Trends, events and potential sources of Xe-detections in the German radioxenon network. (December 2022)

• Record Type: Journal Article
• Authors: Bollhöfer, A.; Brander, S.; Krais, R.; Schmid, S.; Walzer, V.; Ross, O.; Schlosser, C.
• Is Part Of: Journal of environmental radioactivity. Volume 255(2023)
• Publication Date: 2022-12
• Subjects: Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2022.106989
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: The measurement of radioxenons ( 133 Xe, 131m Xe, 133m Xe, 135 Xe) in the atmosphere is a keystone for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). At the German Federal Office for Radiation Protection (Bundesamt für Strahlenschutz, BfS) activity concentrations of radioactive noble gases at several sites in Germany have been measured for more than 5 decades, initially to monitor nuclear facilities and since the mid-1990s also to support the development of measurement and monitoring systems and procedures for verification of the CTBT. Average 133 Xe activity concentration in air measured daily at station RN33 of the International Monitoring System (IMS) of the CTBTO on Mt Schauinsland has decreased since 2008. Due to the decreasing radioxenon background in the atmosphere, laboratory measurements with less sensitive proportional counters developed in-house are increasingly replaced by an isotope specific β-γ laboratory system for radioxenon analyses. Six years of radioxenon activity concentrations measured with the β-γ laboratory system in weekly samples from monitoring sites in Germany are presented. Activity concentrations of 133 Xe in southern Germany are now typically below 1 mBq m −3 and have decreased by an order of magnitude in the past 25 years. Magnitude and variability of 133 Xe activity concentrations are generally larger in northern and western Germany compared to the south, most likely due to the prevailing wind directions in the region. Selected, but typical, periods of elevated radioxenon levels at the stations are investigated and the value of stack emission data is demonstrated. Highlights: 133 Xe activity concentration in air has decreased from about 2008. 133 Xe and its variability is smaller in southern Germany. Major emitter upwind of stations explains most but not all detections in network. Smaller emitters are responsible for elevations on a local scale. STAX data prove useful when investigating multi-source detections.