Abstract:
Compacted bentonite-sand mixtures are considered as potential sealing materials for the deep geological disposal of high-level radioactive waste due to their high swelling pressure, low permeability, and high radionuclide retardation capacity. In the long run, alkaline plumes resulting from concrete degradation can alter the microstructure and the mineralogy of the mixtures. Moreover, gas generated by anaerobic corrosion of the metallic canisters may accumulate, leading to high gas pressure, threatening the sealing system. To address these issues, the hydromechanical behavior and gas breakthrough phenomenon of compacted sand-bentonite mixtures under alkaline conditions were investigated. The samples were hydrated with alkaline solutions of varying pH under constant volume conditions, the swelling pressure and hydraulic conductivity were recorded and analyzed. After the hydration, the samples were injected by step gas pressures to investigate the gas breakthrough behavior. In addition, the associated microstructure and mineralogy changes were also analyzed, helping better understand the observed macroscopic behavior.
Short bio:
Yu LEI obtained a master’s degree in Civil Engineering from Central South University (China, 2023). He is currently a second-year PhD student at CERMES of Navier Laboratory, supervised by Prof. Yu-Jun Cui (CERMES) in collaboration with Dr. Nadia Mokni from ASNR (Autorité de sûreté nucléaire et de radioprotection). His research focuses on the hydromechanical behavior of compacted sand-bentonite mixtures under hydraulic, gas, and chemical loadings; application to radioactive waste disposal.
