Chair ISR-U

Uranium exploitation by in situ recovery: modeling from the lab to the operations

Mining… without moving rocks: operational and environmental benefits, but no direct access to the deposit by the operator

Exploitation by in situ recovery is a mining technique consisting in the circulation of a leaching solution into an ore body to dissolve the metal of interest.  The metal is separated at the plant then the solution is recycled to the well field. This technique is very interesting: low energy consumption (hence reduced CO₂ emissions), relatively low production costs, very low land impact (since the ore stays in place, no generation of waste rock or tailings). However, exploitation management relies on a limited view of the deposit: the operator has only access to its initial estimation of the ore (exploration) and the history of leaching solution (metal produced, reactant consumption).

The ISR-U project aims at better understand the global processes at stake to provide a quantitative dynamic 3D view of the exploitation. Provided it is sufficiently predictive, a model can become an operational decision making tool: test of alternative production scenarios, choice of exploitation strategies, and even short and long term planning tool.

Coupled flow and geochemistry simulation: from a laboratory code to an operational software suite

The Geosciences Department has been developing for more than twenty years a software to simulated the interaction between flow (water, gas), transport (dissolved elements), and geochemical reactions: Hytec. It can simulate flow circulation in the well field and its interaction with the ore minerals. Since the simulation is based on physico-chemical processes on the one hand, and measured (permeability, flow rates) or estimated (metal content of the ore body) parameters on the other hand, the need of fitting parameters is drastically reduced hence an enhanced predictive capacity.

Hence, one of the goals of the project was to characterize the deposits and the production processes in order to provide a simulation both realistic and fast enough to be used in operational conditions. The simulation has to accurately reproduce all the observables useful for the operator: metal produced, reactant consumption, residual metal in place… including gangue minerals with an influence on these results.

Second strong objective: make a research computation code useable for operators. The numerical code was integrated in a software suite: HYSR-Hytec-Paraview. The suite takes operational data, automatically transforms them into model specifications, and yields simulation results in a format familiar to the operators.

Main results

Thanks to a development and qualification of the software faster than anticipated, the suite could be tested in operational conditions on numerous production blocks: simulation of the exploitation, production optimization opportunities, clogging mechanisms…

The project also addressed how to integrate simulations information to improve short-term and long-term planning (optimization, predictions compared to yearly objectives versus sequence of development of new areas of the mine). The impact of geological uncertainty (imperfect knowledge of the deposit) was also integrated.

Scientific production and patents since the beginning of the project

Although reactive transport simulation has been in use for thirty years, this is the first demonstration of its use in an industrial operation. This was highlighted by an invitation to prepare a chapter in Reviews in Mineralogy and Geochemistry, a reference for reactive transport.

The HYSR-Hytec-Paraview suite was extensively tested at the mine site for two years. Very conclusive results led the consortium to change the valorization strategy, with the possibility to license the software.

The simulation approach and results obtained at the mine were presented in several scientific or professional conferences. This is a real showcase of our expertise for future projects: new research contract for the laboratory, an interesting angle to negotiate new permits for Orano.

3D view of a uranium ISR production block (wells, dissolved uranium concentration in the deposit). The figure was obtained by reactive transport simulation with the suite HYSR-Hytec-Paraview, based on operation data (geological model, wells flow rate, concentration of injected reactants).

Basic facts

The ISR-U project is an industrial research chair coordinated by Vincent Lagneau at MINES ParisTech in close collaboration with Orano. The project was largely based on production data from the Katco mine (Kazakhstan, joint venture Orano-KazAtomProm). The project started in October 2016 for four years, with a total funding of 1.8 M€ brought half by ANR and the other half by Orano.