To prevent possible problems of fuel rods leaks, EDF has decided to fully restructure the core of the EPR at unit 3 of France’s Flamanville NPP, Ouest-France has reported. This decision was based on the experience of the Taishan NPP in China, which experienced such problems during its second production cycle.
This came after the reactor was finally restarted after more than two months of delays during which technical problems have repeatedly postponed its restart.
It is necessary to regulate disturbances of neutron flux at the bottom of the reactor vessel, a problem risks fuel rod leakage. As a preventive measure, the core of the EPR reactor in Flamanville 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. “This is a precautionary measure. To date, there is no sealing problem. We are simply taking into account international experience.”
The Flamanville 3 EPR was reconnected to the French power grid on 19 April after being taken offline on 15 February for checks and maintenance operations. The plant, which has a maximum net capacity of 1,630 MWe, resumed operation at a lower level of 90 MWe, EDF said. Tests at various power levels are being carried out. This gradual increase in output is part of the initial startup process which may take several months to comply with safety protocols. Full power is scheduled for this summer.
During the shutdown, 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.
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 series 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 l’Autorité de Sûreté Nucléaire (ASN – Nuclear Safety Authority). EDF was also criticised by the French government for poor co-ordination of the project that involved hundreds of suppliers.
A 2019 report on the project noted that several elements of the project’s construction had begun before the completion of the reactor’s design, leading to certain sections of the work having to be demolished and rebuilt.
Flamanville 3 reactor was first connected to the national grid in December 2024 since when it has undergone two scheduled shutdowns, followed by latest current suspension due to unanticipated technical issues.
Taishan 1&2 were the first two EPR reactors to be built in China. 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 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.
