Abstract
Silicate glasses are durable materials but laboratory experiments reveal that elements that derive from their environment may induce high corrosion rates and reduce their capacity to confine high-level radioactive waste. This study investigates nuclear-glass corrosion in geological media using an in situ diffusion experiment and multi-component diffusion modelling. The model highlights that the pH imposed by the Callovo–Oxfordian (COx) claystone host rock supports secondary-phase precipitation and increases glass corrosion compared with pure water. Elements from the COx rock (mainly Mg and Fe) form secondary phases with Si provided by the glass, which delay the establishment of a passivating interface. The presence of elements (Mg and Fe) that sustain glass alteration does not prevent a significant decrease in the glass-alteration rate, mainly due to the limited species transport that drives system reactivity. These improvements in the understanding of glass corrosion in its environment provide further insights for predictive modelling over larger timescales and space.
Highlights
Glass corrosion that occurs when in contact with aqueous media has been studied in many fields, such as biogeochemical weathering of volcanic glasses in seawater,[1,2] CO2 sequestration,[3] historical and archaeological artefact conservation,[4,5] and industrial applications.[6,7] The chemical durability of silicate glasses makes them suitable for high-level radioactive waste (HLW)containment that arises from dismantling operations or spentfuel recycling processes
Understanding the mechanisms that support aqueous corrosion in glasses relies on an iterative approach that begins with simplified systems [i.e., glass in contact with pure water, groundwater, or simple minerals comparable with several environmental materials present in repository conditions]11–16 and moves toward more realistic disposal conditions
Numerous studies have focused on laboratory experiments to understand the key processes that occur during glass corrosion,[9,17] as well as how to obtain host-rock conditions as accurately as possible.[13,14]
Summary
Glass corrosion that occurs when in contact with aqueous media has been studied in many fields, such as biogeochemical weathering of volcanic glasses in seawater,[1,2] CO2 sequestration,[3] historical and archaeological artefact conservation,[4,5] and industrial applications.[6,7] The chemical durability of silicate glasses makes them suitable for high-level radioactive waste (HLW)containment that arises from dismantling operations or spentfuel recycling processes. In HLW disposal facilities, the different phases, i.e., construction and operation procedures that introduce radioactive waste, induce chemical gradients across the disposal components.[8,9] Due to these chemical gradients, perturbations, such as changes in the pH or redox conditions, may alter the performance of silicate glasses over time.[10] Understanding the mechanisms that support aqueous corrosion in glasses relies on an iterative approach that begins with simplified systems [i.e., glass in contact with pure water, groundwater, or simple minerals comparable with several environmental materials present in repository conditions (corrosion products, mineral phases, and similar factors)]11–16 and moves toward more realistic disposal conditions. Field data are necessary to validate our understanding of the key processes and long-term prediction of glass behaviour in repository conditions.[18,19] For instance, glasscorrosion products are composed of an amorphous layer (or gel) and secondary phases, whose formation depends on environmental conditions (i.e., the temperature, pH, redox, element saturation, groundwater, glass–clay ratio, and transport parameters).[15,20,21,22,23,24,25,26,27,28]
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