Nuclear and radiation accidents and incidents

Three of the reactors at Fukushima I overheated, causing meltdowns that eventually led to explosions, which released large amounts of radioactive material into the air.

Pathways from airborne radioactive contamination to human

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. Examples include lethal effects to individuals, large radioactivity release to the environment, or reactor core melt." The prime example of a "major nuclear accident" is one in which a reactor core is damaged and large amounts of radiation are released, such as in the Chernobyl Disaster in 1986.

The impact of nuclear accidents has been a topic of debate practically since the first nuclear reactors were constructed. It has also been a key factor in public concern about nuclear facilities. Some technical measures to reduce the risk of accidents or to minimize the amount of radioactivity released to the environment have been adopted. Despite the use of such measures, "there have been many accidents with varying impacts as well near misses and incidents".

Benjamin K. Sovacool has reported that worldwide there have been 99 accidents at nuclear power plants. Fifty-seven accidents have occurred since the Chernobyl disaster, and 57% (56 out of 99) of all nuclear-related accidents have occurred in the USA. Serious nuclear power plant accidents include the Fukushima Daiichi nuclear disaster (2011), Chernobyl disaster (1986), Three Mile Island accident (1979), and the SL-1 accident (1961). Stuart Arm states, "apart from Chernobyl, no nuclear workers or members of the public have ever died as a result of exposure to radiation due to a commercial nuclear reactor incident."

Nuclear-powered submarine mishaps include the K-19 reactor accident (1961), the K-27 reactor accident (1968), and the K-431 reactor accident (1985). Serious radiation accidents include the Kyshtym disaster, Windscale fire, radiotherapy accident in Costa Rica, radiotherapy accident in Zaragoza, radiation accident in Morocco, Goiania accident, radiation accident in Mexico City, radiotherapy unit accident in Thailand, and the Mayapuri radiological accident in India.

The International Atomic Energy Agency maintains a website reporting recent accidents: [10].

Nuclear power plant accidents

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

One of the worst nuclear accidents to date was the Chernobyl disaster which occurred in 1986 in Ukraine. That accident killed 56 people directly, as well as damaging approximately $7 billion of property. A study published in 2005 estimates that there will eventually be up to 4,000 additional cancer deaths related to the accident among those exposed to significant radiation levels. Radioactive fallout from the accident was concentrated in areas of Belarus, Ukraine and Russia. Approximately 350,000 people were forcibly resettled away from these areas soon after the accident.

Physicist Amory Lovins has said: "Nuclear power is the only energy source where mishap or malice can destroy so much value or kill many faraway people; the only one whose materials, technologies, and skills can help make and hide nuclear weapons; the only proposed climate solution that substitutes proliferation, major accidents, and radioactive-waste dangers".

Benjamin K. Sovacool has reported that worldwide there have been 99 accidents at nuclear power plants from 1952 to 2009 (defined as incidents that either resulted in the loss of human life or more than US$50,000 of property damage, the amount the US federal government uses to define major energy accidents that must be reported), totaling US$20.5 billion in property damages. Fifty-seven accidents have occurred since the Chernobyl disaster, and almost two-thirds (56 out of 99) of all nuclear-related accidents have occurred in the USA. There have been comparatively few fatalities associated with nuclear power plant accidents.

Nuclear power plant accidents and incidents
with multiple fatalities and/or more than US$100 million in property damage, 1952-2011

