List of civilian nuclear accidents - AbsoluteAstronomy.com

This article lists notable civilian

Civilian

A civilian under international humanitarian law is a person who is not a member of his or her country's armed forces or other militia. Civilians are distinct from combatants. They are afforded a degree of legal protection from the effects of war and military occupation...

accidents involving fissile

Fissile

In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...

nuclear material

Nuclear material

Nuclear material refers to the metals uranium, plutonium, and thorium, in any form, according to the IAEA. This is differentiated further into "source material", consisting of natural and depleted uranium, and "special fissionable material", consisting of enriched uranium , uranium-233, and...

or nuclear reactor

Nuclear reactor

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

s. Civilian incidents not serious enough to be accidents are listed at List of civilian nuclear incidents. Military accidents are listed at List of military nuclear accidents. Civil radiation accidents not involving fissile material are listed at List of civilian radiation accidents. For a general discussion of both civilian and military accidents, see Nuclear and radiation accidents

Nuclear and radiation accidents

A nuclear and radiation accident is defined by the International Atomic Energy Agency as "an event that has led to significant consequences to people, the environment or the facility...

Scope of this article

In listing civilian nuclear accidents, the following criteria have been followed:

There must be well-attested and substantial health damage, property damage or contamination.
The damage must be related directly to radioactive material, not merely (for example) at a nuclear power plant.
To qualify as "civilian", the nuclear operation/material must be principally for non-military purposes.
The event should involve fissile material or a reactor.

1950s

December 12, 1952 — INES Level
International Nuclear Event Scale
The International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....

5 - Chalk River, Ontario
Chalk River Laboratories
The Chalk River Laboratories is a Canadian nuclear research facility located near Chalk River, about north-west of Ottawa in the province of Ontario.CRL is a site of major research and development to support and advance nuclear technology, in particular CANDU reactor...

, Canada - Reactor core damaged
- A reactor shutoff rod failure, combined with several operator errors, led to a major power excursion of more than double the reactor's rated output at AECL
  Atomic Energy of Canada Limited
  Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory...
  
  's NRX
  NRX
  NRX was a heavy water moderated, light water cooled, nuclear research reactor at the Canadian Chalk River Laboratories, which came into operation in 1947 at a design power rating of 10 MW , increasing to 42 MW by 1954...
  
  reactor
  Nuclear reactor
  A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
  
  . The operators purged the reactor's heavy water
  Heavy water
  Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...
  
  moderator, and the reaction stopped in under 30 seconds. A cover gas system failure led to hydrogen explosions, which severely damaged the reactor core. The fission
  Nuclear fission
  In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
  
  products from approximately 30 kg of uranium were released through the reactor stack. Irradiated light-water coolant leaked from the damaged coolant circuit into the reactor building; some 4,000 cubic meters were pumped via pipeline to a disposal area to avoid contamination of the Ottawa River
  Ottawa River
  The Ottawa River is a river in the Canadian provinces of Ontario and Quebec. For most of its length, it now defines the border between these two provinces.-Geography:...
  
  . Subsequent monitoring of surrounding water sources revealed no contamination. No immediate fatalities or injuries resulted from the incident; a 1982 followup study of exposed workers showed no long-term health effects. Future U.S. President Jimmy Carter
  Jimmy Carter
  James Earl "Jimmy" Carter, Jr. is an American politician who served as the 39th President of the United States and was the recipient of the 2002 Nobel Peace Prize, the only U.S. President to have received the Prize after leaving office...
  
  , then a Lieutenant in the US Navy, was among the cleanup crew.
September 29, 1957 — INES Level 6 - Kyshtym disaster
Kyshtym disaster
The Kyshtym disaster was a radiation contamination incident that occurred on 29 September 1957 at Mayak, a nuclear fuel reprocessing plant in Russia...

- Mayak, Russia (then a part of the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

)
- The Kyshtym disaster
  Kyshtym disaster
  The Kyshtym disaster was a radiation contamination incident that occurred on 29 September 1957 at Mayak, a nuclear fuel reprocessing plant in Russia...
  
  was a radiation contamination incident that occurred on 29 September 1957 at Mayak
  Mayak
  Mayak Production Association refers to an industrial complex that is one of the biggest nuclear facilities in the Russian Federation. It housed plutonium production reactors and a reprocessing plant...
  
  , a nuclear fuel reprocessing plant in Russia
  Russia
  Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
  
  (then a part of the Soviet Union
  Soviet Union
  The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
  
  ). It measured as a Level 6 disaster on the International Nuclear Event Scale
  International Nuclear Event Scale
  The International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....
  
