Analysis of trace neptunium in the vicinity of underground nuclear tests at the Nevada National Security Site

Journal Article · Sat Nov 01 00:00:00 EDT 2014 · Journal of Environmental Radioactivity

DOI:https://doi.org/10.1016/j.jenvrad.2014.07.011· OSTI ID:1197796

Zhao, P.; Tinnacher, R. M.; Zavarin, M.; Kersting, A. B.

A high sensitivity analytical method for ²³⁷Np analysis was developed and applied to groundwater samples from the Nevada National Security Site (NNSS) using short-lived ²³⁹Np as a yield tracer and HR magnetic sector ICP-MS. The ²³⁷Np concentrations in the vicinity of the Almendro, Cambric, Dalhart, Cheshire, and Chancellor underground nuclear test locations range from <4 × 10^-4 to 2.6 mBq/L (6 × 10^-17–4.2 × 10^-13 mol/L). All measured ²³⁷Np concentrations are well below the drinking water maximum contaminant level for alpha emitters identified by the U.S. EPA (560 mBq/L). Nevertheless, ²³⁷Np remains an important indicator for radionuclide transport rates at the NNSS. Retardation factor ratios were used to compare the mobility of ²³⁷Np to that of other radionuclides. The results suggest that ²³⁷Np is less mobile than tritium and other non-sorbing radionuclides (¹⁴C, ³⁶Cl, ⁹⁹Tc and ¹²⁹I) as expected. Surprisingly, ²³⁷Np and plutonium (^239,240Pu) retardation factors are very similar. It is possible that Np(IV) exists under mildly reducing groundwater conditions and exhibits a retardation behavior that is comparable to Pu(IV). Independent of the underlying process, ²³⁷Np is migrating downgradient from NNSS underground nuclear tests at very low but measureable concentrations.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1197796
• Alternate ID(s): OSTI ID: 1201503
• Journal Information: Journal of Environmental Radioactivity, Journal Name: Journal of Environmental Radioactivity Vol. 137 Journal Issue: C; ISSN 0265-931X
• Publisher: Elsevier
• Country of Publication: United Kingdom
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ultra-low level
Neptunium analysis
environment
Nevada National Security Site
retardation