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Mining & Processing

In Situ Leaching Method

Where the orebody exists in a saturated sandstone aquifer, boreholes are drilled into it, and the surrounding water is treated with chemicals. This enables all the uranium to be dissolved and leached from the orebody, as the chemical solution circulates through it. The solution is then pumped back to the surface through different boreholes and the uranium is recovered. This process is also known as solution mining.

The aquifer is treated with either an acid or alkali depending on the geological characteristics of the orebody. The uranium at Australia's two in situ leach mines - Beverley and Honeymoon - is contained in aquifers that are naturally acidic.

 

    


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Click the in situ leaching  button to view an interactive description of the  process.

In Situ Leaching

This technique has a number of advantages over open-cut and underground mining.
  1. Miners are not directly exposed to the orebody. There is reduced radon release and radiation because the ore is in solution. Therefore, there is very little dust.
  2. It is less expensive to operate because large amounts of rock do not have to be broken up and removed. There are also shorter lead times to production, that is, it is quicker to produce an end product.
  3. There is no solid waste. Waste is confined to evaporation ponds.
  4. It is less costly to build because it does not need the expensive infrastructure of open-cut and underground mining, i.e. shafts, tunnels, crushers.
  5. There is much less ground disturbance. There are no open pits, shafts, tunnels, earth moving equipment or grinding and crushing facilities. ISL operations take up less land and therefore there is less visual impact.
  6. There is less rehabilitation required because there is less ground disturbance. Upon completion of mining, wells can be sealed and capped, process facilities removed and the surface returned to its original contour and vegetation.
  7. Smaller, lower grade and narrower ore bodies can be mined.

However, because there is a risk of radiation in the extraction process safety procedures are embodied in all in situ leach mine operations. In situ leaching is the preferred method for developing small uranium deposits contained in underground water systems (aquifers). This is because they can be developed without destroying the aquifer, at a lower cost and with less visual impact.

The solution is brought to the surface processing plant. Here, it is treated with chemicals that cause the uranium from the solution to precipitate from the solution. The remaining solution is returned underground from where it originally came.

 

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  1 September 2005

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