  , making it the third most serious nuclear accident ever recorded (after the Chernobyl disaster
  Chernobyl disaster
  The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...
  
  , and Fukushima Daiichi nuclear disaster
  Fukushima Daiichi nuclear disaster
  The is a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tōhoku earthquake and tsunami on 11 March 2011. The plant comprises six separate boiling water reactors originally designed by General Electric ,...
  
  , both Level 7 on the INES scale). The cooling system in one of the tanks containing about 70–80 tons of liquid radioactive waste failed and was not repaired. The temperature in it started to rise, resulting in evaporation and a chemical explosion of the dried waste, consisting mainly of ammonium nitrate and acetate
  Acetate
  An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...
  
  s (see ammonium nitrate bomb
  ANFO
  ANFO is a widely used bulk industrial explosive mixture. It consists of 94 percent porous prilled ammonium nitrate , that acts as the oxidizing agent and absorbent for the fuel — six percent Number 2 Fuel Oil...
  
  ). The explosion, estimated to have a force of about 70–100 tons of TNT threw the concrete lid, weighing 160 tons, into the air. There were no immediate casualties as a result of the explosion, which released an estimated 2 to 50 MCi (74 to 1850 PBq
  Becquerel
  The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
  
  ) of radioactivity. In the next 10 to 11 hours, the radioactive cloud moved towards the northeast, reaching 300–350 kilometers from the accident. The fallout of the cloud resulted in a long-term contamination of an area of more than 800 square kilometers, primarily with caesium-137
  Caesium-137
  Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed...
  
  and strontium-90
  Strontium-90
  Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
  
  . This area is usually referred to as the East-Ural Radioactive Trace (EURT).
May 24, 1958 — INES Level needed - Chalk River, Ontario
Chalk River Laboratories
The Chalk River Laboratories is a Canadian nuclear research facility located near Chalk River, about north-west of Ottawa in the province of Ontario.CRL is a site of major research and development to support and advance nuclear technology, in particular CANDU reactor...

, Canada - Fuel damaged
- Due to inadequate cooling a damaged uranium fuel rod caught fire and was torn in two as it was being removed from the core at the NRU
  National Research Universal Reactor
  The National Research Universal reactor, located in Chalk River, Ontario, is one of Canada’s national science facilities. It is a multipurpose science facility that serves three main roles....
  
  reactor. The fire was extinguished, but not before radioactive combustion products contaminated the interior of the reactor building and, to a lesser degree, an area surrounding the laboratory site. Over 600 people were employed in the clean-up.
October 25, 1958 - INES Level needed - Vinča
Vinca
Vinca is a genus of six species in the family Apocynaceae, native to Europe, northwest Africa and southwest Asia. The English name periwinkle is shared with the related genus Catharanthus .-Description:Vinca plants are subshrubs or herbaceous, and have slender trailing stems 1–2 m long...

, Yugoslavia
Yugoslavia
Yugoslavia refers to three political entities that existed successively on the western part of the Balkans during most of the 20th century....

- Criticality excursion, irradiation of personnel
- During a subcritical counting experiment a power buildup went undetected at the Vinca Nuclear Institute
  Vinča Nuclear Institute
  Vinča Nuclear Institute is a nuclear physics research institution near Belgrade, in Serbia.-History:The Institute was originally established in 1948 as the Institute for Physics. In 1953 it was renamed in favour of Boris Kidrič. Several different research groups started in the 1950s, and two...
  
  's zero-power natural uranium heavy water moderated research reactor. Saturation of radiation detection chambers gave the researchers false readings and the level of moderator in the reactor tank was raised triggering a criticality excursion which a researcher detected from the smell of ozone. Six scientists received radiation doses of 2—4 Sv (200—400 rem
  Röntgen equivalent man
  Named after Wilhelm Röntgen , the roentgen equivalent in man or rem is a unit of radiation dose equivalent...
  
  s) (p. 96). An experimental bone marrow transplant treatment was performed on all of them in France and five survived, despite the ultimate rejection of the marrow in all cases. A single woman among them later had a child without apparent complications. This was one of the first nuclear incidents investigated by then newly-formed IAEA.

July 26, 1959 — INES Level needed - Santa Susana Field Laboratory, California
Santa Susana Field Laboratory
The Santa Susana Field Laboratory is a complex of industrial research and development facilities located on a 2,668 acre portion of the Southern California Simi Hills in Simi Valley, California, used mainly for the testing and development of Liquid-propellant rocket engines for the United States...

