The Canadian Radiological Monitoring Network – Thermoluminescent Dosimetry (TLD)

This dataset contains the historical (prior to 2015) environmental dosimetry results. The current data can be found here: http://open.canada.ca/data/en/dataset/67bedee8-beb0-4b3a-a1c6-24a4cda08afe. The data after 2015 is provided in SI units of millisieverts (mSv) to be more in-line with current best practices. This dataset provides the thermoluminescent dosimetry (TLD) data from monitoring stations across Canada, obtained by Health Canada’s Canadian Radiological Monitoring Network (CRMN). More information about the CRMN network can be found here: http://www.hc-sc.gc.ca/ewh-semt/contaminants/radiation/crmn-rcsr/index-eng.php. The data contains both “monitoring” and “transit” TLDs. Transit TLDs are sent along with the monitoring TLDs to determine if there is a significant dose recorded by the TLD en route to the sampling station. The transit TLD is shipped out with a station monitor TLD, and shipped back with the station monitor from the previous quarter. Note that the monitor TLDs are deployed over a longer time (around three months) than the transit TLD (around 3 weeks); this largely explains the lower recorded dose values for the transit TLD. The results provided for the monitor and transit TLDs are expressed as air Kerma. Air Kerma (kinetic energy released per unit mass), represents the sum of the kinetic energies of all the particles liberated by ionizing radiation per unit mass of air. Hence, this data is given in units of joules per kilogram (J/Kg), which is equivalent to the Gray (Gy). It is important to note that, while natural background radiation fluctuates based on several factors including location, soil characteristics, and seasonal changes, the external dose can be attributed almost exclusively to natural radiation (of terrestrial and cosmic origin). This remained true even in the follow-up to the nuclear accident which occurred at the Fukushima-Daiichi nuclear power station on March 11, 2011. While some specific radionuclides associated with the accident could clearly be observed in our air particulate samples, the total dose was unaffected and remained within normal fluctuation.

Addendum: In the summer of 2015, during a review of its historical environmental radiation data, Health Canada identified a procedural error that resulted in values that were underreported by 34% on average for this particular dataset. The faulty procedure is no longer in place. This dataset contains the corrected and uncorrected TLD values along with, when available, results from optically stimulated luminescence (OSL) dosimeters that were sent to each station as part of an inter-comparison study. The accuracy of the dosimeters is estimated to be ± 15%. The corrected data confirms that environmental radiation levels were well within normal ranges.