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| Home > Publications database > Synthesis and Investigation of Ce-based surrogate mixed oxide fuel (MOX) |
| Conference Presentation (Other) | FZJ-2026-00365 |
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2025
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-00365
Abstract: MOX (mixed oxide Fuel) is a topical nuclear fuel that has been used in nuclear power plants worldwide, in particular in Germany and France. MOX fuel is a ceramic commonly consisting of a mix of UO2 and PuO2 with varying Pu concentrations. Amongst other routes, MOX has been commonlyproduced by what is known as the “MIMAS route” (Micronized Master Blend) [1]. This route is well known to result in a heterogenous material that has microstructural regions of different Pu enrichments [2]. This usually expresses itself in a Pu rich, Pu poor and an indermediate phase [2]. Depending on processing conditions different regions in MOX vary in their Pu enrichment and in their size and distribution. Understanding their chemical properties, in particular the local chemistry and redox states of these regions is critical to ensuring safe and correct eventual disposal of MOX when occuring as spent nuclear fuel (SNF).In this work, the industrial MIMAS process has been down-scaled to the laboratory level. That way, surrogate MIMAS MOX Pellets have been synthesized using CeO2 instead of PuO2. Emphasis has been placed on the influence of the feed UO2 powder origin on the structure and chemistry of the final MIMAS MOX ceramic, namely via the precipitation of either Ammonia diuranate (ADU) or Ammnia uranyle carbonate (AUC). These two routes are inspired by the industrial synthesis of MIMAS MOX[1]. High resolution powder syncrotron X-ray diffraction (S-PXRD) measurements performed at the BM20 of the ESRF unveiled discrete but significant phase differences in the surrogate MOX cermaics. SEMEDS further reveals the contrasting MOX materials that used different precursor materials, highlightnig significant heterogeneity. Remarkebly, high-energy-resolution fluorescence detected Xray absorption near edge structure (HERFD-XANES) measurements performed on the U M4-edge and Ce L3-edge indicate considerable differences in the redox states of the MOX materials, in particular their simultaneous posession of both oxidised and reduced U and Ce respectively. These results suqsequently suggest that in actual Pu based MIMAS MOX considerable diversity in redox states are found, but moreover highlight the siginificance of different synthesis routes in influencing the bulk chemistry of synthesized materials.References[1] D. Haas, A. Vandergheynst, J. van Vliet, R. Lorenzelli, J.-L. Nigon, Nuclear Technology, 106, 60 (1994).[2] R. Delville, M. Verwerft, Microscopy and Microanalysis, 29, 78 (2023).
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