Analysis of radioxenon and Krypton-85 at the BfS noble gas laboratory

Proportional counters and a β-γ coincidence system and their performance characteristics are described, with emphasis on internal and external quality controls. Typical limits of detection (LD) are 8mBqm−3 for 85Kr and 4mBqm−3 for 133Xe for the proportional counters, while for similar xenon volumes the LD for 133Xe in the β-γ system is approximately 4 times lower. Results of comparative analyses agree above the limit of quantification. Xenon-133 levels in southern Germany are presently at or below the LD of the proportional counters, but above the LD of the β-γ system, which is now routinely used for analysis of environmental samples. •Description of proportional counters and β-γ coincidence system for noble gases.•Above the LQ the two systems agree well.•Decreasing Xe-133 and increasing Kr-85 levels in air at Freiburg, Germany.•The low MDC of the β-γ system is required for measurement of Xe-133.