The in situ recovery (ISR) method can be used to mine low-grade uranium deposits when geological conditions are suitable. It consists in pumping a “lixiviant”, or leaching solution, into the deposit to dissolve and recover the uranium. 47%* of uranium ores worldwide are mined using ISR technology.
*Source : IAEA/NEA/OECD - Uranium 2014 Report: Red Book Highlights Continuing Growth Trend
Criteria for use of in situ recovery
The deposit to be mined must satisfy several criteria before in situ recovery technology can be used. The geological formation containing the uranium, mainly sandstone layers, must be permeable enough to allow the leaching and recovery solution to circulate through the mineralization.
"Leaching" is the dissolution of solid material into liquid.
- Permeability must be homogeneous across the formation.
- The mineral must not prevent the formation of a leachable Eh and pH environment in the solution.
- The flow of the solution underground must be controlled, contained within the mineralized zone and kept separate from the other aquifers in the ground (thick impermeable clayish layers at the top and the bottom of the sandy uraniferous reservoir).
This mining method is most suitable for low-grade deposits in permeable rocks.
In situ recovery stages
In situ recovery is a method of recovering uranium from the ground using chemicals. It takes place in the following stages:
- The leaching solution is injected through the ore and it dissolves the uranium as it circulates through the deposit.
- The solution containing the uranium (known as the production solution) is pumped to the production facility located on the surface.
- At the production facility, the uranium is separated from the solution, purified, dried and formed into the saleable product, uranium concentrate.
- The uranium-barren leaching solution is then injected again into the deposit.
In situ mining is a closed-circuit operation.
Throughout in-situ recovery, the solution injected and pumped back through the production well is monitored. Groundwater monitoring also takes place, with analyses carried out to check water quality.
ISR has the following advantages over traditional mining methods:
- It causes little change in the environment of the mining area.
- It significantly reduces radioactivity level for workers.
- It produces very little waste – no heaps or solid waste – so waste storage is not a problem.
- A deposit can enter production in a short space of time.
- It requires little energy.
- It can be used to mine minerals that cannot be mined using traditional methods due to host-rock characteristic, grade, volume, depth or environmental issues.
Discover how in situ recovery (ISR) is used as a standard technique to extract uranium from deposits with characteristics similar to the deposits found in Dornogobi province.