TCOFF-2 is the second phase of the NEA joint project Thermodynamic Characterisation of Fuel Debris and Fission Products Based on Scenario Analysis of Severe Accident Progression now running until 2027.\u00a0<\/p>\n
The first phase focused on analysis of reactor-related aspects of the Fukushima Daiichi Nuclear Power Plant. The current phase builds on the knowledge acquired and also includes studies on other reactor and advanced technology fuels (ATF), as well as other fuel designs. The project brings together 12 organisations from Canada, France, Germany, Japan, Sweden, United States and the European Commission.\u00a0<\/p>\n
The aim of TCOFF-2 is to improve models and underpinning data on the material interactions and their role in the various potential phases of the severe accidents. The ultimate goal is the integration of such models into severe accident simulation codes to increase their accuracy, including in respect of the extent of potential radioactive release. This improvement will be driven by state-of-the-art knowledge of the thermodynamic properties of the relevant combinations of materials.\u00a0<\/p>\n
The NEA convened TCOFF-2 Programme Review Group (PRG) and Management Board (MB) meetings in Tokyo, Japan, on 30 June – 1 July 2026 to review progress of its activities. The meetings were hosted by the Central Research Institute of Electric Power Industry (CRIEPI) and held after the 15-Year Fukushima Daiichi Accident International Workshop<\/a> hosted jointly by the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF), the Nuclear Regulation Authority (NRA) of Japan and the NEA.\u00a0<\/p>\n The meeting gathered 40 participants and progress was reported from each of the five principal tasks of TCOFF-2:<\/p>\n Prioritisation\u00a0of\u00a0the material\u00a0science issues related to severe accident study\u00a0 Sessions\u00a0also\u00a0featured\u00a0updates\u00a0from supplementary\u00a0R&D\u00a0projects:\u00a0<\/p>\n Thermochemistry of fission product phases with a long-term radiological impact: experimental studies of the Ba-Sr-Cs-Mo-O system \u2013 Prof. Anna Smith (TU Delft)\u00a0 More information and next steps<\/p>\n Further details on TCOFF-2 can be found on the dedicated web\u00a0page<\/a> and information about the partnership with the NEA Nuclear Education, Skills and Technology (NEST) Framework is available on the NEST page<\/a>.<\/p>\n
\n Improvement of the materials science knowledge\u00a0regarding\u00a0fuel core degradation and\u00a0fission product\u00a0release (UO2-Zr and ATF)
\n Implementation of improved knowledge for the simulation of the accident behavior (UO2-Zr and ATF)
\n Extension of the leaching experimental database to better evaluate mid-\u00a0and long-term stability of degraded cores\u00a0
\n Training and education (including partnership with the NEA Nuclear Education, Skills and Technology Framework) <\/p>\n
\n Experimental characterisation of representative corium samples under severe accident conditions \u2013 Morgan Collins and Prof. Markus Piro (McMaster University)\u00a0
\n Modelling heavy actinide solute trapping during solidification with data from the CNL cold crucible experiments \u2013 Dr Mike Welland (McMaster University)
\n In situ high-temperature XRD\/XAFS study of phase equilibria for hypo-stoichiometric region in U-Zr-O system \u2013 Prof. Ayumi Itoh (Science Tokyo)
\n The effect of FeO and ZrO2 on the phase equilibrium of CaO-SiO2-Al2O3 simulant of the SiO2-rich concrete at 1673 K \u2013 Dr Ryoto Nakazawa (Science Tokyo)\u00a0
\n Oxidation of Cr-coating layer by steam in accidental conditions: gaseous phase of Cr-Cs-O system description using Knudsen effusion mass spectrometry + Thermodynamic evaluation \u2013 Dr Ioana Nuta (CNRS) <\/p>\n