Canada. It’s all about the ice. Even in the cold winter wonderland of northern Saskatchewan, mining company Cameco has to build an underground curtain of frozen groundwater around the McArthur River mine’s ore body – the world’s highest-grade uranium.
The Athabasca Basin in the Canadian prairie province of Saskatchewan is one of those places meant to be seen during early morning hours, when the first rays of light make the landscape sparkle. The snow that creaks beneath boots can freeze feet through even the heaviest of soles. The air is clean and crisp, but a minus-40-degree wind chill makes miners hustle to the more temperate underground mine environment.
Sandvik fleet at Mcarthur River
• Five Sandvik CRH10SD raise borers
• Three Sandvik DU331-TW drills
• Two Sandvik 6200W drills
• Two Sandvik KW130 water pumps
• One Sandvik LH410 loader
• One Sandvik H205D jumbo
• One Sandvik AM75 alpine miner
Some 500 metres below the surface lies the world’s richest and highest-grade uranium ore body. Its existence has been known since the 1980s, and the ore has been excavated since 2000, but only recently did the mine reach peak production efficiency.
“It’s located in a sandstone formation filled with water,” says Curtis Taylor, freeze drill general foreman at the McArthur River mine. “It looks like a sponge. We’re seeing 500 gallons of water a minute being produced from a drill hole while we’re drilling. When you shut the hole in and close it down, it can have a hydrostatic pressure of up to 600 psi. A regular longhole production drill isn’t built to handle that.”
At the 520-metre level, everything is clean and neatly covered in concrete. Endless pipes of different diameters run along the drifts.
Taylor stops in front of a board on the wall that illustrates the mine. The uniqueness of this situation, which is common only in the Athabasca Basin area, is that the ore body has to be shielded off from the surrounding sandstone for production drilling to take place.
“These are freeze holes,” he says, pointing to some coloured lines on the board in straight formation. “The holes are up to 130 metres deep. We’re using a Sandvik DU331-TW drill and six-and-a-quarter-inch rods. Then we double-case the holes with steel and PVC plastic inner pipes to circulate chilled brine through them.”
McArthur River is Cameco’s richest uranium mine, with some 19 million pounds of ore extracted annually. The ore from McArthur River is transported to nearby Key Lake, where it is processed and turned into the final yellowcake, triuranium octoxide (U3O8).
Cameco as a whole accounts for about 14 percent of the world’s uranium production. That makes the company a world leader, with mines in Canada, the United States and Kazakhstan. Cameco’s leading position is backed by some 465 million pounds of proven and probable reserves and extensive resources. The uranium is sold for use in power plants all over the world. In 2012, Cameco had revenue of 2.3 billion Canadian dollars (2.1 billion US dollars) and net profit of CAD 266 million (USD 248 million).
Huge compressors on the surface pump the brine down the mine and into each hole. It goes first through the centre of the inner PVC tube, then is flushed back out on the outside, still sealed off from the bedrock by an outer casing. The brine is then returned to the compressor loop to be rechilled.
“This cools the ground and makes up a freeze wall, like a curtain around the ore body,” Taylor says.
It’s a 15-metre-thick ice curtain, to be exact, and it keeps water from the basin away from the mine.
“Once the ground is frozen we go up and develop excavation chambers where the ore itself is drilled and extracted,” Taylor says.
Put simply, they drill holes to be able to drill holes, and it’s a technique that takes precision.
The spaces between the holes here are no more than 2.5 metres wide. If the drill were to deviate and reach more than 3.8 metres from the toe of the hole next to it, Taylor’s team would have to make another one.
“The setup of the drill is very critical, and the drill itself has to be able to be easily set up on the hole and drill accurately once in the hole,” says Jordan Letkeman, Sandvik underground ITH product manager, who has been working with the team at McArthur River to get such an accurate rig in place.
The uranium business is as tricky as it is sensitive, both politically and in terms of market uncertainty. The tsunami that caused the nuclear disaster at Japan’s Fukushima Daiichi power plant in 2011 gave many countries second thoughts about their nuclear operations. All such incidents have a big impact and earn a notable place in history, but societies usually return to the idea that nuclear power is an environmentally friendly, safe source of energy.
