Various effects of magnetite on international simple glass (ISG) dissolution: implications for the long-term durability of nuclear glasses

Understanding the effect of near-field materials, such as iron corrosion products, on the alteration of vitreous nuclear waste is essential for modeling long-term stability of these waste forms in a geological repository. This work presents experimental results for which monoliths of International Simple Glass—a six oxide borosilicate glass–, with polished and unpolished cut sides, were aged for 70 days under oxic conditions at 90 °C in a solution initially saturated in 29 SiO 2 at pH 7; then magnetite was added to the leaching environment. Solution and solid analyses were performed to correlate the changes in the surface features and dissolution kinetics. It was found that magnetite primarily influences the mechanically constrained surface of the non-polished sides of the monoliths, with little to no effect on the polished surfaces. This work highlights the importance of the unique chemistry within surface cracks that invokes a drastic change in alteration of glass in environments containing iron corrosion products. Geochemistry: towards durable nuclear glasses Immobilization in glass based hosts is the current geological method for disposal of long-lived radioactive waste from used nuclear fuels. A key factor that has to be understood is the fundamental mechanism that controls the glass dissolution in a geological repository involving complex reactions between glass and iron, and iron corrosion products. The team of Stéphane Gin from DTCD SECM in France and Nathalie Wall from Washington State University in the USA, together with their co-workers, are seeking to decode the alteration of glass waste in the presence of iron corrosion products, specifically magnetite. It is determined that products such as magnetite primarily impact a mechanically constrained surface, particularly in the case of non-polished sides. Conversely, almost no influence can be observed on the polished surface. Such findings have implication for the long term durability of nuclear glasses.