Fabrication of Am-doped UO₂ transmutation targets

Nuclear energy is one of the least CO₂ emitting ways of generating large amounts of electricity. One major challenge in the utilization of nuclear energy is the management of spent nuclear fuel. The radiotoxic minor actinides, particularly Am (< 0.1 wt% of spent fuel), could be extracted and recycled via partitioning and transmutation. An innovative, dust-free method for producing (U,Am)O_2-x targets without the generation of Am-contaminated liquid waste has been successfully demonstrated. The method comprises the fabrication of porous uranium oxide microspheres (UO₃) through internal gelation, using starch as a pore-former and low-temperature calcination. After calcination of UO₃ microspheres were infiltrated using a single-step process with aqueous Am(NO₃)₃. After infiltration, the microspheres were dried, calcined and sintered. Various samples targeting Am contents of 5, 10, 20 and 30 mol% were prepared. The microstructural investigations revealed that the density of the porous host microspheres after the calcination was approximately 65 %TD with 30 vol% accessible porosity, suitable for an efficient infiltration. The examination of cross-sectioned (U,Am)O_2-x microspheres revealed homogeneous mixing of Am and U, without formation of agglomerates with distinct doping levels.