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?
It is somewhat disconcerting that, while discussing the pressure tube situation in Canada, three nuclear experts have made reference to the ongoing, 2011 nuclear disaster at Fukushima in Japan.
As The Globe reported in March:
“In a worse-case scenario, a ruptured tube could lead to a series of ‘cascading failures not unlike what happened at Fukushima’ says Sunil Nijhawan, a nuclear engineer and consultant who once worked for OPG and specializes in accident and safety assessments.”
At Fukushima, the loss of coolant led to three reactor meltdowns.
In April, Gordon Edwards, president of the Canadian Coalition for Nuclear Responsibility, told the National Observer:
“Cooling the fuel is essential in nuclear power. If you don’t cool the fuel even after shutdown, you can have a meltdown. That’s what happened at Fukushima. I’m not saying every loss of coolant will lead to a meltdown, but that’s the precipitating cause that could lead to a meltdown. So therefore the integrity of the piping is a prime concern.”
The aging nuclear plant at Pickering is of special concern. Slated for closure in 2024, OPG has been lobbying the Doug Ford government to keep the plant open until 2025. Pickering reached its operational-life limit in about 2015, but the nuclear regulator has kept allowing it to remain in service.
The Ontario Clean Air Alliance says a moratorium should be imposed until OPG can prove that the Pickering plant poses no risk to public safety. In 2018, the Clean Air Alliance commissioned a study by Ian Fairlie, an independent consultant on radioactivity.
As reported in April by the National Observer, Fairlie’s report about the Pickering plant found that “a Fukushima-level accident” at Pickering “could cause approximately 26,000 cancers, require the evacuation of more than 150,000 homes and more than 650,000 people, and trigger a $125-billion loss in the value of single-family homes in the Greater Toronto Area.”
How serious?
When asked about the seriousness of the pressure tube situation, Greening said a lot depends on the CNSC.
“I would definitely expect the CNSC to demand OPG and Bruce Power do a lot more sampling and analysis of selected tubes in each and every reactor they are operating. Then we will see how widespread this problem is.
“However, given the logistics of doing this, it would take months to complete all the necessary sampling, and each reactor would have be shut down for several weeks to do this. This would cost tens of millions of dollars and result in a serious loss of nuclear energy production. Then, of course, if many units are found to have [hydrogen/deuterium] concentrations well above 120 ppm in many of the examined tubes, the CNSC, and the whole of Canada’s nuclear industry would be in a real pickle!”
As Greening explained: “In Canada, we have one reactor design — the CANDU. If there is a design flaw discovered in one unit, then every operating unit is likely to have the same problem sooner or later.”
So “if the CNSC does the right thing” by ordering the sampling and analysis of pressure tubes in all reactors, “it will cost millions.”
However, Greening suspects that “the nuclear operators are probably going to say that the current limit of 120 ppm is far too restrictive and could be increased without jeopardizing plant safety.”
The CNSC has catered to that argument before, raising the limit from 100 ppm to 120 ppm.
“Believe it or not, our wonderful nuclear regulator, the CNSC, has in fact used that very option to deal with exceedances of things like [deuterium]-pickup, feeder pipe thinning, etc. in the past,” Greening said.
By the end of July, the CNSC had given such contradictory requests to Bruce Power that Greening was asking: “Does the CNSC’s left hand know what its right hand is doing?”
As he wrote to CNSC president Rumina Velshi back on July 14, “maybe it would be better to admit that the CNSC and the Canadian nuclear industry are collectively unable to predict pressure tube corrosion and hydrogen pickup in operating CANDU reactors…and in the interest of public safety, permanently shut down these very old reactors.”
In an email to rabble.ca Greening stated that a good place to start this shut down would be Pickering unit 6 and unit 7, which are both long past their fit for service date.
Otherwise, the consequences could be dire.
Canadian freelance writer Joyce Nelson is the author of seven books. She can be reached via www.joycenelson.ca
Image: Chuck Szmurlo/Wikimedia Commons
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