The purpose of the Thermochemical Database Project is to make available a high-quality, traceable, internally consistent and internationally recognised chemical thermodynamic database of selected elements relevant to the safety of radioactive waste repositories, providing data that are vital to support the geochemical modelling of such systems.
Over a time span of 35 years, the NEA TDB Project has published 15 authoritative volumes containing selected thermochemical values for a vast number of compounds, and it has become the worldwide standard in the field of geological disposal.
The unique feature of the TDB project is that the data are evaluated and selected by teams of leading experts drawn from universities and research institutes around the world, through a critical review of the existing primary experimental sources. The TDB reports document the process leading to the selected values.
The database compiles formation data (Gibbs energies, enthalpies, entropies and heat capacities) for each aqueous species and solid phase of interest, as well as chemical reactions and their corresponding thermodynamic data. Non-thermodynamic data (diffusion or kinetics) and sorption data are not considered in the TDB project.
A detailed description of the project is set out in the TDB-0 guideline.
Current phase: TDB-6
Project period: February 2019 to January 2023
Participating countries: Belgium, Canada, Czechia, Finland, France, Germany, Japan, the Netherlands, Sweden, Switzerland, United Kingdom, United States
During the first phase of the project, a high priority was assigned to the critical evaluation of the data of inorganic compounds and complexes of the actinides uranium, americium, neptunium and plutonium, as well as the inorganic compounds and complexes of technetium.
The second phase of the project provided for further needs of the radioactive waste management programs by updating the existing database and applying the TDB methodology to new elements present in radioactive waste (as fission or activation products): nickel, selenium and zirconium, and also simple organic complexes of the key elements treated in phases I and II.
The third phase started in 2003, with three new reviews on thorium, tin and iron (part 1), and with the constitution of an expert team for the preparation of guidelines for the evaluation of thermodynamic data for solid solutions.
The fourth phase (2008-2013), included in its program of work three reviews concerning molybdenum, iron (part 2) and ancillary data and the initiation of two state-of-the-art reports on cement minerals and high ionic strength solutions.
The fifth phase (2014-2019) launched the state-of-the-art reports on cement minerals and high-ionic strength solutions, as well as the second update of the actinides and technetium volumes.
Several articles have appeared throughout the years in the open literature about the achievements of the TDB Project and its role in the development of national waste management programmes: