Speaker
Gabriele Wallner
(University of Vienna)
Description
Determination of the isotopic ratio 236U/238U in environmental samples
M. Srncik1, P.Steier2, R. Eigl1, G. Wallner1
1 Department of Inorganic Chemistry, University of Vienna, Währingerstr. 42,
A-1090 Vienna, Austria
2 Faculty of Physics – Isotope Research, University of Vienna, Währingerstr. 17,
A-1090 Vienna, Austria
236U with a half-life of 2.3∙107 years is produced via thermal neutron capture on 235U. Natural production results from different neutron sources like from (α,n) reactions on lighter nuclides, spontaneous fission of 238U, induced fission of 235U and at the Earth surface from the cosmic rays. Only small amounts are produced naturally from uranium in ores, soils and rocks but a huge amount is produced in nuclear power plants. Naturally 236U occurs in ultra trace concentration in the environment, therefore it is a big challenge to determine a natural isotopic ratio of 236U/238U in environmental samples which is expected to be in the order of
10-14 to 10-13. For the analysis of this isotopic ratio, water samples from rivers and creeks were collected in the alpine region of Austria, from the Danube, the Black Sea and the Atlantic. From surrounding areas also soil samples were investigated.
After a pre-concentration and an anion exchange step the uranium fraction was
co-precipitated with NdF3 and thin sources were prepared for α-spectrometry to determine the activity ratio of 234U/238U and the chemical yield. Afterwards these filters were reprocessed for the analysis of the isotopic ratio 236U/238U by AMS (Accelerator Mass Spectrometry). The special aim was the characterization of the 236U/238U ratio in natural waters and soils, and to investigate the contribution from anthropogenic sources.
Authors
Gabriele Wallner
(University of Vienna)
Michaela Srncik
(University of Vienna)
Co-authors
Peter Steier
(University of Vienna)
Rosmarie Eigl
(University of Vienna)
