Aerial measurement of radioxenon concentration off the west coast of Vancouver Island following the Fukushima reactor accident

In response to the Fukushima nuclear reactor accident, on March 20th, 2011, Natural Resources Canada conducted aerial radiation surveys over water just off the west coast of Vancouver Island. Dose–rate levels were found to be consistent with background radiation, however a clear signal due to 133Xe was observed. Methods to extract 133Xe count rates from the measured spectra, and to determine the corresponding 133Xe activity concentration, were developed. The measurements indicate that 133Xe concentrations on average lie in the range of 30–70 Bq/m3.

► Xe-133 from Fukushima was detected off the west cost of Vancouver Island.
► Natural background is subtracted from the signal.
► The signal is modelled using a simulation of an infinite uniform plume.
► The plume concentration varies strongly over a ∼15 km distance.
► Concentrations lie in the range of 30–70 Bq/m3.