Disposal of nuclear waste in host rock formations featuring high-saline solutions – Implementation of a thermodynamic reference database (THEREDA)

Highlights: • Facilitate net-worked development and administration of a thermodynamic database. • Data are internally consistent and fully documented: quality, source, type of origin. • Based on Pitzer formalism, optimized for solubility calculations in high-saline media. • Maintained by automatically running internal calculations, triggered by the editors. • Download of parameter files for PHREEQC, Geochemist's Workbench, EQ3/6 8.0a, CHEMAPP. - Abstract: Research on the solubility of hazardous substances in saturated salt solutions is an ongoing task in Germany. Several institutions deliver contributions in line with their respective expertise. Scientific studies ultimately yield thermodynamic data which are used for thermodynamic equilibrium modelling. In order to join forces and render thermodynamic equilibrium calculations comparable it was decided to setup a common thermodynamic reference database (THEREDA) from which ready-to-use parameter files for commonly used geochemical codes should be created. It is the objective of this paper to explain how THEREDA is designed from a data management point-of-view, both conceptionally and technically. Data tables and mutual dependencies are described that allow managing administration of data for aqueous solution, solids, solid solutions, and surfaces. Moreover, quality assurance, traceability, consistency, and efficient, long-term maintenance are major topics shaping the database structure. Finally, robust and flexible human interfaces (to editors as well as end-users) are implemented. This paper is not aimed at giving an account of the model definitions, system selections, evaluation schemes, and thermodynamic data themselves stored in THEREDA, which represent the actual scientific work done by many more scientists within the project. However, this methodological guide to THEREDA has its own merits as it helps to bring thermodynamic data to work. Its specific implementation may serve as a useful example for similar projects going far beyond waste disposal