137Cs/90Sr ratios in the Irish Sea and adjacent waters : A source term for the Arctic

The assessment of the water transport of coastal pollution from European nuclear reprocessing facilities to the Arctic Seas can be achieved by the analysis of conservative radionuclides, such as 90 Sr, 137 Cs and 99 Tc. By obtaining their isotopic signatures in different water masses, it is possible to determine the present contribution of these radionuclides by a known source term and to differentiate this from other inputs. However, in recent years, relatively few environmental measurements have been made of 90 Sr resulting from the discharges by the British Nuclear Fuels plc plant at Sellafield, UK. In 1995, a collaborative expedition was carried out in the northern Irish Sea (and surrounding coastal waters) to determine 90 Sr concentrations in surface sea water samples. The results of this survey, and an intercomparison of the analytical data are presented, together with 137 Cs/ 90 Sr activity ratios. Information concerning the isotopic signature in different water masses enables an assessment of the extent of transport of these radionuclides out of the Irish Sea and the potential source term to the Arctic that this represents.