Radiological implications from the temporal development of radioactivity in marine food from the North Sea

A subject of the revision of authorised limits in 1994 for the discharge of liquid radioactive waste by the reprocessing plant Sellafield (UK) was an increase of these limits for certain radionuclides (H-3, C-14, Co-60, Tc-99 and I-129). It is investigated now how the radioactivity in marine biota f rom the North Sea and subsequently the public radiation exposure of seafood consumers has developed in the years since 1994. This is based on a compar tment model for dispersion in the North-East Atlantic. Discharges from the reprocessing plants Dounreay (UK) and La Hague (F) are included in the asse ssment. It is deduced that about 60% of Cs-137 in the North Sea originate p resently in the remobilisation of old Sellafield discharges from the irish Sea sediment. A comparison with measured biota data shows that the model is conservative in most cases. The public radiation exposure (artificial radi onuclides) from ingestion of fish, crustaceans and molluscs from the centra l North Sea as the sum over 12 considered radionuclides has decreased from 1992 to 1998 from 0.13 to 0.08 mu Sv y(-1).