Survey of radiological contaminants in the near-shore environment at the Hanford Site 100-N Area reactor

Abstract

Past operations at the Hanford Site 100-N Area reactor resulted in the release of radiological contaminants to the soil column, local groundwater, and ultimately to the near-shore environment of the Columbia River. In September 1997, the Washington State Department of Health (WDOH) and the Hanford Site Surface Environmental Surveillance Project (SESP) initiated a special study of the nearshore vicinity at the Hanford Site's retired 100-N Area reactor. Environmental samples were collected and analyzed for radiological contaminants (3H, %r, and gamma emitters), with both the WDOH and SESP analyzing a portion of the samples. Samples of river water, sediment, riverbank springs, periphyton, milfoil, flying insects, clam shells, and reed canary grass were collected. External exposure rates were also measured for the near-shore environment in the vicinity of the 100-N Area. In addition, samples were collected at background locations above Vernita Bridge. River water samples were collected from five sites that bracketed the %Sr groundwater plume. Both 3H and %Sr were measured above background concentrations for the 100-N Area near-shore river water samples, with the highest 3H concentrations measured at the farthest downstream location and the highest %Sr concentration measured near the center of the "Sr groundwater plume. Transect samples of nearshore water showed that 3H and %Sr concentrations were rapidly diluted by the river. Riverbank spring water contained detectable amounts of 3H and %3r. Concentrations of gamma emitters were below levels of detections for both river water and riverbank spring water. Sediment samples collected near the 100-N Area shoreline had detectable concentrations of 6oCo, %Sr, and I3'Cs; however, 6oCo and wSr were the only radionuclides with concentrations above background. Some biota samples collected at the 100-N Area shoreline had concentrations of 6oCo and I3'Cs above background. In general, the biota results mirrored the localized river water and river sediment concentrations. External exposure rates measured along the shoreline in the vicinity of the 100-N Area ranged h m 2 to 14 pR/h, with the highest rates found along the shoreline nearest to the 1301-N and 1325-N liquid waste disposal facilities. The results fiom this study were used to estimate potential human doses resulting from recreational activity near the 100-N Area shoreline. The estimated doses are small and not expected to be harmful to people engaged in these activities. All estimated doses to aquatic biota were below 1 radday.

100-N Area Strontium-90 Treatability Demonstration Project: Phytoextraction Along the 100-N Columbia River Riparian Zone ? Field Treatability Study

“…) by as much as a factor of 1000 at several locations within the Hanford 100-N Area and along the 100-N Area Columbia River shoreline (Figure 1.1; Van Verst et al 1998). The contaminant, migrating to the shoreline through the natural groundwater flow and originating in two separate Liquid Waste Disposal Facilities (LWDFs), operated from 1963 to 1991 and was located several hundred feet away from the river (Figure 1.1A).…”

Summary of Radiological Monitoring of Columbia and Snake River Sediment, 1988 Through 2004

“…The Washington State Department of Health and the Hanford Site Surface Environmental Surveillance Project surveyed radiological contaminants in the near-shore environment adjacent to the 100-N Area during 1997 to 1998 (Van Verst et al 1998). The near-shore sampling sites bracketed the location where the maximum groundwater contours for strontium-90 had been reported.…”

“…River water, sediment, riverbank spring water, periphyton, milfoil, flying insects, clamshells, and reed canary grass from the 100-N Area near-shore environment were collected and selectively analyzed for tritium, strontium, and gamma-emitting radionuclides. Van Verst et al (1998) acknowledged that collecting sediment was difficult along the 100-N Area shoreline because of the absence of sediment; however, sediment samples were obtained at three of five sampling sites by collecting material from depressions under large rocks. Cobalt-60 and strontium-90 were the only radionuclides with elevated concentrations near the 100-N Area compared to samples from the Priest Rapids Dam pool (Dirkes and Hanf 1998).…”

“…However, the riverbank springs at the 100-N Area are composed primarily of large cobble and gravels, which are generally unsuitable for sediment sampling, so routine samples of sediment from the 100-N Area are not collected. A combined study by the Washington State Department of Health and the Surface Environmental Surveillance Project (Van Verst et al 1998) reported localized elevated concentrations of strontium-90 in sediment samples collected along the 100-N Area shoreline. However, the amount of sediment available was limited and was collected using special techniques from depressions under large rocks.…”

Chromium Toxicity Test for Fall Chinook Salmon (Oncorhynchus tshawytscha) Using Hanford Site Groundwater: Onsite Early Life-Stage Toxicity Evaluation

“…Chinook salmon could be exposed to chromium during this early life-stage interval (i.e., during egg development, hatching, and through swim up) at specific locations where contaminated groundwater was upwelling into the river. Surface water monitoring has shown the Columbia River rapidly dilutes the groundwater upwelling (Van Verst et al 1998;Poston et al 2000); thus, free-swimming juvenile salmon rearing along the shoreline before migrating downstream to the Pacific Ocean are not likely to be exposed to elevated concentrations of chromium.…”