2012 – AusIMM Uranium, Adelaide SA

Abstract:

One of the primary objectives of the project was to study the initial response of a uranium ore to In-Situ Leaching (ISL). This was achieved through a tailored testwork program with a stage-wise approach.  The results of each stage were analysed before proceeding to the next step.

The amenability of the sample(s) to ISL hydrometallurgical processing was studied (acid and alkaline), to allow the development of an optimised process flowsheet. This will permitted the modelling of capital and operating costs as well as cash flow related to the predicted recovery determined by the testwork.

The project began with a review of the historical test data.  The gap in the historical metallurgical testwork was clearly identified and recommendations for any further testwork made.

QEMSCAN mineralogical investigation identified the main uranium bearing minerals.  It also provides a comprehensive analysis of the liberation and locking characteristics of the uranium bearing minerals and the associated gangue minerals to highlight any potential issues in leaching.

Head assay of the drill core to match with the lithology of the hole and twin holes was carried out. Bottle roll leach tests gave an indication on the relative rate and amount of uranium extracted and relative consumption of oxidant as a function of leach solution.  This also enabled the determination of the extent of any gangue materials leaching.

The next stage of testing, the column leach test was designed to simulate field condition more closely than the bottle roll test, which allows permeability and hydraulic conductivity be measured.

Preliminary investigation also would be conducted to study the response of the leach liquor to purification by solvent extraction and ion exchange.

Pilot scale testing, involving well field hydrology and leach tests will follow after the specific issues encountered during bottle roll and column leach tests are resolved.  In here, the well plan injection and recovery pattern will be investigated.

The advantages and disadvantages of ISL are outlined. Unless the metallurgy has been demonstrated there are significant risks which could be fatal flaws to the ISL project. Key findings of the study are outlined.

Read the paper here