Japan's Nuclear Regulation Authority has approved an extension of the operating lifetimes of two reactors at Kyushu Electric Power Co's Sendai NPP, which is now approaching 40 years of operation.

The approval will allow the company to extend by 20 years the operating lives of the 890 MWe pressurised water reactors (PWRs) at units 1&2 at the NPP in Kagoshima Prefecture.

These will be the fifth and sixth reactors in Japan allowed to operate beyond the basic lifetime of 40 years. They follow units the 826 MWe PWRs at units 1&2 at Kansai Electric Power Co's Takahama plant in Fukui Prefecture; the 826 MWe PWR at unit 3 at Kansai Electric’s Mihama NPP also in Fukui; and the 1100 MWe boiling water reactor at unit 2 of Japan Atomic Power Co's Tokai NPP in Ibaraki Prefecture.

Sendai 1 will mark its 40th anniversary in July 2024 and Sendai 2, in November 2025. Kyushu Electric applied for the extension in October 2022, after conducting detailed inspections.

In December 2022, NRA approved a draft rule that would allow the reactors to operate beyond the current limit of 60 years. The new policy will effectively extend the period reactors can remain in operation beyond 60 years by excluding the time they have spent offline for inspections from the total service life. The legislation was approved by the government in February, enacted in May and will comes into effect in June 2025.

In April, Kansai Electric submitted an application to NRA for a 20-year operating extension for the 870 MWe PWRs at units 3&4 of the Takahama NPP. The two reactors will reach the end of their 40-year operating lives in 2025. Kansai completed the special inspection required for an operating extension between September and November 2022 and no problems were found. However, damage to heat-transfer pipes of the steam generator was discovered in both reactors. The Fukui prefectural and Takahama municipal governments have both consented to the replacement of the generators and replacement work will take place between June 2026 and February 2027.

Image: The Sendai nuclear power plant in Kagoshima Prefecture, Japan (courtesy of Kyushu Electric Power Co)