While prior to the Fukushima Daiichi accident, nuclear reactors accounted for 25% of Japan’s power output, their share dropped to zero by 2014, following the regulators’ decision to shut down all of the country’s nuclear power units. The process of restarting the reactors began in 2015. According to the IAEA, there are currently 12 nuclear power units with a total net capacity of 11 gigawatts (GW) regularly operating in the country. The remaining 48 reactors can be divided into two categories: 27 units with an aggregate capacity of 17.1 GW that were permanently decommissioned and 21 reactors with a total capacity of 20.6 GW that can resume operation subject to regulatory approval.
New safety requirements established in 2013 prohibit reactors and other nuclear infrastructure facilities from sitting above active faults within Earth’s crust, of which there are tens of thousands in Japan. Since these faults can cause devastating earthquakes, regulators take this factor into careful consideration when issuing permits to restart power plants. This is why the Nuclear Regulation Authority of Japan refused in November 2024 to restart the second power unit of the Tsuruga NPP on the island of Honshu by the Sea of Japan.
Thanks to the gradual restart of nuclear reactors, the share of NPPs in Japan’s energy mix rose from 0.4% in 2015 to 7.6% in 2023. The share of gas-fired power generation over the same period fell from 40.5% to 34.3%, with liquefied natural gas (LNG) imports going down by more than 20% (from 115.9 billion cubic meters to 90.3 billion). Japan plans to increase the share of NPPs in its energy mix to 20% by 2030, including through the introduction of new reactors. These include the single-unit Ōma NPP on Honshu and the third power unit of the aforementioned Shimane NPP, which are currently under construction. Last year, a policy document of Japan’s Cabinet called for the construction of innovative reactors to replace power units that had been completely decommissioned.
