French SON 68 nuclear glass alteration mechanisms on contact with clay media

Leachability of a nonradioactive French SON 68 nuclear glass was tested in the presence of a clay at 90 degree C under conditions favorable to convective transfer. The glass alteration rate remained near the initial value for several hundred days in raw clay. In pure water, the alteration rate rapidly declined by several orders of magnitude after formation of a protective gel layer. The addition of silica gel to clay neutralizes clay sorption capacity and protects the glass from pronounced alteration. The mechanisms limiting glass alteration kinetics in the test media are analyzed.