Abstract
Secondary ion mass spectrometry (SIMS) is a promising tool to measure isotope ratios of individual uranium particles in environmental samples for nuclear safeguards. However, the analysis requires prior identification of a small number of uranium particles that coexist with a large number of other particles without uranium. In the present study, this identification was performed by scanning electron microscopy - energy dispersive X-ray analysis with automated particle search mode. The analytical results for an environmental sample taken at a nuclear facility indicated that the observation of backscattered electron images with × 1000 magnification was appropriate to efficiently identify uranium particles. Lower magnification (less than × 500) made it difficult to detect smaller particles of approximately 1 μm diameter. After identification, each particle was manipulated and transferred for subsequent isotope ratio analysis by SIMS. Consequently, the isotope ratios of individual uranium particles were successfully determined without any molecular ion interference. It was demonstrated that the proposed technique provides a powerful tool to measure individual particles not only for nuclear safeguards but also for environmental sciences.
Highlights
Secondary ion mass spectrometry (SIMS) is a promising technique to measure isotope ratios of individual uranium particles in environmental samples taken at nuclear facilities,[1,2,3] similar to thermal ionization mass spectrometry.[4,5,6] The isotope ratios provide valuable information on the sources of each particle, which are strongly related to nuclear activities in a nuclear facility
Uranium particles in the sample were identified by scanning electron microscope (SEM)-energy dispersive X-ray (EDX) with magnifications of ×250, ×500, ×750, ×1000, ×1300, and ×1600, and with increasing magnification, the analysis times increased, i.e., 6.4, 14.5, 31.5, 55.1, 92.8, and 137.1 h, respectively
The analysis times were strongly dependent on the number of uranium particles and other particles containing elements with relatively higher atomic numbers
Summary
Secondary ion mass spectrometry (SIMS) is a promising technique to measure isotope ratios of individual uranium particles in environmental samples taken at nuclear facilities,[1,2,3] similar to thermal ionization mass spectrometry.[4,5,6] The isotope ratios provide valuable information on the sources of each particle, which are strongly related to nuclear activities in a nuclear facility. Abstract : Secondary ion mass spectrometry (SIMS) is a promising tool to measure isotope ratios of individual uranium particles in environmental samples for nuclear safeguards. The analytical results for an environmental sample taken at a nuclear facility indicated that the observation of backscattered electron images with × 1000 magnification was appropriate to efficiently identify uranium particles.
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