Cameco Corp. (TSX: CCO) has suspended mining at Cigar Lake, the highest grade uranium mine in the world, after the mill that processes its ore broke down.
The trouble sits at Orano’s McClean Lake mill, where the sulfuric acid plant shut down for repairs. Without acid, the mill cannot treat Cigar Lake ore, and with only limited storage at the mine, Cameco has stopped mining until milling can resume.
Orano is working to restart the acid plant and is chasing an alternative supply of acid while it waits on replacement parts. Cameco expects the mill back in operation in roughly two weeks.
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The company is keeping its 2026 production outlook for Cigar Lake unchanged for now, with the operation estimated to produce 17.5 million to 18 million pounds of uranium concentrate this year on a 100% basis. That guidance could slip if the repairs run long. A drawn out outage, or difficulty sourcing acid elsewhere, would put the annual figure at risk.
It marks the second disruption this year at one of Cameco’s Saskatchewan operations. In May, spring flooding partially collapsed a bridge on the main supply route into McArthur River and Key Lake, forcing the company to halt production at Key Lake on May 10 and scale back at McArthur River. Both sites returned to full output after a roughly two and a half week interruption, and Cameco left its consolidated 2026 target of 19.5 million to 21.5 million pounds intact.
Cigar Lake kept running through that episode. The mine has grown into a larger piece of the company of late. Cameco and Orano agreed in June to buy out TEPCO Resources’ 5% stake in the joint venture, a deal that lifts Cameco’s interest to 57.4% and values the operation at a little over $4 billion once it closes in the third quarter.
Cameco last traded at $144.56 on the TSX.
