The No. 1 reactor of the Chooz nuclear power plant, one of the first concerned by the discovery of corrosion problems, restarted in the night from Wednesday to Thursday, after more than 500 days of shutdown. Reactor No. 2 had been shut down for nearly a month. The reactor No. 1 of this plant was reconnected to the grid Wednesday evening following its shutdown on December 18, 2021, and has gradually entered production, said a spokesman for EDF, joined by AFP. "The rise to 100% power will last at least 48 hours," he said.
Microcracks
With a capacity of 1450 MW each, the two reactors, both commissioned in 2000, are among the newest and most powerful in EDF's nuclear fleet, which has 56. These two units had to be shut down shortly after the detection of microcracks in October 2021, during a ten-year visit to a portion of emergency piping at the Civaux power plant, the last of the French nuclear fleet to be commissioned in 2002. The design of the reactors of the two plants is identical. The risk of cracks was then identified at other sites, leading EDF to expand controls and shutdowns, resulting in a record number of reactors shut down last winter and a level of nuclear production at its lowest.
EDF's expertise had revealed the presence of an unprecedented phenomenon of stress corrosion on emergency pipes, crucial for the cooling of power plants, mainly on the most recent and most powerful reactors, those of 1,300 and 1,450 MW. "A total of 60.5 linear meters of pipes have been replaced and controlled on the 2 Chooz reactors, including 33 meters on reactor No. 1," said the management of EDF.
As of 11 May, 20 out of 56 reactors were still shut down, due to planned maintenance visits or the continuation of the crack treatment program.