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

TL;DR

This study reports on the detection and measurement of airborne fission products from the Fukushima nuclear incident in Seattle, over a 23-day period, providing data on the arrival times and activity levels of radioactive isotopes.

Contribution

It provides the first measurements of specific airborne fission products from Fukushima in Seattle, detailing their temporal evolution and activity levels after the incident.

Findings

Detected 131-I, 132-I, 132-Te, 134-Cs, and 137-Cs in Seattle air.

Maximum activity of 4.4 mBq/m^3 for 131-I observed.

Activities declined below detection limits after 23 days.

Abstract

We report results of air monitoring started due to the recent natural catastrophe on 11 March 2011 in Japan and the severe ensuing damage to the Fukushima Dai-ichi nuclear reactor complex. On 17-18 March 2011, we registered the 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 characteristic gamma rays using a germanium detector. We measured the evolution of the activities over a period of 23 days at the end of which the activities had mostly fallen below our detection limit. The highest detected activity amounted to 4.4 +/- 1.3 mBq/m^3 of 131-I on 19-20 March.