Process for the lixiviation of uranium-bearing ores

摘要

Uranium-bearing ores are lixiviated by allowing a dilute aqueous alkali metal, generally sodium, carbonate and/or bicarbonate, to seep uniformly through a mass of crushed ore without filling the interstices between the particles of ore, the volume of solution passing through the mass being between 0,5 and 10 litres per square metre of superficial ore surface per hour. The alkaline solution may contain about 5 grams of alkali metal carbonate per litre of solution. The ore is coarsely crushed and the proportion of fines of less than 1 mm. in diameter should be low. The grains are normally less than 1 cm. in diameter. Extended leaching times which may be up to several months, with recycle of the lixiviating solution, may be employed. The ore may be placed in the open on a hill side adjacent to the mine and formed into a heap, as shown in Fig. 2, supported by a wall 18. A layer of broken pottery 19 facilitates the draining off of the solution which is supplied through sprinkler 17. Porous pipes 20 assist aeration. The alkaline solution supplied is recycled after passage through ion exchange columns to recover the uranium values. In order to obviate the effects of rainfall, the concentration of the alkaline solution supplied from a tank 13 may be controlled by decreasing the quantity of water supplied to tank 13 in accordance with the rainfall. The latter may be assessed by measuring the change in resistivity of a solution, such variations in resistivity controlling a valve through which the dilution water is supplied to vessel 13.