, United States - Partial meltdown
- A partial core meltdown
  Nuclear meltdown
  Nuclear meltdown is an informal term for a severe nuclear reactor accident that results in core damage from overheating. The term is not officially defined by the International Atomic Energy Agency or by the U.S. Nuclear Regulatory Commission...
  
  may have taken place when the Sodium Reactor Experiment (SRE) experienced a power excursion
  Criticality accident
  A criticality accident, sometimes referred to as an excursion or a power excursion, is an accidental increase of nuclear chain reactions in a fissile material, such as enriched uranium or plutonium...
  
  that caused severe overheating of the reactor core, resulting in the melting of one-third of the nuclear fuel
  Nuclear fuel
  Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
  
  and significant releases of radioactive
  Radioactive decay
  Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
  
  gases.

1960s

April 3, 1960 - Waltz Mill, a core melt accident occurred at the Westinghouse Waltz Mill test reactor in Westmoreland County. From what information remains of the event, one fuel element melted resulting in the disposition of two million gallons of contaminated water generated during the accident. At least a portion of the water was retained on site in lagoons, a condition which eventually lead to detectable Sr-90 in ground water plus contaminated soil. The site is currently undergoing cleanup.

July 24, 1964 - INES Level needed - Charlestown, Rhode Island
Charlestown, Rhode Island
Charlestown is a town in Washington County, Rhode Island, United States. The population was 7,827 at the 2010 census.-History:Charlestown is named after King Charles II, and was incorporated in 1738. The area was formerly part of the town of Westerly...

, United States - Criticality Accident
An error by a worker at a United Nuclear Corporation fuel facility led to an accidental criticality
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...

. Robert Peabody, believing he was using a diluted uranium solution, accidentally put concentrated solution into an agitation tank containing sodium carbonate. Peabody was exposed to 10,000rad (100Gy
Gray (unit)
The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....

) of radiation and died two days later. Ninety minutes after the criticality, a plant manager and another administrator returned to the building and were exposed to 100rad (1Gy), but suffered no ill effects.

October 5, 1966 — INES Level needed - Monroe, Michigan
Monroe, Michigan
Monroe is a city in the U.S. state of Michigan. The population was 20,733 at the 2010 census. It is the largest city and county seat of Monroe County. The city is bordered on the south by Monroe Charter Township, but both are politically independent. The city is located approximately 14 miles ...

, United States - Partial meltdown
A sodium cooling system malfunction caused a partial meltdown at the Enrico Fermi demonstration nuclear breeder reactor
Enrico Fermi Nuclear Generating Station
The Enrico Fermi Nuclear Generating Station is a nuclear power plant on the shore of Lake Erie near Monroe, in Frenchtown Charter Township, Michigan. It is approximately halfway between Detroit, Michigan, and Toledo, Ohio. It is also visible from parts of Amherstburg, Ontario. Two units have been...

(Enrico Fermi-1 fast breeder reactor). The accident was attributed to a zirconium fragment that obstructed a flow-guide in the sodium cooling system. Two of the 105 fuel assemblies melted during the incident, but no contamination was recorded outside the containment vessel.

Winter 1966-1967 (date unknown) – INES Level needed – location unknown – loss of coolant accident
- The Soviet
  Soviet Navy
  The Soviet Navy was the naval arm of the Soviet Armed Forces. Often referred to as the Red Fleet, the Soviet Navy would have played an instrumental role in a Warsaw Pact war with NATO, where it would have attempted to prevent naval convoys from bringing reinforcements across the Atlantic Ocean...
  
  icebreaker
  Icebreaker
  An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters. Although the term usually refers to ice-breaking ships, it may also refer to smaller vessels .For a ship to be considered an icebreaker, it requires three traits most...
  
  Lenin, the USSR’s first nuclear-powered surface ship
  Surface ship
  A surface ship is any type of naval ship that is confined to the surface of the sea. The term is primarily used to mean any modern vessel type that is not a submarine; although a "surface ship" may range in size from a cutter to an aircraft carrier, the weapons and tactics have some commonality,...
  
  , suffered a major accident (possibly a meltdown
  Nuclear meltdown
  Nuclear meltdown is an informal term for a severe nuclear reactor accident that results in core damage from overheating. The term is not officially defined by the International Atomic Energy Agency or by the U.S. Nuclear Regulatory Commission...
  
