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The 20 Worst Nuclear Disasters in World History


The principles of nuclear power were initially discovered by scientists back in the early 1900s. In 1939, those same principles achieved their first practical expression when physicists discovered that splitting nuclear bonds could generate energy. You don’t need to be a historian to know what came next…. After witnessing the devastating conclusion of their experiments at Hiroshima and Nagasaki, scientists continued to tap into the latent power of nuclear energy over the coming decades. The result was a crop of nuclear power plants springing up around the globe. Initially hailed as a cheap, clean alternative to traditional power sources, the preceding decades would witness a series of catastrophic, man-made disasters that begged the question of whether nuclear power can ever truly be harnessed.

1. Chernobyl (1986) - Ukraine (USSR)

Built in the late 1970s just north of the Ukrainian capital of Kiev, the Chernobyl plant was one of the world’s largest and oldest nuclear power plants. In 1986, an experiment into one of the facilities reactors resulted in one of the biggest man-made disasters the world has ever witnessed. After the experiment went wrong, a sudden power surge resulted in a series of blasts that lifted the 1000-ton reactor top, sending out a plume of radioactive material over the nearby town of Pripyat and large parts of Europe. The disaster led to 32 people dying from radiation poisoning in the immediate aftermath, and hundreds more experiencing radiation burns. Over the coming years, thousands more would die from the lingering effects of the disaster, and over 70,000 would suffer severe radiation poisoning.

2. Windscale Pile (1957) - United Kingdom

Britain’s first nuclear reactor, Windscale, was built in the late 1940s. 30 years later, the facility sparked the worst nuclear disaster in British history when the reactor’s uranium-filled graphite core caught alight. It took two days for workers to notice the fire, resulting in huge amounts of dangerous particles leaking into the outside world. By the time the fire was extinguished, the UK and large swathes of Europe were already under a radioactive cloud. While no immediate deaths were reported, it’s believed, as Power Technology notes, that the incident resulted in 240 cases of cancer.

3. Kyshtym (1957) - Russia

In the years directly following the end of World War II, Russia began constructing dozens of nuclear facilities in its race to gain nuclear supremacy over the US. In the rush to build as many sites as possible, quality standards slipped to an alarming, and as it turned out, lethal, degree. In 1957, a cooling storage system at a nuclear fuel processing plant in Ozyorsk failed, sending a cloud of radioactive material over a 300 square mile area. By the time the government reacted, a full week had passed, leading many residents of the town to suffer unnecessarily from radiation burns and over 200 to develop cancer as a result of the prolonged exposure.

4. Fukushima Daiichi (2011) - Japan

In 2011, Japan suffered one of the worst years in recent history when it was hit by a volcano and tsunami, a devasting combination that claimed 15000 lives and injured thousands more. To make matters even work, the earthquake triggered meltdowns at several nuclear power plants in Japan’s Fukushima Prefecture, resulting in two further casualties. As EESI notes, the scale of the disaster (along with the Japanese government’s inefficient handling of the cleanup) caused major uproar across the world, with both Germany and Italy declaring their intention to pull out of nuclear power entirely.

5. Fukui Prefecture (2004) Japan

In 2004, the Hihama No. 3 nuclear power station in Fukui prefecture, Japan, suffered a lethal incident. After a steam pipe in a reactor burst, clouds of superheated steam were released, scalding 4 workers to death and injuring 7 others. The incident caused a public outcry in Japan after it was discovered the pipe had never been checked for corrosion in all its 27 years of operation. Further investigation into the plant revealed a series of safety failings that raised serious concerns about the legal framework governing Japan’s nuclear power plants.

6. Buenos Aires (1983) - Argentina

In 1983, a catalog of errors led to a level 4 nuclear disaster and the death of a worker at the RA-2 facility in Buenos Aires, Argentina. After failing to reconfigure a fuel plate correctly, the operator triggered a nuclear fission chain reaction of 3×1017 fissions. During the incident, he absorbed enough quantities of neutron and gamma radiation to result in his death two days later. A further 17 workers were treated for radiation poisoning.

