Nuclear and radiation accidents and incidents facts for kids

Following the 2011 Japanese Fukushima nuclear disaster, authorities shut down the nation's 54 nuclear power plants. The Fukushima site remains radioactive, with some 30,000 evacuees still living in temporary housing, although nobody has died or is expected to die from radiation effects. The difficult cleanup job will take 40 or more years, and cost tens of billions of dollars.

Pathways from airborne radioactive contamination to human

The Kashiwazaki-Kariwa Nuclear Power Plant, a Japanese nuclear plant with seven units, the largest single nuclear power station in the world, was completely shut down for 21 months following an earthquake in 2007. Safety-critical systems were found to be undamaged by the earthquake.

A nuclear and radiation accident is a serious event involving radioactive materials or nuclear power plants. The International Atomic Energy Agency (IAEA) says it's an event that causes major harm to people, the environment, or the facility itself. This could include people getting sick from radiation, large amounts of radioactivity escaping into the environment, or a nuclear meltdown where the reactor core gets too hot and melts.

Some of the most well-known "major nuclear accidents" happened when a nuclear reactor core was damaged. This led to a lot of radioactive materials being released. Examples include the Chernobyl disaster in 1986 and the Fukushima nuclear disaster in 2011.

People have been worried about nuclear accidents since the first nuclear reactors were built in 1954. This concern has greatly influenced public opinion about nuclear facilities. Engineers have developed many safety features to lower the risk of accidents. They also try to reduce how much radioactivity might be released. However, human error can still happen. There have been over 100 serious nuclear accidents and incidents related to nuclear power since 1952. About 60% of these serious events have happened in the USA.

Major nuclear power plant accidents include:

• The Fukushima nuclear disaster (2011)
• The Chernobyl disaster (1986)
• The Three Mile Island accident (1979)
• The SL-1 accident (1961)

These accidents can unfortunately lead to loss of life. They also cost a lot of money to clean up. The IAEA has a website where they report recent nuclear accidents. In 2020, the World Health Organization (WHO) said that past nuclear accidents show that the mental and emotional effects can be even greater than the direct physical harm from radiation.

Understanding Nuclear Plant Accidents

The abandoned city of Pripyat, Ukraine, following the Chernobyl disaster. The Chernobyl nuclear power plant is in the background.

The first nuclear reactor meltdown in the world happened in 1952. It was at the NRX reactor in Chalk River Laboratories, Canada.

The worst nuclear accident so far was the Chernobyl disaster in 1986. It happened in Ukraine, which was then part of the Soviet Union. This accident directly killed about 30 people. It also caused about $7 billion in property damage. A study from 2005 by the World Health Organization suggested that up to 4,000 more cancer deaths might eventually be linked to the accident. These would be among people who were exposed to a lot of radiation.

Radioactive fallout from Chernobyl mostly affected parts of Belarus, Ukraine, and Russia. Other studies have estimated that over a million cancer deaths could eventually be linked to Chernobyl. However, these numbers are debated. Many official agencies tend to report lower numbers of deaths that can be directly proven. Independent studies often use different methods to estimate higher numbers of potential cancers. About 350,000 people had to move away from these areas after the accident. Around 6,000 people helped clean up Chernobyl. An area of about 10,800 square miles was contaminated.

A researcher named Benjamin K. Sovacool looked at nuclear power plant accidents worldwide. He found 99 accidents from 1952 to 2009. These were incidents that caused deaths or more than US$50,000 in property damage. The total cost of these damages was about US$20.5 billion. Compared to other energy sources, nuclear power plant accidents have caused relatively few deaths.

Major Nuclear Plant Accidents and Incidents (1952–2011)

Here is a list of some significant nuclear plant accidents and incidents. These events either caused multiple deaths or more than US$100 million in property damage.

Protecting Nuclear Reactors from Attacks

Nuclear power plants and other nuclear facilities need strong security. This is to prevent attacks that could release harmful radioactive contamination. Attacks could come from ground forces targeting equipment. They could also involve aircraft crashing into a plant or cyber attacks.

