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Several high-purity 233 U items from the repository had been rescued and identified for use in uranium isotopic analyses to support a broad variety of applications in nuclear safeguards, nonproliferation, and nuclear forensics. By preserving and maintaining the supply chain of 233 U materials of different pedigree for use as source materials for certified reference materials (CRMs) it is ensured that the safeguards community has the tools needed for high quality analytical measurements of uranium elemental and isotopic amount contents by mass spectrometry. One of the items identified as a source material for a high-purity CRM had been characterized for the uranium isotope-amount ratios using thermal ionization mass spectrometry (TIMS). Additional verification measurements on this material using quadrupole inductively coupled plasma mass spectrometry (ICPMS) had also been performed. The comparison of the ICPMS uranium isotope-amount ratios with the TIMS data, with much smaller uncertainties, provided validation of the mass spectrometric measurement practices using the ICPMS instrument. ICPMS is the measurement method proposed to be used for the initial screening of the purity of all items in the rescue campaign.

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This report is dedicated to the memory of Joel Chesser, who passed away before it was published. Joel was instrumental in helping lead the assembly of the system described herein, and his coauthors wish to recognize his achievements with this small gesture. He is missed very much by his friends and colleagues at Oak Ridge National Laboratory.

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