A 2D long term advection-dispersion model for the Channel and Southern North Sea Part A: Validation through comparison with artificial radionuclides

A 2D long term advection-dispersion model has been used to compute the fate of two artificial radionuclides discharged at La Hague Cape by a nuclear fuel reprocessing plant, over the last ten years: 125Sb and 99Tc. The model provides a synoptic view of marine mechanisms and a large number of numerical results which have been compared to data supplied by five European laboratories participating in the Mast-52c program. Results show that both kinds of information are coherent and generally within a 20% error margin. Careful examination of these results reveals better correlation with results from some laboratories for 99Tc and with those of others for 125Sb. In the latter case, both kinds of data have tended to become closer over recent years. This would suggest that experimental detection methods have improved. As model indications appear to differ slightly when compared to 125Sb and 99Tc measurements, we can hypothesize that technetiumʹs conservativity in sea water is better than that of antimony.