Basaltic glass: alteration mechanisms and analogy with nuclear waste glasses

A synthetic basaltic glass was dissolved experimentally at 90 degreesC unde r static conditions in initially pure water. The basaltic glass dissolution rates measured near and far from equilibrium were compared with those of S ON 68 nuclear waste glass. Experimental and literature data notably suggest ed that the alteration mechanisms for the two glasses are initially similar . Under steady-state concentration conditions, the alteration rate decrease d of four orders of magnitude below the initial rate (r(0)). The same alter ation rate decrease was observed for basaltic and nuclear glass. These find ings tend to corroborate the analogy of the two glasses alteration kinetics . The effect of dissolved silica in solution, observed through dynamic leac h tests with silicon-rich solutions, cannot account for the significant dro p in the basaltic glass kinetics. Hence, a protective effect of the glass a lteration film was assumed and experimentally investigated. Moreover, model ing with LIXIVER argue for a significant effect of diffusion in the alterat ion gel. (C) 2000 Elsevier Science B.V. All rights reserved.