Thermodynamics of Advanced Fuels – International Database (TAF-ID)

The need for thermodynamic data for analyses involving nuclear fuel

The detailed modelling of the fuel-cladding system is of major importance for several studies related to safety improvement, lifetime extension for Generation II-III reactors, and the design of advanced Generation IV systems.

The use of thermodynamic data is needed for various analyses involving nuclear fuel: design of the fuel element, modelling of the fuel-cladding system under normal conditions in performance codes, up to the analysis of the fuel and cladding behaviour under severe accident conditions (pre-and post-fuel melting) and the interaction of corium with the vessel and sacrificial materials (in-vessel) and the concrete (ex-vessel).

These analyses may involve different types of fuel and cladding for Generation II-III and Generation IV systems:

  • Oxide, nitride, carbide, metal fuels, fuels with thorium, fuels with minor actinides, presence of fission products, etc.;
  • Zircaloy, SiC, ODS steels, standard and advanced cladding materials, etc.;
  • Structural materials: concrete, vessel, control rods, etc.

How is thermodynamic data calculated?

One of the means of obtaining thermodynamic data of the chemical species of interest is by application of the CALPHAD method: this approach allows the calculation of phase diagrams (composition and number of the phases) over a large composition, temperature and pressure range as well as thermodynamic properties of these phases (heat capacity, enthalpy, activity, partial pressure, etc.) which stem from the mathematical function of the Gibbs energy of the phases that may form.

These functions are based on sub-lattice models derived from the crystalline structure of the different phases (a sub-lattice corresponding to a crystalline site). The free parameters in the model are optimised using a least-square minimisation method between experimental and calculated data. The experimental data consist of phase boundaries (liquidus, solidus, solubility limit, etc.) and/or thermodynamic data (heat capacity, mixing enthalpy, enthalpy of formation, activity, etc.). This approach requires a preliminary critical analysis of all experimental information available on the system prior to the modelling phase of the chemical species of interest.

Available tools for thermodynamic calculations

Currently, several tools are used in various laboratories and organisations which are part of the OECD-NEA:

  • Canada: database on uranium oxide developed at RMCC;
  • France: FUELBASE developed at CEA;
  • Japan: a database on metallic fuels developed at CRIEPI and one on corium for BWR developed at JAEA;
  • The Netherlands: TBASE developed at NRG;
  • United States: several databases developed at ORNL, INL and LLNL.

Each of these databases allows performing studies on only a few of the chemical species described above. The unification of these separate databases would greatly benefit all the organisations, each of which relies nowadays solely on its own experience, data, know-how and resources for the use, maintenance, development and validation of its database.

Project Organisation

The OECD-NEA Thermodynamics of Advanced Fuels - International Database Project was established in 2013 to make available a comprehensive, internationally recognised and quality-assured database of phase diagrams and thermodynamic properties of advanced nuclear fuels with a view to meeting the specialised requirements for the development of advanced fuels for a future generation of nuclear reactors.

Specific technical objectives that this programme intends to achieve are to:

  • Predict the solid, liquid and/or gas phases to be formed during fuel-cladding chemical interaction under normal and off-normal conditions;
  • Improve the control of the experimental conditions during the fabrication of the fuel materials at high temperature, for example, by predicting the vapour pressures of the elements (particularly of plutonium and the minor actinides);
  • Predict the evolution of the chemical composition of the fuel under irradiation versus temperature and burn-up.

The Project will also identify the need for and encourage the measurement of further experimental data.

This joint Project was established between nine organisations of six NEA member countries: Canada (CNL, RMCC, UOIT), France (CEA), Japan (JAEA, CRIEPI), The Netherlands (NRG), the Republic of Korea (KAERI) and The United States (DoE), with an initial 3-year period.

The control of the Project is vested to a Programme Review Group, composed by members nominated by the Signatories.

TAF-ID is co-ordinated by the OECD-NEA, as a joint Project, entirely funded by the Signatories of the Project.

The TAF-ID database will be generated and regularly updated by merging the existing databases and those being developed from the Signatories of the Project. The database will be available both in Thermo-Calc and FACTSAGE usable formats.

TAF-ID versions developed: working version and public version

Two versions of the TAF-ID database are being developed:

  • A working version containing the description of all the systems to be investigated in the framework of the TAF-ID Project. This working version is currently accessible only to the Signatories of the Project. As for the version released in December 2013:
    • It contains the following elements: Ag, Al, Am, Ar, B, Ba, C, Ca, Ce, Cr, Cs, Fe, Gd, H, He, I, La, Mg, Mo, N, Nb, Nd, Ni, Np, O, Pd, Pu, Re, Rh, Ru, Si, Sr, Ta, Te, Th, Ti, U, V, W, Zr;
    • Used to model the following binary and ternary systems.
  • A public version containing a limited amount of data – for example, only data that have already been published in the open literature at the time of release. This version, managed by the OECD/NEA, will be accessible to all NEA member countries upon request to the NEA and signature of a non-disclosure agreement (NDA).The public version will be available as from December 2014.

Project Signatories

  • Canada: Canadian Nuclear Laboratories (CNL), The Royal Military College of Canada (RMCC), The University of Ontario Institute of Technology (UOIT);
  • France: Commissariat a l'Energie atomique et aux Energies alternatives (CEA);
  • Japan: Japan Atomic Energy Agency (JAEA), Central Research Institute of Electric Power Industry (CRIEPI);
  • The Netherlands: The Delft University of Technology (DUT);
  • Republic of Korea: The Korea Atomic Energy Research Institute (KAERI);
  • UK: The National Nuclear Laboratory (NNL);
  • USA: The Department of Energy (DoE).

Relevant links


Last reviewed: 10 July 2017