France's EdF has detected possible defects in piping at the 1.5GW Civaux 2 reactor, according to nuclear safety authority ASNR.
Tests revealed two "signs" — typically echoes from ultrasound testing — that could indicate a defect, ASNR said.
The tests — part of its strategy to treat stress corrosion — are continuing. ASNR said there is no confirmation at this point that the potential faults are evidence of stress corrosion.
Stress corrosion is a process by which mechanical stress in the presence of certain chemicals leads to fissures in pipework. The French reactor fleet was heavily affected by this condition in 2021-23, with around a third of the fleet taken off line for inspections and repairs.
Civaux 2 is an N4 reactor — there are two at Civaux and another two at Chooz. They were the last reactors built before Flamanville 3, entering service in 2000-02, and the most powerful built in France up to that time.
Civaux 2 has been off line for maintenance since 5 April and is scheduled to return on 31 July. It was being defuelled for maintenance and inspection and tests, before having a third of the fuel switched out.
The 1.5GW Civaux 1 was the first reactor where stress corrosion faults were discovered, in August 2021. Tests at the other three N4 models in the following months confirmed stress corrosion at all of them. The N4 models — along with a dozen 1.3GW P4 reactors — are particularly vulnerable to stress corrosion, EdF's nuclear and thermic director, Cedric Lewandowski, told a parliamentary commission in 2022.
The French power curve rose sharply on Wednesday morning following reports of the possible defects on Tuesday evening. The front-year contract jumped from an assessment of €62.30/MWh yesterday to over €68/MWh in the morning, before falling to around €66/MWh by mid-afternoon.
