Flamanville-3

Flamanville-3 is France's first third-generation EPR pressurised water reactor, located at the Flamanville nuclear site in Normandy on the English Channel coast. After years of construction delays and cost overruns, it was connected to the grid in late 2024. The reactor has a design capacity of 1,650 MW and is operated by EDF. A major planned overhaul is scheduled to begin in September 2026 and is expected to last approximately one year, effectively removing the reactor from EDF's production base through most of the 2026-27 refill season.

Flamanville-3 was originally scheduled for completion in 2012 at a cost of EUR 3.3 billion. The final cost exceeded EUR 13 billion and completion was delayed by more than a decade, becoming a cautionary case study in nuclear project management cited by critics of new-build programmes across Europe and beyond.

Despite its operational challenges, the EPR design forms the basis of France's planned new-build programme: EDF has received government approval for up to six new EPR2 reactors (a refined design), with Penly as the first site. Flamanville-3's operational experience feeds directly into EPR2 engineering and regulatory approvals, making the current overhaul strategically as well as operationally significant for French energy policy.

EDF declared Flamanville-3 in commercial operation on 5 May 2026, formally ending the commissioning stage that began with first criticality on 12 December 2024. The reactor enters a one-year major overhaul from September 2026, removing approximately 1.6 GW from the French nuclear fleet at the start of the heating season. This reverses the nuclear surplus that suppressed Continental clearing prices through Q1-Q2 2026 and removes France's most modern reactor from service precisely when European gas storage is tracking below the 80% November target.

Flamanville-3 is France's first third-generation EPR (European Pressurised Reactor), located at the Flamanville nuclear site on the Normandy coast. Design capacity is 1,650 MW. The reactor was originally scheduled for completion in 2012 at EUR 3.3 billion; the final cost exceeded EUR 13 billion and completion was delayed by more than a decade, making it the canonical reference for EPR construction risk. Despite this, the EPR design forms the basis of France's approved new-build programme: up to six EPR2 reactors, with Penly as the first site.

Flamanville-3's overhaul is the 'first-of-class' maintenance cycle for the EPR design — its duration is uncertain because there is no prior EPR overhaul from which to set a baseline. EDF has guided approximately one year; the risk is that, as the first such overhaul, engineering surprises extend this into 18-24 months. A two-year absence would encompass the entirety of winter 2027-28, compounding the structural pressure on Continental electricity and gas pricing already visible in the FR-DE spread data.