Themes: Geological Sciences, Earth, Universe
Ionizing Radiation Epidemiology Laboratory (LEPID)(13)
The candidate will have a background in environmental geosciences and proven skills in geochemistry, sedimentology and fluvial geomorphology. He will master statistical tools and demonstrate writing and communication skills. Position based on the Cadarache site (13115).
Age limit: 26 years old unless otherwise stated.
IRSN thesis subject proposal (2021-2024) Trajectory and resilience of radionuclides in large nuclear watersheds watersheds The analysis of sedimentary archives, collected in the alluvial margins of watercourses (banks, floodplain), or in compartments of sediment accumulation of anthropogenic origin (docks, dams), makes it possible to reconstruct retrospectively the levels of radionuclides, medium to long-lived, having passed through rivers during the nuclear era. This thesis aims to use, obtain and exploit datasets on the levels of radionuclide contamination of natural or artificial origin covered the nuclear era (last 100 years) and the seven major French nuclear rivers. These datasets will use monitoring data (SYRACUSE database) and data acquired from the study of sedimentary archives collected downstream from the Rhône and Loire watersheds (data already acquired) from the Seine, the Garonne, the Rhine (data being acquired), the Moselle and the Meuse (data to be acquired). The datasets resulting from the exploitation of the sedimentary archives aims to produce an in-depth knowledge of the levels of contamination of the environments over time (nuclear era) and at the french national level, to verify the main terms sources of contamination and to investigate the environmental consequences (year 1). The coupling of these datasets to those, more qualitative, products of the construction of socio-historical friezes inventorying and characterizing the source terms (drivers), aims to better understand the trajectories of radionuclides at the watershed scale and to pursue resilience of these environments faced with the different types of contamination (Year 2). It will then be necessary to put into perspective the different trajectories of radionuclides within the large rivers studied in order to determine, from all the observations and by statistical analyzes, the key parameters associated with the different typologies of contamination and / or environmental factors, which govern the fate of radionuclides in fluvial environments, and determine the residence times and resilience capacities of aquatic environments (Year 3). This analysis of trajectories and resilience capacities should make it possible to identify generic laws and provide operational tools likely to shed light on economic and political choices on management methods for chronic or accidental releases of radioactivity affecting watersheds. These environmental risk investigation tools, based on observations and case studies, should make it possible to consolidate the mechanistic operational models currently available to IRSN, in particular the CASTEAURX code. The work of this thesis will be directly included in the expectations of ANR TRAJECTOIRE project (2020-2024).