Laboratory-based X-ray spectrometer for actinide science

Abstract

X-ray absorption and emission spectroscopies nowadays are advanced characterization methods for fundamental and applied actinide research. One of the advantages of these methods is to reveal slight changes in the structural and electronic properties of radionuclides. The experiments are generally carried out at synchrotrons. However, considerable progress has been made to construct laboratory-based X-ray spectrometers for X-ray absorption and emission spectroscopies. Laboratory spectrometers are reliable, effective and accessible alternatives to synchrotrons, especially for actinide research, which allow dispensing with high costs of the radioactive sample transport and synchrotron time. Moreover, data from laboratory spectrometers, obtained within a reasonable time, are comparable with synchrotron results. Thereby, laboratory spectrometers can complement synchrotrons or can be used for preliminary experiments to find perspective samples for synchrotron experiments with better resolution. Here, the construction and implementation of an X-ray spectrometer (LomonosovXAS) in Johann-geometry at a radiochemistry laboratory is reported. Examples are given of the application of LomonosovXAS to actinide systems relevant to the chemistry of f-elements, the physical chemistry of nuclear power engineering and the long-term disposal of spent nuclear fuel.

Keywords: X-ray absorption spectroscopy; X-ray emission spectroscopy; X-ray spectrometers; laboratory-based.

Figure 1

Schematic representation of the laboratory X-ray spectrometer for XES and XAS modes, as well as a photograph of the spectrometer in the XAS configuration. In the absorption mode the sample can be both on the detector and on the X-ray tube, while in XES mode the position of the sample remains fixed. SBCA: spherically bent crystal analyser.

Figure 2

CAD model of the X-ray spectrometer with X-ray tube, crystal-monochromator and detector.

Figure 3

(a) CAD model of the security module, in which the left-hand part of the figure shows the separated parts in the assembly, and the right-hand part is a sectional view of the introductory labyrinth type channel. (b) Helium chamber. (c) Simulations of X-ray beam transmission through the air and helium.

Figure 4

(a) Comparison of the Mn K-edge XANES spectra of Mn₂O₃ collected by the laboratory spectrometer (red) and synchrotron radiation (blue, measured on the STM beamline of the Kurchatov Scientific Center). (b) K-edge XANES on manganese oxides. (c) Oscillating parts and Fourier transforms of X-ray spectra of Mn₂O₃. (d) Fourier transforms of X-ray spectra of Mn₂O₃.

Figure 5

Comparison of the experimental XANES spectra of UO₂, ThO₂, NpO₂ ⁺ and PuO₂ ²⁺, recorded at the U L ₃-, Th L ₃-, Np L ₃- and Pu L ₃-edges, respectively, with help of the laboratory spectrometer (red) and at the synchrotron (blue).

Figure 6

Experimental U Lα₁, Th Lα₁, Pt Lα₁, Fe Kα₁ and Kα₂ data recorded on (a) UO₂, (b) ThO₂, (c) Pt-metal and (d) Fe-metal, respectively.