Reactive transport modelling in salt material based on Gibbs energy minimization

The German concept for the geological disposal of high level radioactive waste (HLW) considers salt formations as a suitable host rock for underground repositories. To prevent aqueous solution from accessing waste containments, these need to be scaled off with a material compatible to the host rock. One candidate material for this purpose is anhydrous salt which upon contact with aqueous solution forms hydrates with higher specific volumes thereby closing flow paths. This paper presents a new model to deal with reactive transport in a high-saline environment. It covers conditions where all accessible pores are filled with solution as well as conditions where no aqueous solution is present at all. This paper reports about the conceptual model and provides demonstration test cases.