{"id":20497,"date":"2026-09-19T11:00:54","date_gmt":"2026-09-19T15:00:54","guid":{"rendered":"https:\/\/www.autonocion.com\/us\/?p=20497"},"modified":"2026-09-19T05:39:02","modified_gmt":"2026-09-19T09:39:02","slug":"nuclear-station-toronto-us-reactor","status":"publish","type":"post","link":"https:\/\/www.autonocion.com\/us\/nuclear-station-toronto-us-reactor\/","title":{"rendered":"A 2,064-megawatt nuclear station outside Toronto goes dark next week so crews can pull all 1,520 pressure tubes from its four reactors, a swap no US reactor can make, because every American reactor keeps its fuel inside one steel vessel that has never been replaced"},"content":{"rendered":"

Back in August, we walked through Ontario’s plan to rebuild the four working reactors at the Pickering nuclear station outside Toronto<\/a>, including how crews plan to cut through the reactor building roofs and lift 48 boilers out by crane. That’s at least a few months off. The first step comes next week, and it’s a lot less cinematic. Someone has to switch the reactors off.<\/p>\n

Ontario Power Generation CEO Nicolle Butcher confirmed the timing this week at Prime Minister Mark Carney’s Canada Investment Summit in Toronto, where she shared an energy panel with the heads of Suncor and TC Energy. According to The Narwhal<\/a>, she told the room the station “will come out of service next week and we’ll start its refurbishment.” She also put its time off the grid at five to seven years.<\/p>\n

The reactors in question are Units 5 to 8, which go by Pickering B. They’ve been running since the mid-1980s, and OPG says the station makes about a tenth of Ontario’s electricity. The other four reactors on the site have already been shut down for good, so once these come off, none of Pickering’s eight reactors will be making power.<\/p>\n

As for those five to seven years, OPG’s year-end results get a little more specific. Unit 5 is supposed to come back first, in 2031, with all four done by 2034.<\/p>\n

I can’t give you an exact date for each unit, though. OPG’s financial filings have all four leaving service by the end of September, and I haven’t seen anything saying whether they go down on the same day or one after another.<\/p>\n

So what actually happens once they’re off?<\/p>\n

What’s inside a CANDU, anyway?<\/h2>\n

Every commercial power reactor in the US is a light-water reactor, and each one keeps its fuel inside a single giant steel pressure vessel. The Energy Department’s reactor-life research program calls that vessel the most life-limiting part of the plant, mainly because swapping it out just isn’t on the table.<\/p>\n

A CANDU, the Canadian design Pickering runs on, doesn’t have one. Its fuel sits in hundreds of horizontal tubes that pass through a big tank of heavy water, which is basically water made with a heavier form of hydrogen. Each of those tubes holds the pressure on its own. Each one also sits inside a second, outer tube. Add a fitting on either end and you’ve got what the industry calls a fuel channel.<\/p>\n

Pickering has 380 of those channels per reactor, according to OPG<\/a>, and each one holds 12 fuel bundles. Every channel also gets two feeder pipes, one carrying hot heavy water toward the boilers and one bringing it back. That’s 760 feeders per reactor.<\/p>\n

So why pull the tubes at all? Canada’s nuclear regulator says decades of heat, pressure and radiation slowly change the metal in those tubes, and they soak up a little heavy hydrogen from the water flowing through them. Once they can’t meet their safety margins, a plant isn’t allowed to keep running them.<\/p>\n

The good news is the tubes can be replaced, and frankly, that’s some clever engineering. If you’ve ever had a big diesel rebuilt, it’s a bit like re-sleeving the engine. The block stays put and every cylinder gets a new liner. Pickering just has 380 cylinders per reactor.<\/p>\n

The fuel comes out first<\/h2>\n

No one cuts into a reactor with fuel still in it. OPG plans to defuel all four once they’re off the grid, and each core holds 4,560 bundles, so that’s 18,240 of them to pull out before the real work starts.<\/p>\n

When OPG rebuilt Darlington, the order went like this: fuel out, heavy water drained, then every feeder, then the end fittings, then the pressure tubes and their outer tubes, pulled in pairs. Only after the tank had been cleaned and inspected did anything new go back in.<\/p>\n

OPG compared fitting the new feeders there to doing a jigsaw puzzle, since each one has its own shape and length. Pickering’s version of that puzzle runs to 760 pieces per reactor. I don’t envy the crews doing it.<\/p>\n

\n
\n
Fuel channels<\/div>\n
1,520<\/div>\n
380 in each of the four reactors. Each one is a pressure tube inside an outer tube, with a fitting on both ends.<\/div>\n<\/div>\n
\n
Feeder pipes<\/div>\n
3,040<\/div>\n
Two per channel, 760 per reactor. They carry heavy water between the core and the boilers.<\/div>\n<\/div>\n
\n
Fuel bundles<\/div>\n
18,240<\/div>\n
4,560 per core, 12 to a channel. They all come out before the rebuild starts.<\/div>\n<\/div>\n
\n
TARGET<\/div>\n
First unit back<\/div>\n
2031<\/div>\n
Unit 5, according to OPG’s year-end results. All four are due back by 2034.<\/div>\n<\/div>\n<\/div>\n

So who keeps the lights on?<\/h2>\n

Ontario’s grid operator, the IESO, has Pickering B down as 2,064 megawatts leaving the system this fall. Its June reliability outlook<\/a> says the province has enough supply to cover demand through the end of 2027, with one exception. That’s two weeks in April 2027, and the plan is to get plant owners to move their scheduled maintenance out of the way.<\/p>\n

That’s a slightly awkward ask, since April is normally when a lot of plants do their maintenance, with demand low between the winter and summer peaks. It’s also the month Darlington, OPG’s other nuclear station, is scheduled for a vacuum building outage. That’s the building that’s supposed to suck steam out of a reactor and turn it back into water in a serious accident, and The Globe and Mail says work on it will keep the entire station offline for nearly 46 days next year.<\/p>\n

If you’re in Michigan or New York, your grid is wired into this one. Ontario connects to both states, along with Minnesota, Quebec and Manitoba, and the IESO says the province has been selling more power than it buys lately. But that June report also trimmed how much imported power it’ll count on in summer, to 1,800 megawatts from 2,000, because grids across the continent are getting tighter. So if you were hoping your side of the border had a bunch of spare electricity lying around, apparently not.<\/p>\n

So is this actually approved?<\/h2>\n

Not entirely. The province has signed off, but the Canadian Nuclear Safety Commission<\/a> still has to renew Pickering’s license and approve the rebuild. CNSC staff have already said they’re satisfied OPG is qualified to do the work. The commission itself makes the call.<\/p>\n

OPG keeps pointing to Darlington, which it finished in March ahead of schedule and under budget by its own count. Fair enough. Still, Darlington’s rebuilt units<\/a> have had a bit of a bumpy few months since, and The Globe and Mail reported in late August that three of the station’s four reactors were dealing with prolonged outages.<\/p>\n

The CNSC hears the rest of the case October 6 to 9 at the Durham Convention Centre in Ajax, the next town over from Pickering. The Narwhal reports the commission typically rules within four months of a hearing wrapping up, and if it signs off, OPG plans to start the rebuild with Unit 5 in January.<\/p>\n","protected":false},"excerpt":{"rendered":"

Back in August, we walked through Ontario’s plan to rebuild the four working reactors at the Pickering nuclear station outside … <\/p>\n

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