Abstract
The ACT experimental station of the CAT-ACT wiggler beamline at the Karlsruhe Institute of Technology (KIT) Light Source is dedicated to the investigation of radionuclide materials with radioactivities up to 1000000 times the exemption limit by various speciation techniques applying monochromatic X-rays. In this article, the latest technological developments at the ACT station that enable high-resolution X-ray absorption near-edge structure (HR-XANES) spectroscopy for low radionuclide loading samples are highlighted - encompassing the investigation of actinide elements down to 1 p.p.m. concentration - combined with a cryogenic sample environment reducing beam-induced sample alterations. One important part of this development is a versatile gas tight plexiglass encasement ensuring that all beam paths in the five-analyzer-crystal Johann-type X-ray emission spectrometer run within He atmosphere. The setup enables the easy exchange between different experiments (conventional X-ray absorption fine structure, HR-XANES, high-energy or wide-angle X-ray scattering, tender to hard X-ray spectroscopy) and opens up the possibility for the investigation of environmental samples, such as specimens containing transuranium elements from contaminated land sites or samples from sorption and diffusion experiments to mimic the far field of a breached nuclear waste repository.
Highlights
Synchrotron radiation based speciation methods for radioactive samples are often limited to dedicated beamline endstations due to the strict safety and radiation protection regulations for handling radionuclide materials at light sources (Scheinost et al, 2021)
The ACT experimental station of the CAT-ACT wiggler beamline at the Karlsruhe Institute of Technology (KIT) Light Source is dedicated to the investigation of radionuclide materials with radioactivities up to 1 000 000 times the exemption limit by various speciation techniques applying monochromatic X-rays
The setup enables the easy exchange between different experiments and opens up the possibility for the investigation of environmental samples, such as specimens containing transuranium elements from contaminated land sites or samples from sorption and diffusion experiments to mimic the far field of a breached nuclear waste repository
Summary
Synchrotron radiation based speciation methods for radioactive samples are often limited to dedicated beamline endstations due to the strict safety and radiation protection regulations for handling radionuclide materials at light sources (Scheinost et al, 2021). At the MARS beamline of the SOLEIL synchrotron – belonging to the few dedicated synchrotron radiation stations for the investigation of nuclear materials including waste forms – an He-filled bag between the sample position, a single analyzer crystal with 1 m bending radius in Johann geometry and the detector can be used to reduce absorption in air With this setup, Pu M4-edge HR-XANES/RIXS experiments on plutonium carbonate samples (Pidchenko et al, 2020), PuO2 phases (Gerber et al, 2020) and uranium compounds were performed (Hunault et al, 2019). We present the technical developments at the ACT station towards enabeling those low An loading HR-XANES experiments while still having the flexibility for other experimental techniques such as conventional high-energy X-ray absorption fine structure (XAFS) in transmission or total fluorescence-yield detection mode and Laue-type high-energy or wide-angle X-ray scattering (HEXS/ WAXS) up to $55 keV photon energy As aforementioned, another important point is sample integrity upon irradiation conditions at highly brilliant synchrotron radiation sources. The challenge was to design and approve a system for double encapsulation featuring sufficiently X-ray transparent windows for spectroscopy in the tender X-ray region while – at the same time – withstanding thermal-isolation vacuum conditions
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