Celine DUFFA / Hervé THEBAULT A radioecological risk assessment tool for post-accidental situations: application in the Toulon marine area
Objectives and method IRSN carries out research on the consequences of a possible accidental release of radionuclides into the environment. This project aims to provide an adapted tool to help decision makers to target vulnerable areas, to estimates consequences and to plan sampling strategies. Risk Radionuclide dispersion simulations Concentration maps Sensitivity Ecological and economical intrinsic value for homogeneous zones Vulnerability
Situation First French military harbour
Radionuclide dispersion modelling Risk Radionuclide dispersion simulations Concentration maps Sensitivity Ecological and economical intrinsic value for homogeneous zones Vulnerability
Radionuclide dispersion modelling COUPLING Hydrodynamic sediment transport contaminant behaviour Source Term WATER COLUMN Dissolve + SM Partition coeff., T1/2 U, V, Temp, Sal MARS 3D Initial and boundary cond. Meteorological data Regional scale model MM5 Aladin (Meteo-France) Deposition Resuspension WAVES Bathymetric data SHOM data + Local records Bottom shear stress WW3 SWAN SEDIMENTS Mud - Sand Particulate settling velocity Grain size data Local measurements
Radionuclide dispersion modelling Implementation on Toulon area from Cap Sicié in the west to the Presqu île de Giens in the east. High spatial resolution 100m square meshes / 30 sigma vertical levels.
Radionuclide dispersion modelling Meteorology météo OBC CDL West ouest CDL OBC East est Main forcing: wind (no tide) Meteorological data from Météo-France models CDL OBC South sud Nested models principle: Initial and Open boundary Conditions given by larger models (regional scale model 400m + northwest Mediterranean area model 1200m). MODELE LOCAL / Concentrations en Cs
Radionuclide dispersion modelling Two main wind directions : NW (mistral) and E - SE Surface current vectors and water temperature
Radionuclide dispersion modelling Wind Surface S N Bottom South North profile : current intensities Mid-depth current reversal
Radionuclide dispersion modelling Test : 1 GBq 137 Cs spill into harbour water simulated on 15 June 2009 Dissolve 137 Cs concentration (Bq.m -3 ) - log scale
Radionuclide dispersion modelling Test : 1 GBq 137 Cs spill into harbour water simulated on 15 June 2009 137 Cs in bottom sediments (Bq.m -3 ) - log scale
Sensitivity mapping Risk Radionuclide dispersion simulations Concentration maps Sensitivity Ecological and economical intrinsic value for homogeneous zones Vulnerability
Sensitivity mapping 1/ to characterize defined coastal zones through their environmental and socio-economic aspects. 2/ to elaborate sensitivity maps to identify preferred zones.
Sensitivity mapping 7 homogeneous areas (1) «ecological» aspects defined by remarkable benthic habitats (2) «socio-economic» aspects market activities: fisheries, aquaculture, lodging, restaurants, yachting, scuba diving, etc non market activities: beach going, recreational fishing, etc..
Sensitivity mapping Posidonia Oceanica sea grass beds Coralligène formations Ecological sensitivity
Sensitivity mapping Socio - Economical sensitivity (summer)
Sensitivity mapping Socio - Economical sensitivity (winter)
Conclusion Radionuclide dispersion simulation tool is now implemented in Toulon area - Different in-situ measurements are operated since 2009 for its validation. First modeling results suggest that in case of any accidental release occuring in the Little Bay, the dispersion of radionuclides would be very slow. The Little Bay and the western part of the Toulon Bay would be the most contaminated. Little Bay is of economical importance (more than 64 million euros of direct or indirect benefits). The western part of the studied area, from Cap Sicié to Saint-Mandrier peninsula, is the more ecologically sensitive. Looking at these results, these areas can be qualified as the most vulnerable in any accidental situation concerning the marine environment of Toulon.