Atmospheric radioxenon isotope monitoring in Beijing after the Fukushima nuclear power plant accident

A custom-made, on-site radioxenon sampling, separation and monitoring system was used to monitor atmospheric radioxenon concentrations in Beijing, released from the Fukushima Daiichi nuclear power plant after the earthquake of 11 March 2011. The results show that 133Xe concentrations ranged from 393 to 26 mBq/m3 from 12 to 27 April 2011, and those of 131mXe were 84 and 40 mBq/m3 on 13 and 15 April 2011, respectively. The highest dose rate caused by 133Xe was 2×10−5 mSv/yr, and the average 133Xe/131mXe ratio was 3.8±0.4.

► Two radioxenon isotopes, 133Xe and 131mXe, were detected by XESPM-II.
► The 133Xe/131mXe average ratio was 3.8±0.4, very different from that of nuclear testing.
► Atmospheric 133Xe activity concentrations in Beijing fell gradually in April 2011.
► The dose rate caused by 133Xe was estimated.