PARIS, Feb 21 (Reuters) - The 900-megawatt Chinon 3 nuclear reactor in western France has been taken offline for tests after "stress corrosion" was found on a bend in four pipes comprising a backup safety coolant system, power group EDF (EDF.PA) said.
Portions of piping were sampled and the defects were found to be linked to corrosion involving the pipe material, mechanical stresses and the fluid in circulation, EDF said.
These faults can only be discovered through ultrasonic tests, which are a part of the 10-year reactor inspections, it added.
The safety coolant injection system allows the operator to pump a neutralising agent directly into the nuclear core as an emergency measure to stop the nuclear reaction.
"A programme of checks on the entire nuclear fleet has been launched, gradually integrating the lessons learned from the first appraisals carried out," EDF said.
Due to the specifics of the tests and material conditions required for stress corrosion, EDF established a prioritized list of checks on several reactors following results from tests at the central Civaux and northern Penly plants.
The reactors listed for testing equate to 6.6 gigawatts (GW) of capacity throughout France, which has 56 reactors spread across the country responsible for about 70% of power supply.
EDF did not elaborate on the tests.
The Bugey 3, Flamanville 1 and 2 reactors will be tested during their scheduled shutdowns over the next three months, while the Chinon 3, Cattenom 3 and Bugey 4 reactors will also be shut down over the same period and tested.
More corrosive faults were detected on Feb. 15 in several other plants following the initial discovery at the Chooz, also in the north, and Penly plants in December.
The Chinon 1 and 2 reactors are currently available to the network while the Chinon 4 reactor is offline for scheduled maintenance.
President Emmanuel Macron this month unveiled a new energy strategy that puts nuclear power at the heart of a drive for carbon neutrality by 2050, with public funds of billions of euros to be mobilised.
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