Mitsubishi Heavy Industries (MHI) has received orders from Kansai Electric Power Co for the manufacture and replacement of the reactor core internals for units 1&2 of its Takahama NPP in Japan’s Fukui Prefecture – both 826 MWe pressurised water reactors (PWRs).
Kansai Electric immediately filed applications with Japan’s Nuclear Regulation Authority (NRA) for permission to make the relevant changes to its reactor installations. The replacement work will be done during periodic inspections of unit 1 from June to December 2028, and at unit 2 from November 2028 to April 2029.
Reactor core internals are important structures housing the nuclear fuel assemblies within a reactor vessel. They are made of stainless steel and are about 10 metres long with an outer diameter of about 4 metres, and weigh about 130 tonnes. The lower portion of each (about 89 tonnes) holds the fuel assemblies, while the upper portion (about 44 tonnes) supports the lower portion from above.
MHI is planning an integrated replacement. The new reactor core internals will be manufactured its Kobe Shipyard & Machinery Works, followed by replacement work at the site. Although reactor core internals are large structures, the need for high levels of safety and reliability require processing precision of 0.01mm. Installation within the reactor vessels will require expert positioning skills, techniques, and accuracy.
This is the second order that Kansai has placed to MHI for the integrated replacement of reactor core internals, the first being for its Mihama 3 (826 MWe PWR,) in 2021. These will be the sixth and seventh such replacements worldwide undertaken by MHI.
Takahama 1&2 and Mihama 3 have all been in operation for more than 40 years. Kansai is replacing reactor core internals as a preventive measure to enable the reactors long-term operation.
