IAEA

The Fukushima Daiichi Nuclear Power Plant experienced a severe nuclear accident on March 11, 2011, following a massive earthquake and subsequent tsunami. These natural disasters disabled the plant's primary and backup power systems, preventing the cooling of reactors. This loss of cooling compromised containment structures, leading to the release of radioactive materials into the environment. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has stated that no direct health effects from radiation exposure have been documented among Fukushima residents, although insurance compensation was paid for one death from lung cancer without a proven causal link. Several workers experienced radiation burns, and other injuries occurred due to the accident. Long-term health monitoring is considered important, and while some screening programs show increased detection rates of certain conditions, this is largely attributed to enhanced medical surveillance rather than radiation. Psychological stress and disruption of medical care also significantly impacted the affected population's health. Environmental monitoring has detected radionuclides, but concentrations have generally decreased. The accident caused the displacement of over 41,000 people, with ongoing challenges for evacuees and accusations that the evacuation itself caused harm. Investigations highlighted safety and oversight failures, and the disposal of treated wastewater remains a point of contention. The estimated cost of cleanup and compensation is substantial.

The catastrophic event at Fukushima Daiichi began with the Tōhoku earthquake and tsunami on March 11, 2011. The plant, housing six boiling water reactors, lost external power due to the earthquake. While emergency diesel generators were designed to activate, the tsunami inundated and disabled most of them, which were located in low-lying areas. Backup batteries, intended to provide power for several hours, were also compromised in some units. The plant's design included isolated cooling systems, such as isolation condensers and reactor core isolation cooling systems, which could operate autonomously using steam from the reactors. However, these systems relied on electrical power for control valves and monitoring, which became unavailable after the loss of all power sources. The failure to adequately cool the reactors after their shutdown led to overheating, compromised containment, and the eventual release of radioactive contaminants. The plant's design basis for earthquake tolerance was exceeded by the magnitude of the seismic event.

According to UNSCEAR, direct radiation-induced health effects among Fukushima residents have not been documented. While some individuals suffered radiation burns or other injuries, and a few cases of cancer or leukemia were reported, causal links to the accident's radiation are not definitively established. Experts emphasize the significant role of psychological stress, evacuation trauma, and disruption of healthcare services in the health burdens experienced by the population. For plant workers, health impacts were often linked to occupational strain and difficult working conditions during the emergency response, with most receiving doses below thresholds for deterministic health effects. Environmental monitoring has confirmed the presence of radionuclides in soil, water, and ecosystems, though concentrations have generally decreased over time due to decay and cleanup efforts. Long-term observation continues to assess ecological recovery.

The accident necessitated the evacuation and displacement of over 164,000 residents, with a significant number still living as evacuees years later. The displacement itself led to deaths and considerable psychological distress, with criticisms that the evacuation process may have caused more harm than the immediate radiation risks. Post-accident investigations identified failures in risk assessment, safety protocols, and evacuation planning. The financial repercussions are immense, with cleanup and compensation costs estimated in the tens of billions of dollars. Ongoing controversies include the management and disposal of contaminated wastewater used for cooling the reactors.