Caractère conservatif de l'antimoine 125 dans les eaux marines soumises à l'influence des rejets de l'usine de retraitement des combustibles irradiés de La Hague

Abstract

Conservative behaviour of 125 antimony in marine waters under the influence of discharges from La Hague repmessing plant '%b is one of the soluble radionuclides in the radioactive wastes dumped into the sea by the COGEMA nuclear repmessing plant of La Hague. Its removal from the liquid waste was started in 1976, first by chemical extraction with titane hydroxyde, and since 1990, by evaporation and vitscation of the residues. Compared to 1975, this results in an improvement in the reprocessing process by a factor of 1,500. The behaviour of '=Sb in sea water is depending on hydrolysis of Sb oxydation state V. Its transfer capacity from sea water to other compartments of the environment is low; transfer factor values are below 50 L kg-' (wet weight) for seaweeds and animals and between 60 and 900 L kg-' for sediments (depending on clays fraction). Thus, %b is a reliable tracer of water mass flows which was used to fit hydrodynamic models in the Channel and the North Sea with the real conditions in the environment. Since the setting up of the reprocessing plant in 1%6, the highest rate of '%b discharge was 150 to 180 TBq y-) between 1983 and 1987. Then, it has markedly dropped and it is below 0.5 TBq y.' in 1995 and 1996.