Contact

Porträt Prof. Dr. Kvashnina, Kristina; FWOS

Prof. Dr. Kristina Kvashnina

Head of the Synchrotron Science Department
Responsible for the BM20 (ROBL) beamline at ESRF

Phone: +33 476 88 2367

Department of Synchrotron Science

Molecular Structures

Research

The Department of Molecular Structures conducts synchrotron-based research, offering a robust toolkit for scientists investigating materials containing actinides and lanthanides.

Experiments take place at the Rossendorf Beamline of The European Synchrotron (ESRF), in Grenoble (France) which is specifically dedicated to the actinide science and research on radioactive waste disposal. The beamline consists of four experimental stations -XAFS, XES, XRD-1, XRD-2:

  • XAFS station with fluorescence and transmission detection for X-ray Absorption Fine-Structure (XAFS) spectroscopy, including (conventional) X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray absorption fine-structure (EXAFS) spectroscopies
  • XES with a 5-crystal Johann-type spectrometer for high-energy-resolution fluorescence-detection X-ray absorption near-edge spectroscopy (HERFD-XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) measurements.
  • XRD-1 station with a heavy-duty, Eulerian cradle, 6-circle goniometer for (high-resolution) powder X-ray diffraction (PXRD), surface-sensitive crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements
  • XRD-2 station with a Pilatus3 x2M detector stage for single crystal X-ray diffraction (SCXRD) and in situ/in-operando PXRD measurements.

Our research provides detailed insights into the structural and electronic properties of actinide and lanthanide-containing materials across various scientific disciplines, including physics, chemistry, environmental science, and geoscience. We study fundamental electron interactions, bonding properties, probing the local structures and oxidation states of complex systems. Data analysis is performed with the help of electronic structure calculations. 

EXAFS, HERFD-XANES, XES and RIXS is not restricted to crystalline solids, but can be applied to a wide range of samples, to derive information on e.g. aqueous speciation, complexation with dissolved inorganic ligands like chloride, sulfate or nitrate, complexation with organic ligands like acetate or humic acid, interaction with bacteria and plants, sorption to mineral and rock surfaces for actinides an other metals and metalloids. Due to the high penetration depth of the employed hard X-rays, the methods are suited to study chemical reactions in-situ/in-operando, for instance at very low or high temperatures, under special atmospheres, or under electrochemical potentials.

More about Rossendorf Beamline

Latest publication

Impact of metallic Mo nanoparticles on the dissolution kinetics of UO2 in nitric acid under representative PUREX process conditions

Husainy, M.; Szenknect, S.; Podor, R.; Le Goff, X.; Moisy, P.; Hennig, C.; Dacheux, N.

Abstract

This study is dedicated to the dissolution of UO2-based model compounds incorporating metallic Mo nanoparticles
in 4 mol.L-1 HNO3 at 353 K (representative for PUREX process conditions) following a dynamic protocol.
Compounds of structural and microstructural properties similar to spent nuclear fuel allowed us to
evidence the specific impact of Mo in the metallic form on the dissolution kinetics of UO2. The dissolution of a
pure metallic Mo reference sample under the same dissolution conditions was carried out to gain deeper insights
into the oxidation behavior of Mo in nitric acid and to evaluate its influence on the UO2 dissolution mechanism.
The evolution of the U, Mo, and nitrous acid concentrations in solution was measured and the solid residues of
dissolution were characterized. The results revealed a mutual inhibitory effect between UO2 and metallic Mo
during dissolution in nitric acid. No precipitates of mixed U and Mo were formed under the studied conditions.
The dissolution processes of UO2 and Mo were found to be interconnected and likely compete for the same autocatalytic
nitrogen species necessary for their oxidation and solubilization in the +VI oxidation state. The results
provided crucial insights into how metallic Mo reacts with nitric acid under the representative PUREX process
conditions. The findings suggested that metallic Mo(0) is initially completely oxidized to an amorphous brownred
phase with an oxidation state between +IV and +VI. Further oxidation, then solubilization of this phase as
Mo(VI) species appeared to be facilitated by the auto-catalytic nitrogen species.

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-41531

More publications

Team

Head

NameBld./Office+49 351 260Email
Prof. Dr. Kristina KvashninaROBL/21.6.04+33 476 88 2367

Employees

NameBld./Office+49 351 260Email
Dr. Lucia AmidaniROBL/14.1.04+33 476 88 1982
Dr. Nils BaumannROBL/21.6.03+33 476 88 2849
Clara Lisa E SilvaROBL/14.1.04+33 476 88 2044
Jörg ExnerROBL/BM20+33 476 88 2372
Dr. Christoph HennigROBL/21.6.02a+33 476 88 2005
Dr. Eleanor Sophia Lawrence Bright+33 476 88 2462
Dr. Damien PrieurROBL/21.6.03+33 476 88 2463
Dr. André Roßberg801/P3162758
Anne Thielena.thielenAthzdr.de
Dr. Sami Juhani Vasalas.vasalaAthzdr.de