Browsing by Author "Richter, S"
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- ItemNatural and anthropogenic 236U in environmental samples(Elsevier, 2008-03-06) Steier, P; Bichler, M; Fifield, LK; Golser, R; Kutschera, W; Priller, A; Quinto, F; Richter, S; Srncik, M; Terrasi, P; Wacker, L; Wallner, A; Wilcken, KM; Wild, EMThe 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). © 2008 Elsevier B.V.
- ItemThe provenance of Australian uranium ore concentrates by elemental and isotopic analysis(Elsevier, 2008-04) Keegan, EA; Richter, S; Kelly, I; Wong, HKY; Gadd, PS; Kuehn, H; Alonso-Munoz, AElemental and isotopic ratio analyses of U ore concentrate samples, from the 3 operating U mining facilities in Australia, were carried out to determine if significant variations exist between their products, thereby allowing the U ore concentrate's origin to be identified. Elemental analyses were conducted using inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF). Lead isotope ratios were measured using ICP-MS and U isotope analyses were conducted using thermal ionisation mass spectrometry (TIMS). Minute quantities of sample, such as that obtained from a swipe, were also examined for elemental concentrations using secondary ion mass spectrometry (SIMS). The results of multivariate statistical analysis show clear patterns in the trace elemental composition of the processed U ores, indicating that it is possible to use this feature as a unique identifier of an Australian U ore concentrate's source. Secondary ion mass spectrometry analyses also allow individual particles to be differentiated using this 'fingerprinting' technique. Isotope ratios determined using TIMS reveal that there is a significant difference in the n(U-234)/n(U-238) isotope ratio between the U ore concentrate from each mine. © 2007, Elsevier Ltd.