Hanford's West Lake and the Biota Dose Assessment Committee's screening methodology

Full text: Radionuclide data collected at the Hanford Nuclear Reservation's West Lake (a small seepage pond) was used to test the utility of the U.S. Department of Energy's Biota Dose Assessment Screening Methodology for protection of plants and animals from ionizing radiation. The Hanford Site environmental surveillance database was queried for all 1999 data on radionuclides in surface water, soil and sediment. Maximum and mean radionuclide concentrations were determined for each combination of radionuclide + media. These data were entered into the Biota Dose Assessment Committee's 'Biota Concentration Guide Calculator', a semi-automated tool used to determine compliance with proposed biota dose limits for shorebirds (riparian animals with a proposed dose limit of 0.1 rad/day). Concentrations in the aquatic environment did not pass the screen. Further review of the data indicated that a water sample taken from the lake exceeded the limiting water concentration for uranium. As a consequence of the assessment, a limited biota monitoring effort was established to determine the potential exposure of wildlife at West Lake. The effort involved determining residence time of breeding shorebirds and actual tissue burdens of radionuclides in the birds. In the final analysis, West Lake was determined to be in compliance with proposed radiological dose limits. The application of this methodology has helped to identify a potential exposure problem and provide direction for the sampling program. (author)