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More issues at Bruce power station raise concerns about aging nuclear infrastructure

More issues at Bruce power station raise concerns about aging nuclear infrastructure,  MATTHEW MCCLEARN, The Globe and Mail, 5 Sept 21,

Unexpectedly high levels of hydrogen in pressure tubes at a nuclear power plant in Ontario have renewed questions about how long Canada’s aging CANDU reactors can continue to operate safely.

At a meeting before the Canadian Nuclear Safety Commission (CNSC) on Friday, officials confirmed more pressure tubes at the Bruce Nuclear Generating Station on the eastern shore of Lake Huron were found to contain hydrogen concentrations in excess of regulatory limits, and above what the industry expected. Bruce Power disclosed in July that it had discovered two tubes that exceeded regulatory limits.

The cause has not been determined, nor is it clear how many other pressure tubes in Canadian reactors might also be affected. Bruce Power did not answer questions from The Globe late Friday on how many additional tubes were found to violate the station’s licensing requirements.

Pressure tubes are six-metre rods that contain fuel bundles of uranium, and are considered the major life-limiting component in CANDUs, the reactors in all of Canada’s nuclear power plants. Tubes containing high hydrogen concentrations are more vulnerable to fracturing if they have pre-existing cracks. If one ruptures, coolant could be lost, which could trigger a range of scenarios from a relatively minor incident contained by the plant’s safety systems to a catastrophe in which fuel overheats.

The issue is particularly a concern when the reactor is below normal operating temperatures, such as during shutdown or startup…………

The Bruce station has eight reactors, each containing 480 pressure tubes; the offending tubes were found in Units 3 and 6, neither of which is operating. One tube in Unit 6 exhibited readings of 211 parts per million, approaching double the regulatory limit, and far above Bruce Power’s prediction of 100 ppm. Bruce Power officials said all of the elevated readings were discovered in the same region, close to one end of the tube………

Frank Greening, a retired Ontario Power Generation chemist who worked in the company’s pressure tube group for the last decade of his career, warned that it’s possible the rate of hydrogen pickup may have accelerated in older tubes in the past few years.

“And if that’s true, then the rate at which it’s going in is scary,” he said.

He added: “There is something happening that’s quite serious. And they’re saying ‘We don’t know how or why it’s happening.’ It’s pathetic. I can’t accept that.”

A CNSC commissioner, Marcel Lacroix, said during the meeting that industry officials had not satisfactorily explained what might be causing the problem………..

September 6, 2021 - Posted by | Canada, safety

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