Fukushima nuclear accident, Japan

Nuclear Accidents

Nuclear accidents

Without doubt, the main drawback of nuclear energy is the possibility of nuclear accidents. Despite the safety of nuclear power plants and that nuclear disasters are not common, when they happen, the consequences can be extremely serious.

In addition, it is important to know that not all nuclear accidents occur in nuclear power plants. There are numerous applications of nuclear energy that use radiological sources that can cause uncontrolled radioactive emissions. 

Nucelar Accident Definition

We define nuclear accident to those accidents produced in nuclear power plants or establishments that use nuclear technology. These accidents can be caused by technical or human failure and are characterized by releasing radioactive products into the environment, in the form of radioactive matter or radiation. Nuclear accidents are events that emit a certain level of radiation that can harm public health.

From a more technical point of view we can define a radiation accident as the loss of control over the source of ionizing radiation caused by equipment malfunction, improper actions of employees (personnel), natural disasters or other reasons that could lead to exposure of people above established standards or to radioactive contamination of the environment

What Types of Nuclear Accidents Exist?

One way to define the different types of nuclear accidents is according to their severity. To determine the severity of an accident, an International Nuclear Event Scale has been defined (it is also known as the INES scale).

In reality, nuclear accidents are a type of nuclear event. Nuclear events are classified between nuclear accidents and nuclear incidents according to their severity. This classification includes both nuclear accidents and radioactive accidents. To understand each other, a nuclear accident could be a fault in a nuclear power plant reactor and a radiation accident could be the discharge of a source of radiation to a river.

Although the best known nuclear accidents have occurred in nuclear power plants they can also happen in other centers where nuclear power is worked, such as hospitals or research laboratories.

Due to the secrecy of the governments and the companies that own the nuclear power plants, in certain cases, it is difficult to determine the severity or extent and repercussions that a given nuclear accident can entail.

Another type of classification of nuclear accidents is according to origin: in addition to nuclear accidents in the civil field, nuclear tests have also been carried out in the military field in different parts of the world. Obviously, with military secrecy it is practically impossible to know the real repercussions of these military trials.

What Are the Worst Nuclear Accidents in History?

The worst nuclear disasters in the world so far are the following:

  1. Explosion of the Chernobyl nuclear power plant, Ukraine.
  2. Earthquake and tsunami in central Fukushima, Japan.
  3. Kyshtym nuclear disaster, Russia.
  4. Radiological accident in Goiânia, Brazil.
  5. Radioactive particle emission at Three Mile Island Nuclear Power Plant, USA.
  6. Accident in the laboratories of Chalk River, Canada.
  7. Nuclear accident in Windscale Pile, United Kingdom.
  8. Nuclear disaster at the uranium fuel treatment plant in Tokaimura, Japan.

Nuclear Accident of the Chernobyl Nuclear Power Plant, Ukraine - 1986

Chernobyl Nuclear Power Plant - The worst nuclear accident in history

Classified with level 7 on the INES scale, serious nuclear accident.

The Chernobyl nuclear accident is considered the worst nuclear accident in history.

In April 1986, during a series of tests in the Chernobyl nuclear reactor, a series of explosions occurred in the reactor core. The accident was due to a succession of human errors in the course of previously planned tests.

A cloud of radioactive material spilled from the reactor and fell over large areas around the plant, contaminating them heavily and making it necessary to evacuate and resettle some 336,000 people in other areas. Radioactive clouds also reached Eastern Europe, Finland and Scandinavia with gradually lower levels of pollution, which also affected Italy, France, Germany, Switzerland, Austria and the Balkans, to parts of the eastern coast of North America.

Nuclear Accident at the Fukushima Nuclear Power Plant, Japan -2011

Classified with level 7 on the INES scale, serious nuclear accident.

The Fukushima nuclear accident occurred in 2011 as a result of a series of natural events that seriously affected the plant. This is the second worst nuclear accident in history, after the Chernobyl nuclear accident.

Initially there was an earthquake of 8.9 degrees on the Richter scale near the northwest coast of Japan and a subsequent tsunami severely affected the cooling system of the nuclear reactor core of the Fukushima Japanese nuclear power plant.

 kyshtym Nuclear Disaster, Russia - 1957

Kyshtym's nuclear accident was ranked at level 6 on the INES scale.

Mayak is the name by which a complex with nuclear equipment is known that lies between the cities of Kaslo and Kyshtym, in the province of Cheliabinsk, Russia. In the Mayak nuclear complex there have been numerous radioactive leaks, the worst of which was classified at level 6 of the INES scale.

It is one of the points of the planet with more pollution by radioactive materials, although it is little famous because the Soviet authorities tried to hide for 30 years the nuclear leaks that have been occurring.

