Abstract
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 29SiO2 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.
Highlights
Confinement within a borosilicate glass matrix is currently proposed for the disposal of radionuclides remaining from used nuclear fuel from power reactors.[1]
Experimental validation of these predictive models under accelerated conditions at a laboratory time scale is not possible as glass dissolution is controlled by coupled nonlinear processes, validation instead relies on the study of archeological and basaltic glasses altered in well understood geochemical conditions.[17,18,19,20]
While iron-containing secondary phases are commonly observed in the literature studies mentioned in the introduction, these results suggest that iron incorporation takes place after the reactions that occur at the magnetite surface
Summary
Confinement within a borosilicate glass matrix is currently proposed for the disposal of radionuclides remaining from used nuclear fuel from power reactors.[1] In France, glass containing. Before disposal in a deep geological repository, the canister will be placed into a several centimeter thick carbon steel over pack.[2] A better understanding of the interactions between glass and iron and the associated iron corrosion products is necessary to assess the performance of these waste forms.[3]. The processes that control glass dissolution in a geological repository involve a complex set of reactions, which depend on the nature of the host rock, the near field materials, the temperature, the ground water composition along with its renewal rate, and the glass composition.[5,6,7,8,9,10,11,12,13] The ultimate goal for laboratory scale parametric studies of glass alteration is to build an accurate predictive model that can account for the kinetics of long-term glass alteration under a variety of relevant conditions.[14,15,16] Experimental validation of these predictive models under accelerated conditions at a laboratory time scale is not possible as glass dissolution is controlled by coupled nonlinear processes, validation instead relies on the study of archeological and basaltic glasses altered in well understood geochemical conditions.[17,18,19,20] A more thorough understanding of all mechanisms and the associated kinetics of the glass itself but with the surrounding environment must be achieved to build a robust model
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