After the 9/11 attacks, it was found that nuclear power plants were considered as possible targets. If terrorists could damage safety systems enough to cause a core meltdown, it could lead to widespread radioactive contamination. Experts say that if nuclear power grows, these facilities must be made extremely safe from attacks. Newer reactor designs have "passive nuclear safety" features. These can help keep the reactor safe even without active human control or power.

Nuclear reactors have sometimes been targets during wars. They have been attacked by air strikes or during invasions. There are also concerns about nuclear weapons materials being stolen. A small, crude nuclear weapon or a "dirty bomb" used by a militant group in a city could cause many deaths and a lot of damage.

Cyber attacks are also a growing threat. For example, Stuxnet was a computer worm found in 2010. It is believed to have been made to attack Iran's nuclear facilities. It could turn off safety devices and make centrifuges spin out of control. In 2014, the computers of South Korea's nuclear plant operator were hacked. This involved many fake emails with harmful codes, and information was stolen.

In March 2022, during the Battle of Enerhodar, the Zaporizhzhia Nuclear Power Plant was damaged. A fire started at its training complex when Russian forces took control. This raised worries about nuclear contamination. The IAEA has called for a safety zone around the plant.

Radiation and Other Accidents

Dr. Joseph G. Hamilton was a researcher for human plutonium experiments from 1944 to 1947. He later warned that such experiments could lead to "considerable criticism."

One estimate of the plutonium plume from a 1957 fire at the Rocky Flats Plant in Colorado. Public protests and a government raid stopped production there in 1989.

A corroded and leaking drum used for storing radioactive waste at the Rocky Flats Plant.

The Hanford site holds two-thirds of the USA's high-level radioactive waste. Nuclear reactors line the Columbia River in January 1960.

On Feb. 14, 2014, at the WIPP, radioactive materials leaked from a damaged storage drum. Investigations showed a lack of a "safety culture" at the facility.

The Semipalatinsk Test Site in the Soviet Union. From 1949 to 1989, 456 nuclear tests were done here. The full impact on local people was hidden for many years.

2007 ISO radioactivity danger symbol. The red background means urgent danger. It is for places where very strong radiation could be found or created by misuse.

Here are some serious radiation and other accidents and incidents:

• 1940s:
  • August 1945: A criticality accident at US Los Alamos National Laboratory killed Harry Daghlian.
  • May 1946: Another criticality accident at Los Alamos National Laboratory killed Louis Slotin.
• 1950s:
  • 1952: A partial meltdown at the NRX reactor in Canada released about 10,000 Curies of radiation. Future president Jimmy Carter helped with the two-year cleanup.
  • March 1954: The 15 Mt Castle Bravo nuclear test spread a lot of nuclear fallout on Pacific islands. Some islands were inhabited and had not been evacuated.
  • September 1957: A plutonium fire at the Rocky Flats Plant released plutonium into the air.
  • September 1957: The Kyshtym disaster in Russia involved a nuclear waste storage tank explosion. No immediate deaths, but up to 200 more cancer deaths might have happened. About 270,000 people were exposed to dangerous radiation.
  • October 1957: The Windscale fire in the UK involved a reactor fire that contaminated nearby dairy farms. An estimated 33 cancer deaths resulted.
• 1960s:
  • July 1961: A Soviet submarine, the K-19, had an accident. Eight people died, and over 30 were exposed to too much radiation.
  • January 1966: The 1966 Palomares B-52 crash happened when a US bomber carrying four hydrogen bombs collided with a tanker over Spain. Two of the bombs' non-nuclear explosives went off, contaminating a 2 square kilometer area with plutonium.
  • January 1968: The 1968 Thule Air Base B-52 crash involved a US bomber carrying four hydrogen bombs crashing in Greenland. The bombs broke open, spreading radioactive contamination.
  • May 1968: The Soviet submarine K-27 reactor almost melted down. 9 people died, and 83 were injured.
  • January 1969: The Lucens reactor in Switzerland had a partial core meltdown. This led to massive radioactive contamination of its underground cavern.
• 1970s:
  • July 1978: Anatoli Bugorski accidentally exposed his head to a proton beam from a particle accelerator. He survived but had long-term damage.
  • July 1979: The Church Rock Uranium Mill Spill in New Mexico, USA, released over 1,000 tons of radioactive waste into a river.
• 1980s:
  • 1980-1989: The Kramatorsk radiological accident in Ukraine. A small capsule with highly radioactive caesium-137 was found inside an apartment wall. 6 residents died from leukemia, and 18 more received radiation doses.
  • March 1984: A radiation accident in Morocco caused eight deaths from overexposure to a lost iridium-192 source.
  • 1984: The Ciudad Juárez cobalt-60 contamination incident happened when a medical radiation therapy unit was sold to a junkyard. It was melted down, and the radioactive material was used to make rebar. This exposed about four thousand people to radiation.
  • August 1985: The Soviet submarine K-431 accident caused ten deaths and 49 radiation injuries.
  • September 1987: The Goiania accident in Brazil. Four people died, and 249 received serious radiation contamination from caesium-137. This happened when a radiotherapy source was stolen and opened by scavengers.
• 1990s:
  • December 1990: The radiotherapy accident in Zaragoza (Spain) caused eleven deaths and injured 27 patients.
  • April 1993: An accident at the Tomsk-7 Reprocessing Complex in Russia. A tank exploded, releasing a cloud of radioactive gas.
  • August-December 1996: The Radiotherapy accident in Costa Rica caused thirteen deaths and overdosed 114 patients.
  • May 1998: The Acerinox accident in Spain. A caesium-137 source went through a metal recycling plant. When melted, it released a radioactive cloud.
  • September 1999: Two people died in a criticality accident at Tokaimura nuclear accident in Japan.
• 2000s:
  • January-February 2000: The Samut Prakan radiation accident in Thailand. Three people died and ten were injured when a cobalt-60 radiation-therapy unit was taken apart.
  • August 2000 – March 2001: At the Instituto Oncologico Nacional of Panama, 17 patients died. They received deadly doses of radiation during treatment.
  • August 2004: The Mihama Nuclear Power Plant accident in Japan killed 4 workers. Hot water and steam leaked from a broken pipe.
• 2010s:
  • April 2010: The Mayapuri radiological accident in India. One person died after a cobalt-60 research device was sold to a scrap metal dealer and taken apart.
  • March 2011: The Fukushima I nuclear accidents in Japan. Radioactive material was released from the Fukushima Daiichi Power Station.
  • August 2019: The Nyonoksa radiation accident happened at a testing range in Russia.

Worldwide Nuclear Weapons Testing

Over 2,000 nuclear tests have been conducted worldwide.

Operation Crossroads Test Able, a 23-kiloton nuclear weapon exploded on July 1, 1946.

Radioactive materials were accidentally released from the 1970 Baneberry Nuclear Test in Nevada.

Between 1945 and 1992, the United States carried out many nuclear weapons tests. They conducted 1,054 nuclear tests and two nuclear attacks. Over 100 tests were in the Pacific Ocean, and over 900 were at the Nevada Test Site. Until 1962, most US tests were above ground. After the Partial Test Ban Treaty, all testing moved underground to stop nuclear fallout from spreading.

Atmospheric nuclear testing exposed many people to fallout dangers. It's hard to know the exact number of people affected. However, Marshall Islanders and Japanese fishers were highly exposed during the Castle Bravo incident in 1954. Many US citizens, especially farmers and people living downwind of the Nevada Test Site, have successfully sued for compensation. The Radiation Exposure Compensation Act of 1990 helped people file claims. By June 2009, over $1.4 billion had been paid in compensation.

This view of downtown Las Vegas shows a mushroom cloud in the background. This was common in the 1950s.

This handbill was given out 16 days before the first nuclear device was detonated at the Nevada Test Site.

