Coupled Geochemical and Hydrological Processes Governing the Fate and Transport of Radionuclides and Toxic Metals Beneath the Hanford Tank Farms

Abstract

This project addresses the goals of the Environmental Management Sciences Program (EMSP) that seeks innovative basic research to benefit cleanup technologies and decision-making strategies for contaminated environments. Our proposal specifically addresses Hanford research needs in subsurface science by contributing to the objectives of the Tank Farm Vadose Characterization Project and the 200 Area Remedial Action Project (http://www.bhi-erc.com/projects/vadose/sandt/stdocs/subneeds.pdf) which are components of the Hanford Site Groundwater/Vadose Zone Integration Project (Integration Project). The work described in this proposal will advance the technological and scientific needs associated with the long-term management of the enormous inground inventories of 235/238U, 99Tc, 60Co, and Cr(VI) present at the Hanford site. We believe that scientifically defensible predictions of contaminant transport and strategies for remediation must be based upon a field-relevant understanding of coupled hydrological and geochemical processes that control subsurface contaminant fate and transport. This research project investigates the migration of 235/238U, 99Tc, 60Co, and Cr(VI) in undisturbed sediments from the Hanford site using realistic experimental protocols designed to delineate complex hydrological and geochemical processes controlling contaminant movement. The work complements and builds upon our current EMSP project 70219, which is scheduled to end this year, and our Hanford ST (2) to quantify the rates and mechanisms of radionuclide and toxic metal interaction with the solid phase under various hydrologic conditions; and (3) provide new insights into how physical and mineralogical heterogeneities (e.g. stratification, pore regime connectivity, mineral composition along flowpaths) influence contaminant retardation and the degree of geochemical nonequilibrium during transport.