Why did you build the Flamanville EPR in Flamanville?

The Flamanville EPR was connected to the French electricity network on December 21, 2024. It thus began to produce its first electrons. It is located in Flamanville, a small town on the Normandy coast, roughly opposite Cherbourg-en-Cotentin.

But why choose Flamanville for the construction of a new EPR (“European pressurized reactor”)? How do we choose the site that will host a nuclear power plant? This is the question answered Stéphane V. in his thread this December 23. This SVT professor, associate professor of geology, runs the blog and the popular science account Down to Earth.

Where can a nuclear power plant be built in France?

For a nuclear power plant to be built on a site, it must combine several characteristics, detailed by the SVT professor on X:

• It must be located near a water source so that the plant can be cooled properly,
• In addition, to collect cold water even at low tide, the coastline slope must be sufficiently steep,
• The rock base on which the power station rests must be strong enough to be able to support the constructions. However, often by the sea, this is not necessarily the case, the rock being exposed to strong erosion.
• Finally, it is always more interesting that the power plant is hidden from view so as not to disfigure the landscape.

The Flamanville site provides ideal conditions

The Flamanville site meets all these conditions. It is located by the sea and is distinguished by a rocky promontory, called the “Cap de Flamanville”. The power station is well hidden, because it is located on the “Diélette” site which is at the bottom of a 70 m cliff.

Concerning the rock base, two particular rocks are present on the site: the “Flamanville granite” and “cornean” rocks which are metamorphic rocks.

These two types of rock are very resistant to erosion and very strong, which makes them a good site for the new nuclear power plant, according to Stéphane V.: “These are very resistant and perfectly stable rocks, thus forming the perfect bedrock for the installation of the power station. The nuclear buildings are, in fact, built on granite, and the site structures (pumping station, engine room, etc.) on the slopes. »

Geologically, the site is very well known for these two rock types, but also because its formation began and evolved over more than 500 million years.

The only negative point to all this geological diversity is that it was necessary to take into account the particular characteristics of each rock when digging the site. However, as Stéphane V points out, it was “a real technical challenge for the tunnel boring machines, but which was ultimately not much compared to the difficulties encountered during the construction of the power station itself…”