Optimal exploitation of nuclear fuels is essential to maintain low-carbon energy production for decades to come. To this end, fuels such as mixed oxides U1-yPuyO2-x are being considered. However, the safety of their future use, requires an exhaustive multi-scale understanding of their behavior during both their manufacturing and their irradiation in reactor, as well as their compatibility with the dissolution processes necessary for their recycling. X-ray Absorption Spectroscopy (XAS) is a key technique for fuel characterization that is extensively employed at CEA Marcoule. A complementary approach to the latter is X-ray Emission Spectroscopy (XES). However, while XES studies are numerous in the context of 3d elements, only very few are available for actinides. Those studies suggest the possible access to new knowledge on the properties of fuels, while being characterized by a lower detection limit compared to XAS. The main objective of this thesis work is therefore the development of the methodology and instrumentation necessary for XES analyzes at the lab scale as well as the realization of experimental campaigns dedicated to the understanding of the links between experimental observations and the intrinsic properties of actinides. The thesis will be carried out in collaboration between CEA Marcoule and the University of Helsinki and will begin with a 1.5-year period in Helsinki before continuing at CEA Marcoule. The candidate would have a Master's degree in physics or chemistry of materials and a minimum level of B2 in English and will, if necessary, follow training course in French during his/her stay in Finland. By the end of this thesis, the candidate will have mastered a wide range of experimental techniques as well as the exploitation of the data acquired. These skills will open up a wide range of job opportunities in academic research or industrial R&D, both within and outside the nuclear sector.