The event concerns a risk of damage to the piping owing to their potential contact with the civil engineering structures of the emergency diesel generator (EDG) sets in the event of an earthquake.
Depending on the reactor, emergency diesel generators and their platform are either fixed to the ground or mounted on string boxes or antisismic devices.
In the first case, in case of an earthquake, the EDG has the same movement as the building other structures.
In the second case however, there would be differential movements between the EDG, its platform and pipes connected to the EDG (fixed or flexibles) and the neighboring structures. Those pipes may damage neighboring structures, or vice versa. If those structures damage the pipes, it may prevent the EDG to get fuel, air, oil or water. This may lead to the failure of the EDG.
EDF initially detected this deviation at the end of October 2018 on one of the two EDG sets for reactors 2 and 3 of the Tricastin NPP. On 6 May 2019, EDF informed ASN that, following assessment, it also concerned the two EDG sets for the reactors of the Civaux, Gravelines and Paluel NPPs as well as one of the two EDG sets for the reactors of the Fessenheim, Cruas, Saint-Laurent-des-eaux and Nogent NPPs, reactor 3 of the Dampierre NPP, reactors 2 and 3 of the Tricastin NPP and reactor 1 of the Le Blayais NPP.
Repairs were made to the reactors concerned, except for one EDG set for reactor 4 of the Paluel NPP, which is currently shut down. Repairs will be conducted before the reactor is restarted.
More particularly during the course of its inspections, ASN checks that these repairs are carried out satisfactorily. In its resolution of 19 February 2019, ASN also instructed EDF to inspect the conformity of the electricity sources for its nuclear reactors.
Event date: Mon, 06-05-2019