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|Title:||Development of Uranium Reference Particles for Nuclear Safeguards and Non-proliferation Control|
|Publisher:||University of Antwerpen|
|Abstract:||In the oversight of the nuclear Non-Proliferation Treaty and as part of the Additional Protocol of the International Atomic Energy Agency, environmental sampling has become an important tool for the detection of non-declared nuclear activities. One extensively developed technique in environmental sampling (ES) makes use of pieces of cotton cloth called swipes to wipe surfaces in and around a nuclear facility. The dust collected on these swipes typically contains micrometer-sized uranium particles with an isotopic composition characteristic for the processes at the inspected facility. Since its implementation in the 1990s, ES has proven to be a very effective tool in the detection of clandestine activities owing to a number of highly sensitive and selective techniques, including secondary ion mass spectrometry and thermal ionisation mass spectrometry. However, considering the potential consequences of the ana lyses, these measurements need to be subjected to a rigorous quality management system. In a continuous effort to improve the accuracy and detection efficiency of the uranium isotope ratio measurements, uranium particle reference materials are being developed by different research groups. It was concluded however, that the existing methods for the production of particulate reference materials generally do not reproduce the particles recovered from swipe samples. For this reason, we developed the aerosol deposition chamber at the Institute for Reference Materials and Measurements for the production of reference uranium particles that are representative of the particles collected at enrichment facilities. This method is based on the controlled hydrolysis of milligram amounts of uranium hexafluoride with a certified uranium isotopic composition. After optimization of the experimental set-up, the particles produced by the aerosol deposition chamber were characterized by scanning electron microscopy, transmission electron microscopy, mu-Raman spectroscopy and secondary ion mass spectrometry. The particle morphology and composition were found to be dependent on the relative humidity of the air, the exposure to ultraviolet light and the time elapsed after formation. Possible correlations between the relative amount of fluorine and the age of the particles were investigated. These results were the starting point for the first inter-laboratory measurement evaluation programme (NUSIMEP) on uranium particles.|
|JRC Institute:||Institute for Reference Materials and Measurements|
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