The French electricity supply threatens another stress test. After a mild winter, in which the feared emergency shutdowns failed to materialise and maintenance and repair work on the nuclear power plant fleet progressed, the operating group EDF has encountered new corrosion damage. Affected is the Penly 1 nuclear reactor in Normandy, which was shut down a year and a half ago, where EDF boss Luc Rémont had sprayed hope for a speedy end to the work in December in the presence of France's Economy Minister Bruno Le Maire.

Niklas Záboji

Business correspondent in Paris

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Once again, it is about a cracked weld seam on a pipeline of the emergency cooling system. At 15.5 centimetres long and up to 2.3 centimetres deep, however, it is significantly greater than the other corrosion damage in the 56-reactor nuclear power plant park, which covers about two-thirds of France's electricity needs. The French nuclear regulator ASN suspects a design flaw and on Tuesday asked EDF to revise its ongoing control program.

But that's not all. On Thursday, the ASN also informed about damage to pipelines of the emergency cooling systems in the reactors Penly 2 and Cattenom 3 on the border to Saarland. There, "thermal fatigue" was diagnosed as the cause instead of corrosion and the cracks are less deep at 1.2 and 0.4 centimeters. But this is "not harmless, this is a not inconsiderable depth," the AFP news agency quoted the deputy ASN director Julien Collet. In the French wholesale trade for short-term electricity supplies, the price rose slightly this week.

A quick return is not on the horizon

It is still unclear whether the new damage will delay the recommissioning of the three reactors. What is clear, however, is that, as well as the strike-related production losses at individual plants, they will continue to affect France's already weakened power plant fleet. EDF calculates a nuclear power production of 300 to 330 terawatt hours so far this year. This would be above the 280 terawatt hours produced in the past crisis year, but still far below the 2019 terawatt hours achieved before the maintenance and repair wave in 380.

However, a quick return to the old production level is not on the horizon, even if the corrosion problem is eliminated nationwide. According to an overview by the French electricity grid operator RTE, an average of almost six reactors will be shut down annually until 2033 for the mandatory ten-year inspections alone. RTE therefore expects a reduction in nuclear power production of around 2030 terawatt hours in 350.

France, Europe's largest electricity exporter until 2021 and last year a net importer of electricity for the first time since 1980 due to the malaise in its domestic power plant fleet, threatens to remain dependent on imports for many weeks of the year in the future.

From a German point of view, this would be piquant insofar as the Federal Ministry of Economics in its electricity security report presented at the beginning of February predicted a French export surplus of around 50 terawatt hours for the middle of this decade, which should even climb to 2031 terawatt hours in 90 – and help to secure supply in Germany in dark lulls.

Under the Berlin assumptions

France "has been the dominant electricity exporter in all years," the report says. "The supply of electricity is secure even with a coal phase-out in 2030," was the headline that the ministry of Robert Habeck (Greens) brought to the people. The reports, which specify the assumed generation capacities, were not published until a few days later.

They are revealing. Because they show that the forecast assumes a rapid expansion of renewables in France, which would then enable electricity to be exported on a large scale: from around 25 gigawatts of installed wind capacity and 20 gigawatts of photovoltaics (PV) to 49 gigawatts of wind and 42 gigawatts of PV in 2028 to 67 gigawatts of wind and 58 gigawatts of PV in 2031.