Innovation in fission products behaviour studies: synthesis and characterization of U1-yPuyO2+x SIMfuel

In the context of Generation IV Sodium-cooled Fast Reactors (SFR), U1-yPuyO2-x mixed oxides are currently considered as the most suitable fuel. These materials have to meet precise physico-chemical properties, which are known to change drastically during irradiation, notably due to the formation of Fission Products (FPs) and their subsequent interaction with the (U,Pu)O2 matrix. Some FPs accommodate into the MOX matrix, while others precipitate into metallic or oxide phases, affecting all fuel physical and chemical properties. Investigating the FPs behaviour is thus of the utmost importance for the understanding of the evolution of the fuel properties during irradiation. Considering both high radiotoxicity and complex chemical composition of the spent fuel, model materials called SIMfuel have been developed in the last decades to take into account those issues. SIMFUEL are fresh UO2 fuel doped with stable FPs isotopes. Besides being manipulated in gloveboxes instead of hot cells for the spent fuel, the FPs chemical compositions of these materials can be adjusted and hence allow studying specifically the effect of selected FPs. Furthermore, only UO2 based SIMfuel have been studied while Pu is a major element of the spent fuel. Therefore, in this work, we develop a new method to synthesize Pu-bearing SIMfuel (MOX-SIMfuel) and we characterize them to study the FPs behaviour and impact within the (U,Pu)O2 local microstructure.