Contribution of Phenix to the development of transmutation fuels and targets in sodium fast breeder reactors

Studies focusing on different long-lived radioactive waste transmutation scenarios illustrate the relevance of fast breeder reactors (FBRs) vis-a-vis the incineration of minor actinides (MAs) and certain long-lived fission products. This research program evaluates fuels and targets for transmutation, relying mainly on irradiation data from Phenix to experimentally validate and demonstrate the technical feasibility of the envisaged concepts. As regards the homogeneous transmutation of MAs in fast reactors, PhMix clearly demonstrates the good behavior of MA-bearing oxide fuel, at least up to 6.4 at. % of burnup. Similar results on metallic MA-bearing fuels as well as technetium targets will be available very soon. Important knowledge on innovative composite fuels developed for the transmutation of MAs in fast reactors or in accelerator-driven reactors (accelerator-driven systems) is also gained. Inert matrices resistant to neutron and fission product damage have been selected. The role of the microstructure and irradiation conditions on the composite behavior under irradiation is explained. This program also highlights the possibilities of designing and fabricating transmutation targets, obtaining authorization to irradiate these targets in a power reactor-a series of stages to be accomplished in order to demonstrate the technical feasibility of incinerating MAs and technetium in FBRs.