Reactive transport modelling as a toolbox to compare remediation strategies of aquifers impacted by uranium in situ recovery

Worldwide uranium production is based on the In Situ Recovery mining technique. This exploitation mode directly falls within the scope of the applications of reactive transport modelling to optimize uranium production and limit its associated environmental impact. We hereby propose a modelling approach which is able to represent the natural evolution of the aquifer impacted by the exploitation of an ISR test. Model is calibrated on 12 year-long data obtained from 12 monitoring wells surrounding the ISR pilot cell. Through this process based approach, we simulate the impact of several remediation strategies which could be considered in these contexts. In particular, we model the impact of pump and treat combined with reverse osmosis as well as the circulation of non-impacted fluids through the reservoir with different operating strategies. We show that our approach allows to compare the effectiveness of these strategies. We show that, for this small-scale ISR pilot, monitored natural attenuation constitutes an interesting approach due to its faster pH recovery time with respect to Pump & Treat and circulation of unimpacted fluids. Combined with an economical evaluation of their deployment, this approach can help the mining operator select and design the optimal remediation strategies, from an environmental and economical standpoint.