High resolution isotopic analysis of U-bearing particles via fusion of SIMS and EDS images

• Published in: Journal of analytical atomic spectrometry 2016-01, Vol.31 (7), p.1472-1479
• Main Authors: Tarolli, Jay G., Naes, Benjamin E., Garcia, Benjamin J., Fischer, Ashley E., Willingham, David
• Format: Article
• Language: English
• Subjects: EDS; image fusion; SIMS; uranium
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/C6JA00149A

Image fusion of secondary ion mass spectrometry (SIMS) images and X-ray elemental maps from energy-dispersive spectroscopy (EDS) was performed to facilitate the isolation and re-analysis of isotopically unique U-bearing particles where the highest precision SIMS measurements are required. Image registration, image fusion and particle micromanipulation were performed on a subset of SIMS images obtained from a large area pre-screen of a particle distribution from a sample containing a mixture of several certified reference materials (CRM) U129A, U015, U150, U500 and U850, as well as a standard reference material (SRM) 8704 (Buffalo River Sediment) to simulate particles collected on swipes during routine inspections of declared uranium enrichment facilities by the International Atomic Energy Agency (IAEA). In total, fourteen particles, ranging in size from 5–15 μm, were isolated and re-analyzed by SIMS in multi-collector mode identifying nine particles of CRM U129A, one of U150, one of U500 and three of U850. These identifications were made based on the measured isotopic composition which was accurate to a few percent of the certified value and which proved to be consistent with the respective National Institute of Standards and Technology (NIST) certified atom percent values for 234 U, 235 U, 236 U and 238 U for the corresponding CRMs. This work represents the first use of image fusion for nuclear safeguards application, resulting in improved accuracy and precision of isotope ratio measurements for U-bearing particles. Implementation of image fusion is essential for the identification of particles of interest that fall below the spatial resolution of the SIMS images.