7. Forsmark (2006) - Sweden

In July 2006, a reactor at the Forsmark Nuclear Power Plant in Sweden was shut down after experiencing an electrical fault. While the incident was at first considered minor, it was later discovered that all four reactors at the plant were vulnerable to the same fault, leading the incident to be upgraded from a level 1 to a level 2 incident on the INES scale. Several investigators into the incident have reported that the failing safety system could technically have resulted in a meltdown equivalent to the one experienced in Chernobyl.

8. Saint Laurent des Eaux (1980) - France

In 1980, a critical excursion at the Saint-Laurent Nuclear Power Plant in the small town of Saint Laurent des Eaux in France resulted in a rupture of fuel bundles and the release of 80 GBq (2,200 mCi) nuclear materials. The event, which was significant event to warrant a level 4 classification with INES, remains the worst nuclear incident in French history.

9. Simi Valley (1957) - United States of America

After high levels of radiation were detected around the Sodium Reactor Experiment (SRE) in Simi Valley, workers began a contamination cleanup. 2 weeks after the cleanup operation began, things took a turn for the worse when a power surge occurred in one of the nuclear reactors. When workers were unable to shut the reactor down, they faced a horrendous choice: open the reactor and let the radiation leak into the atmosphere, or let it explode. Ultimately, they went with the former; while undoubtedly the lesser of two evils, the repercussions of the disaster lived on for years. In 1997, a UCLA study indicated increased rates of cancer among SFFL employees, while in 2007, a University of Michigan study found the occurrence of certain cancers to be 60% higher in areas surrounding SSFL.

10. Tokaimura (1999) - Japan

In 1996, a small fuel preparation plant operated by Japan Nuclear Fuel Conversion in Tokaimura decided to start dissolving uranium oxide in stainless steel buckets rather than the dissolution tank. The method was modified again when workers, clearly in too much of a rush to follow the procedures outlined by the regulatory authorities, decided to start tipping the solution directly into the precipitation tank. 3 years later, the decision to start cutting corners bit them severely on the behind when 3 workers triggered a critical nuclear incident as a result of the practice. The incident, which was said by the IAEA to be have been triggered by "human error and serious breaches of safety principles," resulted in 119 people receiving a radiation dose over 1 mSv fr and two fatalities.

11. Goiânia (1987) - Brazil

One of the worst nuclear incidents to hit Brazil took place in 1987 when a forgotten radiotherapy source was removed from an abandoned hospital in Goiânia, in the Brazilian state of Goiás. The incident (which has been described by the International Atomic Energy Agency as "one of the world's worst radiological incidents") resulted in 4 deaths, 249 people receiving treatment for dangerous levels of radioactive material in or on their bodies, the removal of the topsoil from several different affected sites, and the demolition of several hundred houses.

12. Chalk River (1952) - Canada

When a nuclear reactor at the Chalk River Laboratories in Chalk River, Ontario, suffered a loss of coolant, it triggered the first nuclear accident in history. Despite no deaths coming about as a result of the incident, the huge cleanup operation involving hundreds of volunteers and military personnel triggered the first rumblings of public disquiet about nuclear power.

13. Paks (2003) - Hungary

In 2003, large sections of the Hungarian population were evacuated following a nuclear incident that was a hair's breadth away from ending as disastrously as the Chernobyl nuclear meltdown. The level 3 event occurred as a result of the majority of the 30 fuel elements in a cleaning tank sustaining enough damage to cause the release of radioactive material and risking a criticality accident. The release of reactive gasses continued for several days after the incident was first reported, and the reactor remained out of service for over a year.

