LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT to the public on a dedicated website (mesure-radioactivite.fr) all the environmental measurements carried out within a regulatory framework in France. The quality of these measurements is guaranteed by a laboratories approval procedure (see point 5.3.2). The RNM’s guidelines (for example, the new types of measurements to be included in the RNM) are decided by the network’s steering committee, which includes representatives of all the network’s stakeholders: ministerial departments, ARS, representatives of nuclear licensee laboratories or associations, CLI members, Dreal representatives, ASNR, etc. After the RNM website was launched in 2009 and overhauled for the first time in 2016, work to modernise the tool was undertaken in 2022 so that it was more in line with the needs of web users, whether the general public or more informed visitors. To this end, a multi-disciplinary working group made up of the main nuclear licensees, representatives of civil society, government ministries, IRSN and ASN (which have since merged to form ASNR) met to identify areas for improvement and to propose a number of changes to the site, which were implemented in 2024 and 2025, such as improving the search function around the sites and making new data and information available, particularly relating to foodstuffs and data on the radiological impact of facilities. 5.3.1 – Laboratories approved by ASNR to guarantee measurement quality Articles R. 1333‑25 and R. 1333‑26 of the Public Health Code require the creation of an RNM and a procedure to have the radioactivity measurement laboratories approved by ASNR. The RNM working methods are defined by the above-mentioned amended ASN resolution 2008-DC-0099 of 29 April 2008. This network is being deployed for two main reasons: ∙to pursue the implementation of a quality assurance policy for environmental radioactivity measurements by setting up a system of laboratory approvals granted by ASNR resolution; ∙to ensure transparency by making the results of this environmental monitoring and information about the radiological impact of nuclear activities in France available to the public on the RNM website (see point 5.2.1). HIGHLIGHT No. 9 The TRAJECTOIRE project: reconstructing and explaining the history of contamination in major catchment areas It all began in 2015, when IRSN received a request for an in-depth assessment of the consequences of plutonium contamination of the Loire in the early 1980s. Did we have the observation data to answer these questions? Alternatively, could environmental monitoring be “retroactive”? And could we organise it more widely to anticipate the demands and needs for expertise? In other words, could environmental signatures, such as those left in the sedimentary archives of rivers, help us to reconstruct the history of river contamination at a time when environmental concerns were not the same as they are today? Motivated by these questions, ASNR scientists have developed a research programme entitled TRAJECTOIRE, bringing together a consortium of seven scientific partners and soon to be approved by the French National Research Agency (ANR). The project began in January 2020, with the aim of establishing the trajectories of man-made contaminants in the major French river basins (Rhône, Loire, Seine, Garonne, Rhin, Meuse, Moselle). The aim is to study their pathway, from their introduction into the environment to their presence in environmental compartments, over the course of the 20th century. This period was marked by both technological and industrial development, and a gradual awareness of the impact of this development on the environment. Three families of “representative” contaminants were studied: radionuclides, microplastics and their derivatives, and high-tech or “critical” metals. Five years after the start of the project, in December 2025, the main results were presented to a broad scientific community at a final feedback symposium in the ASNR auditorium in Fontenay-aux-Roses. More than 50 metres of accumulated sedimentary archives were extracted downstream from the Loire, Rhône, Rhin, Seine, Garonne, Meuse and Moselle rivers, from which the trajectories of contaminant concentrations could be traced. The results show that, on a catchment scale, the values of the parameters governing the transfer of caesium-137 (137Cs), a man-made radionuclide, from the soil to the watercourse appear similar from one large catchment to another. They are therefore useful references for operational models. The temporal trajectories of tritium show markings significantly higher than the levels recorded in rainwater (free tritium) over the same period. These differences can be explained by the transfer to rivers, via leaching from catchment areas, of organic particles from the degradation of terrestrial biomass exposed to atmospheric fallout from aerial nuclear testing and, in the case of the Seine, from the Valduc CEA centre. For the Rhône and Rhin, diffuse discharges linked to the Franco-Swiss watchmaking industry are the main contributor to these differences. Analysis of potassium-40 (⁴⁰K), a natural radionuclide found in soil, revealed the impact of the use of potassium fertilisers, with peaks in the 1980s, linked to agricultural intensification, followed by a rapid decline reflecting a good capacity for environmental resilience, i.e. a relatively rapid return to the initial state characterising the period prior to contamination. The results for microplastics have not yet been published. Analysis of plastic derivatives such as phthalates nevertheless shows that concentrations increased after the 1950s-1970s, with variations depending on the river. In the metals family, a critical review has shown that, in the Gironde catchment, resilience to historical contaminants (cadmium, copper, lead, zinc) depends on the management of mine tailings and contaminated sediments. An artificial intelligence model, HRHN (Hierarchical Attention-Based Recurrent Highway Networks), has been designed to predict contaminant concentrations in rivers. Tested for 137Cs and ⁴⁰K, the model identifies and prioritises the explanatory variables (minimum flow, leaching, atmospheric deposition, soil inventory and industrial discharges) and correctly represents the interactions between these variables for the vast majority of French rivers. It can also be used to make projections based on scenarios of climate or societal change. Projections up to 2100, carried out on the Rhône, show that, as expected, the decrease in flow increases 137Cs concentrations, whatever the scenario. Extraction of a sediment archive on the banks of the Meuse downstream of the Chooz NPP. ASNR Report on the state of nuclear safety and radiation protection in France in 2025 167 01 02 03 05 09 06 10 07 11 13 04 08 12 A / Z
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