Modelling the distribution of radionuclides in deep ocean water columns. Application to 3H, 137Cs and 239,240Pu

A one-dimensional model to simulate the dispersion of radionuclides down deep water columns has been developed. The model includes the transfers of radionuclides between water, suspended matter and bottom sediments. Such transfers are formulated in terms of kinetic transfer coefficients. A suspended matter sub-model has also been developed to obtain the suspended matter concentration profile. The dependence of the settling velocity of suspended particles on the salinity profile and the dependence of the vertical turbulent diffusion coefficient on the horizontal water current profile are included in the model. The model has been validated by comparing measured and computed profiles of 3H, 137Cs and 239,240Pu in the Atlantic, the Mediterranean and the Pacific. Some predictive studies and sensitivity test have also been carried out.