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Description
The identification of uranium in samples does not have to rely solely on spectrometry of ionizing radiation produced within its radioactive decay. More effective methods could be based on the stimulated emission of characteristic X-ray radiation of uranium in a sample using a suitable radiation source. In X-ray fluorescence analysis (XRF) performed with benchtop devices, these sources could be miniature X-ray tubes with an accelerating voltage of about 50 kV and the X-ray spectrometry is done with silicon semiconductor detectors.
As part of the state control activities in the field of the nuclear forensics, swipe samples are analyzed with secondary-ion mass spectrometry (SIMS) method at the Research Center Řež in the Czech Republic. The procedure used so far included the extraction of particles from a swipe sample and their deposition onto a substrate, the identification of particles of interest among a huge amount of non-specific dust, and the isotopic analysis of a selected set of individual particles. To increase the efficiency of this analysis, samples can be analyzed before the extraction itself with a non-destructive method, such as XRF, to verify the presence of uranium and to determine the location of the particles of interest. The maps of elemental distributions provided with XRF are then used for selecting the locations for particle extraction from a swipe sample.
The paper describes the development of the XRF mapping technique which makes us possible to localize uranium in swipe samples with a lateral resolution of a couple of millimeters and a detection limit at a level of ng/mm2.