The dependence of waste form dissolution on migration phenomena in the host medium

The paper analyzes the effects that diffusion, partitioning, and leachant availability in the host medium have on waste form dissolution. It is shown that, for solubility-limited waste form dissolution, these effects can be significant and that they become rate-controlling in the medium- and long-term. The paper presents relevant leaching expressions which are used to rationalize observed leaching behaviors with glass waste forms. In particular, and explanation is given to (a) the seemingly conflicting evidence according to which glass dissolution in the presence of clays can either be enhanced or reduced or remain unaltered with respect to corrosion in pure clay water, and (b) to the linear dependence between the glass mass loss and the surrounding clay mass which is observed in closed systems nearing saturation. Applications of these findings are suggested to near-field repository design and for testing the hypothesis of constant long-term dissolution rate of waste glass in closed systems. (orig.)