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| Home > Publications database > Aging and Oxidation Processes of UO2 Nanoparticle Materials Under Ambient Conditions Relevant to Interim Storage of Spent Fuel |
| Home > Publications database > Aging and Oxidation Processes of UO2 Nanoparticle Materials Under Ambient Conditions Relevant to Interim Storage of Spent Fuel |
| Abstract | FZJ-2026-01070 |
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2025
Abstract: Mixed Oxide (MOX) nuclear fuel is a topical nuclear fuel that consists of a mixture of UO2 and PuO2 and is used currently to fuel many nations’ nuclear energy programs. After extended burnup, the fuel undergoes heterogenization forming what is known as the high burn-up structure (HBS). HBS regions of the fuel exhibit increased porosity compared to UO2and occur as nanomaterials. A detailed investigation of these materials regarding their formation and thermal stability is necessary to support use of nuclear fuel and further for its eventual disposal within a final geological nuclear repository.[1] The complexity of spent nuclear fuel (SNF) challenges its direct investigation. Therefore, simplified model systemsare prepared and studied to examine single effects in complex systems.Following this line of investigation UO2 based nanomaterial compounds were synthesized as model materials for HBS SNF, using an adapted hydrothermal method and subsequently investigated in the context of their chemistry in relation to the HBS of SNF.[2] Characterization of the synthesized materials were conducted on fresh materials as well as on samples aged over month in air to investigate the oxidation and aging processes by using powder X-ray diffraction and scanning electron microscopy to respectively determine the material structure and morphology of these nanoparticle materials. High Energy Resolution Fluorescence Detected X-ray absorption near-edge structure (HERFD-XANES) measurements were performed at BM20 at the European Synchrotron Radiation Facility (ESRF), to determine the local structure and redox changes to the nanoparticles. Measurements performed on the U-M4 edge revealed surprising diversity in the U redox states where U+4, U+5 and U+6 were identified, although the compounds occur as single-phase structure from PXRD measurements. The origin of this unexpected behavior is reckoned to the unique nanostructure of the materials and their ability to form oxidized layers upon air exposure with subsequent chemical transport of U cations. These hypotheses were subsequently tested using extended X-ray absorption near edge structure measurements. The results of this work will be discussed in relation to the chemistry of UO2 nanomaterials vs. micromaterials in addition to their relevance to HBS nuclear fuel chemistry.References[1] V. V. Rondinella, T. Wiss, Materials Today, Volume 13, Issue 12, Pages 24-32, 2010.[2] R. Zhao, L. Wang, Royal Society of Chemistry, Volume 16, 2645-2651, 2014.
Keyword(s): Chemistry (2nd)
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