Fukushima Daiichi Nuclear Power Station Disaster


The Fukushima Daiichi nuclear power station was operated by Tokyo Electric Power Company (TEPCO) with six units that used atomic energy, or nuclear fission, to create electric power. In March 2011, a massive earthquake struck in the Pacific ocean near the coast of Japan and created a devastating tsunami that rose 15 meters (49 feet) at the plant's location, disabling its power supply and cooling three of its reactors, resulting in a nuclear accident on March 11.


At the time that the Tohoku-Pacific Ocean earthquake occurred on March 11, 2011, Japan was operating 11 nuclear reactors at four nuclear power plants in the region that would be affected by the tsunami. Fukushima Daiichi, which is located on the east coast of the island of Honshu, was operating three of its units at rated output, and the other three were undergoing regular inspections. The earthquake, which was 9.0 in magnitude, created a tsunami much more powerful than anticipated. The nuclear power plants were designed to withstand a tsunami, but at levels about 10 meters (32 feet), which was lower than the waves in the March 2011 tsunami.

Photo taken on November 12, 2011, shows the No. 3 reactor building at the Fukushima Daiichi nuclear power plant in Fukushima Prefecture, northeastern Japan that was damaged by an explosion after the March 11th earthquake and tsunami.

Photo taken on November 12, 2011, shows the No. 3 reactor building at the Fukushima Daiichi nuclear power plant in Fukushima Prefecture, northeastern Japan that was damaged by an explosion after the March 11th earthquake and tsunami.
(Kyodo via AP Images)

According to TEPCO, the reactors in the three operating units shut down automatically when the earthquake occurred, and metal rods that control power output worked correctly when the seismic power of the earthquake was detected. All of the units were made inoperable soon after the tsunami hit. Back-up diesel generators, another typical safeguard, came on to supply power that was designed to cool down the nuclear reactors. However, the unexpectedly large tsunami surge knocked out the electrical equipment and caused batteries to stop working so that the reactor could not cool as intended. This eventually led to fuel rods being damaged by high temperatures and releasing radioactive materials.

The radiation emitted into the air from the accident mostly was iodine-131, a material with a half-life of about eight days. The other radionuclide was cesium-137, which has a half-life of 30 years. The plume from the explosion carried cesium-137, which can settle on water or land. The fallout from Fukushima's plume was estimated to spread tens of kilometers from the plant. People were evacuated from their homes soon after the tsunami if they lived within 20 km (12 miles) from the nuclear power plant.

Except for the radiation materials emitted in the early part of the accident, most of the fuel in the reactors was contained. Still, the water used to cool the reactors escaped into the Pacific Ocean, and TEPCO voluntarily released some water with low levels of radiation to make more storage space for highly contaminated water. The accident also caused radioactive pollution, which then was transported by rainwater. A year later authorities were still measuring radioactivity levels of seafood near Japan and finding short-term levels exceeding regulatory limits in the Japanese sand lance. The World Health Organization expected long-term marine damage, particularly in areas of the world further from the Japanese coast. Investigations and reports were released on causes of the accidents, along with public health effects. TEPCO and the Japanese government continued to assess and manage the damage caused by the plant's meltdown.

Risk factors

The Fukushima Daiichi disaster highlighted problems that can occur from a combination of manmade and natural disasters. Several natural circumstances combined to trigger the accident and produce the disaster's proportions, including the magnitude and location of the Tohoku earthquake and the unusual double surge and height of the tsunami created by the quake. However, the region of Japan struck by the March 2011 earthquake had reportedly been hit by tsunamis in the century before the one in March 2011 at heights of up to 10 meters (32 feet), which was higher than TEPCO's design was prepared to withstand. Japan is one of the world's most active seismic areas. In fact, another strong earthquake struck 72 miles northeast of Sendai, the Japanese city closest to the Tohoku earthquake's epicenter, in June 2012.

A report submitted by the Japanese government in June 2011 blamed TEPCO for faulty planning, and outside investigators faulted Japanese regulators for lax enforcement. After the disaster, critics said that the sea wall was inadequate to protect the plant from surges and that the plant was based on designs from the 1960s, which points out a risk for active and closed plants around the world, especially those in earthquake regions.

A team of local authority workers undertake radiation contamination monitoring in the grounds of Soramame Children's Nursery, in Fukushima city, in Fukushima prefecture, Japan, on Tuesday 7th June 2011.

A team of local authority workers undertake radiation contamination monitoring in the grounds of Soramame Children's Nursery, in Fukushima city, in Fukushima prefecture, Japan, on Tuesday 7th June 2011.
(jeremy sutton-hibbert/Alamy Stock Photo)


Causes and symptoms

For all intents and purposes, it could be said that a massive earthquake and tsunami triggered the nuclear power plant accident at Fukushima Daiichi. Since the event, however, reviews and reports have suggested that the reactors held up to the earthquake but that the tsunami destroyed the emergency generators and cooling systems. The independent Fukushima Nuclear Accident Commission determined that the disaster actually was a manmade one because of organizational and human-related problems. Among these were poor crisis management response and problems with governance. The report particularly blames TEPCO and Japan's Nuclear and Industrial Safety Agency for not taking proper measures to prevent the accident before March 2011. The plant should have been able to withstand a tsunami of higher force and had better crisis plans in place. Further, the report said that the safety agency's regulator had been involved in promoting nuclear power, which caused a conflict of interest and lax regulatory oversight.