“We do believe it’s part of the future,” says Cameron Chapman, Cameco’s operations manager for the McArthur River mine.
The mine is currently producing 8,620 tonnes of uranium annually, up from 8,480 tonnes when it first started. Demand hasn’t decreased, Chapman says.
The top three uranium producers in the world – Kazakhstan, Canada and Australia – account for around two-thirds of the world’s total annual production of 58,000 tonnes.
Tech specs Sandvik DU331-TW
Sandvik DU331-TW boom-mounted Wassara ITH production drill:
• HH mast with 60,000 pounds force
• SAHR (spring applied hydraulic release)
clamping and breakout foot arrangement
• HD underground frame
• HD undercarriage assembly
• 360-degree boom pivot
• Centralized manual grease lubrication
• Petol chain wrench to open hammers,
mounts on feed with hydraulic cylinder
• Soft-start electric system
• Hydraulic oil fill pump
• 2 x 100 amp plugs
Sandvik KW130 triplex plunger pump module:
• Water pump capacity of 350 litres/minute
• 2,600 psi working pressure
• Built-in gear reduction drive
• Engine-mounted charge pump
• Two parallel mounted desilting cones
• Secondary water filter system
• Ultrasonic water flow meter
Kazakhstan, the world leader, produced 21,317 tonnes in 2012, or 37 percent of the global total, according to the World Nuclear Association. Canada produced some 15 percent of the total.
Still, no single mine can measure up to McArthur River. “From a geological perspective, we’ve got a high-grade ore body in a relatively small location,” Chapman says. “Essentially, in zone 2 of the ore body, where we first began commercial production, we’ll get some 136 tonnes out of something the size of a football field.”
The mine has officially reached the halfway mark of what can be excavated. But that was based on earlier estimates, and Chapman believes the McArthur River mine will be operational for decades to come.“Our current life-of-mine plan extends to at least 2035,” he says. “But there is ongoing geological potential within the area.”
From atop the highest nearby hill, looking down from a height of 100 metres provides an overview of the mine’s surface structures. The whole thing looks surprisingly small.
The McArthur River mine is located some 600 kilometres north of the city of Saskatoon. Some of the workers travel in from small settlements even farther north. However, a majority of the 430 employees and the 250 long- or short-term contractors fly in for their week-long shifts from the south. For them, the private airstrip and the planes chartered by Cameco are the only way in and out.
The lone private road leading to the mine is only for equipment and ore transports. During their stays at McArthur River, the men and women have their own rooms in the nearby living quarters. There’s also a gym, a basketball court, a sauna and a big social room at the camp.
After what is usually an 11-hour workday, yellow school buses transport those who don’t want to brave the cold the few hundred metres from the mine to the housing complex.
There they enjoy home-cooked meals in a large cafeteria, which is also open for sandwiches and snacks around the clock. “They take good care of us,” Taylor says.
Taylor’s son Dallas, 25, is a third-generation uranium worker. Currently a machine operator on the latest Sandvik DU331-TW drill, which Sandvik and Cameco developed together, he talks with the same confidence as his father.
“As far as the drill is concerned, we’re able to make a freeze hole, start to finish, in around a week,” he says. “With the older drill, it would take us closer to three weeks.”
“It’s not so much about how big they are,” says Jordan Letkeman, Sandvik underground ITH product manager. “It’s about how small they are.”
At this site, Cameco has to do very specific things to work around the small ore body.
“They really have to make sure they’re doing it right,” Letkeman says. “If they don’t get that freeze curtain, there’s no way they can mine that ore body. They spend time getting everything 100 percent.”
The first Sandvik 6200W drill rigs were delivered in 1998 and refurbished in 2001. This equipment was mainly standard equipment with a few key modifications.
The new DU331-TW drills, which were custom designed to the mine’s specifications, were delivered starting in 2009.
“The new machine has a heavy hoist mast on it, 60,000 pounds, and goes well beyond the 130-metre holes required,” says Curtis Taylor, Cameco freeze drill general foreman.
The equipment is also smaller and easier to mobilize and demobilize.
“We’ve been able to reduce the size of our drifts too,” Taylor says. “We were driving drifts of seven and eight metres high. Now we only have to drive six-and-a-half metres. It’s a huge cost saving for the mine to be able to do that.”