Cameco’s McArthur River mine is the world’s largest high-grade uranium mine, with ore grades 100 times the world’s average. Those qualities, coupled with proven and probable reserves of 324 million pounds of uranium, make the mine one of the company’s (and the world’s) more valuable assets.
Located near Toby Lake in the Athabasca Basin of northern Saskatchewan, 620 kilometres north of Saskatoon, the mine is one kilometre long and half a kilometre wide. This tiny piece of land produces more than 18 million pounds of uranium per year by mining only 150 to 200 tonnes of ore per day. That is more than 10% of the world’s annual production.
It’s a massive operation featuring an underground mine with three shafts: one to safely move workers, one for mine exhaust air ventilation and one for fresh air ventilation and an emergency exit.
Mining McArthur River calls for a number of innovative methods and techniques including ground freezing, because the sandstone that overlays the deposit and basement rocks are water-bearing, with large volumes of water under high pressure. Ground freezing forms an impermeable wall around the area being mined and prevents water in the sandstone from entering the mine. It also helps stabilize weak rock formations.
Cameco developed an innovative cathedral-shaped freezewall around the ore zones, allowing it to mine tunnels above and below the ore body.
Raisebore mining was chosen as the main mining method. It involves drilling a series of overlapping holes through the ore zone from a raisebore chamber above the ore, and collecting the broken ore at the bottom of the raises using line-of-site remote controlled scoop trams, and transporting it to an underground grinding circuit. The ore is pumped to the surface as a slurry where it is put in specially designed containers and transported by truck about 80 kilometres to the mill at Key Lake.
On the surface, about 550 metres above sea level, the site includes a small city’s worth of structures including a minewater treatment plant, a powerhouse, maintenance and warehousing facilities, a concrete batch plant, an ore loadout building and administration and workforce buildings.
Toby Lake is nearby and easy to access for enough water to satisfy all of the mine’s requirements. The site is connected to the provincial power grid, and the McArthur River mine has a set of standby generators for use in emergency situations.
It’s a year-round operation that employs Cameco employees and about 400 contract employees. It has an expected mine life of 24 years.