Natural and anthropogenic p>236 p>U in environmental samples
- 作者：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
- 关键词：Natural
- 刊名：Nuclear Instruments and Methods in Physics Research Section B ; Beam Interactions with Materials and Atoms
- 出版年：2008
- 期刊代码：42_0168583x
- 类别：ph
- 出版时间：May 2008
- 卷：266
- 期：10
- 页码：2246-2250
- 文件大小：167 K
摘要
The interaction of thermal neutrons with p>235 p>U results in fission with a probability of 
p://www.sciencedirect.com/scidirimg/entities/223c.gif" alt="not, vert, similar" title="not, vert, similar" border="0">85%and in the formation of p>236 p>U (t1/2 = 2.3 × 10p>7 p> yr) with a probability of p://www.sciencedirect.com/scidirimg/entities/223c.gif" alt="not, vert, similar" title="not, vert, similar" border="0">15%. While anthropogenic p>236 p>U is, therefore, present in spent nuclear fuel at levels of p>236 p>U/U up to 10p>−2 p>, the expected natural ratios in the pre-anthropogenic environment range from 10p>−14 p> to 10p>−10 p>. At VERA, systematic investigations suggest a detection limit below p>236 p>U/U = 5 × 10p>−12 p> for samples of 0.5 mg U, while chemistry blanks of p://www.sciencedirect.com/scidirimg/entities/223c.gif" alt="not, vert, similar" title="not, vert, similar" border="0">2 × 10p>7 p> atoms p>236 p>U 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).