  — exactly what happened remains a matter of controversy in the West) in one of its three reactors. To find the leak the crew broke through the concrete and steel radiation shield with sledgehammers, causing irreparable damage. It was rumor
  Rumor
  A rumor or rumour is often viewed as "an unverified account or explanation of events circulating from person to person and pertaining to an object, event, or issue in public concern" However, a review of the research on rumor conducted by Pendleton in 1998 found that research across sociology,...
  
  ed that around 30 of the crew were killed. The ship was abandoned for a year to allow radiation levels to drop before the three reactors were removed, to be dumped into the Tsivolko Fjord on the Kara Sea
  Kara Sea
  The Kara Sea is part of the Arctic Ocean north of Siberia. It is separated from the Barents Sea to the west by the Kara Strait and Novaya Zemlya, and the Laptev Sea to the east by the Severnaya Zemlya....
  
  , along with 60% of the fuel elements packed in a separate container. The reactors were replaced with two new ones, and the ship re-entered service in 1970, serving until 1989.

May 1967 — INES Level needed - Dumfries and Galloway
Dumfries and Galloway
Dumfries and Galloway is one of 32 unitary council areas of Scotland. It was one of the nine administrative 'regions' of mainland Scotland created in 1975 by the Local Government etc. Act 1973...

, Scotland, United Kingdom - Partial meltdown
Graphite debris partially blocked a fuel channel causing a fuel element to melt and catch fire at the Chapelcross nuclear power station
Chapelcross nuclear power station
Chapelcross was a Magnox nuclear power plant located near the town of Annan in Dumfries and Galloway in south west Scotland. It was the sister plant to Calder Hall in Cumbria, England, both commissioned and originally operated by the United Kingdom Atomic Energy Authority.The primary purpose of...

. Contamination was confined to the reactor core. The core was repaired and restarted in 1969, operating until the plant's shutdown in 2004.

January 21, 1969 — INES Level: None - Lucens
Lucens
Lucens is a municipality in the Broye-Vully district in the canton of Vaud in Switzerland.-History:Lucens is first mentioned in 964 as in villa Losingus. It was formerly known by the German name Losingen....

, Canton of Vaud
Vaud
Vaud is one of the 26 cantons of Switzerland and is located in Romandy, the French-speaking southwestern part of the country. The capital is Lausanne. The name of the Canton in Switzerland's other languages are Vaud in Italian , Waadt in German , and Vad in Romansh.-History:Along the lakes,...

, Switzerland - Explosion
A total loss of coolant led to a power excursion and explosion of an experimental nuclear reactor in a large cave at Lucens. The underground location of this reactor acted like a containment building and prevented any outside contamination. The cavern was heavily contaminated and was sealed. No injuries or fatalities resulted.
De-fuelling and partial dismantling occurred from 1969 to 1973. In 1988, the lowest caverns were filled with concrete, and a regulatory permit was issued in December 1990. Currently, the archives of the Canton of Vaud are located in the caverns.

1970s

December 7, 1975 – INES Level 3 - Greifswald
Greifswald
Greifswald , officially, the University and Hanseatic City of Greifswald is a town in northeastern Germany. It is situated in the state of Mecklenburg-Vorpommern, at an equal distance of about from Germany's two largest cities, Berlin and Hamburg. The town borders the Baltic Sea, and is crossed...

, Germany (then East Germany) - Partly damaged
Operators disabled three of six cooling pumps' electrical supply circuits to test emergency shutoffs. Instead of the expected automatic shutdown, a fourth pump failed causing excessive heating which damaged ten fuel rods. The accident was attributed to sticky relay contacts and generally poor construction in the Soviet-built reactor.

February 22, 1977 – INES Level 4 - Jaslovské Bohunice
Jaslovské Bohunice
Jaslovské Bohunice is a small village in Slovakia in the Trnava District. It is best known for the nearby Bohunice Nuclear Power Plants complex....

, Czechoslovakia
Czechoslovakia
Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...

- Fuel damaged
Operators neglected to remove moisture-absorbing materials from a fuel rod assembly before loading it into the KS 150
KS 150
KS 150 is a heavy water Gas Cooled Reactor nuclear reactor design. A single example, A-1, was constructed at the Bohunice Nuclear Power Plant in Jaslovské Bohunice, Czechoslovakia. The power plant suffered a series of accidents, the worst being an accident on February 22, 1977 rated INES-4...

reactor at power plant A-1. The accident resulted in damaged fuel integrity, extensive corrosion damage of fuel cladding and release of radioactivity into the plant area. The affected reactor was decommissioned following this accident.

March 28, 1979 – INES Level 5 - Middletown, Dauphin County, Pennsylvania
Middletown, Dauphin County, Pennsylvania
Middletown is a borough in Dauphin County, Pennsylvania, on the Susquehanna River, nine miles southeast of Harrisburg. It is part of the Harrisburg–Carlisle Metropolitan Statistical Area.-History:...

