Multi-parametric devices with innovative solid electrodes for long-term monitoring of ph and redox-potential of the actual pore water of cox formation in a future nuclear waste repository
Abstract
Near-neutral pH and low redox potential (Eh) are considered to be favourable conditions for nuclear waste disposal (NWD) in clay formations, because most radionuclides have a low solubility under such conditions. NWD programs mainly focus on deep geological storage, as this is the most appropriate strategy for ensuring the long-term safety of people and environment. Cigeo is the future deep NWD facility for high-level and intermediate-level long-lived radioactive waste, to be built in France, at 500 m depth within the clayey Callovo-Oxfordian formation (COx). COx is a 130 m thick clay-rich rock, lying at a depth of 400 to 600 m, which is watersaturated with extremely low permeability, porosity and hydraulic conductivity. COx pore-water temperature, pH and pCO 2 are constant at 21-22 °C, 7.2 (±0.2) and 8.10-3 atm, respectively. Anoxic conditions prevail in the COx, thus pH and Eh are key parameters for monitoring the evolution of its pore water.
Origin : Files produced by the author(s)