Abstract
A detailed description of the advanced version of compartment model POSEIDON-R for the prediction of transport and fate of radionuclides in the marine environment is given. The equations of transfer of radionuclides in the water and bottom sediment compartments along with the dynamical food chain model are presented together with dose module to assess individual and collective doses to the population due to the regular and accidental releases of radionuclides. The method for the numerical solution of model equations is also presented. The modelling results for the northeast Atlantic shelf seas were compared with measurements of (137)Cs. •The three-dimensional compartment model POSEIDON-R describes the transfer of radionuclides and their daughter products in marine environment as a results of regular or accidental releases. This includes any transfer through the water column and sediments.•The model is complemented by a dynamic food chain model for transfer of radioactivity in pelagic and benthic food webs.•The dose module in the model calculates internal and external doses for humans and non-human biota.