Nuclear power: heatwaves as a challenge for the environment and power supply

In France, the operator EDF has temporarily shut down reactor 2 of the Golfech nuclear power plant because the water in the Garonne has reached the permissible temperature limit of 28°C. Reactor 1 will remain in operation at the request of the operator of the national power grid and its output will be adjusted, EDF announced.

A river that is too warm is also causing headaches in Hungary. According to media reports, the energy ministry there is planning to issue a permit for the Paks nuclear power plant to increase the temperature limit of 30 °C for the Danube, which flows past the nuclear power plant. Otherwise, the power supply could be jeopardized, it is said. In June, the Federal Office of Energy there had already approved an exception for the Beznau nuclear power plant to discharge water into the River Aare if its temperature is above 25 °C. The nuclear power plant will also continue to operate. The nuclear power plant will also continue to operate so as not to jeopardize security of supply.

Changing climatic conditions with longer periods of drought and heat have been causing problems for nuclear power plants for some time. Nine years ago, for example, the Grohne nuclear power plant in Germany, which was still in operation at the time, was about to be shut down because the Weser had warmed up considerably. In 2022, the output of the Beznau nuclear power plant was reduced due to the high summer temperatures, and the French operator EDF was granted an exemption from environmental regulations so that the Bugay nuclear power plant could continue to operate. Reactors in Belgium also had to be throttled back.

"Not a serious safety problem"

Official environmental regulations require that the water temperature downstream of a nuclear power plant and the temperature of the water that is discharged back into the river or sea do not exceed limit values, explains the German Gesellschaft für Anlagen- und Reaktorsicherheit (GRS). This is to ensure that the animal and plant world is protected and the ecological system is not thrown out of balance. If it is foreseeable that such limits will be reached, the output of the power plant must be reduced to reduce the amount of cooling water required or to prevent the cooling water from heating up too much.

Prolonged periods of heat do not pose a serious safety problem, as they can usually be predicted relatively far in advance and the water temperatures only rise slowly, as GRS has determined in several research projects. The plant could be shut down in good time or its output reduced. However, safety systems such as emergency diesel generators also need to be cooled if they have to be used. Maximum values for the cooling water would also be set here, which would have to be checked.

As is generally the case with power plants with steam turbines, which include nuclear power plants, periods of heat can cause losses in the power generated, resulting in less electricity being produced, adds GRS. Greenpeace Switzerland is also focusing on the environmental impact of higher temperatures. Trout and grayling are under pressure in the Aare, into which water at temperatures of up to 33 °C can now be discharged. They are already rare and react sensitively to the higher water temperatures.

(anw)