Date	Location	Description	Deaths	I-131 Release in 1,000 Ci	Cost (in millions 2006 $US)	INES level
January 3, 1961	Idaho Falls, Idaho, United States	Explosion at SL-1 prototype at the National Reactor Testing Station. All 3 operators were killed when a control rod was removed too far, causing criticality surge and steam explosion.	3	0.08	22	4
October 5, 1966	Frenchtown Charter Township, Michigan, United States	Partial core meltdown of the Fermi 1 Reactor at the Enrico Fermi Nuclear Generating Station. No radiation leakage into the environment.	0
January 21, 1969	Lucens reactor, Vaud, Switzerland	It was intended to operate until the end of 1969, but during a startup on January 21, 1969, it suffered a loss-of-coolant accident, leading to a partial core meltdown and massive radioactive contamination of the cavern, which was then sealed.	0			4
1975	Sosnovyi Bor, Leningrad Oblast, Russia	There was reportedly a partial nuclear meltdown in Leningrad nuclear power plant reactor unit 1.		0.01
December 7, 1975	Greifswald, East Germany	Electrical error causes fire in the main trough that destroys control lines and five main coolant pumps	0		443	3
January 5, 1976	Jaslovské Bohunice, Czechoslovakia	Malfunction during fuel replacement. Fuel rod ejected from reactor into the reactor hall by coolant (CO2).	2			?
February 22, 1977	Jaslovské Bohunice, Czechoslovakia	Severe corrosion of reactor and release of radioactivity into the plant area, necessitating total decommission	0		1,700	4
March 28, 1979	Three Mile Island, Pennsylvania, United States	Loss of coolant and partial core meltdown due to operator errors. There is a small release of radioactive gasses. See also Three Mile Island accident health effects.	0	0.017	2,400	5
September 15, 1984	Athens, Alabama, United States	Safety violations, operator error, and design problems force a six year outage at Browns Ferry Unit 2.	0		110
March 9, 1985	Athens, Alabama, United States	Instrumentation systems malfunction during startup, which led to suspension of operations at all three Browns Ferry Units	0		1,830
April 11, 1986	Plymouth, Massachusetts, United States	Recurring equipment problems force emergency shutdown of Boston Edison’s Pilgrim Nuclear Power Plant	0		1,001
April 26, 1986	Chernobyl, Ukrainian SSR	An improper electrical test leads to overheating, steam explosion, fire, and meltdown, necessitating the evacuation of 300,000 people from Kiev and dispersing radioactive material across Europe (see Chernobyl disaster effects)	56 direct; 4,000 cancer	7000	6,700	7
May 4, 1986	Hamm-Uentrop, Germany	Experimental THTR-300 reactor releases small amounts of fission products (0.1 GBq Co-60, Cs-137, Pa-233) to surrounding area	0	0	267
March 31, 1987	Delta, Pennsylvania, United States	Peach Bottom units 2 and 3 shutdown due to cooling malfunctions and unexplained equipment problems	0		400
December 19, 1987	Lycoming, New York, United States	Malfunctions force Niagara Mohawk Power Corporation to shut down Nine Mile Point Unit 1	0		150
March 17, 1989	Lusby, Maryland, United States	Inspections at Calvert Cliff Units 1 and 2 reveal cracks at pressurized heater sleeves, forcing extended shutdowns	0		120
March 1992	Sosnovyi Bor, Leningrad Oblast, Russia	An accident at the Sosnovy Bor nuclear plant leaked radioactive gases and iodine into the air through a ruptured fuel channel.
February 20, 1996	Waterford, Connecticut, United States	Leaking valve forces shutdown Millstone Nuclear Power Plant Units 1 and 2, multiple equipment failures found	0		254
September 2, 1996	Crystal River, Florida, United States	Balance-of-plant equipment malfunction forces shutdown and extensive repairs at Crystal River Unit 3	0		384
September 30, 1999	Ibaraki Prefecture, Japan	Tokaimura nuclear accident killed two workers, and exposed one more to radiation levels above permissible limits.	2		54	4
February 16, 2002	Oak Harbor, Ohio, United States	Severe corrosion of control rod forces 24-month outage of Davis-Besse reactor	0		143	3
August 9, 2004	Fukui Prefecture, Japan	Steam explosion at Mihama Nuclear Power Plant kills 5 workers and injures 6 more	5		9	1
March 11, 2011	Fukushima, Japan	A tsunami flooded and damaged the 5 active reactor plants at the site located near the Pacific Ocean. Loss of backup electrical power led to overheating and partial meltdowns. Three workers died due to non-radiation causes.	3	2400		7

Nuclear reactor attacks

Nuclear reactors become preferred targets during military conflict and, over the past three decades, have been repeatedly attacked during military air strikes, occupations, invasions and campaigns:

• In September 1980, Iran bombed the Al Tuwaitha nuclear complex in Iraq.
• In June 1981, an Israeli air strike completely destroyed Iraq’s Osirak nuclear research facility.
• Between 1984 and 1987, Iraq bombed Iran’s Bushehr nuclear plant six times.
• In Iraq in 1991, the U.S. bombed three nuclear reactors and an enrichment pilot facility.
• In 1991, Iraq launched Scud missiles at Israel’s Dimona nuclear power plant.
• In September 2003, Israel bombed a Syrian reactor under construction.

