Coupling of fluid flow with step-wise alteration of glass waste forms

The effect of flow of a basalt groundwater on the alteration of a borosilicate glass at 1500C was investigated. The first observable effect is that glass dissolution rates increased appreciably with increasing flow rate. Such effects promote a more rapid alteration of glass to solids that will initially control the release rate of many radionuclides. The second effect is that solution supersaturations are progressively suppressed with increasing flow rate. Under favorable circumstances, this could prevent the formation of some metastable alteration solids and promote the formation of more stable solids and promote the formation of more stable solids. In this way, the progressive step-wise alteration of glass could be studied, and an evaluation made of the long-term controls for radionuclide release from glass waste forms. Failure to demonstrate such step-wise alteration in these preliminary flow tests may be attributable to high initial solution supersaturations developed from non-flow-related factors or to diffusional constraints to continued chemical reaction processes at the glass surface