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
k.kvashnina@hzdr.de
Phone: +33 476 88 2367

Department of Synchrotron Science

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

Crystallographic transformation of UO2 to U4O9, U3O7, and U3O8

Lawrence Bright, E. S.; Harding, L. M.; Springell, R. S.; Lander, G. H.

Abstract

The oxidation of UO2 plays a critical role in the performance and long-term behaviour of nuclear fuel, yet the crystallographic nature of the intermediate uranium oxides and the mechanism of their formation remains poorly understood due to their complex structures and the lack of suitable single-crystal samples. In this work we investigate the oxidation of epitaxial [001] UO2 thin films using in-situ synchrotron X-ray diffraction, enabling direct observation of structural evolution throughout oxidation. We show that oxidation proceeds topotactically from UO2 to U4O9, U3O7, and U3O8, with the U4O9 and U3O7 phases forming as multi-domain single crystals. Comparison with calculated reciprocal space maps identifies the U4O9 structure as the β phase, while the U3O7 phase exhibits complex domain behaviour and additional superstructure reflections indicate a lower symmetry than that in present structural models. The final transformation to U3O8 is accompanied by a large volume expansion and pronounced loss of crystalline coherence, although a clear topotactic relationship between (001) UO2 and (130) U3O8 is retained. The identification of these topotactic relationships allow us to build a mechanistic understanding of the transformations between phases. These results provide insight into the structural mechanisms governing the oxidation and spallation of UO2 and establish a route to accessing single-crystal U4O9 and U3O7 via controlled oxidation.

Acta Materialia 319(2026), 122642
DOI: 10.1016/j.actamat.2026.122642

Permalink: https://www.hzdr.de/publications/Publ-44047

More publications

Team

Name	Bld./Office	+49 351 260	Email
Head
Prof. Dr. Kristina Kvashnina	ROBL/21.6.04	+33 476 88 2367	k.kvashnina@hzdr.de
Employees
Name	Bld./Office	+49 351 260	Email
Dr. Lucia Amidani	ROBL/14.1.04	+33 476 88 1982	l.amidanihzdr.de
Dr. Nils Baumann	ROBL/21.6.03	+33 476 88 2849	n.baumannhzdr.de
Jörg Exner	ROBL/BM20	+33 476 88 2372	j.exnerhzdr.de
Dr. Christoph Hennig	ROBL/21.6.02a	+33 476 88 2005	c.hennighzdr.de
Dr. Eleanor Sophia Lawrence Bright	ROBL/14.1.03	+33 476 88 2462	e.lawrence-brighthzdr.de
Dr. Damien Prieur	ROBL/21.6.03	+33 476 88 2463	d.prieurhzdr.de
Dr. André Roßberg	801/P316	2758	a.rossberghzdr.de
Dr. Sami Juhani Vasala	ROBL/14.1.01		s.vasalahzdr.de