Closed fuel cycle schemes in combination with fast reactors are emerging as the key strategy for sustainable development of nuclear energy. Back end fuel cycles for fast reactors and thermal reactors mainly differ with respect to reprocessing operations. This publication highlights emerging innovations and R&D needs for the back end of the fast reactor fuel cycle, with an emphasis on the reprocessing of spent mixed uranium and plutonium based ceramic and metallic fuels. The publication has been prepared in collaboration with experts from Member States and will serve as a useful resource for nuclear scientists and engineers involved in fast reactor fuel development as well as reprocessing of spent nuclear fuel for sodium cooled fast reactors.