Radiation damages DNA, and cancer is one of the major concerns from radiation exposure. Exposure to lower doses can cause late effects such as cancer. If individuals are exposed to high doses of radiation, they can have effects such as cataracts, nausea, vomiting, and respiratory distress. Depending on the radiation level, the exposed individuals can die within hours or weeks. No acute injuries from high doses were reported from the Fukushima Daiichi accident, even among the nuclear power plant's workers and those involved in recovery efforts. In fact, Hirosaki University researchers found only 10 people with high levels of radiation, though their radiation doses still were below the level that should cause acute injuries. Still, radiation levels were higher than normal background radiation, and long-term effects remained to be seen.


By the end of May 2011, more than 195,000 residents who lived near the plant had been tested for radiation exposure and 1,080 children's thyroid glands were tested for radiation. Authorities also gave radioactive iodine to some residents near the accident, which might have counteracted effects of the leaked radiation. Decontamination efforts were underway to make the area safe before allowing people to return.

A radioactive material that, depending on its form, can be used in diagnosing or treating thyroid disease.
Nuclear fission—
A nuclear reaction that splits a heavy nucleus into lighter ones, or one atom into two. The reaction releases energy.
Set of large ocean waves caused by a disturbance in the ocean, usually an earthquake. Tsunami is a Japanese word that combines the words tsu for “harbor” and nami for “wave.”

Public health role and response

Immediate response

Relief organizations were in place responding to public health problems related to the tsunami. In addition to evacuations, having people shelter indoors, and suggested relocations, Japanese authorities acted quickly to ensure that any contaminated food was removed from the area near the Fukushima accident. WHO acted within hours to assist with travel advisories in surrounding areas and offer technical advice to Japanese authorities on food and drinking water safety, along with monitoring radiation. The primary response following the accident fell on TEPCO as owner and operator of the Fukushima Daiichi nuclear power plant. The company first had to release some contaminated water, with government approval, and then worked to contain and treat additional contaminated water.

When the Japanese reconstruction agency reviewed the effects of the accident on residents, the most harmful health effects were from the forced evacuations. Many people faced physical and emotional burdens from being forced to leave their homes. The evacuations were blamed for the early deaths of 34 elderly people. Stress also was high among the plant's workers.

Long-term response

Sea water, soil, and atmospheric measurements are monitored at the plant, at a dozen locations around the plant's boundaries, and in the surrounding areas.

The government has sent surveys to some 2 million people who live in a large area surrounding the plant to follow their health for 30 years. Some farmers in the surrounding area have worked to study and overcome the effects of radiation on crops. WHO continues to receive updates on food testing, and TEPCO provides regular reports on the plant's clean-up and closure status. After several meetings of TEPCO and various agencies, plans were made to compensate the people and businesses affected by the disaster. In September 2012, Japan announced it would phase out use of nuclear power in favor of renewable energy. The crisis sparked international actions to improve nuclear power plant safety, crisis communications, and other lessons learned from the disaster to prevent future ones.


One year after the accident, the Health Physics Society convened a panel to discuss the risks and effects of radiation from the accident. The panel noted that unlike the Chernobyl, Russia, incident, there were no immediate radiation accident victims to treat. Instead, exposure to populations was very low, and most of the radiation blew toward the Pacific Ocean. Although long-term effects still were unknown, experts on the Health Physics Society panel reported that effects should be minimal to none based on exposures. The effects on those displaced by the tsunami and reactor meltdown are more difficult to measure and project. Some people displaced by the accident may never be able to return to their homes.


The best way to prevent a similar nuclear plant accident is to seek alternative sources of energy, which is a goal announced by Japanese authorities. The industry also has to deal with plants that are shut down to clean up nuclear fuel and waste at the plants. Cleaning up the Fukushima Daiichi plant involves a three-phase plan that could take up to 40 years before all radioactive waste is fully processed and properly disposed of. The Japanese government ordered stress tests on all of its remaining reactors. The International Atomic Energy Agency adopted an action plan a few months following the accident to improve the safety of nuclear power production around the world. The plan includes better transparency and communication and a goal to assess the safety of nuclear power plants with the lessons learned from the Fukushima disaster in mind.

See also Background radiation ; Radiation ; Radiation exposure ; World Health Organization .



Anzai, Kazunori, N, Ban, T. Ozawa, and S. Tokonami. “Fukushima Daiichi Nuclear Power Plant Accident: Facts, Environmental Contamination, Possible Biological Effects, and Countermeasures.” Journal of Clinical Biochemistry and Nutrition 50, no. 1 (2012): 2-8.

“Fukushima's Dirty Inheritance.” New Scientist 2855 (March 9, 2012).


“Report Blames Japanese Government for Nuclear Meltdown.” PBS Newshour. http://www.pbs.org/newshour/bb/world/july-dec12/fukushima_07-05.html (accessed October 3, 2012).

Tokyo Electric Power Company. “Fukushima Daiichi, a One Year Review.” http://www.tepco.co.jp/en/nu/fukushima-np/review/index-e.html (accessed October 3, 2012).

World Nuclear Association. “Fukushima Accident 2011.” http://www.world-nuclear.org/info/fukushima_accident_inf129.html (accessed October 1, 2010).


Health Physics Society, 1313 Dolley Madison Blvd., Ste. 402, McLean, VA, 22101, (703) 790-1745, Fax: (703) 790-2672, hps@burkinc.com, www.hps.org .

International Atomic Energy Agency, 1 United Nations Plaza, Room DC-1-1155, New York, NY, 10017, (212) 963-6010, Fax: (917) 367-4046, iaeany@un.org, www.iaea.org .

Teresa G. Odle

  This information is not a tool for self-diagnosis or a substitute for professional care.