Onet Technologies and MHI have been collaborating for over 20 years to supply replacement steam generators (SGs) for the French fleet of nuclear power plants with a capacity of 900 MWe. After already delivering 5 triplets to EDF, a total of 15 SGs, the fabrication of the 6th triplet has just been completed.

More than 30 Onet Technologies employees, including 15 working on calculations and 2 based in Japan, were mobilized for this project.

Steam generators are the most imposing components of the primary circuit and must be replaced during the operation of nuclear power plants. Their dimensions are impressive: each SG weighs 350 tons, is 21 meters high, and 4 meters wide! Their fabrication requires several years of study before the design is validated by the safety authority.

This success demonstrates Onet Technologies’ high level of expertise, our ability to support major clients on large-scale projects, and our mastery of French regulations concerning nuclear pressure equipment (ESPN). These skills will be essential for the future of nuclear energy, whether in the construction of new high-power reactors or the design of new models.

In this project, Onet Technologies had several responsibilities:

• Engineering studies to validate the design and justify the equipment’s behavior in service.
• Assistance in complying with French regulations and standards.
• Non-destructive testing within the framework of the Irradiation Surveillance Program (PSI), serving as a “zero point” of control during operation.
• Factory inspections of European suppliers.
• Delivery of the steam generators (SGs) on-site for the assembly teams.

These three steam generators will be delivered to EDF in 2026 to be installed at the Cruas nuclear power plant (France).

Onet Technologies’ remarkable expertise in steam generators

The success of this project and the know-how of our employees make Onet Technologies a key player in the nuclear field, both for operating plants and for the construction of new plants and innovative reactors (SMRs).

Our expertise is also based on more than 40 years of experience in steam generator maintenance. For example, our Integrated Service for Steam Generators (PIGV) enables high-pressure cleaning and sludge filtration.

Even after the operation of SGs in the plant, Onet Technologies teams recently achieved a world first by depositing the bowl of a steam generator as part of EDF’s Sherlock project, a true technical challenge.