99Tc in the Irish Sea. Recent trends

The increase in discharges of 99Tc from Sellafield has resulted in an ideal opportunity to study the behaviour of this radionuclide in the aquatic environment. Results, thus far, have demonstrated that 99Tc uptake by seaweeds collected from around the Irish Sea has followed the anticipated trend, with brown seaweeds accumulating 100-1000 times more 99Tc than red or green algae. The large increase in discharges of 99Tc from Sellafield in 1994 had been matched by a similar increase in the levels present in brown seaweeds, mussels and winkles for which concentration factors of 24000, 5000 and 100, respectively, have been derived. This confirms the observation that 99Tc uptake by marine organisms in the field far exceeds that which would be expected from laboratory studies. Thus, it is concluded that, given the radiological importance of this nuclide, the provision of more accurate information on its environmental behaviour is required. (author)