A dam against the North Sea: At Gravelines, France’s largest nuclear power plant is completing a long wall to protect against “extreme” flood risks, “post-Fukushima” work carried out in an area exposed to sea-related elevation climate.
The cries of seagulls echo above the workers, a seal swims in the channel that brings seawater to the plant. Behind a string of dunes, the North Sea is just a few hundred meters away.
With its six reactors commissioned between 1980 and 1985, with a total output of 5,400 MW, Gravelines is already the largest nuclear power plant in Western Europe and will be able to accommodate two new generation EPR reactors in the coming decades.
On the land side, a 4-meter high dike made of clay, rocks and earth forms the junction between walls with watertight floodgates and completes the “peripheral flood protection” system.
Already protected on the east side by Total’s fuel tanks, which surround it by an artificial dune barrier, the plant will find itself completely surrounded by the risk of sea level rise accentuated by a storm.
– Protection at a height of 7.48 m –
Started in 2020 with an investment of 35 million euros, the work is expected to be completed in the autumn.
“The plant is already safe, the risk of flooding is already considered, but not at an extreme level”, explains its director Emmanuel Villard.
The new protection was designed by imagining “a tide with a coefficient of 120, plus a millenary surge, plus a safety factor of 50 cm, to which we added another meter of protection against wind and oscillations”, he says.
Today protected against “a rise of just over 6 meters above static sea level”, the plant will be protected up to 7.48 meters thanks to this “post-Fukushima” work.
The work was conceived “taking into account phenomena never before observed in the territory”, underlines EDF.
In Fukushima, cooling systems broke when the tsunami flooded emergency generators, causing reactor cores to melt.
– “Great wall of China” –
The Gravelines plant is located in the Aa Delta, an area of polder, recovered from the sea and swamps in the Middle Ages and equipped with a network of canals, the wateringues, responsible for the evacuation of water to the sea, and stations of pumping.
“If there really is a heavy flood, the plant will be isolated. EDF always tells us that there will be FARN (fast-acting nuclear force, also created after Fukushima, editor’s note), but to relieve teams, this will not be simple”, underlines Nicolas Fournier, President of the Assembly for the Defense of the Environment of the Flandre-Artois Coast.
For Paulo-Serge Lopes, president of Virage Energie, an association of the Nuclear Exit network, the construction of a “Chinese wall” around the plant does not solve everything: “The breakdowns are, above all, inside it: the aging of the reactor, – maintenance and long-term conservation issues…”
A map from the regional climate observatory shows that a one-meter rise in sea level would cause almost the entire delta to pass underwater, an area that is also very dense at high-threshold Seveso sites.
According to the latest report by the UN climate experts (IPCC), if the emissions responsible for climate change continue to rise, the sea level rise could reach 60 to 110 cm by 2100.
“The purpose of this dike is to protect the Gravelines plant as it is today”, insists its director, while EDF estimates the useful life of the new EPRs announced by President Emmanuel Macron at 60 years. For the EPRs, “these calculations, with the extreme hypotheses, will be taken into account from the design phase”.