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)greater than or equal to 1.69 mol% Al or x(Al)greater than or equal to 0.20 mol% Al, respectively.