Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA

摘要

We report results of air monitoring started due to the recent naturalcatastrophe on 11 March 2011 in Japan and the severe ensuing damage to theFukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registeredthe first arrival of the airborne fission products 131-I, 132-I, 132-Te,134-Cs, and 137-Cs in Seattle, WA, USA, by identifying their characteristicgamma rays using a germanium detector. We measured the evolution of theactivities over a period of 23 days at the end of which the activities hadmostly fallen below our detection limit. The highest detected activity amountedto 4.4 +/- 1.3 mBq/m^3 of 131-I on 19-20 March.