The workshop took place on 10–11 March 2026. Organised by CEA IRESNE as part of the European ESFR-SIMPLE project, it brought together twenty participants, including fuel experts and young research engineers, in Aix-en-Provence, France.

The ESFR-SIMPLE project (European Sodium Fast Reactor – Safety by Innovative Monitoring, Power Level flexibility, and Experimental research), which began in October 2022 and will run until October 2026. It brings together a consortium of 16 European partners, whose primary objective is to design an SMR version of the ESFR core developed in previous projects.

As part of this initiative, the CEA organised a two-day workshop in Aix-en-Provence, France. During these two days, twenty experts and young researchers from various European organisations (CEA Cadarache and Marcoule, KIT, PSI, JRC, Rolls-Royce, University of Cambridge, Institut Polytechnique Paris, Chalmers University, HEXANA, OTRERA) and international organisations (OECD/NEA, IAEA) gathered to share insights and discuss three fuel-related topics:

• R&D on fast reactor fuels, including their behaviour under irradiation in steady-state and transient conditions and their thermophysical properties;
• current limitations and challenges in modelling and validating simulation tools for fuel (behaviour under irradiation, microstructure, etc.);
• challenges related to the fuel cycle.

The technical presentations sparked lively discussions and provided an overview of R&D and fuel modelling for fast reactors, covering MOX and metallic fuels.

The workshop also featured a tour of the ITER construction site, including a visit to the Tokamak building, which the participants greatly appreciated.