Anyone who’s rented a pressure washer knows water will peel paint off a deck and, if you get careless, take a bite out of the wood underneath. Cameco took that idea, scaled it up, and pointed it at some of the richest uranium ore on the planet. At its Cigar Lake mine in northern Saskatchewan, about 410 miles north of Saskatoon, the ore comes out of the ground as mud. A machine working 1,575 feet down cuts it out of frozen rock with a high-pressure water jet, the mud drains into pipes, and the hole it leaves behind gets filled with concrete.<\/p>\n
The mine’s been shipping ore that way since 2014, so why am I writing about it now?<\/p>\n
Because in July the whole operation stopped for two weeks, and what broke sits 43 miles down the road, at a mill Cameco doesn’t even own. We’ll get to that. First the machine, because it’s arguably the strangest piece of production mining gear in North America.<\/p>\n
The Cigar Lake deposit sits between 1,345 and 1,475 feet below the surface, right where a layer of waterlogged sandstone meets the older basement rock underneath. The ore runs about 1.2 miles long, 65 to 330 feet wide and up to 44 feet thick, and Cameco calls it the highest-grade uranium mine in the world. The company’s latest technical report<\/a> puts the average grade of what’s left at 17 percent uranium oxide. A lot of uranium mines work ore that’s a fraction of 1 percent.<\/p>\n Rich ore is also the problem. The rock around it is weak, the sandstone above it is full of water under pressure, and radon comes off any water that touches the ore. Cameco learned the water part the hard way: the workings flooded twice in 2006 and again in 2008, and the mine didn’t get pumped dry until early 2010. Going at that with a normal drill-and-blast setup was never going to happen, and Cameco’s report notes that jet boring had never been the main way of mining anything, anywhere, before Cigar Lake.<\/p>\n So they freeze it. Cameco pumps calcium chloride brine chilled to 22 below zero through 1,265 freeze holes drilled from the surface, with 75 more holes carrying thermometers so engineers can watch the cold spread. The brine turns the ore and the rock around it into a block frozen to somewhere between 23\u00b0F and 13 below. That takes two to four years, depending on how wet the ground is and how far apart the pipes sit. The freeze holes for the main deposit are all in; the extension Cameco wants to mine next still needs 560 more, plus 28 temperature holes.<\/p>\n The freeze plants on the surface deliver roughly 3,100 tons of refrigeration to pull that off. If you have central air at home, you probably have a 3-ton unit, so picture something like a thousand of those running flat out, year-round, to keep one patch of rock frozen. The same trick is holding 261,000 tons of arsenic dust<\/a> in place under an old gold mine in Yellowknife, so there’s apparently a market for it.<\/p>\n Cameco calls it a jet boring system, JBS for short, and there are three of them. They work from a tunnel level 1,575 feet down, about 130 feet below the ore. From there, a machine drills a pilot hole straight up through the frozen ore, lines it with casing, and runs a jetting tool up to the top of the ore layer. Then the water comes on.<\/p>\n The jet cuts a thin slice, the machine backs the tool down a little, the jet cuts the next slice, and it keeps going until it’s carved out a cylinder 15 to nearly 20 feet across and as tall as the ore is thick, up to about 44 feet. Everything it cuts turns into slurry, which is basically rock mud, and the mud drains back down into pipes.<\/p>\n From there it’s plumbing. The slurry goes through an underground crusher and ball mill, gets thickened, and is pumped up the shaft to the surface, where it’s loaded into 1,320-gallon containers, four to a truck, for the 43-mile drive to the mill. The operator runs the machine remotely and nobody sets foot in the ore zone at any point. The technical report is pretty blunt that this is the whole point: the ore stays wet and sealed up from the cavity to the mill, which keeps dust and radon away from the people working down there. Frankly, it’s an elegant fix for a nasty problem.<\/p>\n How fast does it go? Cameco’s figure is roughly 93 cubic yards of ore a day while a machine is jetting, call it nine or ten concrete-mixer loads. Only two of the three machines cut at the same time, because the mine can’t supply enough high-pressure water for all of them, so the third is always on the move, drilling its next pilot hole, backfilling or getting fixed.<\/p>\n Cameco doesn’t publish the jet pressure in the technical report. I’ve seen a number floating around in older trade coverage and I’m not going to repeat it, because I can’t verify it. What I can tell you is that it’s a lot more than anything you’ll rent at the hardware store.<\/p>\n Once a cavity is empty, a 3D laser scanner surveys it and then concrete goes in. The mix is designed to set hard and fast in frozen ground, and Cameco says ten years of production show the plug stays intact while the jet carves out the cavity right next to it. That matters, because the deposit gets mined as a honeycomb of cylinders, each one leaning on its concrete neighbors.<\/p>\n There’s a catch. When you cut a 20-foot cylinder through an ore layer that’s only about 18 feet thick on average, you take some of the rock above and below with it, plus a sliver of the concrete next door. Cameco calls that dilution, and it averages 34 percent, with individual cavities ranging from 7 percent to 70 percent. That’s a pretty wide spread, frankly. Still, the company counts 572 completed cavities over ten years and an overall recovery of 86 percent of the ore it planned to get.<\/p>\n All of that slurry goes to one place: Orano’s McClean Lake mill, 43 miles northeast by road. The mill basically dissolves the uranium out of the mud with sulfuric acid, then pulls it back out of the liquid as yellowcake, the yellow powder that enrichment plants like the centrifuge hall in Ohio<\/a> eventually turn into reactor fuel. The ground-up rock left over is called tailings, and if that word sounds familiar, it’s because 17 million tons of it<\/a> just got hauled off the bank of the Colorado River at Moab. Cigar Lake, meanwhile, doesn’t have much room to store ore on site. When the mill stops, the mine stops.<\/p>\n On July 1, Cameco announced<\/a> that McClean Lake’s sulfuric acid plant had broken down and the mill had shut for repairs. Orano went looking for acid from other suppliers while it waited on replacement parts, and Cameco suspended mining. Two weeks later, on July 14, the mill was back<\/a>, Cigar Lake started trucking its stockpiled ore again, and the machines went back to cutting. Cameco said the pause didn’t dent its 2026 outlook for the mine, which stays at 17.5 million to 18 million pounds of uranium oxide.<\/p>\n Cigar Lake packaged 2.9 million pounds in the second quarter of 2026 against 5.1 million in the same quarter of 2025, and 7.9 million in the first half against 10.1 million a year earlier, according to Cameco’s second-quarter report<\/a>. Cameco says that’s down to timing: the annual maintenance shutdown fell in the second quarter this year and in the third quarter last year. I’d still argue the acid plant is the softest spot in the whole chain. You can spend four years freezing rock and cut it with water from underneath, and a single busted plant 43 miles away idles all of it.<\/p>\n The machines have been cutting again since July 14. Cameco’s current plan keeps Cigar Lake at 18 million pounds a year through 2034, then winds it down to a final 700,000 pounds in 2036.<\/p>\nSo what does the machine actually do down there?<\/h2>\n
The hole gets filled before the next one is cut<\/h2>\n
The mill is the weak link<\/h2>\n