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Canada’s nuclear reactors may not be fit for service

Canada’s nuclear reactors may not be fit for service,  Rabble ca,  Joyce Nelson, 11 Aug 21,  On July 13, Bruce Power announced that two reactors at its Bruce Nuclear Generating Station in Kincardine, Ontario had violated its operating license.

It had “higher than anticipated readings” of hydrogen-equivalent concentration (Heq) in pressure tubes in two units. Pressure tubes must not exceed the allowable limit of 120 parts per million of Heq. Each pressure tube in a reactor contains 12 bundles of uranium, which are the basis for the nuclear reaction, but the pressure tubes also contain the coolant that keeps the fuel from overheating and triggering a meltdown. Pressure tubes with high levels of Heq can develop cracks and fractures, thereby compromising a reactor’s safety.

As The Globe and Mail reported:

“In response to Bruce Power’s contraventions, on July 13, the CNSC [Canadian Nuclear Safety Commission] ordered the company, along with fellow CANDU [Canada Deuterium Uranium] operators Ontario Power Generation (OPG) and New Brunswick Power, to review the fitness for service of their pressure tubes and report back no later than the end of July.”

Aging reactors

Many of Canada’s aging CANDU reactors are older than their design-life for pressure tubes, which originally was designated as 210,000 effective full power hours (EFPH), or about 30 years.

When Hydro Quebec’s Gentilly-2 CANDU reactor reached that limit, it closed the plant.

As The Globe and Mail reported:

“Thierry Vandal, chief executive at the time, testified before Quebec’s national assembly that he considered 210,000 EFPH ‘the extreme limit’ beyond which his management team dared not go. ‘I would no more operate Gentilly-2 beyond 210,000 hours than I would climb onto an airplane that does not have its permits and that does not meet the standards,’ he said, according to a translated transcript.”

Under industry pressure, the Canadian Nuclear Safety Commission subsequently raised the limit to 247,000 EFPH in 2014, and then to 295,000 EFPH in 2018.
In 2018, the CNSC extended OPG’s license for its Pickering Nuclear Generating Station for 10 years. Rather than require that OPG replace aging pressure tubes, the regulator mandated more frequent inspections.
When asked how often pressure tubes are checked, retired nuclear scientist and radioactive chemistry expert Dr. Frank Greening answered by email:

“Pressure tubes are checked for their hydrogen/deuterium concentrations about every two years, but it’s a little more complex than that. Each CANDU unit contains about 400 tubes and each tube is about six meters in length. This means it’s next to impossible to check every tube at every location, so only about 10 tubes are checked at a time. In addition, corrosion and [hydrogen/deuterium] pickup are expected to be most significant at the hot, outlet end of each tube, so samples are usually restricted to this location.”

As a result of such limited inspections, the industry relies on mathematical models to predict how long the untested tubes can safely remain in service. But this modeling is not necessarily accurate, as evidenced by the July 13 “higher than anticipated readings” at Kincardine.

Indeed, in March 2021, The Globe reported:

“Documents obtained under the federal Access to Information Act by Ottawa researcher Ken Rubin, and provided to The Globe, show that since 2017, CNSC staffers had grown increasingly concerned about unreliable data arising from OPG’s inspections of pressure tubes…The whole method by which operators assessed fitness for service of pressure tubes had been called into question.”

Another Fukushima?………………….

August 21, 2021 - Posted by | Canada, safety

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