Flamanville-3 reaches full power

For the project, which has been plagued by years of delays and significant cost overruns, it represents one of the last steps before the reactor finally enters commercial operation. For the broader sector, Flamanville-3 is a sign of good progress; it will be the first power reactor to come on line in the country in 23 years.

Project background: Flamanville-3 is an EPR (or European Pressurized Reactor), a Generation III+ pressurized water reactor supplied by Framatome. Construction on the project—which is located on the northern coast of France on the English Channel—began in 2007 and has a long and troubled history.

Originally estimated to cost €3.3 billion (about $3.9 billion), the project’s price has ballooned over the course of repeated delays and difficulties. In December 2022, EDF announced a new cost estimate of €13.2 billion ($15.5 billion). In January 2025, the French Court of Auditors released a new estimate that includes the interest accrued during construction: €23.7 billion (about $27.8 billion). In all, the project is set to enter commercial operation at a price tag anywhere from four to seven times its original budget.

Naturally, costs and timelines are linked, and Flamanville-3’s construction was significantly extended. The project was originally planned to take 54 months. If EDF had kept to its original schedule, Flamanville-3 would have entered commercial operation in 2012. However, year by year, that timeline was pushed back due to a variety of reasons both technical and administrative.

On the technical side, of particular note was EDF’s April 2018 announcement that it had found quality deviations in the welding of the pipes of the main secondary system. That setback alone cost the project between three and four years and resulted in 53 welds being redone, eight of which required the use of remote-controlled robots. In total, this delay increased the cost of the project by €1.5 billion.

Today’s progress: Despite the difficult road EDF has walked to get to this point, Flamanville-3 is now only a few steps away from entering full commercial operation. In its press release, EDF said, “Reaching the 100% mark for the first time enables testing of equipment at full power, taking of measurements and verifying that everything is functioning properly” over the coming weeks. EDF has previously said that the plant would enter commercial operation by the end of 2025, but this deadline was not reiterated in this newest press release, indicating that the utility may now be planning for the reactor to enter operation in early 2026.

Broader sector: In April 2002, Civaux-2 in western France—a 1495-MWe PWR—entered commercial operation. Flamanville-3 will be the first power reactor in the country to open since then.

Despite that long gap in projects, the reactor represents France’s continuing commitment to nuclear power. According to the International Energy Agency, as of 2024, 67 percent of the country’s electricity generation comes from nuclear, and the French government has been broadly supportive of the sector. In 2022, President Emmanuel Macron announced a new expansion plan to build six new EPR2 units, and this year, the government tentatively agreed to provide government-subsidized loans for half of that project’s construction cost.

Other EPRs: Flamanville-3 is the fourth EPR in the world to reach full power. The first EPR to enter construction was Finland’s Olkiluoto-3 in 2005. Next came Flamanville in 2007, followed by Taishan-1 and -2 in China, where construction began in 2009 and 2010, respectively. Despite Taishan entering construction after its two counterparts, those units were the first to reach commercial operation, in 2018 and 2019. Olkiluoto followed in 2023.

In 2010, Framatome anticipated building more than 20 EPRs, including four in the United States (at Bell Bend, Callaway, Calvert Cliffs, and Nine Mile Point), most of which did not come to fruition. Still, there is significant momentum in the U.K. on new EPR projects between Sizewell C and Hinkley Point C.