The marine impact of caesium-134 and -137 from the Chernobyl reactor accident

134Cs and 137Cs from the Chernobyl reactor accident were detected in UK shoreline seawater very quickly after activity from the accident reached this country. Concentrations were highest in areas adjacent to those where deposition over land was highest, but they declined quickly and did not reach radiologically significant levels in therms of public radiation exposure. Subsequently, the distribution in seawater was investigated further afield. Radio-caesium attributable to the Chernobyl accident was found to be widespread: it was readily distinguished from other sources by having a different 137Cs:134Cs ratio (about 2:1). Its presence was especially noticeable in northern UK waters rather than those to the south; much of the North Sea has been surveyed as well as the Norwegian Sea. Evidence of Chernobyl radiocaesium was found as far north as 700 N and in many of these areas, including the northern North Sea, it overshadowed the effect of BNFL (British Nuclear Fuels plc) Sellafield discharges, previously the main source of these radionuclides. (author)