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.