Moving Forward with Stronger Radiation Protection Programs
March 26, 2012
A little over two years ago, the CNSC received notice of an incident involving radiation contamination at an Ontario nuclear reactor being refurbished. Protecting workers being a priority, the Canadian Nuclear Safety Commission (CNSC) requested swift actions of the facility operator. Learning from these events, the CNSC and Canada’s nuclear power plant (NPP) operators have evolved and are now moving forward with enhanced regulatory oversight and radiation protection practices.
Bruce A restart project
Since the radiation contamination event took place,
the CNSC and Canada’s four nuclear power plant
operators have taken many steps to address the
hazards posed by alpha radiation contamination.
In November 2009, feeder work started in the reactor vault of Unit 1 at the Bruce A Nuclear Generating Station, as part of the refurbishment activities. A routine survey detected the presence of radioactive alpha contamination in the reactor vault. The contamination was attributed to the grinding of feeder tubes, and all work was stopped in order to decontaminate the area.
Following the alpha contamination event at Bruce A Unit 1, and given the potential exposure to alpha radiation of workers in the industry, the CNSC instructed all NPP operators to take immediate actions to protect workers, assess alpha hazards in their facilities, and enhance their radiation protection programs related to alpha monitoring and control.
In total, 557 workers were affected by the event. A careful assessment of the workers’ individual doses indicated that none of these exceeded regulatory limits. As shown in Figure 1, the majority of workers (554) accumulated less than 10% (< 5 mSv) of the annual allowable dose for nuclear energy workers. No health effects are expected for any of the workers involved.
Figure 1. Final dose results for the 557 workers affected by the alpha contamination event at the Bruce A Unit 1 in 2009
Of the 557 affected workers: 410 workers were assigned a dose of less than 1.0 mSv, 104 workers were assigned a dose between 1.0-2.0 mSv 40 workers were assigned a dose between 2.0-5.0 mSv, 3 workers were assigned a dose between 5.0-10 mSv, and 0 workers were assigned a dose greater than 10 mSv.
Drawing on best practices in radiation protection and experience gained from the event, the CNSC has ensured that each Canadian NPP operator has developed a long-term action plan to enhance their radiation protection programs related to alpha monitoring and control, so as to prevent a similar event from happening again. The action plans cover 17 specific areas, including workplace surveillance, work planning, dosimetry, signage, personal protective equipment and training.
Canada’s NPP operators have now made significant progress in implementing action plans. The CNSC has been monitoring their progress very closely, through regular inspections and reviews, to ensure that licensees incorporate adequate long-term measures, in a timely manner.
On March 28, 2012, the CNSC’s Commission Tribunal members will be updated on the final doses for all 557 workers affected by the Bruce A Unit 1 alpha contamination event, as well as the status of the long-term action plans undertaken by Canada’s NPP operators. Representatives from Bruce Power and CNSC radiation protection experts will attend the proceedings, to respond to Commission members’ questions.
About alpha radiation
Due to their size and charge, alpha particles are barely able to penetrate skin and can be stopped completely by a sheet of paper. Other types of radiation can penetrate more deeply, as shown in Figure 2. The main risk related to alpha radiation is internal exposure caused by inhalation or ingestion.
Text equivalent for Figure 2. Alpha radiation can be stopped by a piece of paper, whereas beta, gamma, X-ray and neutron radiation can penetrate more deeply.Related Commission Member Documents
- Alpha Radiation Contamination Update for CANDU Stations, December 8, 2010 – Request document by Email
- Alpha Event Closure – Contamination Event at the Bruce Nuclear Generating Station, March 28, 2012 – Request document by Email