Should France fear a generic problem for all of its nuclear fleet, the country’s main source of electricity? A phenomenon of corrosion – known as “under stress” – has been worrying the sector for several months now. In question, cracks on the pipes of the reactors, in particular on their safety injection system. An important part: using borated water, this backup system is intended to cool the primary circuit in the event of an accident.
Checks have already detected cracks on five reactors, between the second half of 2021 and the beginning of 2022: two in Civaux (Vienne), two in Chooz (Ardennes) and one in Penly (Seine-Maritime). On April 14, on its website, the Electricité de France (EDF) group provided a discreet update on the situation. At least four other reactors could be affected: in Flamanville (Manche), Golfech (Tarn-et-Garonne), Cattenom (Moselle) and Chinon (Indre-et-Loire). For each of them, a doubt remains, after checks “by ultrasound on portions of piping”, specifies the information note. Investigations are continuing for “characterize the nature and origin” of these indications.
In other words: subject to additional expertise, the problem could affect all levels of the French nuclear fleet. This is already the case for all the 1,450 megawatt (MW) models – those of Civaux and Chooz, the most recent and most powerful -, as well as for at least one 1,300 MW reactor – in Penly, in the meantime the conclusions for those of Flamanville, Golfech and Cattenom. The question could therefore also, with Chinon, extend to the category of 900 MW reactors. That is the oldest and most widespread, since 32 of the 56 reactors in the nuclear fleet fall under this power.
“Cutting and expertise in the laboratory”
The organizations responsible for nuclear safety in France are careful not to come to any hasty conclusions. “The result of the ultrasonic inspection confirms the need to go and cut the weld to assess it in the laboratory”, indicates Julien Collet, Deputy Director General of the Nuclear Safety Authority (ASN). “This cutting, carried out by EDF and authorized by the ASN, will begin by the end of April for laboratory expertise, the results of which we will have in May. »
The presence of echoes revealed by ultrasound does not necessarily mean the existence of cracks. “It is too early to know if all the reactors in the fleet are affected by the stress corrosion phenomenon”emphasizes Karine Herviou, Deputy Director General of the Institute for Radiation Protection and Nuclear Safety. “The echo can be linked to stress corrosion, to a peculiarity of the piping, or to other types of degradation”, says Mr. Collet. “Today, EDF does not have a non-destructive testing device suitable for stress corrosion, it is essential to wait for cutting and laboratory expertise”, he adds.
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