A critique of Canadian regulatory documents for tritium emissions from NPPs
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Frank R. Greening
Abstract
The calculation of a set of Derived Release Limits or DRLs for radioactive species released to effluent streams from nuclear facilities in Canada is a licensing requirement imposed by the Canadian Nuclear Safety Commission (CNSC) to ensure that radiation doses to the public are kept below 1 mSv/year. All DRLs currently accepted by the CNSC for radionuclides in gaseous and waterborne effluent streams are calculated using computer codes that assume essentially constant emission rates and idealized dispersion conditions averaged over 1 year. This approach leads to unrealistic release limits that actually permit the release of a station’s entire inventory of tritium and therefore impose no meaningful restrictions on plant operations. In May 2024, through REGDOC-2.9.2, the CNSC proposed an alternative approach to setting radionuclide emission limits based on a facility’s Maximum Predicted Design Release Concentrations or MPDRCs that depend on a facility’s design and historical operational performance. Unfortunately, at the present time, the CNSC is yet to provide specific examples of how REGDOC-2.9.2 is to be implemented. Nevertheless, in this report a preferred approach is presented using previously reported Maximum Probable Emission Rates or MPERs, which takes into account the significant contribution to annual doses from non-routine spike emissions and leads to a more stringent, yet realistic and readily achievable, airborne tritium release limit of 2.5 × 1015 Bq/yr.
Acknowledgments
I am sole author with no acknowledgements.
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Research ethics: I believe I have been ethical in writing my submission.
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Informed consent: Not applicable.
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Author contributions: Sole author.
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Use of Large Language Models, AI and Machine Learning Tools: AI has not been used.
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Conflict of interest: No conflicts of interest.
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Research funding: No funding.
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Data availability: All data are available on request.
References
Bruce Nuclear Generating Station B (2011). 2011 Safety Report. Report No: NK29-SR-01320-00002.Search in Google Scholar
Bruce Power (2013). Weekly per Stack Tritium Emissions Data 2003 – 2013. Bruce Power Internal Reports.Search in Google Scholar
Chouhan, S.L., Davis, P.A. (2001). Testing the Atmospheric Dispersion Model of CSA N288.1 with Site-Specific Data. AECL Report AECL-12099, January 2001.Search in Google Scholar
CNSC (2012). Radioactive Release Data from Canadian Nuclear Power Plants 2001 – 10. CNSC INFO-0210/Rev.14, January 2012, Canadian Nuclear Safety Commission.Search in Google Scholar
CNSC (2020). Process for Establishing Release Limits and Action Levels at Nuclear Facilities. DIS-12-02CNSC, Canadian Nuclear Safety Commission Discussion Paper for Public Consultation.Search in Google Scholar
CNSC (2024). Environmental Protection: Controlling Releases to the Environment. REGDOC-2.9.2, Canadian Nuclear Safety Commission.Search in Google Scholar
COG-06-3090-R2-1.IAEA (2018). Regulatory Control of Radioactive Discharges to the Environment. IAEA Safety Standard Series No. GSG-9, International Atomic Energy Agency, Vienna.Search in Google Scholar
CSA (2020). Guidelines for modelling radionuclide environmental transport, fate, and exposure associated with the normal operation of nuclear facilities. CSA Standard N288.1:20, Canadian Standards Association.Search in Google Scholar
Greening, F.R. (2013).Maximum Probable Emission Rate Calculations for Bruce A, Bruce B, and CMLF. Bruce Power report B-REP-03480-00005 REV 001.Search in Google Scholar
Hart, D. (2008). Derived Release Limits Guidance. CANDU Owners Group Report.Search in Google Scholar
Leblanc, K. (2025). CNSC Staff, private email communication, March 4, 2025.Search in Google Scholar
McNeil, S. (2004). Updated Site-Specific Atmospheric Dilution Factors for use in Safety Analysis. Bruce Power report B-REP-03611-00001-R01.Search in Google Scholar
UK NDAWG (2011). Short-term Releases to the Atmosphere. NDAWG Guidance Note NDAWG/2/2011, UK National Dose Assessment Working Group report.Search in Google Scholar
Wong, K.Y., Khan, T.A., and Guglielmi, F. (1984). Canadian Tritium Experience. CFFTP Report, Ontario Hydro, 1984.Search in Google Scholar
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