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5. Summary of 2011 ORSP

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

5.1  Overall Program Performance

  • The objectives of the Ontario Reactor Surveillance Program (ORSP) to establish, operate and maintain a radiological surveillance network to assess radionuclide concentrations in the regions around designated nuclear installations were achieved.
  • Surveillance samples were collected in a manner that is representative of what the public would be exposed to. Respirable air, potable water, milk and other foodstuff were sampled close to specified nuclear installations in Ontario and analysed for specific radionuclides.
  • The volume of data gathered in 2011 is consistent with that collected in previous years. A total of 1540 samples were collected and 3164 analyses reported for the ORSP. The results of these measurements were all well below the DSC's for the monitored radionuclides.
  • The measured concentrations of radionuclides monitored in the ORSP were well below the DSC that would result in a dose commitment of 0.1 mSv to the public from either inhalation or ingestion.
  • The results of the current year have been compared with the monitoring data of previous years to examine for notable trends or changes. A nine-year summary of results is presented in Appendix 3 which shows the median annual tritium concentration in drinking water, air and precipitation measured by the RPMS in the Bruce, Darlington and Pickering Surveillance Areas.
  • Moderate variations can be seen in the results from year to year; however, no extreme changes are observed in the concentration of tritium in these matrices. Graph A-1 shows a modest decrease in the tritium concentration in the Darlington regions while little change is noted in the other regions. As in previous years, Graphs A-2 and A-3 show tritium concentrations are higher in air and precipitation in the Pickering Surveillance Area when compared with the Bruce or Darlington Surveillance Areas. An explanation for this difference can be attributed to the positioning of a sampling station in close proximity to the Pickering Nuclear Generating Station. This sampling station is located downwind of Pickering Nuclear Generating Station and is close enough to detect a large proportion of the tritium that is vented from the plant.
  • The milk sampling program at farms in both the Bruce Surveillance Area and Pickering Surveillance Area by the Dairy Farmers of Ontario has been brought back to its original level with the addition of two new farms.
  • In summary, the purpose of the Ontario Reactor Surveillance Program has been met and the public in the vicinity of nuclear installations can be assured their health, safety, welfare and property are not adversely affected by emissions from the nuclear installations.

5.2  Summary of Dose Calculation

As discussed in section 3.4 the DSC's are set at levels which if received for one year would give a dose commitment of 0.1 mSv. Based on the findings of environmental monitoring conducted by the RPMS tritium (3H) has been found to be present in greater concentrations than other radionuclides being measured. The sample dose calculation, presented in Appendix 2, demonstrates the incremental dose to a hypothetically exposed adult member of the public from tritium is significantly less than 0.1 mSv. The value obtained in this calculation of 0.00026 mSv is approximately 400 times less than the annual dose commitment.

A further comparison can be made between the annual dose received from natural background and the estimated dose from the ingestion and inhalation of tritium. In Southern Ontario the annual dose from natural background is around 1.6 mSv.[R-9] In comparison the incremental dose from tritium is approximately 6,000 times smaller.

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ISSN 1929-2899