THEREDA (Thermodynamic Reference Data Base) is a collaborative project whose goal is to establish a comprehensive and internally consistent thermodynamic reference data base for geochemical model calculations of aqueous electrolyte solutions up to high concentrations. This is essential for near- and far-field processes in different rock formations, which are discussed as potential repositories for radioactive and chemo-toxic waste in Germany and other countries.

THEREDA provides thermodynamic data and Pitzer interaction coefficients for aqueous solutions. Coupled to appropriate codes, this allows the calculation of solubilities of radiotoxic and chemo-toxic elements. Here we follow the approach of the OECD-NEA thermochemical database. Currently, for the host rock salt, THEREDA represents the only database in the world that polythermally covers the entire system of oceanic salts, including acids and bases.

Our work focuses on critically evaluating and providing data that support the calculation of solubilities in highly concentrated saline solutions, such as those that may occur in rock salt or various clay formations. Data from the NEA database will be adjusted or supplemented as needed. In particular, Pitzer interaction coefficients consistent with standard thermodynamic data provided in THEREDA will be added.

In contrast to the very restrictive quality requirements of the OECD NEA database, we also provide lower quality data when needed to calculate experimentally confirmed solubility data. A classification by the source, quality, and type of primary experimental data from which the input thermodynamic data were derived has been developed to guide THEREDA users.

The internal data structure of THEREDA is kept decidedly flexible, paving the way for future extensions of the database, e.g., for other potential host rocks or contaminants. All work on THEREDA is performed decentrally via a web interface to the database. Compliance with quality requirements and internal data consistency is ensured by control mechanisms embedded in the database. Comprehensive documentation of the data accompanies the web interface.
THEREDA was and is planned, implemented and further developed jointly by established research institutions conducting research in the field of radioactive waste disposal and potential host rocks. THEREDA partners are open to cooperation with other institutions from Germany and abroad that are active in a similar field. Questions about the possibilities of an associated partnership with THEREDA can be addressed to the project coordinator Helge Moog or to all other project partners.