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UP: Fachverband Umweltphysik
UP 7: Applied Noble Gas Physics Part 1
UP 7.1: Hauptvortrag
Donnerstag, 26. März 2015, 11:00–11:30, C/gHS
Development of a new facility for measuring 81Kr and 85Kr at ultratrace level in environmental samples. — •Bernard Lavielle1, Eric Gilabert1, Bertrand Thomas1, Romain Rebeix1, Grégory Canchel1, Christophe Moulin2, Sylvain Topin2, and Fabien Pointurier2 — 1CENBG, University of Bordeaux, BP 120, F-33175 Gradignan Cedex, France — 2CEA-DASE, F-91297 Arpajon, France
Mainly produced on Earth by nuclear reactions induced by cosmic rays in the atmosphere, the radionuclide 81Kr (t1/2=229,000yr) is considered as the best tracer for absolute dating of old groundwaters or ice cores in the range of 50,000 yr to 1,000,000 yr. Kryton-85 (t1/2=10.76yr) is mainly released into the atmosphere by the reprocessing facilities for nuclear fuel. This isotope is of great interest as a tracer for nuclear activities but also for dating young groundwater (<50 yr). Several instruments and lines are being developed at CENBG in order to measure both 81Kr and 85Kr in groundwater using small volume of water (20 l). It includes: 1) a line for gas extraction from water, Kr separation and purification; 2) A double-focusing mass spectrometer operating a 81Kr and 85Kr enrichment process based on implantation of separated Kr isotope in Al foils; 3) An instrument based on RIS-TOF technique capable to perform Kr isotopic abundance measurements from samples containing only a few thousands of atoms. The extremely high sensitivity of this instrument also allows measurements of cosmogenic Kr at very low concentration to determine cosmic ray exposure of small meteorite samples.