Measurement of 233U/234U ratios in contaminated groundwater using alpha spectrometry

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Date
2016-01-01
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Publisher
Elsevier
Abstract
The uranium isotope 233U is not usually observed in alpha spectra from environmental samples due to its low natural and fallout abundance. It may be present in samples from sites in the vicinity of nuclear operations such as reactors or fuel reprocessing facilities, radioactive waste disposal sites or sites affected by clandestine nuclear operations. On an alpha spectrum, the two most abundant alpha emissions of 233U (4.784 MeV, 13.2%; and 4.824 MeV, 84.3%) will overlap with the 234U doublet peak (4.722 MeV, 28.4%; and 4.775 MeV, 71.4%), if present, resulting in a combined 233+234U multiplet. A technique for quantifying both 233U and 234U from alpha spectra was investigated. A series of groundwater samples were measured both by accelerator mass spectrometry (AMS) to determine 233U/234U atom and activity ratios and by alpha spectrometry in order to establish a reliable 233U estimation technique using alpha spectra. The Genie™ 2000 Alpha Analysis and Interactive Peak Fitting (IPF) software packages were used and it was found that IPF with identification of three peaks (234U minor, combined 234U major and 233U minor, and 233U major) followed by interference correction on the combined peak and a weighted average activity calculation gave satisfactory agreement with the AMS data across the 233U/234U activity ratio range (0.1–20) and 233U activity range (2–300 mBq) investigated. Correlation between the AMS 233U and alpha spectrometry 233U was r2 = 0.996 (n = 10). © 2015, Elsevier Ltd.
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Keywords
Ground water, Alpha spectroscopy, Uranium, Accelerators, Mass spectroscopy, Emission
Citation
Harrison, J. J., Payne, T. E., Wilsher, K. L., Thiruvoth, S., Child, D. P., Johansen, M. P., & Hotchkis, M. A. C. (2016). Measurement of 233U/234U ratios in contaminated groundwater using alpha spectrometry. Paper presented at SPERA 2014, 1-5 September 2014, 13th South Pacific Environmental Radioactivity Association Conference Charles Darwin University, Darwin, Northern Territory, Australia. In Journal of Environmental Radioactivity, 151, Part 3, 537-541. doi:10.1016/j.jenvrad.2015.08.013