Dynamical models for uranium leaching: production and remediation cases.

A dynamic compartmental model has been developed to combine solute transport in double-porosity media with geochemistry, using the US Geological Survey's PHREEQC code to describe both kinetics and thermodynamics. Among other applicationa, the model has been used to simulate quite different real-world scenarios related to uranium mining. In the case of acid in-situ leaching at Beverley mine in South Australia, the model was adapted to optimising wellfield operation and uranium processing under various orebody conditions. The leaching dynamics was first studied within a simple analytical mode for a single wellfield of 28 injection and 14 extraction wells; this mathematical description is presented and the numerical model calculations for cycle operation are discussed, including the incorporation of dissolution kinetics for coffinite and other primary silicate minerals as well as taking account of chemical equilibrium with secondary minerals such as gypsum, hydroxides and amorphous silica. The second case study is of the use of the model to simulate remediation, in the flooding of the deep Konigstein uranium mine in Saxony. The compartments in the model included 18 mine workings and the 7 sandstone pillars between the workings and the control tunnel, where water was collected and pumped to the surface for treatment; in each compartment the geochemical mass transformations of leaching and flushing were described with reference to two subspaces, the pore space and the mine void.
A dynamic compartmental model has been developed to combine solute transport in double-porosity media with geochemistry, using the US Geological Survey's PHREEQC code to describe both kinetics and thermodynamics. Among other applicationa, the model has been used to simulate quite different real-world scenarios related to uranium mining. In the case of acid in-situ leaching at Beverley mine in South Australia, the model was adapted to optimising wellfield operation and uranium processing under various orebody conditions. The leaching dynamics was first studied within a simple analytical mode for a single wellfield of 28 injection and 14 extraction wells; this mathematical description is presented and the numerical model calculations for cycle operation are discussed, including the incorporation of dissolution kinetics for coffinite and other primary silicate minerals as well as taking account of chemical equilibrium with secondary minerals such as gypsum, hydroxides and amorphous silica. The second case study is of the use of the model to simulate remediation, in the flooding of the deep Konigstein uranium mine in Saxony. The compartments in the model included 18 mine workings and the 7 sandstone pillars between the workings and the control tunnel, where water was collected and pumped to the surface for treatment; in each compartment the geochemical mass transformations of leaching and flushing were described with reference to two subspaces, the pore space and the mine void.