Fukushima Daiichi Nuclear Power Plant

The Fukushima Daiichi Nuclear Power Plant (福島第一原子力発電所, Fukushima Daiichi Genshiryoku Hatsudensho, Fukushima number 1 nuclear power plant) is a disabled nuclear power plant located on a 3.5-square-kilometre (860-acre) site in the towns of Ōkuma and Futaba in Fukushima Prefecture, Japan. The plant suffered major damage from the magnitude 9.1 earthquake and tsunami that hit Japan on March 11, 2011. The chain of events caused radiation leaks and permanently damaged several of its reactors, making them impossible to restart. The working reactors were not restarted after the events.

First commissioned in 1971, the plant consists of six boiling water reactors. These light water reactors drove electrical generators with a combined power of 4.7 GWe, making Fukushima Daiichi one of the 15 largest nuclear power stations in the world. Fukushima was the first nuclear plant to be designed, constructed, and run in conjunction with General Electric and Tokyo Electric Power Company (TEPCO). The sister nuclear plant Fukushima Daini ("number two"), 12 km (7.5 mi) to the south, is also run by TEPCO. It also suffered serious damage during the tsunami, at the seawater intakes of all four units, but was successfully shut down and brought to a safe state. See the timeline of the Fukushima II nuclear accidents.

The March 2011 disaster disabled the reactor cooling systems, leading to releases of radioactivity and triggering a 30 km (19 mi) evacuation zone surrounding the plant; the releases continue to this day. On April 20, 2011, the Japanese authorities declared the 20 km (12 mi) evacuation zone a no-go area which may only be entered under government supervision. In November 2011, the first journalists were allowed to visit the plant. They described a scene of devastation in which three of the reactor buildings were destroyed; the grounds were covered with mangled trucks, crumpled water tanks and other debris left by the tsunami; and radioactive levels were so high that visitors were only allowed to stay for a few hours.

In April 2012, Units 1–4 were shut down. Units 2–4 were shut down on April 19, while Unit 1 was the last of these four units to be shut down on April 20 at midnight. In December 2013 TEPCO decided none of the undamaged units will reopen. In April 2021, the Japanese government approved the discharge of radioactive water, which has been treated to remove radionuclides other than tritium, into the Pacific Ocean over the course of 30 years.