Radiological benchmarks for effects on aquatic biota at the Oak Ridge reservation

Radiological benchmarks for aquatic biota were developed for use at the U.S . Department of Energy's Oak Ridge Reservation as screening values to deter mine the spatial extent of potential ecological effects and to identify the need for additional site-specific investigation. The Point Source Dose Dis tribution approach was used to calculate water and sediment activities for selected radionuclides that result in a total dose rate to small and large fish of 1 Rad d(-1), which is the National Council on Radiation Protection and Measurements' recommended acceptable dose rate to natural populations o f aquatic biota. These screening values incorporate internal and external e xposures from parent isotopes and all short-lived daughter products. They a lso include exposures from all major alpha, beta, and gamma emissions for e ach isotope. Unlike exposures to chemicals, exposures to radionuclides are expressed as the dose rate received by the organism. Dose rates that accoun t for the biological effects to the organism are additive. If the total dos e rate from all radionuclides and pathways exceeds a recommended acceptable dose rate, further analysis is needed to determine the hazards posed by ra dionuclides. If, however, the total dose rate falls below an acceptable dos e rate, radionuclides may be eliminated from further study.