Normally, France delivers its nuclear power to all of Europe. However, the country has been dependent on imports for around a year. The warmer it gets, the more electricity has to be purchased. German consumers are also feeling the effects.

In Paris, the thermometer scratched the 30-degree mark again on Thursday. The French capital is feeling the same heat wave this year as most German cities. But not only the air in France is heating up. The rivers are also warming up. This is a joy for bathers, but a cause for concern for politicians and engineers. Because France often uses river water to cool its nuclear reactors. And at higher temperatures, they now have to be shut down in rows or even switched off.

For the time being, the nuclear reactor itself does not care whether its cooling water is fed in at 20, 25 or 30 degrees. After all, the temperatures inside are significantly higher, so that the river water fulfills its cooling function in any case. But the warmer the incoming water, the warmer the water that flows out of the nuclear power plants back into the rivers. There are legal limits to how warm the waste water from the power plants can be. Because if the operators heat up the rivers too much, it harms the animals and plants that live in the stream. Usually the limit is between 26 and 30 degrees.

Many nuclear power plants cannot meet these environmental protection standards in view of the current high temperatures. The French energy giant EDF has therefore now announced that it will cut production in four power plants on the Rhone in the Alps and the Garonne in the south-west of the country. Specifically affected are the nuclear power plants in Bugey (1.8 gigawatts), Saint-Alban (2.6 GW), Tricastin (3.6 GW) and Blayais (3.6 GW). It’s not the first time this year that these power plants have been throttled. EDF also took similar measures during the July heat wave. During a similar heat wave in 2018, numerous power plants also had to be shut down.

The measures are necessary, but come at a bad time for consumers. Even before the start of the warm period, the electricity prices on the Leipzig trading exchange EEX for Germany had risen by 134 percent from 150 to 350 euros per megawatt hour. Since the end of June it has gone up by a further 63 percent to 567 euros most recently. Part of the price problem is France. Normally, France is a net exporter of electricity to other European countries. Every year, Germany imports more energy from the neighboring country than it delivers there. Since 2015, the German deficit has always been at least two terawatts per year in the first half of the year, and in 2020 it even grew to almost eight terawatts.

But in November 2021 the situation changed. Since then, France has almost always been an importer of German electricity. In the first half of 2022, Germany exported around two terawatts of electricity net to the neighboring country. In July alone, another 1.1 terawatts were added. Most of the surplus energy in this country came from renewable energies. Almost half of the energy generated in Germany from January to June came from wind power, solar systems and other renewable energies.

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In addition to the heat problems, France has previously had to shut down some reactors for scheduled maintenance or repairs. But France isn’t the only country whose nuclear power plants are now unable to operate at full power in the heat. In Switzerland, too, nuclear reactors had to be throttled to take account of the rivers that cool them.

The problem will not get any smaller in the coming years, after all the earth will continue to heat up, making heat waves more frequent and severe. This does not only apply to countries like France and Switzerland, which use river water for cooling. Countries like the USA and Japan, which like to build nuclear power plants close to the sea in order to use seawater, are also facing more and more problems. Here the water is getting closer and closer to the reactors due to the rising sea level. At the same time, the risk of tsunamis is increasing and higher seawater temperatures promote the formation of algae carpets and huge populations of jellyfish, which make it difficult to suck in seawater for cooling.

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