The Stability of Tritium Permeation Barriers and the Self-Healing Capability of Aluminide Coatings in Liquid Pb-17Li

The thermodynamic stabilities of various barrier materials and the self-healing of aluminide coatings in oxygen saturated Pb-17Li have been evaluated. Binary nitrides and carbides are stable, but binary oxides display diverse behaviour; Al₂O₃ and MgO are stable, Cr₂O₃ is unstable to reduction to chromium metal and SiO₂ exhibits intermediate properties. Ternary oxides behave similarly, but are intrinsically more stable, their stabilities increasing with Li₂O content. Self-healing of aluminide barriers should occur to form either Al₂O₃ or LiAlO₂, the latter being favoured. For Fe-rich Fe-Al solid solutions, self-healing is dependent on their aluminium content; at 723 K, Al₂O₃ or LiAlO₂ formation only occurs for x_Al≥1.69 mol% Al or x_Al≥0.20 mol% Al, respectively.