Radiation and other accidents

Serious radiation and other accidents include:

• February 13, 1950 - a Convair B-36B crashed in northern British Columbia after jettisoning a Mark IV atomic bomb. This was the first such nuclear weapon loss in history.
• 1952 - AECL Chalk River Laboratories, Chalk River, Ontario, Canada. Partial meltdown, about 10,000 Curies released. [11][12]
• September 1957 - a plutonium fire occurred at the Rocky Flats Plant, which resulted in the contamination of Building 71 and the release of plutonium into the atmosphere, causing US $818,600 in damage.
• September 1957 – Mayak nuclear waste storage tank explosion at Chelyabinsk. Two hundred plus fatalities, believed to be a conservative estimate; 270,000 people were exposed to dangerous radiation levels. Over thirty small communities had been removed from Soviet maps between 1958 and 1991. (INES level 6).
• October 1957 - Windscale fire, UK. Fire ignites plutonium piles and contaminates surrounding dairy farms. An estimated 33 cancer deaths.
• 1959, 1964, 1969 - Santa Susana Field Laboratory, Los Angeles, California. Partial meltdowns.
• 24 January 1961 - The 1961 Goldsboro B-52 crash occurred near Goldsboro, North Carolina. A B-52 Stratofortress carrying two Mark 39 nuclear bombs broke up in mid-air, dropping its nuclear payload in the process.
• July 1961 – Soviet submarine K-19 accident. Eight fatalities and more than 30 people were over-exposed to radiation.
• 1962 – Radiation accident in Mexico City, four fatalities.
• January 17, 1966 - The 1966 Palomares B-52 crash occurred when a B-52G bomber of the USAF collided with a KC-135 tanker during mid-air refuelling off the coast of Spain. The KC-135 was completely destroyed when its fuel load ignited, killing all four crew members. The B-52G broke apart, killing three of the seven crew members aboard. Of the four Mk28 type hydrogen bombs the B-52G carried, three were found on land near Almería, Spain. The non-nuclear explosives in two of the weapons detonated upon impact with the ground, resulting in the contamination of a 2-square-kilometer (490-acre) (0.78 square mile) area by radioactive plutonium. The fourth, which fell into the Mediterranean Sea, was recovered intact after a 2½-month-long search.
• January 21, 1968 - The 1968 Thule Air Base B-52 crash involved a United States Air Force (USAF) B-52 bomber. The aircraft was carrying four hydrogen bombs when a cabin fire forced the crew to abandon the aircraft. Six crew members ejected safely, but one who did not have an ejection seat was killed while trying to bail out. The bomber crashed onto sea ice in Greenland, causing the nuclear payload to rupture and disperse, which resulted in widespread radioactive contamination.
• May 1968 – Soviet submarine K-27 reactor near meltdown. 9 people died, 83 people were injured.
• January 1969 – Lucens reactor in Switzerland undergoes partial core meltdown leading to massive radioactive contamination of a cavern.
• July 1978 - Anatoli Bugorski was working on U-70, the largest Soviet particle accelerator, when he accidentally exposed his head directly to the proton beam. He survived, despite suffering some long-term damage.
• July 1979 - Church Rock Uranium Mill Spill in New Mexico, USA, when United Nuclear Corporation's uranium mill tailings disposal pond breached its dam. Over 1,000 tons of radioactive mill waste and millions of gallons of mine effluent flowed into the Puerco River, and contaminants traveled downstream.
• March 1984 – Radiation accident in Morocco, eight fatalities. 　
• August 1985 – Soviet submarine K-431 accident. Ten fatalities and 49 other people suffered radiation injuries.
• 1986 - Soviet submarine K-219 reactor almost had a meltdown. Sergei Preminin died after he manually lowered the control rods, and stopped the explosion. The submarine sank three days later.
• September 1987 – Goiania accident. Four fatalities, and following radiological screening of more than 100,000 people, it was ascertained that 249 other people received serious radiation contamination.
• December 1990 – Radiotherapy accident in Zaragoza. Eleven fatalities and 27 other patients were injured.
• April 1993 - accident at the Tomsk-7 Reprocessing Complex, when a tank exploded while being cleaned with nitric acid. The explosion released a cloud of radioactive gas. (INES level 4).
• 1996 – Radiotherapy accident in Costa Rica. Thirteen fatalities and 114 other patients received an overdose of radiation.
• September 1999 - Criticality accident at Tokai nuclear fuel plant (Japan)
• February 2000 - Three deaths and ten injuries resulted in Samut Prakarn when a radiation-therapy unit was dismantled.
• April 2010 - Mayapuri radiological accident, India, one fatality.
• March 2011- Fukushima I nuclear accidents, Japan.
• March 2011- Fukushima Daiichi Power Station - radioactive discharge

Accident types

For a list of many of the most important accidents see the International Atomic Energy Agency site.

