Natural and anthropogenic 236U in environmental samples
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Date
2008-05
Publication Type
Conference Paper
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yes
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Abstract
The interaction of thermal neutrons with 235U results in fission with a probability of ∼85% and in the formation of 236U (t1/2 = 2.3 × 107 yr) with a probability of ∼15%. While anthropogenic 236U is, therefore, present in spent nuclear fuel at levels of 236U/U up to 10−2, the expected natural ratios in the pre-anthropogenic environment range from 10−14 to 10−10. At VERA, systematic investigations suggest a detection limit below 236U/U = 5 × 10−12 for samples of 0.5 mg U, while chemistry blanks of ∼2 × 107 atoms 236U per sample limit the sensitivity for smaller samples. We have found natural isotopic ratios in uranium reagents separated before the onset of human nuclear activities, in uranium ores from various origins and in water from a subsurface well in Bad Gastein, Austria. Anthropogenic contamination was clearly visible in soil and rivulet samples from Salzburg, Austria, whereas river sediments from Garigliano river (Southern Italy) were close to the detection limit. Finally, our natural in-house standard Vienna-KkU was calibrated against a certified reference material (IRMM REIMEP-18 A).
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published
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Book title
Volume
266 (10)
Pages / Article No.
2246 - 2250
Publisher
Elsevier
Event
9th European Conference on Accelerators in Applied Research and Technology (ECAART9)
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Subject
Natural 236U; Uranium; AMS
Organisational unit
08619 - Labor für Ionenstrahlphysik (LIP) / Laboratory of Ion Beam Physics (LIP)