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Why Dilution may not always be a Solution Winnie Cheng, Regional Radiation Specialist AARST 2014 International Radon Symposium Charleston, South Carolina.

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Presentation on theme: "Why Dilution may not always be a Solution Winnie Cheng, Regional Radiation Specialist AARST 2014 International Radon Symposium Charleston, South Carolina."— Presentation transcript:

1 Why Dilution may not always be a Solution Winnie Cheng, Regional Radiation Specialist AARST 2014 International Radon Symposium Charleston, South Carolina September 30, 2014

2 The Canadian Regulations & Guidelines; Occupational & Environmental Exposure Case Study Lessons Learned 2

3 Nuclear Safety & Control Act (Canadian Nuclear Safety Commission): Nuclear facilities and materials 3 Occupational Exposure: Regulations

4 4 Occupational Exposure: Guidelines

5 NORM Industries: mineral extraction and processing oil and gas production metal recycling forest products and thermal-electric production tunnelling and underground workings water treatment facilities 5 Occupational Exposure: Guidelines

6 Canada Labor Code  General workplaces of federal building should not be >800 Bq/m 3 (21.6 pCi/L)—is currently under review 6 Workplace Environmental Exposure

7 Occupational Exposure Ionizing Radiation Canadian Regulations & Guidelines Federal Law: Nuclear Safety & Control Act Nuclear mines HC NORM Guidelines (Occupational) 7 Federal Guidelines

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9 Slab on grade >1,000 m 2 Numerous “rooms + open spaces” 9 In some rooms >200 Bq/m 3 (>5.4 pCi/L) With one room >5,000 Bq/m 3 (137 pCi/L)

10 Stage 1 : Sealed pipe penetrations, and cracks on floors and walls Set dampers to increase the outdoor air ventilation Installed a new HVAC system to improve the overall ventilation Stage 2 : HVAC adjustments: 24/7 Stage 3 : positive indoor pressureAchieved positive indoor pressure Further sealing of perimeter walls 10

11 Dilution is the solution via ventilation does not apply where There are multiple sources of entry Radon level is very high Key: positive indoor pressureAchieving positive indoor pressure Having all occupied rooms tested at once Testing enclosed areas that are outside of the HVAC system may help identify various entry points and the need of other mitigation actions 11

12 Risk Management: NORM Program 12 Average Annual Concentration a NORM Program Classification 800 – 3,000 Bq/m³Radiation Protection Management Bq/m³NORM Management Background Bq/m³Unrestricted Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM)

13 Risk Management: NORM Program 13 NORM Management Bq/m³ ( pCi/L) 1.Introduction of public and incidentally exposed worker access controls 2.Changes in work practices 3.Reducing the radon concentration levels to below 200 Bq/m³

14 Employers should have their workplaces tested in order to ensure that workers are not exposed to high levels of radon, and to conform to guidelines set out by the appropriate jurisdictions. In radon prone areas, employees could also be receiving significant exposure at home. Staff who live in radon prone areas are encouraged to test their homes. The need for protection against radon both at home and at work. 14

15 Lessons Learned “Dilution is the solution” – may not be applicable in reducing high levels of radon or when there are multiple entry routes. Adjustment of the HVAC system should be considered along with achieving a positive indoor pressure to effectively reduce the radon levels. Check rooms that are outside of the HVAC system; may need to consider a separate radon reduction system such as an Active Sub-slab Depressurization Unit. 15

16 Conclusion Where applicable, employers should consider the NORM Guidelines for radon risk management and protection of workers while mitigation is underway. Once remedial work is completed, a long term post- remediation measurement must be carried out in the building to ensure that radon concentrations are below 200 Bq/m 3. Precautionary principle: To reduce radon below 200 Bq/m 3 or to as low as reasonably achievable (ALARA). 16

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