Radiation dose rate estimates to marine biota resulting from the routine radioactive releases of the nuclear power plants in Daya Bay

Five marine organisms in Daya Bay are selected for estimating the dose rate s. Internal exposure and its 5 pathways are also considered.,The concentrat ions of 43 kinds of background and additional radionuclides in seawater are from the survey of background radioactivity and the prediction of routine radioactive releases of the 4 reactors. Point source dose distribution func tions are used to estimate the dose rates to various organisms from alpha a nd beta radiation. Monte-Carlo method is used to determine the absorbed fra ctions in the organisms from gamma radiation. Results indicate that the bac kground dose rates are 2.72 mGy . a(-1) to phytoplankton and 1.75 mGy . a(- 1) to zooplankton. The dose rates to other organisms are in the range of 0. 31-0.49 mGy . a(-1). The additional dose rates from the routine releases ar e varied to different organisms. They reach the range of 5.7-6.1 times of t he background dose rates to benthic crustaceans and mollusks, which are 8.3 %-15.3% to fishes, and only 0.2% to plankton. beta internal irradiation fro m additional radionuclides is the critical pathway to plankton. I-131 and C o-60 are the major contributors to zooplankton, while Ru-103, Co-60 and Co- 58 are the main contributors to phytoplankton, gamma external irradiation f rom sediment is the critical pathway to benthic organisms. Co-58 and Co-60 are the main contributors. The main pathways to fishes are internal beta an d gamma irradiation. Sb-124 is the critical radionuclide.