Effects of MgO on the Short- and Long-Term Stability of R7T7 and M7 Nuclear Waste Glass in Aqueous Media

Abstract

ABSTRACTExperiments were conducted in initially pure water at 90°C and 100°C with glass specimens enriched in MgO and in alkali metals relative to the standard light water R7T7 reference glass. Three experimental protocols were implemented: Soxhlet testing with leachant renewal, static leaching according to a modified MCC-1 method with an SA/V ratio of 50 m−1, and static leaching with glass powder for an SA/V ratio of 8000 m−1 The results clearly show that the short and, especially, the long term dissolution rates depend on the initial glass composition. Higher MgO, Na2O, Li2O and B2O3 concentrations reduce the glass resistance to aqueous corrosion, as already indicated by the calculated hydration energy values. These experiments illustrate the importance of the glass composition in insuring long-term material integrity.