Nuclear Safety Project Advances Severe Accident Modeling
International Collaboration Aims to Improve Reactor Safety
A global initiative to enhance the accuracy of simulations predicting nuclear accident scenarios concluded a key review meeting in Tokyo this month, bringing researchers closer to understanding the complex behavior of reactor fuel during severe events. The project focuses on improving safety measures in the wake of the 2011 Fukushima disaster.
Progress Reported at Tokyo Review
The second phase of the Thermodynamic Characterisation of Fuel Debris and Fission Products (TCOFF-2) project, a joint effort of the Nuclear Energy Agency (NEA), convened experts from 12 organizations across Canada, France, Germany, Japan, Sweden, the United States, and the European Commission. The meeting, held May 19-20, 2025, and hosted by the Central Research Institute of Electric Power Industry (CRIEPI), assessed progress on five core tasks.
Masaki Kurata of the Japan Atomic Energy Agency (JAEA) and Kinya Nakamura (CRIEPI) facilitated the review, which involved 31 participants. Key areas of focus included prioritizing material science issues, improving knowledge of fuel degradation, and implementing this knowledge into accident simulation codes.
Focus on Advanced Fuels and Data
Unlike the first phase, which centered on the Fukushima Daiichi reactors, TCOFF-2 expands its scope to encompass a wider range of reactor designs, including advanced technology fuels (ATF). Christophe Journeau (CEA) and Sevostian Bechta (KTH) are leading efforts to pinpoint critical material science challenges in severe accident studies.
The project aims to refine models predicting radioactive release during accidents. According to the World Nuclear Association, as of early 2024, there are approximately 441 nuclear reactors operating worldwide, highlighting the importance of robust safety protocols. World Nuclear Association
Research Highlights and Future Directions
Updates were presented on supplementary research, including studies on the thermochemistry of fission products and the oxidation of chromium coatings. Anna Smith (TU Delft) presented research on the long-term radiological impact of barium, strontium, cesium, molybdenum, and oxygen systems. Ioana Nuta (CNRS) detailed work on chromium-cesium-oxygen interactions during accident conditions.
Koji Nishida of the Institute of Nuclear Safety System (INSS) delivered a technical lecture outlining industry expectations for fuel material science research. A technical tour of the Shimane Nuclear Power Station, organized by JAEA, allowed participants to observe the implementation of lessons learned from Fukushima, including the restart of Unit 2 and preparations for Unit 3.
The next TCOFF project review meeting is scheduled for November 12-14, 2025, in France. Further information is available on the project’s web page and the NEA Nuclear Education, Skills and Technology (NEST) Framework page.