Environmental and public heath consequences of the controlled disposal of transuranic elements to the marine environment

Experience from the controlled disposal of liquid radioactive wastes from the nuclear power programme of the United Kingdom has shown that the only releases of transuranic elements of potential environmental significance occur following fuel reprocessing. In this context attention has been directed principally to plutonium because of its long half-life and high radiotoxicity, although the next most important transuranic element, americium, has also been studied. The paper reviews the radiological significance of these radionuclides following discharge to the marine environment, in terms of both dose to man and to environmental resources. Both plutonium and americium are found in each of the three compartments, water, seabed sediment and biota, the highest concentrations being found in sediment, particularly the fine mud found in estuaries close to the Windscale outfall. Both elements have been detected in a range of biota including seaweeds, fish and shellfish. The public health significance of those biota which represent potential human exposure pathways has been evaluated and estimates of the dose rate to critical groups from current discharges have been made. In parallel studies attention has been focussed on the exposure of fish and shellfish stocks. The dose rates have been estimated by use of environmental data on contamination levels combined with simple dosimetry models, and the results and their significance are discussed. (author)