Mechanisms for regulating the chemistry of argillite waters

摘要: [en] The regulating mechanisms in the chemistry of argillite waters are studied as part of a scientific partnership between two French mining and nuclear safety organizations. This project is called'THERMOAR'for thermodynamics of water in clay formations. Its main objectives are to provide experimental protocols and numeric models to define the processes of acquisition and regulation of argillite water chemistry. These rocks are the target rocks for the storage of long-term radioactive waste. Beforehand to all reflexions on the geochemistry models of the waters, it is necessary to define the water-argillite system. As a reductive medium, the first experience consists of controlling the redox state of the drills. A fine mineralogic analysis is then carried out. In a third phase, the number of reaction sites on the surface of the minerals is determined as well as their occupation by cations. The quantities in conservative anions (Cl-, Br-, SO 4 2-) can be determined by the classical experiments of leaching. Other basic parameters are more difficult to obtain. These include geochemical porosity and CO 2 partial pressure. The role of organic material is also evaluated. In addition to the experimental facts defining the system, it is necessary to provide digital simulations with the laws of mass action and the values of the corresponding thermodynamic constants. This can be achieved through a critical analysis of data banks and, when the constants are missing, by an experimental acquisition of new constants. The review of the different models of water-clay balance described in literature allows to evaluate the progress made by different teams of scientists on this …