Nuclear Accident in Goiania, Brazil - 1987

The Goiâna nuclear accident is classified in level 5 on the INES scale.

In September 1987, the city of Goiânia in Brazil suffered a radioactive contamination accident. Two men robbed one of a tele-therapy device and manipulated it. They removed a cesium capsule from its protective housing which made it a radioactive source of cesium-137.

The International Atomic Energy Agency (IAEA) highlighted this nuclear accident as one of the worst radiological incidents in the world.

The Goiânia nuclear accident was considered Level 5 on the INES scale. The residences and public places were seriously contaminated. Four people died and another 28 suffered radiation burns. Several buildings were demolished and conreo lands were removed as part of the decontamination operations.

Nuclear Accident at Three Mile Island Nuclear Power Plant, USA - 1979

The Three Mile Island plant had an escape from radioactive products.

The Three Mile Islant nuclear accident is classified at level 5 on the INES scale.

The Three Mile Island plant had an escape from radioactive products.

In March 1979, the Three Mile Island nuclear power plant had a serious nuclear accident after the first year of operation.

The misinterpretation of the data caused very serious errors in certain decisions of the staff of the plant. Although the core of the nuclear reactor was severely damaged, it had a limited escape of radioactive products abroad.

The accident was classified as level 5 on the International Nuclear Event Scale (NES Scale).

Nuclear Accident at Chalk River Nuclear Power Station, Canada - 1952 and 1958

Ranked with level 5 on the INES scale.

On December 12, 1952, the first Chalk River nuclear accident occurs in Canada, in the NRX nuclear reactor.

On May 24, 1958, also in Canada and at the same Chalk Rriver nuclear power plant: in the NRU reactor a uranium nuclear fuel rod caught fire and broke in two when trying to remove it from the reactor core.

At the time the Chalk River nuclear accidents occurred, the INES scale had not yet been created, but due to the accident characteristics it would have been classified in level 5.

Nuclear Accident in Windscale Pile, United Kingdom - 1957

Ranked with level 5 on the INES scale.

In October 1957, a nuclear accident occurs at Windscale Pile in reactor number one. This accident became the worst nuclear accident in the history of the United Kingdom classified in level 5 of the INES scale.

The nuclear reactor fire led to the release of radioactive materials in the surrounding area. The radiation could have caused about 240 cases of cancer. No one was evacuated from the affected area, but there was concern about the possible contamination of the milk.

The outlet air ducts of the reactor were sealed and the fuel cartridges were removed. The second reactor at the site was also closed, although without fire damage.

Nuclear Accident at the Uranium Fuel Treatment Plant in Tokaimura, Japan - 1999

Ranked with level 4 on the INES scale.

In September 1999, the nuclear accident of the Tokaimura uranium fuel treatment plant, owned by the JCO company in Tokaimura, occurred. All indications pointed out that it was due to human failure. The accident was classified as level 4 on the INES Scale (“accident without significant risk off site”), since the amounts of radiation released abroad were very small, and within the limits established within the site. The damages produced in the equipment and biological barriers were significant, in addition to the fatal exposure of the workers.

In this accident, a worker at the plant (Hisashi Ouchi) received the highest amount of radiation to which a human being has been exposed: between 10 and 20 sieverts. Unfortunately, he died within a few weeks.

Accidente Nuclear En La Central Nuclear Saint Laurent Des Eaux, Francia - 1980 -4

The worst nuclear accident in France occurred at the Saint Laurent des Eaux nuclear power plant on the Loire River. It happened in March 1980, a failure in the cooling system caused the melting of a fuel channel in the Saint Laurent A2 reactor.

The nuclear accident was classified as level 4 on the INES scale. No radioactive material was released outside the plant.

Other Famous Radiological Accidents

  • The fall of the Transit-5V satellite with the SNAP-9A nuclear power plant on board, April 21, 1964
  • The destruction of three nuclear bombs in the town of Palomares (Spain), January 17, 1966.
  • The destruction of four thermonuclear bombs in a plane crash over Greenland, 1968 In general, approximately 20 aviation incidents are known in the United States with the loss and / or destruction of nuclear weapons.
  • Radioactive contamination in Kramatorsk, early 1980s
  • Radiation accident in Chazhma Bay, August 10, 1985
  • Radiological incident in Goiania, 1987
  • Numerous accidents in the place of Santa Susanna, Spain
  • The accident in the experimental reactor SL-1 in the United States, January 3, 1961
  • The accident on the submarine K-19, July 3, 1961
  • Nuclear accident at the Krasnoe Sormovo plant, 1970



Published: March 26, 2010
Last review: March 10, 2020