Radioactive contamination in the marine environment. Report no. 3 from the national surveillance programme

The data collected as part of the National Surveillance Programme indicate that radioactivity in the water surrounding Norway remains at low levels. In fish and shrimps, 137Cs activity concentrations are approximately 1.2 Bq/kg or less. 137Cs levels in the water surrounding Norway have decreased significantly since their peak concentrations detected around 1980. However, in recent years the variation in radiocesium concentration in the sea water can largely be explained by variations in the water exchange with the Baltic Sea. The influence of Chernobyl fallout on the concentrations of these radionuclides is clearly seen. The levels decrease with increasing distance away from the Baltic Sea. Other radionuclides, i.e. 238Pu, 239,240Pu, 60Co and 241Am were found in low concentrations only. The reprocessing plant at Sellafield in United Kingdom began operating a new waste treatment in 1994. This has resulted in changes in the composition of radionuclides being discharged into the sea as waste. As a result, the concentration of 99Tc in the waters surrounding Norway has increased in recent years and the highest levels of radioactivity detected in marine biota during the surveillance program were for 99Tc in lobster. The increase in 99Tc is also clearly observed in seaweed