[en] Leaching of glasses made from radioactive wastes of very high activity was studied. Leaching agents used were water for temperatures below 100⁰C; molten nitrates for temperatures higher than 100⁰C; solutions of various pH or charged with either sodium chloride or cesium; and dry or wet air. From the quantities of entrained radioactive elements, overall apparent diffusion coefficients were determined for fission products with long periods such as cerium, cesium, ruthenium, and strontium. Diffusion activation energies were also determined. These results are applied to the calculation of the potential risk of storage for vitrified fission products