Denison Mines Corp. has agreed to buy Fission Uranium Corp. in a $500-million deal that will give the Lundin family control over a large uranium discovery in the Athabasca Basin.

Denison, which is controlled by mining tycoon Lukas Lundin, is offering the equivalent of $1.25 for every Fission share. Mr. Lundin will serve as chair of the combined company, and Fission’s top two executives, chief executive officer Dev Randhawa and chief operating officer Ross McElroy, will remain in the same positions at the new Denison.

The deal will allow Denison to consolidate uranium projects in northern Saskatchewan. Fission owns the Patterson Lake South Project, a property that it always intended to sell to a bigger company. Denison owns uranium projects in the Athabasca Basin as well as other uranium properties in Mali, Mongolia and Zambia.

“We get to run the company, Ross and I, so it’s a unique situation where you’re not just taken over. We are actually running the company,” Mr. Randhawa said in an interview. “The Lundin family and Denison have access to capital that we simply don’t have.”

The offer of 1.26 Denison shares plus 0.0001 cent for every Fission share represents an 18-per-cent premium to Fission’s average stock price over 30 days, the companies said.

The takeover requires approval from Fission shareholders.

Mr. Lundin and his brother run the Vancouver-based Lundin Group, a conglomerate of mining and energy companies.