Physics Physics Of Elementary Particles And Fields

Hanford Site Vadose-Zone Studies: An Overview

Authors: Gee, Glendon W. Oostrom, Mart Freshley, Mark D. Rockhold, Mark L. Zachara, John M.
 
Abstract: Large quantities of radioactive and chemical wastes, created from plutonium production for nuclear weapons, are located in a remote desert setting at the U. S. Department of Energy�s Hanford Site, north of Richland, Washington, USA. Much of the waste currently resides in the vadose zone. At Hanford, the vadose zone is characterized by glacial-fluvial sediments that are often highly stratified. The extremely heterogeneous sediments give rise to complex subsurface-flow paths that contribute to uncertainty of contaminant fate and transport. Research efforts have focused on answering questions of contaminant transport from the viewpoint of geologic, biologic, geochemical and hydrologic controls. This special section of the Vadose Zone Journal highlights key research topics that are systematically addressing vadose zone problems at the Hanford Site. Research to date indicates that some of the contaminant species (e.g., Cs-137, Co-60, Sr-90, uranium, etc.) are highly reactive with Hanford sediments, as predicted by geochemical considerations, rendering them effectively immobile, except under extremely saline or acidic conditions, while other species (e.g., Tc-99, I-129, H-3) are typically mobile and have moved deep into the vadose zone and subsequently into groundwater. In addition, large quantities of organics, including carbon tetrachloride, have moved in complex ways as both vapor and liquid, and have reached the water table at some locations where they represent a potential long-term threat to groundwater. Observed transport of mobile species is linked to liquid discharges and to elevated recharge rates that occur primarily at waste sites where land surfaces are void of vegetation and where winter rains have subsequently penetrated the subsurface wastes. A series of papers in this special issue document progress to date in understanding transport rates at Hanford, why anisotropy strongly affects the distribution of subsurface contaminants, why organic contaminants such as DNAPLs (e.g., carbon tetrachloride) are so difficult to find in the deep vadose zone, and what are the impacts of hypersaline fluids on waste form degradation and subsequent transport.
Publication Date: 01 Nov 2007
Report numbers: PNNL-SA-53286
DOE Contract number: AC05-76RL01830
Resource Type: Journal Article
Resource Relation: Journal: Vadose Zone Journal, 6(4):899-905; Journal Volume: 6; Journal Issue: 4
Research Organizations: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Organizations: USDOE
Country of Publication: United States
Language: English
Keywords relating to this report:
ANISOTROPY
CARBON TETRACHLORIDE
CHEMICAL WASTES
DISTRIBUTION
MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
NUCLEAR WEAPONS
PLANTS
PLUTONIUM
PRODUCTION
SEDIMENTS
TRANSPORT
URANIUM
WASTE FORMS
WASTES
WATER TABLES

Subjects:
Related subjects:
CHEMICAL CONTAMINATION
GEOCHEMICAL MODELING
GLACIAL FLUVIAL SEDIMENTS
GROUNDWATER RADIONUCLIDES
HYDROLOGIC MODELING
HYPERSALINE FLUIDS
LYSIMETERS
NUCLEAR WASTE
VADOSE ZONE