Comparison of the MARINA II dispersion model with CSERAM for estimating concentrations of radionuclides in UK waters.

A strategy was agreed in 1998 by the OSPAR Commission to achieve, by 2020, near zero concentrations of anthropogenic pollutants and near to background levels for pollutants that also occur naturally. One of the uses of the MARINA II model was to test the feasibility of this strategy, given inherited activity concentrations. The model has been validated extensively within the OSPAR region using spatial measurements of nine radionuclides, including ⁹⁹Tc, ¹³⁷Cs and ^239/240Pu, over the period 1990-2000. Typically the model is found to agree with measurements to within a factor of three, with a marginal spatial bias towards underestimating activity concentrations. In this study, future estimates of activity concentration were tested in a comparison to CSERAM, a high-resolution, physically based model of the Irish Sea, for Sellafield discharges of ¹³⁷Cs and ^239/240Pu. Both models show good agreement to the year 2000, although differences of up to an order of magnitude can be observed close to the discharging source by 2020. Typically both models agree to within a factor of five elsewhere by 2020. This study illustrates that MARINA II is a computationally inexpensive but effective tool for calculations of activity concentration in radiation protection. [ABSTRACT FROM AUTHOR]