In April 2005, a new 4-year Integrated Project on Very High Temperature Reactors (RAPHAEL: ReActor for Process Heat And ELectricity) was started as part of EURATOM’s 6th Framework Programme. The Sub-Project on Fuel Technology (SP-FT) is one of eight sub-projects in RAPHAEL, with 8 partners from industry, R&D organizations and a nuclear-safety expertise organization: CEA, FZ Jülich, JRC, Nexia Solutions, AREVA-NP, NRG, Belgonucléaire and IRSN. While the earlier HTR-F and HTR-F1 projects aimed at re-mastering fuel fabrication technology, testing existing state-of-the-art HTR fuels at high burn-up and high temperature and understanding fuel behaviour), the R&D conducted in RAPHAEL SP-FT focuses on understanding fuel behaviour and determining the limits of state-of-the-art fuel as well as on potential further performance improvements. Fabrication processes will be developed for an alternative kernel composition (UCO), with potential for decreasing CO pressure build-up, and for an alternative coating layer (ZrC) which remains more stable at higher temperature than SiC, thus providing increased margins in accident conditions. Post-irradiation examinations and heat-up tests performed on irradiated fuel will allow investigation of the behaviour of state-of-the-art fuel in a VHTR’s normal and accidental conditions. Based on the fuel particle models established in FP5, the fuel modelling capabilities will be improved:
- an irradiation will be performed in HFR Petten for measuring the changes in coating material properties as a function of fluence and temperature, with samples coming from the new fabrication process; this will allow introduction of particle behaviour models for coatings which are not only more accurate than those presently based on old data, but also more relevant to present materials;
- fission-product release modelling and statistical methods will be developed to integrate the individual behaviour of thousands of particles within fuel elements;
- code benchmarking, started in FP5, will be continued with the acquisition of new experimental data.
This paper presents progress in RAPHAEL SP-FT as well as the remaining activities of the earlier HTR-F1 project.