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4. Emergency Response

  • Issued: July 2013
  • Content last reviewed: April 2013

The events which followed the earthquake and tsunami in Japan on March 11, 2011, and subsequent emergency at the Fukushima reactor raised many questions as to whether any radioactivity could reach Ontario. While this was not considered an emergency event by EMO, the RPMS responded by increasing its sampling at a number of its air monitoring stations as well as collecting precipitation and surface water samples. Enhanced monitoring was also carried out at Toronto region Water Treatment Plants and milk that is part of the Ontario Reactor Surveillance Program to determine if any effect could be detected.

The air filters collected were analysed using high purity germanium detectors to determine concentration estimates for the gamma emitting nuclides: Iodine-131, Cesium-134, Cesium-137, Tellurium-132, and Xenon-133. Precipitation, milk and water samples were similarly analysed for the gamma emitting nuclides: Iodine-131, Cesium-134, Cesium-137, and Cobalt-60.

The measured concentrations of the radionuclides monitored during the Fukushima incident were extremely low when compared with the levels that would result in a dose commitment of 0.1 mSv to the public from either inhalation or ingestion. No measurable increase was observed in the levels of radioactivity in the majority of samples collected. Iodine-131, however, was detected at extremely low concentrations on some air filters. The values that were determined were far below the level recommended by the CNSC (0.2 Bq/cu. m) that would result in an annual dose of 0.1 mSv.

The results of the enhanced monitoring were meant to be a proactive measure and provide background data should a significant radioactive plume reach Ontario from Japan. As it turned out this incident did not have the immediate impact it was originally thought it would and for that we are very thankful. A total of 103 additional samples were collected which required 486 analyses.

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ISSN 1929-2899