PNNL

Abstract

The persistence of a hexavalent uranium [U(VI)] plume in the subsurface at the Hanford 300 Area is of concern to the U.S. Department of Energy (DOE). This work focusses on the quantification of groundwater flow and subsequent U(VI) transport uncertainty due to heterogeneity in the sediment permeability at the site. U(VI) migration at the Hanford 300 Area is simulated with multiple realizations of stochastically-generated high resolution permeability fields and comparisons are made of cumulative water and U(VI) flux to the Columbia River. The massively parallel code PFLOTRAN developed under the DOE SciDAC-2 project is employed on up to 40,960 processor cores on DOE's petascale Jaguar supercomputer to simultaneously execute 10 transient, variably-saturated groundwater flow and U(VI) transport simulations within 3D random permeability fields using the code's multi-realization simulation capability. Simulation results demonstrate that the cumulative U(VI) flux to the Columbia River is less responsive to fine scale heterogeneity in permeability and more sensitive to the distribution of permeability within the river hyporheic zone and mean permeability of larger scale geologic structures at the site.