A Mathematical Model of the Accumulation of Radionuclides by Oysters (C. virginica) Aquacultured in the Effluent of a Nuclear Power Reactor to Include Major Biological Parameters

Abstract

The uptake, accumulation and loss of radionuclides by the American oyster (C. uirginica) acquacultured in the effluent of a nuclear power reactor has been measured monthly for 3 yr at four field stations in the Montsweag Estuary of the Sheeuscot River and at a control station in the nearby Damariscotta River Estuary, southern central coastal Maine, U.S.A. A mathematical model for the time variation of the specific activity of the oysters has been developed to include the physical half-lives of the various radionuclides, the biological half-lives of the various radionuclides (biological depuration), the water temperature (oyster hibernation) and shell growth. The resulting first order linear differential equation incorporating these phenomena is driven by the liquid radionuclide effluent release schedule of the Maine Yankee Nuclear Reactor. Comparison of the monthly measurements of the specific activity for 58C0, 6oCo, "Mn, 134Cs and I3'Cs in oysters with model calculations show close agreement over all ranges of variation observed. A special feature of this mathematical model is its ability to describe the non-chemostatic field situation. INTRODUCllONtics of the loss of radionuclides in chemostatic THE ROUTINE discharge of radionuc-aquarium experiments (Cr75). lides in the liquid effluent of nuclear powerIn the presentation that folbws, we discuss reactors sited on estuarial and coastal waters a mathematical model for the uptake, acprovides an ideal field situation for the testing cumulation and loss of radionuclides by OYSof mathematical models for the uptake, ac-ters (c. uirghica) cultured in the efflent Of a cumulation and loss of radionuclides in the nuclear power reactor. This field situation, marine ecosystem. Concentration factor mod-characterized by abrupt discharges of various els (p067), power law models (~~7 1 ) and ex-radionuclides in an aperiodic manner and with ponential models (Cu74; Hi69) have been varying concentrations, Seems to be adeused by various authors to describe the kine-quately described by the model Over the 36-tics of several radionuclides in marine organ-month experimentation Period. isms. Certain experimental situations and limiting cases are best described by one of these specific models. For example, the conIn order to measure the specific activity of centration factor model best describes a gamma-ray radionuclides, a group of about 20 steady-state condition or equilibrium concent-oysters were collected from each of five raftration; the details of the loss of bone-seeking ing stations, scrubbed with a stiff brush to radionuclides seem best described by a power remove fouling organisms and transported to law m d e l while single compartment the environmental radioactivity laboratory at models are usually used to describe the kine-the Universtiy of Maine, Department of 121 EXPERIMENTAL METHOD