New Models of Uranium Migration at the Hanford Site Shed Light on its Persistance

Summary

Three recent modeling studies shed light on the importance of the coupled physical, chemical, and geological factors that have caused a uranium plume at the Hanford 300 Area to persist over three decades. In contrast, legacy models of the site predicted that natural flushing of the aquifer would reduce the uranium concentration in the groundwater to drinking water standards within 10 years. These new simulations, performed by different teams, ranged in duration from a few days to 20 years and in spatial scale from laboratory columns to a massive 3-D field-scale simulation of the Hanford 300 Area. The smaller scale experiments elucidated the importance of various geochemical factors that control the adsorption and release of uranium from sediments. The field scale simulations executed on ORNL’s Jaguar supercomputer (Hammond and Lichtner, 2010), tested how pore scale processes couple with larger scale factors to control the evolution of the uranium plume over longer time periods. The results indicate that rapid fluctuations in the Columbia River stage combined with the slow release of bound uranium from contaminated sediment are the primary cause for the persistent uranium plume at the Hanford 300 Area. These DOE funded modeling studies are guiding the design of additional field and laboratory investigations to better understand the spatial and temporal dynamics of the plume and to inform future remediation efforts at the site.

References

Hammond, G. E., and P. C. Lichtner. 2010. “Field-scale model for the natural attenuation of uranium at the Hanford 300 Area using high-performance computing,” Water Resour. Res., 46, W09527, doi: 10.1029/2009WR008819.

Ma, R., C. Zheng, H. Prommer, J. Greskowiak, C. Liu, J. Zachara, and M. Rockhold. 2010. “A field-scale reactive transport model for U(VI) migration influenced by coupled multirate mass transfer and surface complexation reactions,” Water Resour. Res., 46, W05509, doi: 10.1029/2009WR008168.

Greskowiak, J., H. Prommer, C. Liu, V. E. A. Post, R. Ma, C. Zheng, and J. M. Zachara. 2010. “Comparison of parameter sensitivities between laboratory and field-scale model of uranium transport in a dual domain, distributed rate reactive system,” Water Resour. Res., 46, W05509, doi: 10.1029/2009WR008781.