At 11:48 on 21 December 2024, Flamanville 3 was synchronised to the French national electricity grid. It is the first nuclear reactor to be connected to the grid in France since 1999, when Civaux 2 entered service. A twenty-five-year wait, brought to a close with a precise technical milestone: 1.65 gigawatts of installed capacity, making this unit the most powerful in the entire French nuclear fleet.
The reactor is an EPR — European Pressurized Reactor — a third-generation advanced design. It is located in Normandy, on the English Channel coast, at the Flamanville nuclear plant, which already hosts two 1,300 MWe units in operation since 1986 and 1987. With the addition of the third unit, the site’s total output exceeds 4,200 MW. At full capacity, Flamanville 3 is expected to generate approximately 13–14 TWh per year, enough to power around 2 million homes. The reactor achieved first criticality — its first sustained nuclear reaction — on 3 September 2024, followed by months of progressive testing and verification by France’s Nuclear Safety Authority, the ASN. Grid connection came with the reactor operating at 25% power, initially delivering 100 MW. The ramp-up was gradual: the ASN only authorised exceeding the 80% threshold on 12 December 2025, with full power reached later that same month.
Flamanville 3 is the fourth EPR in commercial operation worldwide. The other three are Taishan 1 and Taishan 2 in China, and Olkiluoto 3 in Finland — all based on the same design developed primarily by Framatome and EDF. Two additional EPR units are under construction in the United Kingdom at Hinkley Point C. From a technical standpoint, the EPR design features quadruple redundancy in its safety systems and a core catcher for molten fuel containment, characteristics that set it apart from previous generations. Construction at Flamanville began in December 2007, with a target completion date of 2012. The project ran into significant difficulties, including the need to demolish and rebuild certain sections because work had started before the design was fully finalised. The outcome was a timeline far longer than anticipated, ending with grid connection seventeen years after groundbreaking.
Normandy, the region where the plant is located, generated roughly two and a half times the electricity it consumed in 2024, almost entirely from low-carbon sources. Flamanville 3 further strengthens this energy profile. France already relies on nuclear power for around 62% of its electricity generation — the highest share in the world. President Emmanuel Macron welcomed the grid connection as “a great moment for the country,” framing it within his strategy for low-carbon reindustrialisation. EDF has plans to build six new reactors, a commitment announced by Macron in 2022 as part of a structural revival of the sector. The first planning applications for the two EPR2 units at the Penly site, also in Normandy, were filed in July 2023.
The completion of Flamanville 3 closes a long and complicated chapter, but opens a phase of tangible expansion. France is once again building reactors in series after decades of stagnation, this time with the more standardised EPR2 design. If EDF succeeds in applying the lessons learned at Flamanville to the industrial supply chain for future projects, the French nuclear programme could become a benchmark for other European countries that are assessing or launching their own construction plans.
