XAS investigation of fission product speciation in (U,Pu)O2 MOx fuel and dissolution residues

Platinum group fission products such as Rh, Ru, and Pd are of strategic interest but are not currently recovered during spent MOx fuel ((U,Pu)O2) reprocessing. Under PUREX conditions, most of these elements remain undissolved, often as metallic or oxide phases, which limits their potential valorization. However, due to the radiotoxicity of irradiated fuel, direct studies on their chemical behavior are extremely challenging. To overcome this, we use SIMMOx, (U,Pu)O2 matrix with 11 %w Pu, doped with 12 non-irradiated fission products (FPs), reproducing the physico-chemical complexity of spent fuel. This project proposes to investigate the oxidation states and local environments of FPs in SIMMOx materials and in the undissolved residues formed after nitric acid dissolution. XANES and EXAFS analyses at relevant L3 and K edges will provide insights into their speciation, redox behavior, and structural incorporation.