In situ leaching tests of a uranium orebody in a granitic medium

Crystalline formations (mainly in France) have been found to contain amounts of uranium too small to be extracted by usual methods. This has led to a study of several methods of in situ leaching in a fractured medium accompanied by studies of how to prepare the site and develop tools for carrying out and controlling the operation. The first step was a geostatistical survey by radioactive logging. As the first experiment with vertical circulation of water between an infiltration basin and a series of drains drilled from an underlying horizontal gallery yielded too small amounts of water, blasting was used to fracture the rock. A suitable experimental field was thus obtained and equipped with: - 8 injections wells (diameter: 140 mm, depth: 20 m); - 1 central well (diameter: 140 mm, depth: 25 m) with a submersible pump. In the course of the operation 1140 m3 of acid fluids were injected and 1300 m3 of solutes pumped out. The amount of uranium recovered was only 14.4%. The reasons for this low figure were determined by hydrogeological analysis and the results interpreted