Fabrication of oxidic uranium-neodymium microspheres by internal gelation

A promising concept after reprocessing and partitioning is the embedding of minor actinides in uranium-based nuclear fuel (co-conversion). Through this, the minor actinides can be eliminated by nuclear reactions with fast neutrons (transmutation) in upcoming reactor concepts. The internal gelation process allows the production of this nuclear fuel in form of microspheres directly out of a liquid feed stream. In this work, a study of parameters involved in internal gelation, essentially the quantity of the organic additives urea and hexa-methylene-tetra-amine present in the precursor solution, was performed, in order to better understand their role and optimise the properties of the materials obtained. To reduce radiotoxical risks, neodymium was used as a surrogate for trivalent minor actinides. After gelation, UO₂-based ceramics were obtained through thermal treatment of the gels. Characterisation was carried out by methods such as XRD and SEM. Crystalline microspheres with an almost integer and crack-free surface were obtained in case of proper formulation of the precursor solutions and thermal treatment.