[en] This chapter reviews recent research on mixed actinide precipitation using oxalates with a view to obtaining an oxide powder that is homogeneous at the atomic level. These powders can be made into new nuclear fuel that help to avoid hot spots from segregated metal oxide phases and will help in the dissolution of the spent fuel when it comes to reprocessing. By introduction, plutonium oxalate precipitation and calcination is placed in the context of current industrial-scale processes, before discussing the structures of mixed actinide oxalates. Examples of areas where this technology has been demonstrated in the COEX™ process and for minor actinide bearing blanket fuel are also discussed. (author)