, United States - Partial meltdown
Equipment failures and worker mistakes contributed to a loss of coolant and a partial core meltdown at the Three Mile Island Nuclear Generating Station
Three Mile Island Nuclear Generating Station
Three Mile Island Nuclear Generating Station is a civilian nuclear power plant located on Three Mile Island in the Susquehanna River, south of Harrisburg, Pennsylvania. It has two separate units, known as TMI-1 and TMI-2...

15 km (9.3 mi) southeast of Harrisburg
Harrisburg, Pennsylvania
Harrisburg is the capital of Pennsylvania. As of the 2010 census, the city had a population of 49,528, making it the ninth largest city in Pennsylvania...

. While the reactor was extensively damaged, on-site radiation exposure was under 100 millirems (less than annual exposure due to natural sources). Area residents received a smaller exposure of 1 millirem (10 µSv), or about 1/3 the dose from eating a banana
Banana equivalent dose
A banana equivalent dose is a whimsical unit of radiation exposure, informally defined as the additional dose a person will absorb from eating one banana...

per day for one year. There were no fatalities. Follow-up radiological studies predict between zero and one long-term cancer fatality.

1980s

March 13, 1980 - INES Level 4 - Orléans
Orléans
-Prehistory and Roman:Cenabum was a Gallic stronghold, one of the principal towns of the Carnutes tribe where the Druids held their annual assembly. It was conquered and destroyed by Julius Caesar in 52 BC, then rebuilt under the Roman Empire...

, France - Nuclear materials leak
A brief power excursion in Reactor A2 led to a rupture of fuel bundles and a minor release (8 x 10¹⁰ Bq) of nuclear materials at the Saint-Laurent Nuclear Power Plant
Saint-Laurent Nuclear Power Plant
The Saint-Laurent Nuclear Power Station is located in the commune of Saint-Laurent-Nouan in Loir-et-Cher on the Loire River – 28 km downstream from Blois and 30 km upstream from Orléans....

. The reactor was repaired and continued operation until its decommissioning in 1992.

March, 1981 — INES Level 2 - Tsuruga, Japan - Radioactive materials released into Sea of Japan + Overexposure of workers
More than 100 workers were exposed to doses of up to 155 millirem per day radiation during repairs of the Tsuruga Nuclear Power Plant
Tsuruga Nuclear Power Plant
The is a nuclear power plant located in the town of Tsuruga, Fukui Prefecture. It is operated by the Japan Atomic Power Company. The total site area amounts to 5.12 km2 with 4.80 km2, or 94% of it, being green area that the company is working to preserve.The Tsuruga site is a dual site with the...

, violating the Japan Atomic Power Company
Japan Atomic Power Company
The is a company initially formed to jump start the commercial use of nuclear power in Japan, and currently operates two different sites. According to the official web site, JAPC is "the only power company in Japan solely engaged in nuclear energy"....

's limit of 100 millirems (1 mSv
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...

) per day.

September 23, 1983 — INES Level 4 - Buenos Aires
Buenos Aires
Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...

, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

- Accidental criticality
An operator error during a fuel plate reconfiguration in an experimental test reactor led to an excursion of 3×10¹⁷ fissions at the RA-2 facility. The operator absorbed 2000 rad (20 Gy) of gamma and 1700 rad (17 Gy) of neutron radiation which killed him two days later. Another 17 people outside of the reactor room absorbed doses ranging from 35 rad (0.35 Gy) to less than 1 rad (0.01 Gy). pg103

April 26, 1986 — INES Level 7 - Prypiat, Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

(then USSR
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

) - Power excursion, explosion, complete meltdown
An inadequate reactor safety system led to an uncontrolled power excursion, causing a severe steam explosion, meltdown and release of radioactive material at the Chernobyl
Chernobyl
Chernobyl or Chornobyl is an abandoned city in northern Ukraine, in Kiev Oblast, near the border with Belarus. The city had been the administrative centre of the Chernobyl Raion since 1932....

nuclear power plant located approximately 100 kilometers north-northwest of Kiev
Kiev
Kiev or Kyiv is the capital and the largest city of Ukraine, located in the north central part of the country on the Dnieper River. The population as of the 2001 census was 2,611,300. However, higher numbers have been cited in the press....

