Radionuclide Concentrations in Terrestrial Vegetation and Soil Samples On and Around the Hanford Site, 1971 Through 2008

Abstract

SummaryEnvironmental monitoring is conducted on the U.S. Department of Energy (DOE) Hanford Site to comply with DOE Orders and federal and state regulations. Major objectives of the monitoring are to characterize contaminant levels in the environment and to determine site contributions to the contaminant inventory. This report focuses on surface soil and perennial vegetation samples collected between 1971 and 2008 as part of the Pacific Northwest National Laboratory Surface Environmental Surveillance Project performed under contract to DOE. Areas sampled under this program are located on the Hanford Site but outside facility boundaries and on public lands surrounding the Hanford Site. Additional samples were collected during the past 8 years under DOE projects that evaluated parcels of land for radiological release. These data were included because the same sampling methodology and analytical laboratory were used for the projects.The spatial and temporal trends of six radionuclides collected over a 38-year period were evaluated. The radionuclides-cobalt-60, cesium-137, strontium-90, plutonium-238, plutonium-239/240, and uranium (reported as either uranium-238 or total uranium)-were selected because they persist in the environment and are still being monitored routinely and reported in Hanford Site environmental reports. All these radionuclides were associated with plutonium production and waste management of activities occurring on the site. Other sources include fallout from atmospheric testing of nuclear weapons, which ended in 1980, and the Chernobyl explosion in 1986. Uranium is also a natural component of the soil.Spatial trends involved comparing data from onsite locations with data from offsite locations. Offsite locations were divided into three categories based on distance from the site. These distance categories were perimeter (which included sites that were on the Hanford Site but away from facilities and reactors, such as sites on Rattlesnake Mountain (i.e., Fitzner/Eberhardt Arid Lands Ecology Reserve) and across the Columbia River); nearby locations (sample sites within 20 miles of the closest site boundary); and distant sites (locations greater than 20 miles from the closest site boundary).Additional spatial analysis evaluated data collected from the various onsite operational areas. Onsite areas included• the 100 Areas where the reactors were located along the Columbia River• 200 Areas on the Central Plateau and the site of much of the fuel reprocessing and waste storage• 300 Area on the southern edge of the site near the Columbia River where fuel fabrication and testing occurred• the 400 Area, which was the site of the Fast Flux Test Facility (FFTF)• the 600 Area, which included open areas between the other industrialized areas, such as the Hanford town site, near the Energy Northwest plant, and FFTF; and two perimeter locations at the Prosser and Yakima barricades.For temporal analysis, data were compared across decades (1970s, 1980s, 1990s, and 2000s).Soil and vegetation concentrations of radi...