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