Radionuclides in Lake Michigan Fish

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Nelson, D. M.
Romberg, G. P.
Prepejchal, W.
Lake Michigan ; Fish ; Nuclear Power Plants ; Contamination ; Radionuclide concentrations ; Big Rock Station ; Point Beach Nuclear Reactor ; Samples
One apsect of the siting of nuclear power plants on Lake Michigan which has received considerable attention is the question of reactor-produced radionuclides entering the aquatic ecosystem. Once released into the environment, many of these isotopes reconcentrate in the biota, producing potentially important routes to man. Since fish constitute the most important food sources derived from Lake Michigan, it is important to know the concentrations of radionuclides present in food fishes, as well as any changes in these concentrations near power reactors. In assessing the biological significance of reactor-produced isotopes, it is necessary to consider also the natural radioactivity and the substantial inventories of nuclides already present in Lake Michigan owing to the testing of nuclear weapons. In order to provide baseline information needed to evaluate any additional radioactive releases, fish samples were collected from Lake Michigan during 1970 and 1971 and analyzed for gamma-ray emitting radionuclides. Data collected during October 1970 at the Big Rock Nuclear Reactor near Charlevoix, Michigan (a 70-MW boiling water reactor completed in 1962) indicated radionuclide concentrations in fish to be higher than expected for fish elsewhere in the lake. A repeat sampling trip was made to Big Rock in June of 1971, as well as several visits to the Point Beach Nuclear Reactor near Two Rivers, Wisconsin (a 480-MW pressurized water reactor completed in 1970).
TABLE 1. Radionuclide Concentrations in Lake Michigan Fish during 1971.; TABLE 2. Radionuclide Concentration of Fish Collected near the Big Rock Reactor.; FIG. 1 . Cs/K ratio in Lake Michigan fish. Trout, salmon, bass, and carp were measured as fillets , the others as whole fish.; TABLE 3. Contribution of Big Rock Fish Toward the Maximum Permissible Ingestion of Radionuclides.