0000000000138932
AUTHOR
Melissa A. Denecke
X-ray absorption spectroscopic study of trivalent and tetravalent actinides in solution at varying pH values
Abstract We perform X-ray absorption spectroscopy (XAS) investigations to monitor the stabilization of redox sensitive trivalent and tetravalent actinide ions in solution at acidic conditions in a pH range from 0 to 3 after treatment with holding reductants, hydroxylamine hydrochloride (NH2OHHCl) and Rongalite (sodium hydroxymethanesulfinate, CH3NaO3S). X-ray absorption near edge structure (XANES) measurements clearly demonstrate the stability of the actinide species for several hours under the given experimental conditions. Hence, structural parameters can be accurately derived by extended X-ray absorption fine structure (EXAFS) investigations. The coordination structure of oxygen atoms be…
The influence of natural trace element distribution on the mobility of radionuclides. The exemple of nickel in a clay-rock
International audience; The natural distribution of nickel (Ni) in the Callovian–Oxfordian clay-rich rock of Bure (France) was investigated, together with that of cobalt (Co), zinc (Zn) and lead (Pb). The most Ni-enriched phases are pyrite (∼400 × 10−6 g g−1 Ni), sphalerite (∼300 × 10−6 g g−1), chlorite (∼285 × 10−6 g g−1), organic matter (∼300 × 10−6 g g−1), muscovite (100–200 × 10−6 g g−1) and possibly carbonate minerals (mainly calcite and minor dolomite, ∼10 × 10−6 g g−1). Despite their high abundance (up to ∼80% in the upper part of the formation), carbonate minerals are quantitatively a minor Ni reservoir; most of the Ni is borne by chlorite and pyrite, which are minor mineral phases.…