Model for Leaching Behavior of Aluminosilicate Glasses Developed as Matrices for Immobilizing High-Level Wastes

A field trial initiated in 1960 has shown very low release rates of 137Cs and 90;Sr from aluminosilicate glasses developed as potential matrices for the immobilization of radioactive fission products. Recent laboratory work in closed glass-water systems shows that certain sodium-calcium aluminosilicate glasses effectively cease to dissolve in water after a short time. This behavior is thought to be associated with the formation of a protective mineralized surface layer. Models were developed for the release of radionuclides from a glass covered by a mineralized surface layer, with leaching in both closed and open systems. The leaching equation for release in an open system is fitted to 90Sr release data.