Canadian Occupational Safety (COS) magazine is the premier workplace health and safety publication in Canada. We cover a wide range of topics ranging from office to heavy industry, and from general safety management to specific workplace hazards.
Issue link: https://digital.thesafetymag.com/i/353330
April 2014 19 Extensive training, monitoring help shield Bruce Power workers from dangerous radioactive particles I n late 2009, Bruce Power was in the process of refurbishing two dor- mant nuclear reactors at its power plant in Tiverton, Ont., three hours north of Toronto. The Unit 2 refur- bishment went off without a hitch, but when it came time to complete Unit 1, contractors were unknow- ingly exposed to radiation. When the workers were cutting and grinding feeder pipes, a radioactive particulate from their work was being released into the air. While the workers were being moni- tored for beta radiation, they were not being monitored for the more dan- gerous alpha radiation because "all calculations would have told you there wouldn't be an expectation of alpha in the area," says Duncan Hawthorne, president and CEO of Bruce Power. While the ratio of beta to alpha is typically 10,000 to one, in this case, the ratio was seven to one. A total of 557 workers were poten- tially exposed to the alpha radiation. Bruce Power underwent an exhaustive campaign of testing these workers. It found less than 10 workers received radiation doses greater than fi ve mil- lisieverts (mSv) and all had doses less than 10 mSv. The regulatory limit set by the Canadian Nuclear Safety Com- mission (CNSC) is 50 mSv per year for a nuclear energy worker. At the time of the incident, Bruce Power offered a helpline for con- fi dential assistance to workers and their families trough the Radiation Safety Institute of Canada, and it subsequently implemented a compre- hensive routine program to monitor workers for alpha radiation using spe- cialized instrumentation. "We changed the rules to assume alpha would be there rather than assume it wouldn't be there," says Hawthorne. "We wanted to get back to the principle of as low as reasonably achievable." This incident is a reminder that nuclear power plant operators need to be constantly aware of the poten- tial for radiation exposure and put all appropriate measures in place to pro- tect their workers. Radiation is of particular concern because it has been linked to certain types of cancer. Also, at extremely high doses, radiation exposure can cause biological effects, skin redden- ing, nausea, vomiting, cataracts and even death. PROTECTION PROGRAM The government of Canada's Radia- tion Protection Regulations stipulate all nuclear power plant operators must implement a radiation protection program. One of the fi rst steps is to undergo a risk assessment process for all job types to determine which ones are most at risk for radiation exposure. About 70 per cent of employees at Bruce Power are classifi ed Nuclear Energy Workers (NEWs) who regularly face a greater risk of radiation exposure. Also, operations and maintenance per- sonnel often work with equipment that either contains radioactive material or has been contaminated with radioac- tive materials, says Steve Mahoney, president of the Radiation Safety Insti- tute of Canada in Toronto. But a large number of the 4,200 workers at Bruce Power do not face radiation risks, including human resources, engineer- ing and clerical staff. Once the risks are identifi ed, the radiation protection program should outline the hazards, protection — from PPE to training — controls and work permits. For example, one common hazard in nuclear reactors is tritium. It's a radioactive isotope of hydrogen that can be absorbed into the skin or inhaled. Workers at Bruce Power are given an instrument to measure for tritium as well as an air supply suit to protect themselves. They also need a permit to work with the substance, says Frank Saunders, vice-president of nuclear oversight and regulatory affairs at Bruce Power. When it comes to radiation expo- sure, Bruce Power follows the basic principle of as low as reasonably achievable (ALARA), says Hawthorne, and the tenets of achieving that are time, distance and shielding. "We need to plan, train, rehearse in such a way to minimize the time employees spend in an area where there may be a radiation fi eld," he says. For example, when workers need to access high-risk areas for maintenance or to conduct a specifi c job, they are given a special radiation meter with an alarm. It is preset, so once the radia- tion levels reach a certain number, an alarm goes off. "Once that alarm goes off, you have to leave the area, whether you're fi n- ished the job or not," says Hawthorne. If at all possible, the company tries to create an increased distance away from radiological hazards. During the dismantling of the reactors, a lot of work was done using robotic equip- ment so there was no worker exposure. Shielding is a common control mechanism, which is often achieved through lead blankets. For example, if a worker has to do some welding and opens a pipe valve, a lead blanket will be wrapped around the pipe, which reduces the radiation fi eld by about one thousand, says Saunders. Bruce Power has 100 radiation protection technicians who are responsible for ensuring all aspects of the radiation protection program run smoothly. It also has about 30 health physicists who are very spe- cialized workers — the most senior ones are signed off by the CNSC — and they are responsible for reviewing and approving a high-risk job before workers can do it. MONITORING SYSTEMS Nuclear power plants are required to monitor workers and send dosage information to the federal govern- ment's National Dose Registry several times per year. To monitor exposure, all NEWs and workers in the plant at Bruce Power are required to have a dosimeter on them at all times, which gets sent to the lab every two weeks to see if they have been overexposed. NEWs also undergo monthly urine samples to make sure nothing has been inhaled or ingested, and they are required to undergo an annual whole body scan that looks for any pickup of radioac- tive materials in the body. There are specialty dosimeters for workers where certain body parts may face a higher exposure. For example, a mechanic working on something that has a radiation fi eld might get a differ- ent dose on his hands than his body, so he will receive a specialty dosimeter to wear on his fi nger, says Saunders. The CNSC prescribes equivalent dose limits for certain organs and tissue sets per year: lens of an eye (150 mSv); skin (500 mSv); and hands and feet (500 mSv). There are also different levels for pregnant workers as the fetus is very vulnerable. When a worker becomes pregnant, she is required under the CNSC to notify her employer in writing, then her dose amount is limited to four mSv for the balance of the pregnancy. Bruce Power does not allow preg- nant women in the power plant at all, and it regularly accommodates them into other roles. "For example, if an operator was pregnant, she'd work in procedure writing areas or training, typically where they know their knowledge is valued, but they don't need to be in the plant to do that," says Hawthorne. In any case, if a worker is exposed to too much radiation, he needs to be removed from that workplace By Amanda Silliker Extensive training, Extensive training, Extensive training, I n late 2009, Bruce Power was in the By Amanda Silliker POWERING UP POWERING UP POWERING UP RADIATION RADIATION RADIATION PROTECTION PROTECTION PROTECTION By Amanda Silliker PROTECTION By Amanda Silliker PHOTOS: BRUCE POWER