Fukushima Meltdown
In March 2011, a massive undersea earthquake off Japan's northeastern coast generated a tsunami that crippled the Fukushima Daiichi nuclear power plant, causing meltdowns in three of its reactors. It was the worst nuclear accident since Chernobyl in 1986, and one of only two events ever rated at the highest level, 7, on the International Nuclear Event Scale. The disaster forced a global reassessment of nuclear safety and reshaped Japan's energy policy.
The plant, operated by the Tokyo Electric Power Company (TEPCO), stood on the Pacific coast in Fukushima Prefecture and had been running since the 1970s. Japan, poor in domestic fossil fuels, had embraced nuclear power as a pillar of its energy supply. The country is also among the most seismically active in the world, and its engineers had built reactors to withstand strong quakes. Critics, however, had long warned that the plant's defenses against very large tsunamis were inadequate, and later official inquiries agreed that the risk had been underestimated and that regulators and the operator had been too close.
On 11 March, the Tohoku earthquake, one of the most powerful ever recorded, struck offshore. The operating reactors at Fukushima Daiichi shut down automatically, as designed. But the tsunami that followed overtopped the plant's seawall and flooded its basements, knocking out the emergency generators and electrical systems needed to circulate cooling water. Without cooling, fuel in the reactors overheated and melted in units 1, 2 and 3. Hydrogen explosions damaged several reactor buildings, and radioactive material was released into the air and the sea. Workers struggled in difficult conditions to pump in water and stabilize the site.
Authorities ordered evacuations that eventually affected well over 100,000 people, many of whom were away from home for years, and some areas remain restricted. The earthquake and tsunami themselves killed roughly 18,000 people, while the nuclear accident is not generally credited with causing radiation deaths on that scale. Health agencies have reported that the main harms were psychological stress and disruption linked to evacuation, though debate continues over long-term cancer risks, which are expected to be small but are difficult to measure.
The consequences were wide-ranging. Japan temporarily idled nearly all of its reactors, created a new, more independent regulator, and imposed stricter safety standards; only some reactors have since restarted. Germany decided to phase out nuclear power, while other countries reviewed their own plants. Cleanup and decommissioning of Fukushima Daiichi is expected to take decades, and the controlled release of treated water stored at the site has remained contentious both at home and abroad.