactor was confirmed. The tritium inventory can be reduced by controlling the temperature of the blanket system.