Protecting workers

An estimated 40,000 people work in Canada's nuclear industry. A great many more people work in jobs where they are exposed to radiation on a daily basis.

There are two ways in which Canada's workers are exposed to radiation. They either work with sources of man-made radiation (nuclear industry, health care, research institutions or manufacturing) or they are exposed to elevated levels of natural radiation (mining, air crews, construction).

The CNSC regulates the nuclear sector in Canada. Licensees and organizations applying for licences are subject to many rules and regulations that make nuclear energy and materials safe. As such, CNSC limits the amount of radiation that the people who work in Canada's nuclear industry can receive when they work in a job where they may be exposed to radiation. The CNSC also regulates the use of nuclear substances and nuclear devices for its licensees in all sectors, including health care.

Occupational exposure

The nuclear power, research, health care, manufacturing and defence sectors all use man-made radiation.

There are approximately 800,000 nuclear industry workers worldwide, and more than two million workers in health care that are exposed to radiation.

Some occupations also require protection from natural sources of radiation. Radon exposure poses a risk for miners and for people who work in facilities where radon levels are high. Cosmic rays are a concern for people in the airline industry who spend much of their time flying in planes.

2007 Canadian Occupational Dose by Facility Type. Average effective Dose (All Monitoring results) (millisieverts)for: Nuclear Power Pants. 0.9. Uranium Mines and Mills. 0.6. Uranium refineries. 0.4. Fuel Fabrication Facilities. 1.32. Research and radioisotope Production Facilities. 0.6. Tritium Light source production facilities. 0.15. Industry and Research. 0.57. Medicine. 0.1. Particle accelerators. 0.41.

*May include exposure from x-rays.

Source: National Dose Registry (Health Canada) - Based on most recently published data.

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Dose limits for workers

The Canadian Radiation Protection Regulations (SOR/2000-203) set limits on the amount of radiation the public and nuclear energy workers can receive.

According to the United Nations Scientific Committee on the Effects of Atomic radiation (UNSCEAR) the average effective dose received from all natural radiation (radon, cosmic rays, etc.) combined is approximately 2.4 mSv a year. The average effective dose from man-made radiation ranges based on the sources of exposure, but most of man-made radiation exposure is from medical procedures.

Radiation Dose Limitation Framework. Dose limit is unacceptable above ALARA Program. Acceptable dose limit below ALARA program.

The Linear No-Threshold model (LNT) is a risk model used internationally by most health agencies and nuclear regulators to set dose limits for workers and members of the public. This model plays a key role in how the CNSC approaches radiation protection. The LNT conservatively assumes there is a direct relationship between radiation exposure and cancer rates.

For people who operate or work with nuclear energy, the regulated dose limit is set just below the lower boundary of what is considered unacceptable exposure. For example, effective dose limits are 50 mSv per year and 100 mSv over 5 years. These limits protect against stochastic effects such as cancer. The equivalent dose limits for hands and feet (500 mSv/year), skin (500 mSv/year), and eyes (150 mSv/year) control deterministic effects, such as radiation burns or cataracts.

Typically, effects such as sterility can be seen with acute doses exceeding 1-2 sieverts. Effects such as cancer, on the other hand, are more difficult to attribute to a specific dose. They typically result from doses that are lower, but delivered over a longer period of time. However, studies to date have not been able to show any excess cancers or other diseases in people chronically exposed to radiation at doses lower than about 100 mSv.

The CNSC regulates what licensees must do should they become aware that a worker has received a dose exceeding the regulatory dose limits.

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Setting dose limits

In Canada, the CNSC sets the dose limits for workers and the public. This is done by following the recommendations of the International Commission on Radiological Protection, which comprises some of the world's leading scientists and other professionals in the field of radiation protection, and by using many of the standards and guides of the International Atomic Energy Agency.

Monitoring doses

Dosimetry is the act of measuring or estimating radiation doses and assigning those doses to individuals. The Radiation Protection Regulations require licensees to control doses to workers and to the public and to ascertain these doses. Licensees must use a licensed dosimetry service to measure doses when there is a reasonable probability that the effective annual dose to a nuclear energy worker (NEW) will exceed 5 millisieverts (mSv). Read more about dosimetry - INFO-0827: Introduction to Dosimetry (PDF).

The CNSC licenses dosimetry services in order to ensure accurate and precise dose measurements. Dosimetry service licensees are obligated to regularly file information with Health Canada's National Dose Registry (NDR).

The NDR, operated by Health Canada's Radiation Protection Bureau, includes radiation dose records from all commercial dosimetry processors, nuclear power generating facilities, Canadian Nuclear Laboratories Ltd., and uranium mines. The NDR also includes dose records from X-ray users such as dentists, radiologists, chiropractors as well as radon progeny exposures from some hard rock mines not licensed by the CNSC.

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Protective measures

Strict standards and regulations exist to ensure safety systems are in place to protect people inside facilities that use nuclear substances and devices. The CNSC also regulates the design of all nuclear facilities in Canada. The designs must be approved by the CNSC prior to construction to ensure dose limits and ALARA requirements are met.

Radiation protection is based on the basic principles of time (reduce the amount of time people are exposed), distance (increase the distance between the worker and the radiation source to reduce exposure), and shielding (use barriers such as lead or concrete between workers and the source of radiation) to protect people in the work place.

People who work with nuclear substances are also required to use protective equipment and to wear protective clothing as well as dosimeters to ensure they do not exceed dose limits. They may also be required to submit bioassay samples (i.e. urine samples) so that intakes of radionuclides can be estimated.

Dosimeters measure the amount of ionizing radiation people have been exposed to. Workers use this measurement to control the amount of exposure they receive and thus guard against the possibility of overexposure.

In addition, there are a number of redundant systems in place to limit accidents in nuclear facilities and to provide radiation protection to workers (e.g., built-in shielding and ventilation). These are known as “defence in depth”.

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Doses exceeding limits

The CNSC regulates what licensees must do should they become aware that a worker has received a dose exceeding the regulatory dose limits.

The regulations specify that licensees must:

  • Immediately notify the person and the CNSC of the dose;
  • Require the person to leave any work that is likely to add to the dose;
  • Conduct an investigation to determine the magnitude of the dose and to establish the causes of the exposure;
  • Identify and take any action required to prevent the occurrence of a similar incident; and,
  • Report to the CNSC the results of the investigation or the progress that has been made in conducting the investigation within 21 days after becoming aware that the dose limit has been exceeded.

CNSC staff investigate overexposures and verify that the above actions have been taken. If the exposure is above the limit or if the dose to the worker is not known, the CNSC will conduct its own investigation. CNSC staff will also verify that steps have been taken to prevent a similar occurrence and make sure that the final report adequately addresses the incident. At this point, the CNSC will authorize the worker's return to work.

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Related Information

CNSC Web Site

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