Uranium milling operations at McClean Lake

The McClean Lake mill commenced operations in June 1999, with a design production capacity of 6 million pounds of U3O8 per year. The grinding circuit consists of a SAG mill and a ball mill in closed circuit with cyclones. The cyclone overflow is fed to a two-stage leaching circuit, which uses hydrogen peroxide as the oxidizing agent. A six-stage counter-current decantation circuit minimizes soluble losses to tailings. Solvent extraction uses tertiary amine as the extractant and ammonium sulphate as the stripping agent. The unit process consists of extraction, water wash, stripping and regeneration stages. Anhydrous ammonia is added to precipitate the uranium. The precipitate is then calcined to yield a high purity uranium oxide product. The process is described in detail, and operating data is presented.