Thermodynamic and structural models compared with the initial dissolution rates of open-quotes SONclose quotes glass samples

The experimentally determined initial dissolution rate R0 of nuclear glass was correlated with thermodynamic parameters and structural parameters. The initial corrosion rates of six open-quotes R7T7close quotes glass samples measured at 100 degrees C in a Soxhlet device were correlated with the glass free hydration energy and the glass formation enthalpy. These correlations were then tested with a group of 26 SON glasses selected for their wide diversity of compositions. The thermodynamic models provided a satisfactory approximation of the initial dissolution rate determined under Soxhlet conditions for SON glass samples that include up to 15 wt% of boron and some alumina. Conversely, these models are inaccurate if the boron concentration exceeds 15 wt% and the glass contains no alumina. Possible correlations between R0 and structural parameters, such as the boron coordination number and the number of nonbridging oxygen atoms, were also investigated. The authors show that R0 varies inversely with the number of 4-coordinate boron atoms; conversely, the results do not substantiate published reports of a correlation between R0 and the number of nonbridging oxygen atoms