Theft of Radioactive Materials

The International Atomic Energy Agency says that stealing or losing nuclear and other radioactive materials is a "persistent problem." Their database shows 1,266 incidents reported by 99 countries over 12 years. This includes 18 cases of highly enriched uranium or plutonium being trafficked.

Experts believe that up to 50 nuclear weapons were lost during the Cold War.

Types of Nuclear Accidents

Nuclear Meltdown Explained

A nuclear meltdown is a very serious nuclear reactor accident. It happens when the nuclear reactor core gets too hot and is damaged. This means the core accidentally melts, either partly or completely. A core melt accident occurs when the heat produced by the reactor is more than the cooling systems can remove. This causes the nuclear fuel to reach its melting point.

Meltdowns can be caused by:

• A loss of coolant (the liquid that cools the reactor).
• A loss of coolant pressure.
• A low coolant flow rate.
• Or when the reactor operates at a power level higher than it was designed for.
• An outside fire might also endanger the core, leading to a meltdown.

Major nuclear meltdowns at civilian power plants include:

• The Three Mile Island accident in the United States in 1979.
• The Chernobyl disaster in Ukraine in 1986.
• The Fukushima Daiichi nuclear disaster in Japan in 2011.

Other core meltdowns have happened at various experimental or military reactors, and on several Soviet Navy nuclear submarines.

Criticality Accidents

A criticality accident happens when a nuclear chain reaction accidentally starts in fissile material. This material could be enriched uranium or plutonium. The Chernobyl accident is sometimes considered a criticality accident because control of the chain reaction was lost in an operating reactor. This destroyed the reactor and made a large area uninhabitable.

In a smaller accident at Sarov, Russia, a technician was exposed to radiation. This happened while he was working with highly enriched uranium. The system stayed critical for many days but was safely located in a shielded hall. This shows a smaller accident where only a few people were harmed, and no radioactivity was released into the environment.

Another criticality accident happened at Tokaimura, Japan, in 1999. It involved enriched uranium fuel. Two workers died, one was permanently injured, and 350 people were exposed to radiation.

Decay Heat Accidents

Decay heat accidents happen when the heat from radioactive decay causes harm. After a large nuclear reactor is shut down, it still produces heat from radioactive materials. If this heat isn't removed, the reactor core can get dangerously hot. For example, at Three Mile Island Nuclear Generating Station, a reactor was left without cooling water after it was shut down. This damaged the nuclear fuel, and the core partly melted.

Removing decay heat is very important for reactor safety, especially right after shutdown. If the heat isn't removed, the core temperature can rise to dangerous levels and cause accidents. Usually, there are many backup systems to remove this heat.

Nuclear facilities usually get power from outside electrical systems. They also have emergency backup generators. An event that stops both outside power and emergency power is called a "station blackout." In 2011, an earthquake and tsunami caused a power loss at the Fukushima Daiichi nuclear power plant in Japan. This meant the decay heat could not be removed. The reactor cores overheated, the fuel melted, and radioactive materials were released into the air and ocean.

Transport Accidents

Transport accidents can release radioactivity. This can cause contamination or damage to shielding, leading to direct exposure to radiation. For example, in Cochabamba, a faulty gamma radiography device was carried on a passenger bus. The gamma source was outside its protective shield, and it exposed some bus passengers to radiation.

In 1966, a fatal collision happened between a US bomber and a tanker over Spain. This was called a "Broken Arrow" incident. It means an accident involving a nuclear weapon that doesn't risk war.

Equipment Failure

Equipment failure is one type of accident. In Białystok, Poland, in 2001, a particle accelerator used for cancer treatment had an electronic malfunction. This led to at least one patient receiving too much radiation. A simple failure of a semiconductor diode started a chain of events that caused the radiation injury.

Another cause of accidents is problems with control software. The Therac-25 medical radiotherapy machines had several accidents. A new design removed a hardware safety feature. This exposed a hidden bug in the software. It could cause patients to receive massive overdoses of radiation under certain conditions.

