Radon in the Air:Why Dilution may not always be a Solution

Winnie Cheng, Regional Radiation SpecialistAARST 2014 International Radon SymposiumCharleston, South CarolinaSeptember 30, 2014

Radon in the Air: Outline

• The Canadian Regulations & Guidelines; Occupational & Environmental Exposure

• Case Study

• Lessons Learned

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• Nuclear Safety & Control Act (Canadian Nuclear Safety Commission):

•Nuclear facilities and materials

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Occupational Exposure: Regulations

• Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM): Uranium Thorium Potassium Any of their radioactive decay products, such as radium

and radon)• Jurisdiction over the use and radiation exposure to NORM

rests with each Canadian province and territory

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Occupational Exposure: Guidelines

• 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

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Occupational Exposure: Guidelines

• Canada Labor Code General workplaces of federal building

should not be >800 Bq/m3 (21.6 pCi/L)—is currently under review

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Workplace Environmental Exposure

Occupational ExposureIonizing Radiation

Environmental (Workplace) Exposure

Radon

Canadian Regulations & Guidelines

Federal Law: Nuclear Safety & Control Act• Nuclear mines

Federal Law: Canada Labour Code (Workplace): • Radon: 800 Bq/m3 (21.6

pCi/L)

• HC NORM Guidelines (Occupational)

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• HC Radon Guideline (Workplace): 200 Bq/m3 (5.4 pCi/L)

Federal GuidelinesFederal Guidelines

“Radon in the Air?”

Radon in the Air: Non-residential Building

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Case StudyRn

Radon in the Air: Non-residential BuildingFeatures

• Slab on grade• >1,000 m2

• Numerous “rooms + open spaces”

Radon

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In some rooms >200 Bq/m3 (>5.4 pCi/L)With one room >5,000 Bq/m3 (137 pCi/L)

Radon in the Air: Mitigation Actions

• 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:• Achieved positive indoor pressure• Further sealing of perimeter walls

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Radon in the Air: Considerations

• Dilution is the solution via ventilation does not apply where• There are multiple sources of entry• Radon level is very high

• Key:• Achieving 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

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Risk Management: NORM Program

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Average Annual Concentration a

NORM Program Classification

800 – 3,000 Bq/m³ Radiation Protection Management

200 - 800 Bq/m³ NORM Management

Background - 200 Bq/m³ Unrestricted

Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM)

Risk Management: NORM Program

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NORM Management200 - 800 Bq/m³ (5.7-21.6 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

Radon Risk Communication

• 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.

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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.

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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/m3.

• Precautionary principle: To reduce radon below 200 Bq/m3 or to as low as reasonably achievable (ALARA).

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THANK YOU

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