THEREDA – Thermodynamic Reference Database

Thermodynamic data are necessary for the estimation of the maximum likely solubility of hazardous contaminants such as radio nuclides in aqueous solutions. Such assessments are done within the frame of long term safety analysis for repositories of radioactive waste. For this purpose various databases exist in the world. But they are poorly comparable and furthermore reflect the needs of the respective national disposal programme.
Not only activities related to the identification of a suitable site for disposal, for the construction of a repository, its operation and finally its closure, but also the establishment of reliable thermodynamic data is a time-consuming, expensive and long-term effort which spans generations of scientists. It is necessary to store the results of many research projects, national and international, in a way that ensures internal consistency, allows for easy access, and allows for an easy application in thermodynamic equilibrium calculations with some of the most popular codes. Therefore, the establishment of such a database is a national task and an important part for a long-term knowledge management.
To meet this demand a project was launched in 2006 to create a common, mutually agreed and web-based Thermodynamic Reference Database – THEREDA (Moog et al. 2015). The database is run by the following institutions:

• GRS: Gesellschaft für Anlagen- und Reaktorsicherheit mbH, Abteilung Prozessanalyse, Theodor-Heuss-Straße 4, D-38122 Braunschweig, Germany
• KIT-INE: Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal, P.O. Box 3640, D-76021 Karlsruhe, Germany
• HZDR-IRC: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiochemistry, Bautzner Landstraße 400, D-01328 Dresden, Germany
• TU-BAF: Technische Universität Bergakademie Freiberg, Fakultät für Chemie und Physik, Institut für Anorganische Chemie, Leipziger Straße 29, 09596 Freiberg, Germany
• PSI-LES: Paul Scherrer Institut, Laboratory for Waste Management, Villigen, Switzerland

In the initial phase of the project the participating institutions agreed upon quality objectives:

• Transparency: all data should be traceable to a publicly available reference.
• Consistency: all data should be stored in a way which ensures internal consistency between data directly entered and other data, which are internally calculated from the former ones.
• Comprehensiveness: the database should cover the whole range of possible applications with regard to safety assessments for nuclear disposal sites. Where data are missing, appropriate estimates should be added.
• Uncertainties: wherever possible, uncertainties of data were to be captured.
• Data assessment: the referenced source, the data quality and the way in which every particular datum was derived should be captured in terms of pre-defined identifiers. Thus, data of poor quality and estimates, which were added to meet the objective "comprehensiveness", are marked accordingly for the user.

Criteria for the quality of thermodynamic data were largely adopted from a database established by OECD-NEA. However, provisions had to be met for additional parameters needed to cover the specific conditions in northern German deep geologic strata as they are likely to occur in clay or rock salt formations.
The development of recommended thermodynamic data follows an internal scheme for quality assurance. Additional documentation is available about the selection of data, but also about technical specifications of the databank to enable future users the maximum possible benefit of today’s work.
In technical terms stored data are managed in ways to keep them accessible as long as possible. This includes the use of open source rather than proprietary software. The data structure was designed to be flexible to cover potential future needs in safety assessment. Databases are issued in plain text files which can be processed as long as computers exist. Internal project communication as well as public access to the database is realized by a graphical user interface accessible over the world wide web: www.thereda.de.
Acknowledgements
This project was and is jointly funded by the Federal Ministry of Education and Reearch (BMBF) (GRS: 02C1426/02C1628, FZD: 02C1436, TU-BAF: 02C1446), the Federal Ministry of Economics and Technology (BMWi) (FZK/KIT: 02E10126/02E1067, FZD: 02E10136, GRS: 02E10146, TU-BAF: 02E10709), and the Federal Office for Radiation Protection (BfS ) with funds from the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU).
REFERENCES
H. C. Moog et al., Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem. (55), 72-84 (2015). http://dx.doi.org/10.1016/j.apgeochem.2014.12.016