Human Error

A sketch used by doctors to estimate radiation exposure during the Slotin excursion.

Many major nuclear accidents have been partly caused by operator or human error. At Chernobyl, operators did not follow test procedures. They allowed reactor settings to go beyond safe limits. At Three Mile Island, operators let thousands of gallons of water escape from the reactor. They didn't realize the coolant pumps were acting strangely. They turned off the pumps to protect them, which then caused the reactor to be destroyed because it lost all cooling.

A detailed investigation into the SL-1 accident found that one operator accidentally pulled a control rod out too far.

Experts from France's Commissariat à l'Énergie Atomique (CEA) believe that no amount of technology can completely remove the risk of human errors in nuclear power plants. They found two types of mistakes to be most serious:

• Errors during maintenance or testing that can cause an accident.
• Human errors during small accidents that make them much worse.

In 1946, physicist Louis Slotin performed a risky experiment. He was bringing two halves of a neutron reflector together around a plutonium core to make it critical. He used a screwdriver to keep them apart, which was against safety rules. The screwdriver slipped, causing a chain reaction and a flash of blue light. Slotin quickly separated the halves, preventing more radiation exposure to his co-workers. However, Slotin received a deadly dose of radiation and died nine days later. The plutonium used was called the demon core.

Lost Radiation Sources

Lost source accidents, also called orphan sources, happen when a radioactive source is lost, stolen, or abandoned. This source can then harm people. The most famous example is the 1987 Goiânia accident in Brazil. A radiotherapy source was left in a hospital, then stolen and opened by scavengers. A similar event happened in 2000 in Samut Prakan, Thailand. A radiation source from an old medical unit was sold illegally and stolen from an unguarded parking lot.

The International Atomic Energy Agency has created guides for scrap metal collectors. This helps them identify what a sealed radioactive source might look like. The scrap metal industry is where lost sources are most often found.

Comparing Energy Safety

Hypothetical number of global deaths if all energy came from one source in 2014.

When comparing the safety of nuclear energy to other ways of making electricity, studies show interesting results. From 1970 to 1992, only 39 nuclear power plant workers died on the job worldwide. In the same time, 6,400 coal power plant workers died. Also, 1,200 people died from natural gas power plants. And 4,000 people died from hydroelectric power plants. The failure of the Banqiao Dam alone in 1975 caused 170,000-230,000 deaths.

Coal power plants are estimated to cause 24,000 American deaths each year from lung disease. They also cause 40,000 heart attacks yearly in the United States. According to Scientific American, an average coal power plant releases 100 times more radiation each year than a similar-sized nuclear power plant. This radiation comes from toxic coal waste called fly ash.

In terms of money, nuclear power plant accidents are the most expensive. They account for 41 percent of all property damage from energy accidents. Oil and hydroelectric accidents follow, each at about 25 percent. Natural gas is 9 percent, and coal is 2 percent.

Nuclear Safety Measures

Nuclear safety involves all the steps taken to prevent nuclear and radiation accidents. It also includes limiting their effects and damage to the environment. This applies to nuclear power plants, other nuclear facilities, transporting nuclear materials, and using and storing nuclear materials for medical, industrial, and military purposes.

The nuclear power industry has made reactors safer and perform better. They have also suggested new, safer reactor designs. However, there's no guarantee that reactors will always be designed, built, and operated perfectly. Mistakes can happen. For example, the designers of the Fukushima reactors in Japan did not expect a tsunami to disable the backup systems. These systems were supposed to stabilize the reactor after the earthquake.

Some experts, like Charles Perrow, argue that unexpected failures are built into complex systems like nuclear reactors. He believes that some major accidents are unavoidable. An MIT team estimated that with the expected growth of nuclear power from 2005 to 2055, at least four serious nuclear accidents could happen. Since 1970, there have been five serious accidents worldwide (Three Mile Island, Chernobyl, and three at Fukushima-Daiichi). This means, on average, one serious accident happens every eight years.

