Safety improvement work to enable Mihama unit 3 and Takahama unit 1 - both in Japan's Fukui Prefecture - to operate for an additional 20 years, to 60 years, has now been completed, Kansai Electric Power Company announced today. Work needed to extend the operation of unit 2 of the Takahama plant continues.
Under revised regulations which came into force in July 2013, Japanese reactors have a nominal operating period of 40 years. Extensions may be granted once only and are limited to a maximum of 20 years, contingent on exacting safety requirements.
In June 2016, Takahama 1 and 2 - both 780 MWe (net) pressurised water reactors (PWRs) - became the first Japanese units to be granted a licence extension beyond 40 years under the revised regulations. The units began operating in 1974 and 1975, respectively. In November 2016, the Nuclear Regulation Authority (NRA) approved an extension to the operating period for Mihama 3, also a 780 MWe PWR, which entered commercial operation in 1976.
At Takahama 1 and 2, work has been carried out to reinforce their containment buildings. Kansai has reinforced the existing concrete wall surrounding the containment vessel of each unit and as well as installed secondary domes. The utility has also improved fire protection at the two units by replacing fire-resistant cabling and installing fire protection sheeting, as well as installing additional fire detectors and fire extinguishing facilities. It has also replaced the refueling water tank and constructed an anti-tornado wall around the tank. The seawater intake facility of unit 2 is also being relocated by excavating a new tunnel in the bedrock. An anti-tornado wall is also to be built around the new seawater intake facility. The existing central control panels of both units have also been replaced.
Most of the work at Mihama 3 has been related to improving the unit's seismic resistance. Kansai has reinforced the used fuel storage pool and replacing its fuel assembly rack. It has also replaced the internal structure of the reactor core and improved the seismic resistance of the reactor containment vessel. Other work at Mihama included improving fire protection work, including replacing old cables with fire-resistant cabling, installing fire protection panels and fire detectors, as well as installing new fire extinguishing equipment. A new, higher tidal barrier has also been constructed at the plant.
Kansai announced today that this work has now been completed at Mihama 3 and Takahama 1. It plans to restart the reactors in January 2021 and March 2021, respectively. Prior to their restart, Kansai must secure approval from local governments.
Upgrade work at Takahama 2 continues and is expected to be completed in January 2021.
"Going forward, we will continue to strive to make people in society, including the local area, understand the necessity and safety of operation beyond 40 years, and will continue to work on safety improvement measures for Takahama unit 2," Kansai said.