RADIOLOGICAL ASSESSMENT OF RADIOACTIVITY IN TIDE WASHED PASTURES IN SOUTH-WEST SCOTLAND

A study has been carried out to determine the impact of Sellafield dis charges on the levels of radioactivity in tide washed pastures in sout h-west Scotland. Likely areas of tidal inundation along the Nith, Urr, Dee, Fleet and Cree rivers were assessed using maps and aerial photog raphs. These were then visited and gamma radiation measurements taken at regular intervals to enable the external dose from anthropogenic nu clides to be estimated. A further survey followed, in which soil cores were taken from the areas on each river where the external dose appea red highest and analysed for a range of radionuclides. The levels of C s-137, Cs-134, Pu-238, Pu-239+240 and Am-241 found, although small, we re clearly in excess of the background from other sources and confirme d that there was a significant contribution from Sellafield marine dis charges. A habit survey was undertaken to provide site specific inform ation of tide washed pasture usage, which, with the spatial radionucli de data was used to estimate doses to appropriate critical groups. The maximum annual dose calculated to arise was 60 muSv which is less tha n 6% of the ICRP principal dose limit of 1 mSv.