Development of management tools for accidental radiological contamination of the French coastal areas - Development of management tools for accidental radiological contamination in the French marine coastal areas

The Fukushima nuclear accident led to the most important accidental release of artificial radionuclides into the sea. This accident has underlined the importance of being able to adequately reproduce the fate of radioactive releases and to estimate their consequences for the marine environment. For its Crisis Centre, the French Institute for Radioprotection and Nuclear Safety (IRSN) has operational tools, in order to help experts and decision makers in case of any atmospheric accidental release and terrestrial environment contamination. The on-going project aims to develop tools to manage any marine contamination of the French coastal areas. We should be able to evaluate and anticipate the marine post-accidental situation: contaminated areas localization and contamination levels, and possible consequences. Many sites has be considered as potential source terms into the sea: the Coastal Nuclear Power Plants, the La Hague reprocessing Plant, the Brest and Toulon Military Harbours as home-ports of nuclear powered vessels, and different river mouths (Rhone River, Gironde, Loire, Seine) that could be contaminated by upstream accidental release. To achieve this goal, two complementary approaches are developed: Marine sheets and a dedicated modelling tool (STERNE). - Marine sheets aim to summarize marine environment characteristics for the different sites, identify potential stakes for human protection such as aquaculture areas, beaches, or industrial water intakes, and ecological stakes. Whenever possible, a local climatology (main currents depending on meteorological or tide conditions) that could be a support to first environmental measurement strategy is proposed. A list of available local contacts for any operational management is also provided. - The modelling tool, STERNE (Simulation du Transport et du transfert d'Elements Radioactifs dans l'environNEment marin), must predict radionuclide dispersion and contamination of water, marine species and sediments, incorporating spatial and temporal processes. 3D hydrodynamic forecast data will be provided routinely to IRSN Crisis Center via ftp by the operational coastal oceanographic system of IFREMER (French Institute for Exploitation of the Sea). Different radiological source terms can be taken into account: direct liquid releases, atmospheric depositions or river inputs of radionuclides. STERNE calculates radionuclides transport using advection and diffusion equations offline from hydrodynamic calculation. Radioecological model based on dynamic transfer equation to evaluate concentrations in marine organisms and sediments is also implemented. Needed radioecological parameters (partition coefficients, concentration factors and single or multicomponent biological half-lives) have been compiled for some important radionuclides and for generic marine species (fishes, molluscs, crustaceans, macro-algae). Dispersion and transfer calculations are carried out simultaneously on a 3D grid. Results, available as netcdf files can be represented on maps, with possibility to follows temporal and spatial evolution. Post-treatment and representation are then possible. The development of these tools still requires many data collection and validation process before integration as an operational decision support system. (authors)