14. Oak Harbor (2002) - United States of America

Davis–Besse Nuclear Power Station in Oak Harbour Ohio, has experienced several critical incidents since it opened in 1978, none more so than the 2002 safety breach that resulted in First Energy, the owner of Davis–Besse, entering into a prosecution agreement with the United States Department of Justice. After staff discovered a reactor coolant leak had eaten through more than six inches of the reactors pressure vessel head, an investigation into the plant was opened. The findings revealed intuitional negligence of such a degree that First Energy was forced to hand over $28 million in settlement with the DOJ. Unfortunately, the lessons of 2002 didn’t seem to stick, and the plant has continued to come under fire for the almost yearly incidents it seems to generate.

15. Greifswald (1975) - East Germany

In 1975, the now-defunct Greifswald nuclear power station in East Germany suffered a level 3 incident after an electrician inadvertently sparked a fire in the main trough while showing his apprentice how to build electrical circuits. Despite being bought under control quickly enough, the fire managed to destroy the current supply and the control lines of five of the unit's six main coolant pumps. Although details of the incident were kept from the public until 1989 (which, coincidentally enough, was the year of the plant’s 2nd almost -fatal disaster), it did have the positive outcome of strengthening fire protection and safety regulations at the plant

16. Jaslovské Bohunice (1976) - Slovakia

The A1 Nuclear Power Plant in Jaslovske Bohunice, Slovakia, experienced several major incidents in the 1970s, one of the most serious of which occurred in 1976. During a routine refueling, gas coolant began leaking into the reactor hall, leading to the deaths of two workers through Co2 inhalation. The reactor itself didn’t incur any damage, and the plant reopened shortly after.

17. Jaslovské Bohunice (1977) - Slovakia

A year after the gas coolant leak of 1976, the A1 Nuclear Power Plant in Jaslovske Bohunice suffered one of the most serious incidents in Slovakian history. In a fatal combination of human error and design flaws, a routine fuel change resulted in local overheating of the fuel, damage to the active zone, and contamination of both the primary and secondary circuits. As a result of the severity of the incident (which ranked as a level 4 on INES), the decision was made to shut down the plant permanently.

18. Three Mile Island (1979) - United States of America

One of the worst nuclear disasters to hit the States took place at the Three Mile Island plant near Harrisburg, Pennsylvania, in 1979. The plant, which had only recently opened, had received a great deal of press thanks to its state-of-the-art design and reported efficiency. In a catastrophic combination of human error and faulty equipment, an incident led to the plant’s core heating to over 4,000 degrees (just 1,000 degrees below the point of meltdown), with the resulting radioactive steam contaminating a four-county area. While no deaths were reported at the time, the scale of the incident led to nationwide demonstrations against nuclear power, and the call for increased safety regulations and procedures.

19. Vaud (1969) - Switzerland

In 1969, the Lucens reactor in Vaud, Switzerland, experienced a major loss of coolant that led to a partial core meltdown and radiative contamination of the (fortunately) sealed cavern. Further to the incident (which rates as a Level 4 "Accident with local consequences" on INES), the cavern was decontaminated, and the reactor dismantled.

20. Marcoule (2011) - France

in 2011, the Marcoule Nuclear Site (a nuclear facility near Bagnols-sur-Cèze in the Gard department of France) experienced an explosion in an oven used to melt metallic waste containing “negligible amounts” of radioactive material. The resulting blast resulted in 1 fatality and four people suffering serious injuries. A safety cordon was set up in case of leakage, but fortunately, the incident remained contained to the plant.

Liz Flynn

Written by Liz Flynn

Liz Flynn has worked as a full-time writer since 2010 after leaving a career in education. She finds almost all topics she writes about interesting, but her favorite subjects are travel and food. Liz loves the process of researching information, learning new things, and putting into words what others who share her interests might like to read. Although she spends most of her time writing, she also enjoys spending time with her husband and four children, watching films, cooking, dining out, reading, motorsports, gaming, and walking along the beach next to her house with her dog.

Read more posts by Liz Flynn

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