Geochemical Modeling of the Down Gradient Transport Potential of Uranium at an in-Situ Recovery (ISR) Facility.

The goal of uranium in-situ recovery (ISR) restoration is a return of the site to pre-operation baseline conditions, but historically, this is not always feasible. Uranium ISR sites typically exhibit varying degrees of natural attenuation potential that may influence the degree of restoration required, with reactive iron and organic carbon shown to strongly influence uranium transport and fate.  Reactive transport modeling provides useful insight into the inherent restoration potential of a mined aquifer, providing stakeholders with a better understanding of potentially necessary restoration requirements.  1-D uranium transport surface complexation modelling efforts were completed for an existing ISR site.  Batch adsorption isotherm experiments were conducted using post-mining and post-reclamation soil core samples, site upgradient groundwater, and completed using varying pH, carbon dioxide, and uranium concentrations.  The results from the batch experiments were used to determine the soil attenuation capacity using a combination of PHREEQC for geochemical and transport calculations, and PEST for parameter calibration.  A general composite, site-specific sorption approach was used for the surface complexation estimates.  Forward model runs were completed to predict the potential transport of uranium during various mine restoration scenarios