Uranium orebody, leaching

Equilibrium, Kinetic, and Chromatographic Controls of the Solution Composition Obtained during the in situ Leaching of a Uranium Orebody... 

A suite of 314 groundwater-lixiviant samples were collected from monitoring wells located in an uranium orebody before and while the orebody was being situ leached. The collected samples cover a 61-day period. The major chemical species initially present in the groundwater were Na , K , Mg ", ... 

A good example is the contamination of groundwater by mineral acids from in situ leach projects. In the Stratz mining area of the Czech Republic, over a 25-year period over 3.8 million tons of sulfuric acid, 100000 tons each of nitric and hydrofluoric acid and 1 million tons of ammonia was injected into a fracture and litholgically controlled uranium orebody. Considerable leakage of the system has resulted in major contamination which is currently being re-addressed (Thomas 1996). 

The modelling that has been applied to date to the situ leaching of uranium has primarily consisted of modelling the hydrologic behavior of the lixiviant as a function of time. A more sophisticated model has combined a chemical model v/ith the hydrologic model to describe the dissolution of uranium and the pore volumes of lixiviant required to leach the orebody (2). 

One popular ettneept holds that the metals are progressively leached from the host rock as the roll front passes through it. Uranium districts are found in areas where the background levels of uranium are elevated. Based on the nature of the alteration, leaching trf the host rock on the oxidized side of a roll can be extremely inten.se. With the remarkable efficiency of the precipitating mechanism only a few parts per million of uranium have to be removed from the volume of oxidized rock associated with most roll-front deposits to account for the amount of uranium in the orebody. 

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