Uranium Mobility During In Situ Redox Manipulation of the 100 Areas of the Hanford Site

This study investigates the remobilization of uranium during the end of an in situ sediment reduction process targeted for remediation of chromate- and chlorinated solvent-contaminated sediments at the Hanford Site in Washington. The primary objective is to evaluate the behavior of uranium species undergoing changes from the +6 valence state [U(VI)] to U(IV) during the reduction process. A series of laboratory experiments, including computer simulations, were conducted to quantify uranium accumulation and assess the potential risks of groundwater contamination. The method involved subjecting groundwater samples (initially containing uranium at 10 ppb as U(VI)) to specified reduction conditions, followed by detailed analysis of uranium concentrations using a calibrated uranium analyzer. Results indicate that under defined sediment remediation conditions, U(VI) concentrations can be effectively reduced and precipitated as U(IV), which suggests a feasible approach to mitigate groundwater contamination risks in the Hanford area. Findings from this research contribute to a better understanding of uranium mobility and its implications for subsurface remediation efforts in contaminated sites.