Development of a spent PWR MOx fuel using the SIMMOx approach

In France, the UOx spent fuel irradiated in Pressurised Water Reactor (PWR) is reprocessed to recover uranium and plutonium through the PUREX process. The final waste from this process contains fission products (FPs), such as platinum-group metals (Rh, Ru, Pd), which are now considered critical materials [1]. These FPs are more abundant in irradiated MOx (U,Pu)O2 but this fuel is not currently reprocessed. The aim is therefore to develop an enhanced route allowing the recovering of Rh, Ru, Pd during MOx spent fuel reprocessing. To achieve this goal, the first step is to have a comprehensive understanding of these fission products behavior. Given the high radiotoxicity of MOx spent fuel, studying such materials remains limited.This study aims to develop a manufacturing route for a model material with the same microstructure and physicochemical properties as irradiated PWR MOx fuel with an initial plutonium content of 11 wt% and burnup of 45 GW/d/thm. Our strategy is based on the development of a SIMMOx material [2] consisting on a fresh (U,Pu)O2 doped with precursors of 12 fission products during fabrication. The fission products used belong to 3 groups described by kleykamp [3] based on their behavior in irradiated fuel: FPs soluble in the (U,Pu)O2 (Ce, Nd, La, Y, Zr), FPs present in metallic secondary phase (Rh, Ru, Pd, Tc, Mo) and FPs forming secondary oxide phase (Ba, Sr, Zr, Mo). The first step of this study involves manufacturing dense (U,Pu)O2 pellets doped with fission product precursors using the industrial MIMAS process for MOx fuel fabrication. The second step consists of characterizing the manufactured material through different characterization methods to assess its representativeness.