. Approximately fifty fatalities (mostly cleanup personnel) resulted from the accident and the immediate aftermath. An additional nine fatal cases of thyroid cancer in children in the Chernobyl area have been attributed to the accident. The explosion and combustion of the graphite reactor core spread radioactive material over much of Europe. 100,000 people were evacuated from the areas immediately surrounding Chernobyl
Chernobyl
Chernobyl or Chornobyl is an abandoned city in northern Ukraine, in Kiev Oblast, near the border with Belarus. The city had been the administrative centre of the Chernobyl Raion since 1932....

in addition to 300,000 from the areas of heavy fallout in Ukraine, Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...

and Russia. An "Exclusion Zone"
Zone of alienation
The Chernobyl Nuclear Power Plant Zone, which is sometimes referred to as The Chernobyl Zone, The 30 Kilometer Zone, The Zone of Alienation, or simply The Zone The Chernobyl Nuclear Power Plant Zone, which is sometimes referred to as The Chernobyl Zone, The 30 Kilometer Zone, The Zone of...

was created surrounding the site encompassing approximately 1,000 mi² (3,000 km²) and deemed off-limits for human habitation for an indefinite period. Several studies by governments, UN agencies and environmental groups have estimated the consequences and eventual number of casualties. Their findings are subject to controversy.

May 4, 1986 – INES Level 3-5 (need ref) - Hamm-Uentrop, Germany (then West Germany
West Germany
West Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....

) - Fuel damaged
A spherical fuel pebble became lodged in the pipe used to deliver fuel elements to the reactor at an experimental 300-megawatt THTR-300
THTR-300
The THTR-300 was a thorium high-temperature nuclear reactor rated at 300 MW electric . The German state of North Rhine Westphalia, in the Federal Republic of Germany, and Hochtemperatur-Kernkraftwerk GmbH financed the THTR-300’s construction. Operations started on the plant in Hamm-Uentrop,...

HTGR. Attempts by an operator to dislodge the fuel pebble damaged its cladding, releasing radiation detectable up to two kilometers from the reactor.

1990s

April 6, 1993 — INES Level 4 - Tomsk
Tomsk
Tomsk is a city and the administrative center of Tomsk Oblast, Russia, located on the Tom River. One of the oldest towns in Siberia, Tomsk celebrated its 400th anniversary in 2004...

, Russia - Explosion
A pressure buildup led to an explosive mechanical failure in a 34 cubic meter stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

reaction vessel buried in a concrete bunker under building 201 of the radiochemical works at the Tomsk-7 Siberian Chemical Enterprise plutonium reprocessing facility. The vessel contained a mixture of concentrated nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

, uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

(8757 kg), plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

(449 g) along with a mixture of radioactive and organic waste from a prior extraction cycle. The explosion dislodged the concrete lid of the bunker and blew a large hole in the roof of the building, releasing approximately 6 GBq of Pu 239 and 30 TBq of various other radionuclides into the environment. The contamination plume extended 28 km NE of building 201, 20 km beyond the facility property. The small village of Georgievka (pop. 200) was at the end of the fallout plume, but no fatalities, illnesses or injuries were reported. The accident exposed 160 on-site workers and almost two thousand cleanup workers to total doses of up to 50 mSv (the threshold limit for radiation workers is 100 mSv per 5 years).

June, 1999 — INES Level 2 - Ishikawa Prefecture
Ishikawa Prefecture
is a prefecture of Japan located in the Chūbu region on Honshū island. The capital is Kanazawa.- History :Ishikawa was formed from the merger of Kaga Province and the smaller Noto Province.- Geography :Ishikawa is on the Sea of Japan coast...

, Japan - Control rod malfunction
Operators attempting to insert one control rod during an inspection neglected procedure and instead withdrew three causing a 15 minute uncontrolled sustained reaction at the number 1 reactor of Shika Nuclear Power Plant
Shika Nuclear Power Plant
The is a nuclear power plant located in the town of Shika, Ishikawa, Japan. It is owned and operated by the Hokuriku Electric Power Company. It is on a site that is 1.6 km2 .-Reactors on Site:-1999 Criticality Event:...

. The Hokuriku Electric Power Company
Hokuriku Electric Power Company
The Hokuriku Electric Power Company supplies power by a regulated monopoly to the Toyama Prefecture, Ishikawa Prefecture, the northern part of Fukui Prefecture, and northwestern parts of Gifu Prefecture...

who owned the reactor did not report this incident and falsified records, covering it up until March, 2007.

September 30, 1999 — INES Level 4 - Ibaraki Prefecture
Ibaraki Prefecture
is a prefecture of Japan, located in the Kantō region on the main island of Honshu. The capital is Mito.-History:Ibaraki Prefecture was previously known as Hitachi Province...

