(Bloomberg) -- Electricite de France SA has found corrosion on key piping on four nuclear reactors during recent checks, taking the number of affected units at its French fleet of atomic generators to nine.

Corrosion issues have forced the French energy giant to halt some of its 56 reactors for lengthy checks and repairs, just as Europe faces its worst energy crisis in half a century. The state-controlled utility previously said its nuclear output will fall to the lowest in more than three decades this year and hardly rebound next year due to the reactor works.

Signs of corrosion were found in pipings of the Chinon-3, Cattenom-3 and Flamanville-2 reactors, three of the six units that EDF had decided to check in February, EDF said in a statement posted on its website last week. Indications of corrosion have also been found at the Golfech-1 unit during a planned maintenance halt, and deeper checks will be carried out, the utility said.

Plunging nuclear production, combined with government measures to cap power prices to protect consumers and companies, will deprive EDF of 26.2 billion euros ($28.3 billion) in earnings this year as the utility needs to buy back power on the wholesale market, the company estimated last month.

News of the issues first emerged in December and January, when EDF said two reactors in Civaux, two in Chooz, and one in Penly needed to be halted for checks and repairs.     

The company is continuing talks with the nuclear safety authority on ways to tackle the problem, while it carries out further checks on its fleet of reactors during planned maintenance and refueling halts through 2024.  

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