Steam generators transfer the thermal energy generated in the reactor vessel of a pressurised water reactor (PWR) from the primary (reactor) cooling system to the secondary (turbine) cooling system, producing the steam to drive the electricity generation turbine.
The steam generators – each about 21 metres in height and weighing some 330 tonnes – are pressure-resistant vessels made with strong low-alloy steel (steel with not more than 5% alloying element). Each steam generator contains more than 4,500 heat transfer tubes made of TT690 – a state-of-the-art nickel, chromium, and iron alloy, specially heat-treated for enhanced corrosion resistance.
EDF ordered the replacement components from Mitsubishi Heavy Industries (MHI) in 2019 following an international bidding process. MHI received the order jointly with Onet Technologies – its alliance partner in the French nuclear power market since 2002.
Manufacturing of these replacement steam generators was completed at MHI’s Kobe facility in January 2024. At the end of February this year, they obtained a certificate complying with the standards required by the French nuclear regulatory authority, and were subsequently transported to France.
MHI has received orders for a total of nine replacement steam generators from EDF, and the remaining six units are currently being manufactured at MHI’s Kobe facilities, with delivery scheduled from 2028 onwards.
MHI noted that it has delivered a cumulative total of 15 replacement steam generators to EDF since 2005, excluding those delivered this time. EDF operates 57 PWR plants in France. In accordance with French government policy to extend the operating life of nuclear power plants beyond 40 years, EDF had been progressively replacing steam generators at its PWR plants that started operation in the 1980s.
MHI said it has a proven track record of delivering more than 30 replacement steam generators to overseas countries including France, Belgium, and the USA. The company has received orders for more than 130 steam generators in total, including both new installations and replacements projects in Japan.
