The European Pressurised Reactor (EPR) at Flamanville has reached 80% of its nominal power for the first time, according to EDF. This progressive ramp-up, initiated after reconnecting to the grid in October, marks a significant step for the utility, which aims to achieve full power output by the end of autumn 2025. Tests conducted at 60% power were deemed successful, allowing the transition to this new operational phase.
Gradual power ramp-up pending final validation
Tests at the 80% threshold must now be validated before EDF can seek authorisation from the Autorité de sûreté nucléaire et de radioprotection (ASNR) to move to full output. Approval will depend on technical results and operational performance over several weeks. EDF has not yet confirmed whether the final output will reach the initially announced 1,620 MW, as a provisional maximum of 1,585 MW was submitted to the Commission de régulation de l’énergie (CRE), 35 MW below expectations.
Regulatory shutdown planned for 350 days
At the same time, EDF has announced a scheduled shutdown of the reactor starting on September 26, 2026. This first major stoppage, lasting 350 days, will include the mandatory full inspection required 30 months after the initial fuel loading. The procedure will involve replacing the reactor vessel head, previously identified with known anomalies.
During the shutdown, around 20,000 operations will be carried out, with nearly 200 industrial partners involved. This phase will also include fuel replacement. EDF stated that the vessel head replacement, although technically demanding, has been previously executed across the nuclear fleet and poses no major technical uncertainties.
Project marked by cost overruns and delays
Initially budgeted at €3.3bn, the Flamanville EPR now carries a reference cost of €20bn ($21.34bn) based on 2015 figures, rising to €23.7bn ($25.3bn) under 2023 conditions. The project has experienced multiple delays, with grid connection achieved only in December 2024, twelve years later than originally planned.
The Flamanville EPR is now the first nuclear reactor commissioned in France in 25 years. Located on the Channel coast, it is designed to generate electricity for up to two million households. Its full power performance will depend on the optimisation of technical settings and the cooling capacity of the sea, key factors in the final evaluation of its output capacity.
