Abstract: The annual radioactivity monitoring reports (2005—2011) for 38 typical inland nuclear power plants in US were investigated, and the artificial radioactivity levels in the sediments of receiving water of liquid effluent were analyzed. It was indicated that the long term operation of these NPPs had no obvious cumulative impacts on sediment, only at a few of which were found radioactivity originated from liquid effluents around discharge points, and much lower than the natural radioactivity concentrations. Only a very few NPPs had an effect with relatively higher concentration levels of radioactivity in sediment, which was due to the poor hydrological conditions of the receiving water for the dilution of radioactive liquid effluents. According to the dose assessments of artificial radioactivity in sediment to public individuals, all American typical inland NPPs had negligible impacts on public health compared to the natural public background and the personal dose constraint of liquid effluent regulated by NRC.

Key words: inland NPP, American environmental radioactivity, sediment, cumulative effects, dose assessment