NMR study of a gel layer formed on an irradiated Na-aluminoborosilicate glass during aqueous alteration.

Simplified borosilicate glass powders were irradiated by 952 MeV ¹³⁶Xe ions and then altered in a solution at a high S/V ratio at pH 9 and 90 °C for 33 days. Compared to the alteration of a non-irradiated sample, the irradiated sample altered 3–5 times more. Overall, both the gels had a similar structure as indicated by ²⁹Si, ²⁷Al, ²³Na, and ¹⁷O NMR experiments. Nevertheless, according to ¹¹B and ¹H NMR experiments, differences were observed in the quantity and speciation of B retained in the gels. The results suggest that the glass alteration mechanisms responsible for passivation are not changed because of the irradiation-induced structural damages. However, the alteration kinetics, gel morphology related to porosity, and the degree of maturation are different. It seems that the gel formed on irradiated glass matures faster and retains B, which in turn influences the glass dissolution rate. [ABSTRACT FROM AUTHOR]