The TCOFF-2 initiative aims to enhance expertise and knowledge dissemination in thermodynamics modelling applied to material science. Its objectives include improving the management of thermodynamic data's impact, including validation, uncertainty propagation and sensitivity analysis, within severe accident codes. This initiative will offer training opportunities for current engineers and researchers in data manipulation and the application of thermodynamic calculations specific to accident scenarios. Furthermore, it seeks to facilitate knowledge exchange and raise awareness within the scientific community regarding the dearth of fundamental data concerning severe accidents and their repercussions.
The TCOFF-2 joint project aims to improve the models describing the materials interactions and the role they play in the various phases of the severe accidents, the ultimate goal being the integration of such models in severe accident simulation codes to increase their accuracy.
This improvement will be driven in particular by state-of-the-art knowledge of the thermodynamic properties of the material systems relevant to the description of core materials degrading through a severe accident sequence. Such knowledge, partially developed and accumulated during the execution of the first phase of the TCOFF (TCOFF-1) project and previous international efforts, will be systematised and further extended in this second phase of TCOFF (TCOFF-2) through joint experts’ evaluations, thermodynamic modelling, and focused R&D efforts.
The project focuses on the accident sequence going from the early stages of the fuel degradation, through the fuel relocation, the molten pool formation, reactor pressure vessel (RPV) failure, and the interaction between the corium and the concrete. The project will also address the fission products (FPs) behaviour, their distribution in the various phases forming during the accident and the source term evaluation.
The main objectives of the TCOFF-2 NEST project are:
This project will provide training for current engineers and researchers in data handling and the use of thermodynamic calculations dedicated to accidental scenarios. For younger people, it will enable them to take advantage of the current momentum and renewal in the nuclear field to develop the skills of new generations of professionals. More broadly, this transfer of knowledge will also raise awareness throughout the scientific community of the lack of fundamental data in the field of severe accidents and their consequences.
Organisations that have supported the project by hosting or arranging Fellowships and training schools.
Applications for 2025-26 NEST TCOFF-2 fellowships are now closed. Applicants were selected for the following fellowship programmes:
The NEST TCOFF-II International Winter School 2025 was held at KIT, Germany from 15–19 December 2025, in combination with “30th International QUENCH Workshop (QWS)” simultaneously held on 16–18 December.
This school presented an opportunity for students and early career researchers to participate in an international workshop and experience exchange of findings, knowledge-sharing and networking. The selected participants presented their current research work as a poster and visited the world leading facilities of KIT and the JRC of the European Commission in Karlsruhe.
NEST Fellows at the TCOFF-II Winter School with a cross-section of simulated corium from KIT MOCKA facility
From September to December 2025, Brock conducted his fellowship at the severe accident research laboratories of KIT under the supervision of Dr. Martin Steinbrück. His research involved testing the oxidation behaviour of self-provided samples of chromium-coated zirconium cladding for ATF application.
Brock Nowak’s presentation of his work at the 30th International QUENCH Workshop at KIT, Germany 16-18 December 2025 – available to view online in the proceedings (p871-905)
Brock summarised his personal experience of the fellowship as follows:
‘It has been a profound privilege to participate as a TCOFF-2 NEST fellow. This has been instrumental in advancing my research on ATF cladding, specifically concerning implementation within CANDU-Pressurised Heavy-water Reactor (PHWR) systems.
The TCOFF-2 NEST project’s emphasis on international collaboration allowed me to benchmark my findings against global safety standards and engage with experts across the OECD-NEA network, notably through my participation in the 30th International QUENCH Workshop.
I am sincerely grateful to the OECD-NEA and my colleagues at KIT for their mentorship and for providing the world-class facilities that made this research possible. This fellowship has significantly strengthened my technical expertise and my commitment to advancing nuclear materials science.’
Participant in the NEST TCOFF-II International Winter School.
‘A really enriching experience, even at the very beginning of my PhD. The programme was well structured, with a good balance between visits to highly specialised facilities at KIT and the JRC, and the scientific discussions during the QUENCH workshop. What stood out most was the particularly collegiate and accessible atmosphere of the workshop, which made it easy to interact with distinguished nuclear scientists and have meaningful, in-depth exchanges. I am very grateful for this opportunity, and I would definitely recommend.’
Participant in the NEST TCOFF-II International Winter School.
‘An incredible experience as a young researcher. Since the QUENCH Workshop was embedded within the conference, it gave me the opportunity to network with scientists outside of the United States about whose research I may not have otherwise known and opens the door for future collaboration. The workshop was particularly beneficial to me as it related to my research directly, and I knew the work of many scientists there. It was beneficial to learn what is happening now, instead of being subject to the publication cadence which may be years delayed. I also appreciated being able to tour all of the research facilities at Karlsruhe, as they were impressive. I also enjoyed my time meeting the other students involved with the program and hearing about their research and graduate programs while exploring a new culture.’
Participant in the NEST TCOFF-II International Winter School.
‘It was a very valuable experience for me to witness firsthand the strong international interest in the Fukushima issue. Engaging with participants from different backgrounds made me realise how widely this topic is recognised and discussed beyond Japan. At the same time, as a Japanese participant, this experience strengthened my determination to take a central role in addressing the challenges related to Fukushima in the future. It has motivated me to contribute more actively and responsibly to this important issue.’
Participant in the NEST TCOFF-II International Winter School.
‘I sincerely appreciated the planning that went into the Winter School. The itinerary was well organised, and the tours and presentations were engaging, with guides and speakers who were not only knowledgeable but also approachable and genuinely interested in both sharing their work and learning about ours. I am also grateful for the efforts coordinating student activities outside of program hours, which helped us feel welcomed, acclimated, and more connected throughout the experience.’
NEST Fellows at the NEST TCOFF-II Winter School, December 2025
Thermodynamic Characterisation of Fuel Debris and Fission Products Based on Scenario Analysis of Severe Accident Progression (TCOFF)
