Nuclear substance safety

The Canadian Nuclear Safety Commission (CNSC) issues licences to organizations that plan to work with nuclear substances or in nuclear facilities; these licences require that the organizations comply with Canada’s nuclear laws and regulations – and can be revoked at any time that the organization does not.

To verify compliance, in 2012, the CNSC conducted some 2,500 inspections of organizations involved in four broad areas of activity:

  • medical – use of nuclear energy and nuclear substances for medical diagnostics and therapies, principally for heart diseases and cancer;
  • industrial – use of nuclear substances in fixed and portable gauges for activities such as civil engineering, industrial radiography, and oil-well logging;
  • academia and research – use of nuclear substances for biological and biomedical research, and with particle accelerators and research irradiators; and
  • commercial – production and sale of devices and equipment containing nuclear substances, such as smoke detectors, self-lighting exit signs, and security-screening equipment.

The CNSC evaluates licence compliance on five performance-measurement categories: radiation exposure, operating performance, radiation protection, sealed-source tracking, and reported events.

Radiation exposure

In 2012, CNSC sampled 590 licence holders, representing about 23,000 workers, to ensure that workers were not exposed to unsafe levels of radiation.

dosimeter

Dosimeter. Source: Cameco.

Of the 23,000 workers, some 10,300 qualified as nuclear energy workers: those who worked with nuclear substances or at a nuclear facility. These workers carry devices called “dosimeters” that measure the accumulated exposure of the worker to radiation over a set period (usually one year).

All but one of the workers received radiation doses well below the regulatory limit of 50 millisieverts (mSv) per year for nuclear energy workers. The one exception was a worker employed in the oil-well logging sector, who turned in a dosimeter reading of 75 mSv. Investigation revealed that the worker had accidently dropped the dosimeter on the floor near a sealed source of cesium-137 radiation, which may explain the abnormally high reading.

The remaining 10,300 workers who used nuclear substances also showed dose rates below the regulatory limit of 1 mSv/year for the public, with two exceptions. In the first case, at a radiation-therapy facility, the worker’s dosimeter recorded an effective dose of 2.17 mSv – more than twice the regulatory limit. Investigation revealed that the worker had never worked in or near a treatment room. A replacement dosimeter showed no subsequent high readings, raising the possibility that the dosimeter had not been stored properly. The second case involved a portable gauge, with the worker’s dosimeter recording an exposure of 1.16 mSv. An investigation concluded that the dosimeter had been stored near the portable gauge; the worker had not received the above-limit exposure.

Operating performance

The CNSC conducted 1,492 operating performance inspections in 2012. It found nearly 91% of licence holders in the medical sector had fully complied with safety laws and regulations, as did 88% of holders in the industrial sector and nearly 85% of holders in the commercial and academic and research sectors. The licence holders that did not fully comply with safety laws and regulations were required to take corrective measures, such as re-evaluating and revising their procedures, or retraining their workers.

Radiation protection

All licence holders are required to have a radiation-protection program that ensures that contamination levels and radiation doses received are monitored, controlled and maintained as low as reasonably possible.

Through 1,585 radiation-protection inspections carried out in 2012, the CNSC found that the medical, academic and research, and commercial sectors had continued to improve their performance. However, only 73% of inspections in the medical sector returned satisfactory results. As the CNSC notes, large institutions such as hospitals hold several licences; a single issue in a corporate radiation-protection program can become evident in several inspections and thus reduce the institution’s overall compliance score.

Sealed-source tracking

NDT pipeline inspection

Pipeline inspection by non-destructive testing, using industrial radiography equipment that contains a sealed source.

Licence-holders are required to maintain and manage“sealed sources”: to reduce exposure, certain nuclear substances must be contained in a sealed capsule or bonded to a cover in a way that shields the substance from contact with people and the environment. In 208 inspections conducted in 2012, the CNSC found 100% compliance by the medical, commercial, and academic and research sectors. The industrial sector achieved nearly 93% compliance. Non-compliant licence holders carried out corrective actions such as a complete verification of their sealed-source inventories.

The CNSC reports on its sealed-source tracking system on its website.

Reported events

The CNSC received 139 reports of events in 2012, including 52 malfunctioning or damaged devices, 31 spills or contaminations, 18 missing or found nuclear substances or radiation devices, 11 security breaches, and 27 issues related to packaging or transport. In all cases, no worker or member of the public received a radiation dose exceeding regulatory limits, and the environment received no adverse exposure.