, Japan - Accidental criticality
Inadequately trained part-time workers prepared a uranyl nitrate
Uranyl nitrate
Uranyl nitrate is a water soluble yellow uranium salt. The yellow-green crystals of uranium nitrate hexahydrate are triboluminescent.Uranyl nitrate can be prepared by reaction of uranium salts with nitric acid...

solution containing about 16.6 kg of uranium, which exceeded the critical mass, into a precipitation tank at a uranium reprocessing facility in Tokai-mura northeast of Tokyo, Japan. The tank was not designed to dissolve this type of solution and was not configured to prevent eventual criticality. Three workers were exposed to (neutron) radiation doses in excess of allowable limits. Two of these workers died. 116 other workers received lesser doses of 1 mSv or greater though not in excess of the allowable limit.

2000s

April 10, 2003 — INES Level 3 - Paks
Paks
Paks is a town in Tolna county, central Hungary, on the banks of the Danube River. Paks is the home of the only Hungarian nuclear power plant, which provides about 40% the country's electricity....

, Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

- Fuel damaged
Partially spent fuel rods undergoing cleaning in a tank of heavy water ruptured and spilled fuel pellets at Paks Nuclear Power Plant
Paks Nuclear Power Plant
The Paks Nuclear Power Plant , located from Paks, central Hungary, is the first and only operating nuclear power station in Hungary. Altogether, its four reactors produce more than 40 percent of the electrical power generated in the country.-Technical parameters:VVER is the Soviet designation for...

. It is suspected that inadequate cooling of the rods during the cleaning process combined with a sudden influx of cold water thermally shocked
Thermal shock
Thermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...

fuel rods causing them to split. Boric acid was added to the tank to prevent the loose fuel pellets from achieving criticality. Ammonia and hydrazine were also added to absorb iodine-131.

April 19, 2005 — INES Level 3 - Sellafield
Sellafield
Sellafield is a nuclear reprocessing site, close to the village of Seascale on the coast of the Irish Sea in Cumbria, England. The site is served by Sellafield railway station. Sellafield is an off-shoot from the original nuclear reactor site at Windscale which is currently undergoing...

, England, United Kingdom - Nuclear material leak
20 metric tons of uranium and 160 kilograms of plutonium dissolved in 83,000 litres of nitric acid leaked over several months from a cracked pipe into a stainless steel sump chamber at the Thorp nuclear fuel reprocessing plant
Thorp nuclear fuel reprocessing plant
The Thermal Oxide Reprocessing Plant, or THORP, is a nuclear fuel reprocessing plant at Sellafield in Cumbria, England. THORP is owned by the Nuclear Decommissioning Authority and operated by Sellafield Ltd...

. The partially processed spent fuel was drained into holding tanks outside the plant.

November 2005 — INES Level needed - Braidwood, Illinois
Braidwood, Illinois
eBraidwood is a city in Will County, Illinois, United States, approximately southwest of Chicago and south of Joliet. The population was 5,203 at the 2000 census....

, United States - Nuclear material leak
Tritium contamination of groundwater was discovered at Exelon
Exelon
Exelon Corporation is an electricity generating and distributing company headquartered in the Chase Tower in the Chicago Loop area of Chicago. It was created in October, 2000 by the merger of PECO Energy Company and Unicom, of Philadelphia and Chicago respectively. Unicom owned Commonwealth Edison...

's Braidwood station
Braidwood Nuclear Generating Station
Braidwood Generating Station is located in Will County in northeastern Illinois, USA. The nuclear power plant serves Chicago and northern Illinois with electricity. The plant was originally built by Commonwealth Edison company, and subsequently transferred to Com Ed's parent company, Exelon...

. Groundwater off site remains within safe drinking standards though the NRC
Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...

is requiring the plant to correct any problems related to the release.

March 6, 2006 — INES Level 2 - Erwin, Tennessee
Erwin, Tennessee
Erwin is a town in and the county seat of Unicoi County, Tennessee, United States. The population was 5,610 at the 2000 census. It is part of the Johnson City Metropolitan Statistical Area, which is a component of the Johnson City–Kingsport–Bristol, TN-VA Combined Statistical Area...

, United States - Nuclear material leak
Thirty-five litres of a highly enriched uranium solution leaked during transfer into a lab at Nuclear Fuel Services
Nuclear Fuel Services
Nuclear Fuel Services Inc. is an American company that has been a major supplier of fuel for the United States Navy's fleet of nuclear-powered vessels since the 1960s. In recent years it has also processed weapons-grade uranium into nuclear reactor fuel...

Erwin Plant. The incident caused a seven-month shutdown. A required public hearing on the licensing of the plant was not held due to the absence of public notification.

