Abstract Current concepts for future nuclear systems aim at improving the fuel cycle with the main following criteria: economy of resources, minimized volume and lower long-term potential radiotoxicity of ultimate wastes and proliferation risk reduction. Co-management of two (or more) actinides has recently been proposed for recycling reusable energy-producing actinides (mainly U and Pu) together, or for transmuting radiotoxic minor actinides within UO 2-based materials. Co-conversion processes play an important role by closing the actinide separation–purification operations and at the same time producing mixed actinide solid compounds for the fabrication of fresh fuel. Handling of actinides mixtures, from the initial solution up to the solid product, requires innovative synthesis methods and structures, particularly for the minor actinides such as americium and curium. Considering the different designs of future nuclear fuels, various uranium–actinide co-conversion routes are currently investigated in the CEA-ATALANTE facility.