Mining Methods "in-situ leaching"

In situ leaching (ISL), also known as solution mining, involves leaving the ore where it is in the ground, and using liquids which are pumped through it to recover the minerals out of the ore by leaching. With this method of mining there is little surface disturbance and no tailings or waste rock generated.  The only requirement however is that the orebody is  permeable to the liquids used, and located so that they do not contaminate ground water away from the orebody. Uranium deposits suitable for ISL occur in permeable sand or sandstones, confined above and below by impermeable strata, and which are below the water table. There are two operating regimes for ISL, determined by the geology and groundwater. If there is significant calcium in the orebody (as limestone or gypsum), alkaline (carbonate) leaching must be used. Otherwise, acid (sulfate) leaching is generally better. Techniques for ISL have evolved to the point where it is a controllable, safe, and environmentally benign method of mining which can operate under strict environmental controls and which often has cost advantages. In-situ leaching gains importance for the exploitation of low grade ore deposits, for its low production cost. Many new projects for uranium in-situ leaching are being planned at present.

The advantages of this technology are:

• the reduced hazards for the employees from accidents, dust, and radiation,
• the low cost;
• no need for large uranium mill tailings deposits