Host laboratory: Research Laboratory for Radionuclide Transfer in Aquatic Ecosystems (LRTA)
Beginning of the thesis: October 2018
Student name: Adrien DELAVAL
The Rhone River is a major source of anthropogenic radionuclides to the Mediterranean Sea due to the installations on its banks. Contamination of these environments is a permanent and ubiquitous risk that needs to be characterized and controlled as best as possible. A solution to this characterization depends on the ability of numerical models to predict the dispersion of radionuclides in the continental and marine environment in emergency situations.
IRSN has the CASTEAUR software for the river line and the STERNE software for the Mediterranean Sea. These simplified models must induce the minimum error in the approximations. Understanding transfers in the reaction zone constituted by the river/sea interface is therefore of strategic importance.
Indeed, for many radionuclides, the transfer from the river to the sea takes place in the form of adsorption on the particles in suspension, but this speciation is not definitive. At the mouth of the river, the medium is enriched in cations (Ca, Na, K...) with salinity, the radionuclides which have a metallic element behaviour and which are weakly adsorbed (137Cs, 60Co, 54Mn,...) can be desorbed by cation exchange processes.
The aim of this work is to develop a model-terrain approach to achieve realistic modelling of the transfer of radionuclides in a river-sea continuum. The study site is the Rhone corridor and the Rhone delta at sea.
The main objectives are :
- The improvement of the CASTEAUR river modeling tool, by integrating field data that allow a concrete representation of the Rhone River.
- The establishment of typical scenarios (upstream/downstream location of discharges, different types of NR, variations in flood vs. low flows, on-shore/off-shore winds).
- Conducting estuary sampling and laboratory experiments to assess the effect of the desorption mechanism on radionuclides
- Take into account the desorption mechanism and the salt wedge phenomenon to ensure consistency in terms of input-output data for the two models used: on the river and at sea.