LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 2.6 Prevention and management of environmental and health impacts and non-radiological risks 2.6.1 – Water intake, discharges, waste management and health impacts Limiting water intake and environmental discharges The NPPs intake water and discharge liquid and gaseous effluents into the natural environment. Water intake is primarily to cool the reactor’s systems and, to a lesser extent, for industrial uses such as the production of demineralised water or the supply of fire-fighting systems. The effluents, which can be radioactive or chemical, come from the selective collection and treatment of water from the primary system, chemical conditioning of the systems, which helps preserve them, the production of demineralised water, biocidal treatments and effluent from the wastewater treatment plant. For each site, ASNR sets the limit values for water intake and effluents discharge on the basis of the best available techniques in technically and economically acceptable conditions and taking into consideration the characteristics of the installation, its location and the local conditions of the water resource. It verifies that these limits have acceptable environmental and health impacts. ASNR also sets the rules concerning the management of detrimental effects and the impact on health and the environment of the reactors. These rules are notably applicable to the management and monitoring of water intake and effluent discharge, to environmental monitoring and to information of the public and the authorities (see chapter 3, point 4.1). Finally, every year, the licensee of each NPP publishes an annual environmental report on its website and sends it to ASNR; this report notably contains a summary of the intakes from and discharges into the environment, any impacts they may have, and any significant events which have occurred. The impact of thermal discharges from the NPPs NPPs discharge heated water into water courses or the sea, either directly, from those NPPs operating with “once-through” cooling, or after cooling of this water in cooling towers (so-called “closed” systems), enabling most of the heat to be dissipated into the atmosphere. These thermal discharges lead to a temperature rise in the natural environment between the points upstream and downstream of the discharge which, depending on the reactors, can range from a few tenths of a degree (closed circuit) to several degrees (open circuit). These thermal discharges are regulated by ASNR resolutions specific to each NPP. Since 2006, provisions have been incorporated into ASNR resolutions for advance definition of the operations of NPPs in cases of exceptional climatic conditions leading to significant warming of the watercourses upstream of the NPPs. These special provisions are nonetheless only applicable if the security of the electricity grid requires it (see Highlight No. 9). Waste management In compliance with the provisions of the Environment Code, EDF carries out waste sorting at source, differentiating in particular between waste from nuclear zones and other waste. For each installation, EDF produces a summary of the management of this waste, in particular presenting a description of the operations which are the cause of production of the waste, the characteristics of the waste produced or to be produced, an estimation of the waste traffic volumes and a waste zoning plan. In addition, each NPP submits a report on its waste production and destination channels in its annual environmental protection report. Prevention of the health impacts caused by the growth of legionella and amoeba in certain cooling systems of the NPP secondary systems The secondary cooling systems of nuclear reactors equipped with a cooling tower are environments favourable to the development of legionella and other amoeba. EDF monitors the legionella and amoeba concentrations and takes preventive measures and, if necessary, remedial measures in accordance with the provisions of ASN resolution 2016-DC-0578 of 6 December 2016 on the prevention of risks resulting from the dispersion of pathogenic micro-organisms (legionella and amoeba) by the cooling installations of the systems. Preventive and remedial measures to limit the development of legionella and amoeba are based on the injection of a biocidal product (monochloramine) into the cooling system. The NPPs concerned are now implementing this treatment, with the exception of the Civaux NPP, which plans to do so from 2026 under certain conditions (see box on page 81 in the regional overview in the introduction to this report). HIGHLIGHT No. 9 Thermal discharges from the Nuclear Power Plants during periods of heatwave or drought To help cool its reactors, an NPP draws water from a watercourse or from the sea. The water returned to the watercourse is at a higher temperature, which warms the watercourse downstream of the plant. This represents a few degrees for NPPs without cooling towers and a few tenths of a degree for those with them. These warm water discharges, known as thermal discharges, are liable to have an impact on the aquatic environment. They are thus regulated by ASNR resolutions specific to each NPP. These set limits for heating of the watercourse between upstream and downstream of the plant and the maximum temperature downstream of it. When these limits are liable to be exceeded, the licensee reduces the power of the reactors and may even shut them down completely. These power reductions notably take place during periods of heatwave or drought. ASNR defined a second, higher, limit level, applicable when the manager of the Réseau de Transport d’Électricité (RTE) expresses the need to maintain a minimum power to ensure the security of the grid. This applies with no intervention on the part of ASNR, which is informed, as are the other administrations concerned and the Local Information Committee (CLI). It is associated with a reinforced environmental monitoring programme. In the event of an exceptional situation and public necessity, ASNR may also temporarily modify the limits it has defined. This was the case in the summer of 2022. During the summer of 2025, the Bugey, Golfech and Saint-Alban NPPs resorted to occasional power reductions in order to remain within the regulatory limits for thermal discharges. In mid-August 2025, the Golfech NPP applied the second level of limits because the Garonne had become warmer during a period of severe hot weather and, at the same time, RTE had requested a minimum power level for the safety of the electricity network. The tightened environmental surveillance carried out by the Golfech NPP has not revealed any immediate impact on the aquatic ecosystems of the Garonne in the vicinity of the site. Faced with the continuing increase in the effects of climate change, ASNR has asked EDF to develop a medium and long-term vision to address the thermal discharges in a period of severe heatwave, given their implications for each region and the potential combined effects linked to the presence of several NPPs in the same catchment area. ASNR Report on the state of nuclear safety and radiation protection in France in 2025 299 01 05 02 06 03 07 04 08 09 10 11 13 12 A / Z
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