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Microanalysis (Micro-XRF, Micro-XANES, and Micro-XRD) of a Tertiary Sediment Using Microfocused Synchrotron Radiation

Published online by Cambridge University Press:  09 May 2007

Melissa A. Denecke ,
Andrea Somogyi ,
Koen Janssens ,
Rolf Simon ,
Kathy Dardenne  and
Ulrich Noseck
Melissa A. Denecke
Affiliation:
Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, P.O. Box 3640, D-76021 Karlsruhe, Germany
Andrea Somogyi
Affiliation:
Synchrotron Soleil, Saint-Aubin—BP 48, F-91192 Gif-sur-Yvette, France
Koen Janssens
Affiliation:
Department of Chemistry, University of Antwerp, Universiteitsplan 1, B-2610 Antwerp, Belgium
Rolf Simon
Affiliation:
Synchrotron Soleil, Saint-Aubin—BP 48, F-91192 Gif-sur-Yvette, France
Kathy Dardenne
Affiliation:
Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, P.O. Box 3640, D-76021 Karlsruhe, Germany
Ulrich Noseck
Affiliation:
Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) mbH, Theodor-Heuss-Straße 4, D-38122 Braunschweig, Germany
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Abstract

Micro-focused synchrotron radiation techniques to investigate actinide elements in geological samples are becoming an increasingly used tool in nuclear waste disposal research. In this article, results using μ-focus techniques are presented from a bore core section of a U-rich tertiary sediment collected from Ruprechtov, Czech Republic, a natural analog to nuclear waste repository scenarios in deep geological formations. Different methods are applied to obtain various, complementary information. Elemental and element chemical state distributions are obtained from μ-XRF measurements, oxidation states of As determined from μ-XANES, and the crystalline structure of selected regions are studied by means of μ-XRD. We find that preparation of the thin section created an As oxidation state artifact; it apparently changed the As valence in some regions of the sample. Results support our previously proposed hypothesis of the mechanism for U-enrichment in the sediment. AsFeS coating on framboid Fe nodules in the sediment reduced mobile groundwater-dissolved U(VI) to less-soluble U(IV), thereby immobilizing the uranium in the sediment.

Keywords

micro-XANESmicro-XRFnatural analoguraniumarsenicmicrofocus
Type
SPECIAL SECTION: MICROANALYSIS OF MATERIALS TODAY
Information
Microscopy and Microanalysis , Volume 13 , Issue 3 , June 2007 , pp. 165 - 172
Copyright
© 2007 Microscopy Society of America

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References

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