Freiburg 2024 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 9: Accelerator Mass Spectrometry IV
MS 9.5: Vortrag
Freitag, 15. März 2024, 12:15–12:30, HS 3042
Towards the half-life of 135Cs — •Alexander Wieser1,2, Johannes Lachner2, Serge Nagorny3, Martin Martschini1, Anton Wallner2, and Robin Golser1 — 1University of Vienna - Faculty of Physics, Isotope Physics — 2HZDR - Accelerator Mass Spectrometry and Isotope Research — 3Queen’s University Kingston - Engineering Physics and Astronomy
135Cs is a long-lived radionuclide which is produced both naturally via spontaneous fission of 238U and anthropogenically in neutron induced fission. The half-life of 135Cs is of special interest for geological repositories for high-level nuclear waste. The dose from the repository is dominated by 135Cs on a million year timescale, however the half-life is not very well known. Published values range from 0.7 Myr to 3.0 Myr. For determining the half-life we need both, an activity measurement and a mass-spectrometric determination of the number of 135Cs atoms in a sample, however, both measurements are challenging. 135Cs is a pure beta-emitter and has a low end-point energy of only 268 keV, making low-level beta-measurements difficult, mainly due to interferences from other short-lived cesium isotopes. For the mass spectrometric determination, Cs measurements suffer from isobaric interference from the highly abundant 135Ba. We present in this talk first results of accelerator mass spectrometry measurements of 135Cs in a Cs2ZrCl6-crystal which was previously analyzed at Laboratori Nazionali del Gran Sasso, where a 135Cs activity in the 100 mBq/kg-range was determined Belli et al. 2023, EPJ A.
Keywords: 135Cs; Half-life; beta spectrometry; ILIAMS; laser photodetachment