"It was a huge day for us," CEO Tim Gitzel said by phone from the mine site.
The mine — a partnership with French nuclear giant Areva — first encountered underground flooding in 2006. Crews were able to safely re-enter the mine's main working level almost a half-kilometre underground in 2010 once water was pumped out.
But the mine was further delayed last year to repair a leaking tank — a relatively small setback in the grand scheme of things.
"We didn't want to start up the mine like that. We wanted to make sure everything was perfect and so we took some time to reline that tank with stainless steel," said Gitzel.
"We've done that. We've tested it many times. In fact it's in operation today and absolutely holding the product it should."
On Thursday, employees watched as trucks left the mine's load-out bay to be processed at the McClean Lake mill, 70 kilometres to the northeast.
"The employees were lined up down the road, cheering the truck down the road, so it was pretty exciting," said Gitzel.
"I had a chance to speak with all the employees at lunch, just to thank them for their perseverance, for their commitment, for their ingenuity in finding solutions to the numerous problems and challenges we faced here and I can tell you they're a proud group today. It's a huge sense of satisfaction to see ore come out of that mine safely and be put in the truck and sent down the road."
Between Cameco and Areva, the cost of the Cigar Lake mine came in at $2.6 billion.
The McClean Lake mill, operated by Areva, is expected to begin processing the ore to uranium concentrate by the end of the second quarter and produce between two million and three million pounds of uranium concentrate this year. It expects to ramp up to its full production rate of 18 million pounds by 2018.
The McClean Lake joint venture is 70 per cent owned and operated by Areva. The other McClean Lake joint venture partners are Denison Mines Corp. (TSX:DML), 22.5 per cent and OURD (Canada) Co. Ltd., 7.5 per cent.
About three quarters of McClean Lake's capacity will be used to process Cigar Lake ore.
Cameco hired as many as 1,000 workers at Cigar Lake during construction. During its operation, it will employ more than 600, most of whom live in northern Saskatchewan.
"One thing we're very proud of is the impact here in northern Saskatchewan. I'm up at the mine site today and I see the aboriginal people we have working here, over half of our workforce is aboriginal," said Gitzel.
"We are already the largest industrial employer of aboriginals in Canada and we'll just add to that with the Cigar Lake folks. So that's one thing I have to say I'm really proud of, as the CEO and so we'll continue to work on that."
Shares in Cameco closed up 72 cents, or 2.68 per cent, at $27.62 Thursday on the Toronto Stock Exchange.
Follow @LaurenKrugel on Twitter