Members of the Second Framework for Irradiation Experiments (FIDES-II) joint undertaking gathered on 29 September – 3 October 2025 in Ketchum, Idaho, United States, for the Technical Advisory Group and Governing Board meetings hosted by Idaho National Laboratory (INL). The FIDES-II Framework aims to ensure and foster competences in experimental nuclear fuel and structural materials in-reactor experiments through a diverse set of Joint Experimental Programmes, JEEPs.
First irradiations of cladding materials and reactivity tests for fuel have been performed in previous years, and several in-reactor experiments took place in 2025. The online results of the first high-burnup test performed at TREAT reactor were presented to around 100 meeting participants from 14 countries and the European Commission. Participants also discussed several other recently conducted experiments.
The main focus of the meeting was the review of the process of the ongoing JEEPs. The second three-year term of the Framework, which started in April 2024, has nine ongoing JEEPs:
- P2M aiming to perform power ramp experiments;
- HERA and LOC-HBU performing accident simulations;
- INCA and MCA-ATF with cladding irradiations to study irradiation creep;
- ATOMIC to investigate various novel fuel forms;
- INCREASE phases 1 and 2 to irradiate light water reactor structural materials; and
- HITEC to irradiate advanced reactor structural materials.
The FIDES-II meeting also included discussions of the programme of work for the next term of FIDES-II, which will start in April 2027. The proposals for the third term were discussed, and a competitive process to review and rank them during the next half a year was decided on.
The Framework has several cross-cutting activities that are carried out concurrently to the experiments. Modelling and simulation activities are actively pursued within projects, with the exercises using non-proprietary data also open to participants outside of FIDES-II community. Simulation exercises on ramp tests, reactivity insertion transients, and loss of coolant experiments under JEEPs P2M, HERA, and LOC-HBU have been recently finalised. More than ten organisations have been involved in each of these exercises, and these represent significant additional value to the experimental work.
The week finished with a technical visit to the INL, where the participants visited the EBR-I and ATR reactors.
