High Mediterranean Sea temperatures are limiting cooling at the Martigues plant while several nuclear plants reduce output.
The heatwave in France has increased pressure on the country’s power system after a southern gas plant was exposed to a possible operational interruption. Rising Mediterranean temperatures are making it harder to access water cold enough to keep equipment within normal operating parameters.
The affected facility is the Martigues plant, operated by EDF and with a capacity of around 930 MW. The company received exceptional authorization to operate with cooling water above the usual 30°C limit. However, sea temperatures approached the newly authorized threshold of 32°C.
The Mediterranean limits the plant’s cooling
The operation of a thermal power plant depends on systems capable of dissipating the heat generated during electricity production. When the water used for cooling becomes too warm, the facility loses efficiency and may exceed its environmental or operational limits.
For this reason, EDF may be forced to reduce generation or temporarily shut down the gas plant in France. A shutdown would add strain to a grid that is already facing lower availability of nuclear energy.
Gas-fired generation represents a small share of France’s power mix. Even so, its role becomes more relevant when nuclear reactors reduce output due to a lack of water or elevated river temperatures.
Nuclear output also falls due to the heat
France gets around 70% of its electricity from nuclear power plants. This dependence makes reactor availability a key factor for the stability of the national supply.
During the heat episode, around 4.9 GW of nuclear capacity was affected by high river temperatures. Another 2.5 GW remained offline due to low water levels.
Overall, weather-related restrictions represent around 14% of France’s total generation capacity. The situation includes reductions or shutdowns at plants such as Bugey, Golfech, and Chooz.
Likewise, some reactors must adjust output to comply with limits on the temperature of water returned to rivers. These rules aim to reduce thermal impacts on aquatic ecosystems.
Drought worsens pressure on the energy system
The lack of significant rainfall since late May has reduced the flow of several French rivers. At the same time, exceptional temperatures have increased evaporation and water consumption.
The Chooz nuclear power plant faces restrictions linked to the low level of the Meuse River. This watercourse is part of a distribution agreement between France and Belgium, so its availability has operational and cross-border implications.
According to Météo-France, the heatwave should gradually lose intensity. The highest temperatures are expected to be concentrated in the southeast of the country over the coming days.
However, the temperature drop will not immediately resolve the drought. The recovery of rivers and reservoirs will depend on sustained rainfall capable of restoring the water levels needed for industrial cooling.
EDF applies exemptions to maintain generation
The authorization granted to EDF allows the Martigues plant to operate above the usual thermal limit until September 15. This measure aims to preserve power capacity during a period of lower nuclear output.
The exemption does not eliminate the technical risk. If Mediterranean water exceeds 32°C, the company would have to adopt new restrictions to protect equipment and comply with environmental conditions.
The case shows how high temperatures can affect different generation sources at the same time. Heat reduces the cooling capacity of gas plants and limits the operation of nuclear reactors installed alongside rivers.
In this scenario, water availability becomes an essential element for energy security. France will need to manage the evolution of the heatwave, the drought, and the gradual recovery of its plants over the rest of the summer.
Source: Reuters
Photo: Shutterstock
