Thermochemical Database (TDB) Project
Program development concept (Africa Studio; ShutterStock)

Go to the Chemical Thermodynamic Series Volumes Go to the electronic TDB Go to the TDB Project Guidelines  

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.

Key info

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

Current activities:

  • completion of the reviews from the fifth phase
  • preparation of an update of the phase three organics volume
  • preparation of a lanthanides’ review
  • preparation of a state-of-the-art report on high-temperature data.

TDB past phases

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.

current timeline of TDB publications


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:

  1. Ragoussi M. E., Costa D., “Fundamentals of the NEA Thermochemical Database and its influence over national nuclear programs on the performance assessment of deep geological repositories”, J. Environ. Radioact. 2019, 225-231, doi:
  2. Martinez J. S., Santillan E. F., Bossant M., Costa D., Ragoussi M. E., “The new electronic database of the NEA Thermochemical Database Project”, Appl. Geochem. 2019, 159-170, doi:
  3. Costa D., Ragoussi M. E., “Selection of reference thermodynamic data for modelling of deep geological repositories: Present and future of the NEA Thermochemical Database Project”, J. Solution Chem. 2017, 1760-1766, doi:
  4. Ragoussi M. E., Brassinnes S., “The NEA Thermochemical Database Project: 30 Years of Accomplishments”, Radiochim. Acta 2015, 679-685, doi:
  5. Hummel, W., Puigdomènech, I., Rao, L., Tochiyama, O., “Thermodynamic data of compounds and complexes of U, Np, Pu and Am with selected organic ligands”, C. R. Chimie 2007, 948-958, doi:
  6. Mompeán, F. J., Wanner, H., “The OECD Nuclear Energy Agency Thermochemical Database Project”, Radiochim. Acta 2003, 617-621, doi:

TDB Project highlights

Download the TDB Project flyer