Nuclear power plants in Switzerland and France have been forced to stop operating reactors to avoid cooling water released that would harm the ecosystems of rivers that have already warmed due to harsh weather.
Record heat in Europe has caused river water temperatures, which are used for cooling at several nuclear power plants, to rise, forcing operators to temporarily suspend at least three reactors at two different locations.
Last weekend, one of the two reactors at the Golfech Nuclear Power Plant in southern France was shut down after forecasts showed that the temperatures of the Garonne River, where the plant collects water, could exceed 28 degrees Celsius.
In Switzerland, the Beznau Nuclear Power Plant near the Aare River, which is close to the northern border, also stopped two reactors on July 1 and 2.
Both of these nuclear power plants are designed to cool reactors with river water, then release water at higher temperatures back into the river. Regulations in both France and Switzerland require reduced electricity output when river water temperatures increase, in order to protect the environment downstream.
Beznau plant operator Axpo confirmed that temperatures have continuously exceeded the 25C limit for several days.
Several other nuclear reactors, including the Bugey plant in southeastern France, have also reduced production. This week, temperatures in many places across Europe have frequently exceeded 38 degrees Celsius.
Most nuclear reactors in the US and Europe were built between the 1960s and the 1980s, when climate change was not factored in the design. As global temperatures rise, preventive stops due to hot weather are also becoming more frequent.
Nuclear power is France's largest energy source, with 18 plants supplying nearly two-thirds of the country's electricity needs. In Switzerland, nuclear power accounts for about a third of total energy consumption.
In 2022, a heat wave combined with a decline in power generation capacity forced the French nuclear agency to temporarily relax regulations on maximum wastewater temperatures. Similarly, in that year, the Beznau plant in Switzerland continued to operate despite rising temperatures in the Aare River.
This is the first time the plant has had to stop operating due to water temperature. In 2022, although the water in the Aare River is very hot, the plant will continue to operate because the power supply at that time does not allow stopping" - said a representative of the Swiss Federal Energy Agency.
