Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies

Gabriel L. Murphy; Robert Gericke; Sara Gilson; Elena F. Bazarkina; André Rossberg; Peter Kaden; Robert Thümmler; Martina Klinkenberg; Maximilian Henkes; Philip Kegler; Volodymyr Svitlyk; Julien Marquardt; Theresa Lender; Christoph Hennig; Kristina O. Kvashnina; Nina Huittinen

doi:10.1038/s41467-023-38109-0

Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies

Gabriel L. Murphy, Robert Gericke, Sara Gilson, Elena F. Bazarkina, André Rossberg, Peter Kaden, Robert Thümmler, Martina Klinkenberg, Maximilian Henkes, Philip Kegler, Volodymyr Svitlyk, Julien Marquardt, Theresa Lender, Christoph Hennig, Kristina O. Kvashnina, Nina Huittinen

Isotope Applications Research

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14 Scopus citations

Abstract

Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U⁺⁴ in the fluorite lattice as Cr⁺³ with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr⁰) and oxide related Cr⁺² and Cr⁺³₂O₃ were identified and attributed to grain boundary species and precipitates, with concurrent (Cr⁺³_xU⁺⁴_1-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

Original language	English
Article number	2455
Journal	Nature Communications
Volume	14
Issue number	1
DOIs	https://doi.org/10.1038/s41467-023-38109-0
State	Published - Dec 2023

Funding

The authors, G.L.M., S.G., V.S., J.M., T.L., C.H. and N.H., are grateful to funding and support from the German Federal Ministry of Education and Research (BMBF), Project No. 02NUK060, that enabled this research. Dr. Juliane März is kindly acknowledged for her help collecting single crystal grains for the EPR measurements. The ESRF Chemistry Laboratory personnel Harald Muller and Léa Bourcet are acknowledged for their help with the glove-box facility. Dr. Andrey Bukaemskiy is kindly acknowledged for assistance in pellet pressing and polishing. Dr. Gregory Leinders is kindly thanked for fruitful discussions on the thermodynamics of UO. 2

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Murphy, G. L., Gericke, R., Gilson, S., Bazarkina, E. F., Rossberg, A., Kaden, P., Thümmler, R., Klinkenberg, M., Henkes, M., Kegler, P., Svitlyk, V., Marquardt, J., Lender, T., Hennig, C., Kvashnina, K. O., & Huittinen, N. (2023). Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies. Nature Communications, 14(1), Article 2455. https://doi.org/10.1038/s41467-023-38109-0

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title = "Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies",

abstract = "Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.",

author = "Murphy, \{Gabriel L.\} and Robert Gericke and Sara Gilson and Bazarkina, \{Elena F.\} and Andr{\'e} Rossberg and Peter Kaden and Robert Th{\"u}mmler and Martina Klinkenberg and Maximilian Henkes and Philip Kegler and Volodymyr Svitlyk and Julien Marquardt and Theresa Lender and Christoph Hennig and Kvashnina, \{Kristina O.\} and Nina Huittinen",

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doi = "10.1038/s41467-023-38109-0",

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Murphy, GL, Gericke, R, Gilson, S, Bazarkina, EF, Rossberg, A, Kaden, P, Thümmler, R, Klinkenberg, M, Henkes, M, Kegler, P, Svitlyk, V, Marquardt, J, Lender, T, Hennig, C, Kvashnina, KO & Huittinen, N 2023, 'Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies', Nature Communications, vol. 14, no. 1, 2455. https://doi.org/10.1038/s41467-023-38109-0

TY - JOUR

T1 - Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies

AU - Murphy, Gabriel L.

AU - Gericke, Robert

AU - Gilson, Sara

AU - Bazarkina, Elena F.

AU - Rossberg, André

AU - Kaden, Peter

AU - Thümmler, Robert

AU - Klinkenberg, Martina

AU - Henkes, Maximilian

AU - Kegler, Philip

AU - Svitlyk, Volodymyr

AU - Marquardt, Julien

AU - Lender, Theresa

AU - Hennig, Christoph

AU - Kvashnina, Kristina O.

AU - Huittinen, Nina

PY - 2023/12

Y1 - 2023/12

N2 - Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

AB - Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

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DO - 10.1038/s41467-023-38109-0

M3 - Article

C2 - 37117177

AN - SCOPUS:85159241777

SN - 2041-1723

VL - 14

JO - Nature Communications

JF - Nature Communications

IS - 1

M1 - 2455

ER -

Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies

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