2010s

March 11–20, 2011 - INES Level 7(previously rating is 5) as of April 12 (A final rating is expected after the situation has been completely resolved).
Fukushima I Nuclear Power Plant
Fukushima I Nuclear Power Plant
The , also known as Fukushima Dai-ichi , is a disabled nuclear power plant located on a site in the towns of Okuma and Futaba in the Futaba District of Fukushima Prefecture, Japan. First commissioned in 1971, the plant consists of six boiling water reactors...

, Japan - partial meltdowns in multiple reactors

After the 2011 Tōhoku earthquake and tsunami
2011 Tōhoku earthquake and tsunami
The 2011 earthquake off the Pacific coast of Tohoku, also known as the 2011 Tohoku earthquake, or the Great East Japan Earthquake, was a magnitude 9.0 undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday, 11 March 2011, with the epicenter approximately east...

of March 11, the emergency power supply of the Fukushima-Daiichi nuclear power plant failed. This was followed by deliberate releases of radioactive gas from reactors 1 and 2 to relieve pressure. On March 12, triggered by falling water levels, a hydrogen explosion occurred at reactor 1, resulting in the collapse of the concrete outer structure. Although the reactor containment itself was confirmed to be intact, the hourly radiation from the plant reached 1,015 microsievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...

(0.1015 rem
Röntgen equivalent man
Named after Wilhelm Röntgen , the roentgen equivalent in man or rem is a unit of radiation dose equivalent...

) - an amount equivalent to that allowable for ordinary people in one year." Residents of the Fukushima area were advised to stay inside, close doors and windows, turn off air conditioning, and to cover their mouths with masks, towels or handkerchiefs as well as not to drink tap water. By the evening of March 12, the exclusion zone had been extended to 20 kilometres (12.4 mi) around the plant and 70,000 to 80,000 people had been evacuated from homes in northern Japan. A second, nearly identical hydrogen explosion occurred in the reactor building for Unit 3 on March 14, with similar effects. A third explosion in the “pressure suppression room” of Unit 2 initially was said not to have breached the reactor’s inner steel containment vessel, but later reports indicated that the explosion damaged the steel containment structure of Unit 2 and much larger releases of radiation were expected than previously.
Disposed rods of reactor Unit 4 were stored outside the reactor in a separate pool which ran dry, yielding fire and risk of serious contamination.
Staff was brought down from 800 Fukushima, who have been named the "Fukushima 50" by the press. Events are still developing.
March 11–13, 2011 - INES Level 3, Fukushima II Nuclear Power Plant
Fukushima II Nuclear Power Plant
The , or Fukushima Dai-ni , is a nuclear power plant located on a site in the town of Naraha and Tomioka in the Futaba District of Fukushima Prefecture, Japan...

, Japan - Overheating, possible radioactivity emergency.
After the 2011 Tōhoku earthquake and tsunami
2011 Tōhoku earthquake and tsunami
The 2011 earthquake off the Pacific coast of Tohoku, also known as the 2011 Tohoku earthquake, or the Great East Japan Earthquake, was a magnitude 9.0 undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday, 11 March 2011, with the epicenter approximately east...

of March 11, the cooling systems for three reactors (numbers 1, 2 and 4) of the Fukushima-Daini nuclear power plant were compromised due to damage from the tsunami. Nuclear Engineering International reported that all four units were successfully automatically shut down
Scram
A scram or SCRAM is an emergency shutdown of a nuclear reactor – though the term has been extended to cover shutdowns of other complex operations, such as server farms and even large model railroads...

, but emergency diesel generators at the site were Damaged by the 9.0 magnitude earthquake People were evacuated around 10 kilometres (6.2 mi) from the plant. An evacuation order was issued, because of possible radioactive contamination
Radioactive contamination
Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...

. October 2011, events are still developing.

External links

Nuclear power plant accidents: listed and ranked since 1952
Timeline: Nuclear plant accidents
ProgettoHumus - Mondo in Cammino: List updated of nuclear accidents in the history
Schema-root.org: Nuclear Power Accidents 2 topics, both with a current news feed
US Nuclear Regulatory Commission (NRC) website with search function and electronic public reading room
International Atomic Energy Agency website with extensive online library
Canada's Nuclear Safety Commission (CNSC)
Concerned Citizens for Nuclear Safety Detailed articles on nuclear watchdog activities in the US
World Nuclear Association: Radiation Doses Background on ionizing radiation and doses
Canadian Centre for Occupational Health & Safety More information on radiation units and doses.
Radiological Incidents Database Extensive, well-referenced list of radiological incidents.
Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security Online book by Albert J. Fritsch, Arthur H. Purcell, and Mary Byrd Davis
- Annotated bibliography on civilian nuclear accidents from the Alsos Digital Library for Nuclear Issues.

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