Cr2+ solid solution in UO2 evidenced by advanced spectroscopy.
Hannah Smith1, Luke T Townsend1, Ritesh Mohun1
1NucleUS Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Sheffield, UK.
Communications Chemistry
|January 25, 2023
Summary
Chromium (Cr) doping in uranium dioxide (UO2) nuclear fuel was directly studied. Results show Cr substitutes for uranium, impacting fuel chemistry and enabling new material development.
Area of Science:
- Nuclear materials science
- Solid-state chemistry
- Materials characterization
Background:
- Advanced chromium-doped uranium dioxide (UO2) fuels are crucial for safe and efficient nuclear energy generation.
- Fundamental chemistry of these fuels is poorly understood, hindering new material development and waste management.
Purpose of the Study:
- To directly investigate the fundamental chemistry of Cr2O3-doped UO2.
- To elucidate the charge compensation mechanisms and Cr speciation in UO2 fuels.
Main Methods:
- Utilized advanced X-ray absorption spectroscopy (XAS) with high flux and spectral purity.
- Corroborated findings with diffraction, Raman spectroscopy, and high energy resolved fluorescence detection-XAS.
- Analyzed heat-treated simulant nuclear fuel samples.
Main Results:
- Directly evidenced Cr2+ substituting for U4+ in UO2.
- Identified U5+ and oxygen vacancies as charge compensation mechanisms.
- Revealed a mixed Cr2+/3+ oxidation state and multiple Cr physical forms in heat-treated fuels.
Conclusions:
- Established the detailed chemistry of Cr-doped UO2 fuels.
- Explained discrepancies in existing literature regarding Cr speciation.
- Opened avenues for utilizing a wider range of dopants in advanced UO2 nuclear fuels.
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