Experiments of in-situ tritium release from Li2O powder under neutron irradiation at high temperatures (Φ = 108 n/cm2 · s, 400–700 ° C) were conducted using the research reactor YAYOI at the University of Tokyo to study the chemical form of the released tritium and the tritium release kinetics. The chemical form of the released tritium was found to depend upon the experimental conditions such as (i) sweep gas chemistry, (ii) pre-treatment of the sample, and (iii) choice of structural material for the sample holder. It was concluded that the dependence of the chemical form of released tritium on these parameters can be explained by the thermodynamic equilibrium of the metal/oxide/hydrogen/water system. The tritium release kinetics, especially tritium diffusions in a crystal grain and through grain boundaries, were studied by utilizing several polycrystalline samples of different particle sizes. Diffusivities of tritium in the grain (Dg) and through grain boundaries (Dint) were calculated as Dg(cm2/s) = 1.27 × 10−5 exp(− 54.9(kJ/mol)/RT), Dint(cm2/s) = 1.61 × 102 exp(− 95.1(kJ/mol)/RT) over the temperature range from 360 to 600 ° C.
Li2O粉末からのトリチウムのその場放出実験を、東京大学の研究炉YAYOIを用いて、中性子照射下、高温（Φ = 10⁸ n/cm²・s、400～600℃）で実施し、放出トリチウムの化学形とトリチウム放出速度論を研究した。放出トリチウムの化学形は、(i)スイープガス組成、(ii)試料の前処理、および(iii)試料ホルダーの構造材料の選択などの実験条件に依存することが見出された。放出トリチウムの化学形がこれらのパラメータに依存することは、金属/酸化物/水素/水蒸気系の熱力学的平衡によって説明できると結論づけられた。トリチウム放出速度論、特に結晶粒内のトリチウム拡散と粒界を通じた拡散は、異なる粒子径を持つ複数の多結晶試料を用いて研究された。結晶粒内のトリチウム拡散係数（Dg）と粒界拡散係数（Dint）は、360～600℃の温度範囲において、Dg(cm²/s) = 1.27 × 10⁻⁵ exp(−54.9(kJ/mol)/RT)、Dint(cm²/s) = 1.61 × 10² exp(−95.1(kJ/mol)/RT) と算出された。