Numerical modelling for the distribution of 137Cs and 131I in the scheldt basin after a potential nuclear accident

Using the discontinuous Galerkin method in the SLIM modelling framework, we study the transport in the Scheldt basin and adjacent coastal area of radionuclides possibly emitted by Doel nuclear power plant in the aftermath of an accident. The contamination pathways taken into consideration are direct liquid releases into the water and deposition via the atmosphere. In past nuclear accidents, several radionuclides were released, among which, 131I and 137Cs were considered herein. The hydrodynamics and atmospheric conditions are selected to simulate the worst-case scenario in the domain of interest. The radionuclide deposition towards the North Sea results in 131I and 137Cs being transported to the Belgian coastal region. In case of deposition towards the river, radioactivity from upstream tributaries can reach the estuary within days. Direct liquid releases spread downstream until the mouth of the estuary after about few weeks and extend upstream into the Scheldt River. In all cases, due to tidal influence, the estuary becomes most vulnerable, with radioactivity potentially circulating for over a month. Additionally, higher river discharge resulted in decreased radioactivity levels in the estuary. •Multiscale transport model for simulating the dispersion of 137Cs and 131I releases.•1D-2D coupled model for the tidal river-estuary-sea continuum of the Scheldt.•Spatial and temporal distribution for accidental atmospheric and direct releases.•Transport of radioactivity from the tributaries into the estuary is within days.•Radioactivity concentration stays in the estuary for over a month.