The French Nuclear Safety and Radiation Protection Authority (ASNR – L’Autorité de Sûreté Nucléaire et de Radioprotection) has approved the transition of the EPR reactor at unit 3 of the Flamanville NPP to a power level greater than 80% of its nominal power.
Commissioning of the 1,630 MWe (net) EPR pressurised water reactor was authorised in May 2024, allowing EDF to continue increasing the reactor’s power until its nominal power is reached, then to complete the start-up test programme. This was followed by fuel loading, with the start-up process beginning in September 2024.
Flamanville 3 was connected to the grid in December 2024. In January 2025, ASNR gave its agreement to continue start-up tests of the reactor beyond 25% of its nominal power. It was taken offline in February for checks and maintenance operations and reconnected to the power grid in April. The plant then resumed operation at a lower level of 90 MWe, according to EDF, and tests at various power levels were carried out with full power scheduled for mid-year.
During the February-April shutdown at Framanville 3, EDF carried out work on a cooling system, the turbo-alternator unit and in a number of other areas necessary to ensure a safe power-up sequence. EDF said adjustments had been made to the bearings guiding the turbine rotors, adding that more than 1,500 safety criteria are assessed during initial startup, which can require several planned stoppages or unexpected adjustments.
However, in August EDF said Flamanville 3 was expected to achieve full power “before the end of autumn 2025”. This is the latest in a long series of delays. Construction of Flamanville 3 started in 2007 and the plant was originally expected to be completed in 2012. The unit is some 12 years overdue and the expected final construction costs have increased from an initial estimate of €3.3bn ($3.7bn) to over €13.2bn.
The project faced a number of problems. In 2022, work was needed following repairs on welds that proved to be more complicated than expected. EDF attributed that delay to additional studies needed to establish a new process for the stress-relieving heat treatment of some welds that were subsequently upgraded. In addition, components for the complex design had to be retooled, some after complaints from ASN (now ASNR).
Taishan 1&2 in China were the first two EPR reactors to begin operation. The project is owned by the Guangdong Taishan Nuclear Power Joint Venture Company Limited (TNPJVC), a joint venture between EDF (30%) and China General Nuclear. Construction of the units began in 2009 and 2010, and they began commercial operation in 2018 and 2019, some five years behind schedule.
In April Ouest-France reported that EDF has decided to fully restructure the core of the EPR to prevent possible problems of fuel rods leaks. This decision was based on the experience of Taishan 1in China, which had experienced such problems during its second production cycle.
In 2021, an increase in radiation levels was detected in the primary circuit of Taishan 1. The increase was caused by damage to the cladding in a small number of fuel rods, which China’s Ministry of Ecology & Environment said was normal during the production, transportation and loading of fuel. It estimated that around five of more than 60,000 fuel rods in the Taishan 1 reactor core had been damaged.
However, it is necessary to regulate disturbances of neutron flux at the bottom of the reactor vessel, a problem that risks fuel rod leakage. As a preventive measure, the core of the Flamanville EPR in will therefore be restructured with reinforced fuel after its first shutdown at the end of 2026 or early 2027, Ouest-France cited EDF as saying.
ASNR said it carried out several inspections of the reactor from the 25% power stage and also analysed the significant events declared by EDF and monitored the corrective actions implemented. “ASNR will continue to provide specific control of the subsequent stages of the reactor ramp-up until the end of the start-up tests.”
EDF subsequently announced that Flamanville 3 reactor achieved 100% power on 14 December.
“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,” EDF noted. “Over the coming weeks, and as part of the start-up programme, the power of the reactor will vary to continue testing at different power levels and an operation will be carried out on an internal electrical substation.”
