Atmospheric 85Kr and 133Xe activity concentrations at locations across Japan following the Fukushima Dai-ichi Nuclear Power Plant accident

Abstract

Atmospheric 85Kr and 133Xe activity concentrations were determined from weekly air samples collected at Sapporo, Akita and Chiba, Japan, throughout 2011. The results demonstrated that the Fukushima Dai-ichi Nuclear Power Plant accident in early March 2011 resulted in high 133Xe activity concentrations as well as elevated levels of 85Kr activity; there was a striking increase in the concentrations of both isotopes over the week running from 14 to 22 March as the radioactive plume released from the plant was captured. At Chiba, following the accident, the 85Kr activity concentration increased from 1.38 to 17.7 Bq/m3, while the 133Xe levels increased from below the minimum detectable concentration (MDC ≤ 1.9 × 10−3 Bq/m3) to 1.3 × 103 Bq/m3. Conversely, at Sapporo and Akita, high 85Kr activity concentrations were not observed, due to differences in air transportation mechanisms based on wind directions. Duplicate samples were collected at Chiba to allow the simultaneous analyses of 85Kr and 133Xe at the Japan Chemical Analysis Center and the Bundesamt für Strahlenschutz in Germany and the results were in good agreement. The external effective radiation doses resulting from 85Kr and 133Xe releases following the accident were estimated to be approximately 7.0 × 10−3 and 1.3 μSv, respectively, based on the activity concentrations of these nuclides from March to June in 2011 at Chiba.