SORA Station

Context

As one of the most nuclearised rivers in the world, the Rhône was the subject of studies from a very early stage, particularly due to the location of the Marcoule irradiated fuel reprocessing centre. From the 1990s onwards, the significant drop in radioactive effluent discharges forced IRSN to acquire a facility capable of monitoring the downward trend in radionuclide activity in the Rhône. In partnership with the Rhône Méditerranée et Corse Water Agency, the Rhône Observatory Station in Arles (SORA station) was inaugurated in 2002. Located downstream of all the facilities discharging artificial radionuclides and downstream of the last tributary of the Rhône, the station makes it possible to acquire data on the concentrations of the main substances present in the river, just before it flows into the Mediterranean Sea.

Research areas

The partnership with the Agence de l'Eau Rhône Méditerranée et Corse to set up this river observatory was primarily aimed at improving knowledge of the radionuclide activity levels that could be measured in the Rhône. Gradually, a research programme was developed to answer the questions raised by the operation of the station and the interpretation of the results obtained. The first studies carried out using the SORA station aimed to :

• Define the role of flood events in the export of radionuclides in dissolved and particulate form,
• Determine the origin of radionuclides transiting a river whose recent history is marked both by global atmospheric fallout that has affected the soils of its catchment area and by direct effluent discharges into the aquatic environment.

Since then, the results obtained from the samples collected at the SORA station have been used in various research programmes aimed at improving knowledge of the partitioning of radionuclides between particulate and dissolved fractions, the transfer of contaminants on the scale of the Rhone catchment area and at the river-sea interface, and the chemical and radiological toxicity of the river for fauna and flora. The data acquired also contributes to the calibration of IRSN's operational models designed to simulate the transfer of radionuclides from a point of discharge to the marine environment.

Thanks to its remote control and independent sampling lines, the facility can also offer IRSN's scientific partners samples tailored to their needs.