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There was a leak of mildly radioactive heavy water at Canada’s oldest nuclear reactor in early December, but Atomic Energy of Canada Ltd. says almost nothing escaped and there’s no danger.
Forty-seven kilograms of heavy water (less than 47 litres) leaked from the NRU reactor on Dec. 5, the company says.
But the leak stopped of its own accord — before the source could be identified for certain — and so AECL hasn’t made any repairs.
“We didn’t pinpoint it definitely. We had indication that it was coming from a seal,” said Bill Pilkington, AECL’s vice-president in charge of the plant.
“Losing 47 kg of heavy water is not insignificant,” he said. “At the same time, we wouldn’t characterize it as a large, sustained leak.” He said there was no danger to the public.
Most of the leaked heavy water was caught and the radioactive tritium in it will be recovered, he said. A few litres evaporated, but the amount was within one-thousandth of the amount permitted as air emissions under the plant’s license.
Tritium forms when heavy water is exposed to radiation, usually in a reactor. Heavy water is used as coolant in NRU, and also as a “moderator” — something that helps the process of breaking apart uranium atoms.
“In this case, the concentration was quite low,” Mr. Pilkington said. “We don’t consider that there’s a safety issue here. There was no significant radiation exposure to workers, there was no release to the environment, there was no exposure to the public.” The NRU has been working since 1957, producing medical isotopes.
Last year AECL finally abandoned the two new reactors that were supposed to replace NRU. The twin MAPLE-1 and -2 reactors, also at Chalk River, were supposed to have been commissioned years ago, but both ran into repeated technical problems and breakdowns after hundreds of millions of dollars in construction costs. Neither was ever brought into service.
“The NRU continues to operate safely and reliably,” Mr. Pilkington said.
“However it is not going to operate indefinitely, so there do need to be plans to replace NRU for isotope production at some point.”
Ottawa Riverkeeper Meredith Brown is on an environmental stewardship council set up by AECL to deal with the plant’s relationship to its surroundings. But she said she couldn’t get anyone at the company to talk to her yesterday.
“I’ve tried to get through,” she said, but no one at the company would take her call yesterday. The council does have a meeting set for next week.
“I did receive a couple of convoluted messages from them (AECL) back in December,” she said. “None of it say anything about a spill or a leak. It made it seem like it’s ongoing maintenance.”
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