Abstract
Simulations of atmospheric carbonation of Intermediate-Level Long-lived radioactive Waste (ILLW) concrete packages were conducted to evaluate their possible chemical degradations. Two-phase liquid water-air flow is combined with gas component diffusion processes leading to a progressive drying of the concrete.Complete drying of the 11 cm thick waste disposal package wall occurs over a period ranging from 2 years for the low-performance concrete to 10 years for the high-performance concrete. The drying process slows down when transport characteristics of concretes are enhanced. Carbonation depths in the order of 2 to 3 cm in 100 years are predicted for this cementitious component. However, these values are slightly overestimated compared to experimental data. Also the kinetic model of mineral reactivity requires improvements with respect to the protective effect of secondary carbonates and to thermodynamic data.
Highlights
Complete drying of the 11 cm thick waste disposal package wall occurs over a period ranging from 2 years for the low-performance concrete to 10 years for the highperformance concrete
The French management of High-level Long-lived Waste (HLW) and Intermediate-Level Long-lived radioactive Waste (ILLW) is entrusted to Andra and is based on waste disposal in deep geological formation of CallovoOxfordian claystone located in the eastern part of the Paris Basin [1]
Integrated 1D simulations of atmospheric carbonation coupled with the drying process of ILLW concrete disposal packages in deep geological conditions during the operating period were performed
Summary
The French management of High-level Long-lived Waste (HLW) and Intermediate-Level Long-lived radioactive Waste (ILLW) is entrusted to Andra (the French National Radioactive Waste Management Agency) and is based on waste disposal in deep geological formation of CallovoOxfordian claystone located in the eastern part of the Paris Basin [1]. The ventilation air, drawn from the surface, will desaturate the concrete components, leading to atmospheric carbonation and potentially progressive lowering of pH inside the cement paste. This process could favour corrosion of the steel reinforcements, which may have deleterious effects on the waste disposal package integrity. The modelling of concrete degradation takes into account different processes such as the feedback between the diffusion coefficient and the saturation/porosity evolution, which are linked through volumetric balance of mineral dissolution and precipitation reactions using a generalized Millington-Quirk relationship
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