Current state of partitioning and transmutation studies for advanced nuclear fuel cycles

Abstract

This paper aims at giving a general overview of the current state of partitioning and transmutation (P&T) studies for advanced nuclear fuel cycles across the world. P&T usually refers to the entire fuel cycle steps linked with minor actinides transmutation, from separation of the minor actinides from the spent fuel to manufacturing of new fuels suited for transmutation, irradiation, handling and reprocessing or disposal of the spent transmutation fuels. The feasibility of most of these steps has been demonstrated in the laboratory scale since the beginning of the nuclear era, however the physical-chemical and radiological properties of minor actinides make their handling considerably more complicated than standard UOX or MOX fuel. As such, research on this topic is still ongoing around the world.Due to the shutdown of various experimental installations since the 90′ (EBR-II in the US in 1994, PFR in the UK in the same year, Joyo in Japan in 2007, Phénix and Osiris in France in 2009 and 2016 respectively), few irradiation experiments have been carried out in the past decade. The MARIOS and DIAMINO experiments were carried out in the HFR and OSIRIS reactor and showed that the irradiation of fuel with a micro-structure optimized for helium release (and thus limited swelling) was achievable. The irradiation of metallic and oxide containing minor actinides and/or rare earths was carried out in the ATR reactor in the US. The good behaviour of oxide fuel containing minor actinides was demonstrated, although pin failures occurred with the metallic fuel. Furthermore, Post-Irradiation Examinations of various irradiation experiments have been carried out, the most salient one being the METAPHIX experiment in Phenix, which demonstrated the safe behaviour under irradiation of the base alloy considered in the experiment.Nevertheless, encouraging results in the field of americium separation from the spent fuel have been obtained, the main one being the successful demonstration of the ExAm process to isolate americium from a PUREX raffinate. Furthermore, progress has been made on the manufacturing of UAmO2 targets during the preparation of DIAMINO and MARIOS experiments. Finally, interest in minor actinides transmutation has started to rise again, notably linked with the current trend in molten salt reactor, which are suitable for minor actinides transmutation.