Groundwater data from the natural analogue site Ruprechtov have been evaluated with special emphasis on the uranium behaviour in the so-called uranium-rich clay/lignite horizon. In this horizon in-situ Eh-values in the range of −160 to −280 mV seem to be determined by the /HS− couple. Under these conditions U(IV) is expected to be the preferential redox state in solution. However, on-site measurements in groundwater from the clay/lignite horizon show only a fraction of about 20% occurring in the reduced state U(IV). Thermodynamic calculations reveal that the high CO2 partial pressure in the clay/lignite horizon can stabilise hexavalent uranium, which explains the occurrence of U(VI). The calculations also indicate that the low uranium concentrations in the range between 0.2 and 2.1μg/l are controlled by amorphous UO2 and/or the U(IV) phosphate mineral ningyoite. This confirms the findings from previous work that the uranium (IV) mineral phases are long-term stable under the reducing conditions in the clay/lignite horizon without any signatures for uranium mobilisation. It supports the current knowledge of the geological development of the site and is also another important indication for the long-term stability of the sedimentary system itself, namely of the reducing geochemical conditions in the near-surface (30m to 60 m deep) clay/lignite horizon. Further work with respect to the impact of changes in redox conditions on the uranium speciation is on the way.
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ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management
October 11–15, 2009
Liverpool, UK
Conference Sponsors:
- Nuclear Engineering Division and Environmental Engineering Division
ISBN:
978-0-7918-4408-3
PROCEEDINGS PAPER
Geochemical Behaviour of Uranium in Sedimentary Formations: Insights From a Natural Analogue Study
Ulrich Noseck,
Ulrich Noseck
Gesellschaft fu¨r Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig, Germany
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Vaclava Havlova,
Vaclava Havlova
Nuclear Research Institute Rˇezˇ plc, Rˇezˇ, Czech Republic
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Juhani Suksi,
Juhani Suksi
University Helsinki, Helsinki, Finland
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Thomas Brasser,
Thomas Brasser
Gesellschaft fu¨r Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig, Germany
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Radek Cervinka
Radek Cervinka
Nuclear Research Institute Rˇezˇ plc, Rˇezˇ, Czech Republic
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Ulrich Noseck
Gesellschaft fu¨r Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig, Germany
Vaclava Havlova
Nuclear Research Institute Rˇezˇ plc, Rˇezˇ, Czech Republic
Juhani Suksi
University Helsinki, Helsinki, Finland
Thomas Brasser
Gesellschaft fu¨r Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig, Germany
Radek Cervinka
Nuclear Research Institute Rˇezˇ plc, Rˇezˇ, Czech Republic
Paper No:
ICEM2009-16340, pp. 839-844; 6 pages
Published Online:
December 12, 2010
Citation
Noseck, U, Havlova, V, Suksi, J, Brasser, T, & Cervinka, R. "Geochemical Behaviour of Uranium in Sedimentary Formations: Insights From a Natural Analogue Study." Proceedings of the ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management. ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management, Volume 2. Liverpool, UK. October 11–15, 2009. pp. 839-844. ASME. https://doi.org/10.1115/ICEM2009-16340
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