The relevance of vapor phase hydration aging to nuclear waste isolation

Abstract The aging of nuclear waste glasses by vapor phase hydration is shown to be a process that: 1. may occur under currently envisioned repository conditions; and 2. causes significant alteration of the glass. This alteration results in large leach rate increases and radionuclide migration deviations when compared to results observed for unaged glass. Samples of both defense and commercial type glasses were aged to simulate long and short term repository storage. These aged glasses were then leached using MCC-1 and repository-oriented-analog type tests and the results were compared to similar tests done with unaged glass. It was found that actinide release from the aged glass was up to 185 times greater than from unaged glass. These results, coupled with anticipated surface storage and repository conditions in which glass/water vapor contact is possible under specific production and failure modes, suggest vapor phase hydration is an aging effect that should be addressed in long term release projections.