Natural and anthropogenic 236U in environmental samples

Peter Steier*, Max Bichler, L. Keith Fifield, Robin Golser, Walter Kutschera, Alfred Priller, Francesca Quinto, Stephan Richter, Michaela Srncik, Philippo Terrasi, Lukas Wacker, Anton Wallner, Gabriele Wallner, Klaus M. Wilcken, Eva Maria Wild

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    171 Citations (Scopus)

    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).

    Original languageEnglish
    Pages (from-to)2246-2250
    Number of pages5
    JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
    Volume266
    Issue number10
    DOIs
    Publication statusPublished - May 2008

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