EDF said on 11 October that it is repairing pumping station pipes at 20 nuclear reactors to increase seismic safety after an in-depth investigation revealed that metal is thinning in some sections of the piping. EDF reported the piping system problem to the French Nuclear Safety Authority (ASN) as a Level 2 incident on the International Nuclear and Radiological Event Scale (INES) scale.

The pipe system is part of a fire safety system, designed to supply and filter water.  “In-depth investigations have revealed thinning of the metal in certain sections of piping, thus making it impossible to justify their seismic resistance in the event of a design-base-type earthquake." 

“This could potentially cause flooding in the pumping stations of twenty reactor units, thereby resulting in the functional loss of both reactor cooling water systems,” an EDF statement said.

So far, EDF has reinforced the pipes for units at the following reactors: Belleville 1&2, Cattenom 3&4, Dampierre 1&2, Golfech 1&2, and Saint-Laurent-des-Eaux B1. 

Work is ongoing at five reactor units currently undergoing routine outage and is expected to be completed before restarting these units, which include Chinon B3, Cruas 1, Dampierre 3, Nogent 1, and Saint-Laurent-des-Eaux B2. At six other reactors now online – Cattenom 1&2, Chinon B4, Cruas 4, Dampierre 4 and Nogent 2 – reinforcements had been completed on one of each reactor’s two cooling water systems, ensuring the plants could operate safely in the event of an earthquake. Reinforcement work on the second cooling water systems is underway. 

EDF said investigations at nine other reactors – Cruas 2&3, Paluel 3&4, Saint-Alban 1&2 and Tricastin 1, 3&4 – had revealed that a risk of pump-house flooding or loss of the reactor cooling water system could not be ruled out. Reinforcement works are now underway.

France, which depends on nuclear power for over 75% of its electricity, could face reduced power supplies in the coming weeks because of prolonged outages at several reactors. The restart of some reactors has already been delayed following maintenance and a review ordered by ASN which resulted in 21 out of France’s 58 nuclear reactors being shut down.