As nuclear reactors get older, they need more careful monitoring and maintenance to stay safe. These measures can be expensive. Many existing nuclear facilities are old. To prevent accidents from aging plants, building new, safer reactors and retiring old ones might be a good idea. In the United States, over 50 companies are working on new, more affordable nuclear power plant designs.

Environmental Impacts of Accidents

Impact on Land

When isotopes are released during a meltdown, they usually spread into the air. Then they settle on the ground. These isotopes can stay in the top layer of soil for many years because they decay slowly. This can harm farming, agriculture, and livestock for a long time. This can also affect human health and safety long after the accident.

After the Fukushima Daiichi accident in 2011, nearby farmlands were contaminated. As a result, food production in eastern Fukushima was greatly limited. Due to Japan's landscape and weather, radioactive deposits settled on soils across eastern and northeastern Japan. Luckily, mountain ranges protected western Japan.

The Chernobyl disaster in 1986 contaminated about 125,000 square miles of land in Ukraine, Belarus, and Russia. The high radiation severely damaged plant reproduction. Most plants could not reproduce for at least three years.

Impact on Water

Fukushima Daiichi Accident's Water Impact

In 2013, contaminated groundwater was found at the Fukushima Daiichi facility. This included areas near the Pacific Ocean. The Tokyo Electric Power Company (TEPCO) found that much of the contamination came from underground cable trenches. Both the IAEA and TEPCO confirmed this contamination was due to the 2011 earthquake. The Fukushima plant released nuclear material into the Pacific Ocean and continued to do so. After five years, the contaminants reached all parts of the Pacific Ocean.

In 2014, the Woods Hole Oceanographic Institution (WHOI) found small amounts of Fukushima contaminants off the coast of California. Even with these increases, the contamination levels were still safe for drinking water according to the World Health Organization (WHO).

In 2019, the Japanese government considered dumping contaminated water from the Fukushima reactor into the Pacific Ocean. TEPCO had collected over a million tons of water and was running out of storage space.

Many groups and governments monitor the spread of radiation in the Pacific. They track potential dangers to food, water, and ecosystems. In 2014, the US Food and Drug Administration (FDA) reported that radioactive materials from Fukushima were in the US food supply. However, they were not at levels that threatened public health. It's generally believed that the ocean water will dilute most isotopes. They also become less radioactive over time due to decay. Cesium (Cs-137) is the main isotope released from Fukushima. It has a long half-life, meaning it could have long-term effects. But levels 200 km outside Fukushima are now close to pre-accident levels, with little spread to North American coasts.

Chernobyl Accident's Water Impact

The Chernobyl accident in 1986 released many radioactive particles into the atmosphere. Many of these settled in groundwater systems nearby, and also in Russia and Belarus. Radioactive materials carried by groundwater were taken up by plants. Then they moved up the food chain into animals and eventually humans. One of the main ways people were exposed was by eating farm products contaminated by radioactive groundwater.

One of the biggest worries for people near the 30 km exclusion zone is taking in Cs-137 from contaminated farm products. Thanks to environmental conditions outside the zone, levels are now below those needing cleanup. During this event, radioactive material traveled across borders through groundwater. In Belarus, about 250,000 hectares of farmland were unusable for a long time.

Off-site radiation risk can also come from flooding. Many people near Chernobyl are at risk of radiation exposure because the reactor is close to floodplains. A 1996 study looked at how far the radioactive effects spread across Eastern Europe. Lake Kojanovskoe in Russia, 250 km from Chernobyl, was one of the most affected lakes. Fish from the lake were 60 times more radioactive than the European Union Standard. The water source for this lake provides drinking water for about 9 million Ukrainians. It also provides irrigation and food for 23 million more.

A cover was built around the damaged Chernobyl reactor. This helps stop radioactive material from leaking. But it does little to protect the local area from isotopes that spread into soils and waterways over 30 years ago. Cleanup efforts have been less active compared to the initial actions and more recent accidents like Fukushima. Monitoring stations are still found in key affected locations.

|

See also

In Spanish: Accidente nuclear para niños