Distribution of 137Cs and inventories of 238Pu, 239/240Pu, 241Am and 137Cs in Irish Sea intertidal sediments

Estimated total inventories of 41 TBq 137Cs, 19 TBq 241Am, 13 TBq 239/240Pu and 2 TBq 238Pu were calculated for the intertidal sediments of the eastern Irish Sea to a depth of 50 cm. These estimates should be more accurate than previous inventory figures since they are based on a much greater number of observations; most earlier estimates were based on extrapolation from analysis of small numbers of samples. However, they will almost certainly be underestimates, by up to an order of magnitude, since full account has not been taken of the vertical distribution of radionuclides in the sediments and because there are almost certainly significant quantities of radionuclides at depths greater than 50 cm. The inventories were obtained from field and laboratory studies of the distribution of gamma-emitting radionuclides (principally 137Cs) in the sediments with data for the actinides being derived by establishing their relationships to 137Cs through analysis of sediment samples by gamma and alpha spectrometry.