Conventional mines have a mill where the ore is crushed, ground and then leached — typically with sulfuric acid to dissolve the uranium oxides. The solution is then processed to recover the uranium.

Most of the ore is barren rock or other minerals, which remain undissolved in the leaching process. These solids or ‘tailings’ are separated from the uranium — rich solution, usually by allowing them to settle out. The remaining solution is filtered and the uranium is recovered in a resin/polymer ion exchange (IX) or liquid ion exchange (solvent extraction — SX) system. The pregnant liquor from ISL or heap leaching is treated similarly.

Further treatment for IX involves stripping the uranium from the resin/polymer either with a strong acid or chloride solution or with a nitrate solution in a semi­continuous cycle. The pregnant solution produced by the stripping cycle is then precipitated by the addition of ammonia, hydrogen peroxide, caustic soda or caustic magnesia.

SX is a continuous loading/stripping cycle involving the use of an organic liquid (usually a kerosene-based product) to carry the extractant, which removes the uranium from solution. The uranium is then stripped from the loaded organic liquid using ammonia followed by an ammonia precipitation.

The final chemical precipitate is filtered and dried. Peroxide products can be dried at ambient temperatures to produce a product containing about 80% U3O8. Ammonium or sodium diuranate products are dried at high temperatures to convert the product to uranium oxide concentrate — U3O8 — about 85% uranium by mass. This is sometimes referred to as yellowcake, though it is usually khaki.

In the case of carbonate leaching the uranyl carbonate can be precipitated with an alkali, e. g. as sodium or magnesium diuranate.

The product is then packed into 200-litre steel drums, which are sealed for shipment. The U3O8 is only mildly radioactive (the radiation level one metre from a drum of freshly-processed U3O8 is about half that — from cosmic rays — on a commercial jet flight). In ISL mills the process of uranium recovery is very similar, without the need for crushing and grinding.