Tepco applied for Nuclear Regulation Authority (NRA) approval of its design and construction plan for Kashiwazaki-Kariwa units 6 and 7 in September 2013. It submitted information on safety upgrades across the site and at those two units. These 1356 MWe Advanced Boiling Water Reactors began commercial operation in 1996 and 1997, respectively, and were the first Japanese boiling water reactors to be put forward for restart.
In 2017, Tepco received permission from the NRA to restart units 6 and 7. However, in early 2021, Tepco notified the NRA of malfunctions in intruder detection equipment on the Kashiwazaki-Kariwa site. In addition, it reported the unauthorised use of an ID card. In April 2021, the NRA issued an administrative order to Tepco prohibiting it from moving nuclear fuel at the plant until improvements in security measures there have been confirmed by additional inspections. This order was lifted in December last year after inspections confirmed that measures had been enhanced at the site.
Tepco announced in April 2024 that it had completed loading fuel into unit 7, which it aimed to restart as early as this summer. The unit, however, would have to be taken offline again in October to implement anti-terrorism safety measures. The company has determined that unit 7 cannot be restarted before the completion of the antiterrorism facility scheduled for August 2029.
“As the installation deadline for the Specially Designated Severe Accident Response Facilities approaches on 13 October 2025, we have decided to suspend the test operation of the reactor itself, as we will be removing the loaded fuel without conducting inspections involving critical reaction operations,” the company has now announced.
According to Tepco, the fuel removal work will begin on 14 October, Jiji Press reported. A total of 872 nuclear fuel assemblies will then be transferred to a used fuel storage pool over about two weeks from 21 October.
Tepco is now prioritising restarting Kashiwazaki-Kariwa unit 6, where fuel loading was completed in June. The company has until September 2029 to implement anti-terrorism safety measures at unit 6, and it could operate until that time, pending local approval.
