Molybdenum isotope compositions of uranium ore concentrates by double spike MC-ICP-MS

Journal Article · 08 April 2019 · Applied Geochemistry

DOI: https://doi.org/10.1016/j.apgeochem.2019.03.001 · OSTI ID:1502043

Rolison, John M. ^[1]; Druce, Matthew ^[2]; Shollenberger, Quinn R. ^[3]; Kayzar-Boggs, Theresa M. ^[4]; Lindvall, Rachel E. ^[1]; Wimpenny, Josh ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division, Physical and Life Sciences Directorate
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division, Physical and Life Sciences Directorate; Univ. of Otago, Dunedin (New Zealand). Dept. of Chemistry and Centre for Trace Element Analysis
3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division, Physical and Life Sciences Directorate; Univ. of Munster, Munster (Germany). Inst. fur Planetologie
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division, Physical and Life Sciences Directorate; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

The molybdenum (Mo) isotope composition of uranium ore concentrate (UOC) has been proposed as a nuclear forensic signature due to the ubiquitous presence of Mo in the nuclear fuel cycle and to the possibility that different UOC production pathways lead to characteristic Mo isotope fractionation. Furthermore, Mo forms a volatile hexafluoride which leads to the retainment of Mo in the nuclear fuel cycle through U enrichment and reactor operation processes. As a result, it is possible that the nuclear fuel cycle generates a rich array of Mo isotope signatures. The first step in interpreting Mo isotope signatures generated during the nuclear fuel cycle is to characterize the Mo isotope composition of starting materials. In this study, a suite of UOC samples were analyzed for their Mo isotope composition in order to constrain the range of Mo isotope compositions entering the front end of the nuclear fuel cycle. Analytical protocols were developed to purify Mo from a U rich matrix prior to Mo isotope analysis by double spike MC-ICP-MS. A >3‰ variation in the ⁹⁸Mo/⁹⁵Mo ratio was observed in the suite of UOC samples with δ⁹⁸Mo ranging from -1.15 to +1.96‰ relative to the NIST 3134 Mo standard reference material. The δ98Mo range observed in the UOC samples is very similar to the δ⁹⁸Mo range observed in crustal igneous rocks and Mo-bearing minerals, suggesting that Mo isotope variability in UOC is driven by variability in the parent U ores. However, Mo isotope fractionation during UOC production is evident with one of the UOC samples being isotopically heavy relative to its parent U ore by 0.75‰, suggesting that different UOC production processes also contribute to the total Mo isotope variability observed. Overall, it is expected that the Mo isotope signatures generated during enrichment and reactor process will be clearly discernible from those generated during UOC production.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344; 18-ERD-016
• OSTI ID: 1502043
• Alternate ID(s): OSTI ID: 1636664
• Report Number(s): LLNL-JRNL-758218; 944136
• Journal Information: Applied Geochemistry, Vol. 103, Issue C; ISSN 0883-2927
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English