Loss of coolant accident

Main article: Loss of coolant

See also: Nuclear meltdown and Design basis accident

Criticality accidents

A criticality accident (also sometimes referred to as an "excursion" or "power excursion") occurs when a nuclear chain reaction is accidentally allowed to occur in fissile material, such as enriched uranium or plutonium. The Chernobyl accident is an example of a criticality accident. This accident destroyed a reactor at the plant and left a large geographic area uninhabitable. In a smaller scale accident at Sarov a technician working with highly enriched uranium was irradiated while preparing an experiment involving a sphere of fissile material. The Sarov accident is interesting because the system remained critical for many days before it could be stopped, though safely located in a shielded experimental hall. This is an example of a limited scope accident where only a few people can be harmed, while no release of radioactivity into the environment occurred. A criticality accident with limited off site release of both radiation (gamma and neutron) and a very small release of radioactivity occurred at Tokaimura in 1999 during the production of enriched uranium fuel. Two workers died, a third was permanently injured, and 350 citizens were exposed to radiation.

Decay heat

Decay heat accidents are where the heat generated by the radioactive decay causes harm. In a large nuclear reactor, a loss of coolant accident can damage the core: for example, at Three Mile Island a recently shutdown (SCRAMed) PWR reactor was left for a length of time without cooling water. As a result the nuclear fuel was damaged, and the core partially melted. The removal of the decay heat is a significant reactor safety concern, especially shortly after shutdown. Failure to remove decay heat may cause the reactor core temperature to rise to dangerous levels and has caused nuclear accidents. The heat removal is usually achieved through several redundant and diverse systems, and the heat is often dissipated to an 'ultimate heat sink' which has a large capacity and requires no active power, though this method is typically used after decay heat has reduced to a very small value. However, the main cause of release of radioactivity in the Three Mile Island accident was a pilot-operated relief valve on the primary loop which stuck in the open position. This caused the overflow tank into which it drained to rupture and release large amounts of radioactive cooling water into the containment building.

In 2011, an earthquake and tsunami caused a loss of power to two plants in Fukushima, Japan, crippling the reactor as decay heat caused 90% of the fuel rods in the core of the Daiichi Unit 3 reactor to become uncovered. As of May 30, 2011, the removal of decay heat is still a cause for concern.

Transport

Transport accidents can cause a release of radioactivity resulting in contamination or shielding to be damaged resulting in direct irradiation. In Cochabamba a defective gamma radiography set was transported in a passenger bus as cargo. The gamma source was outside the shielding, and it irradiated some bus passengers.

In the United Kingdom, it was revealed in a court case that in March 2002 a radiotherapy source was transported from Leeds to Sellafield with defective shielding. The shielding had a gap on the underside. It is thought that no human has been seriously harmed by the escaping radiation.

Equipment failure

Equipment failure is one possible type of accident, recently at Białystok in Poland the electronics associated with a particle accelerator used for the treatment of cancer suffered a malfunction. This then led to the overexposure of at least one patient. While the initial failure was the simple failure of a semiconductor diode, it set in motion a series of events which led to a radiation injury.

A related cause of accidents is failure of control software, as in the cases involving the Therac-25 medical radiotherapy equipment: the elimination of a hardware safety interlock in a new design model exposed a previously undetected bug in the control software, which could lead to patients receiving massive overdoses under a specific set of conditions.

Human error

A sketch used by doctors to determine the amount of radiation to which each person had been exposed during the Slotin excursion

Many of the major nuclear accidents have been directly attributable to operator or human error. This was obviously the case in the analysis of both the Chernobyl and TMI-2 accidents. At Chernobyl, a test procedure was being conducted prior to the accident. The leaders of the test permitted operators to disable and ignore key protection circuits and warnings that would have normally shut the reactor down. At TMI-2, operators permitted thousands of gallons of water to escape from the reactor plant before observing that the coolant pumps were behaving abnormally. The coolant pumps were thus turned off to protect the pumps, which in turn led to the destruction of the reactor itself as cooling was completely lost within the core.

A detailed investigation into SL-1 determined that one operator (perhaps inadvertently) manually pulled the 84-pound (38 kg) central control rod out about 26 inches rather than the maintenance procedure's intention of about 4 inches.

An assessment conducted by the Commissariat à l’Énergie Atomique (CEA) in France concluded that no amount of technical innovation can eliminate the risk of human-induced errors associated with the operation of nuclear power plants. Two types of mistakes were deemed most serious: errors committed during field operations, such as maintenance and testing, that can cause an accident; and human errors made during small accidents that cascade to complete failure.

In 1946 Canadian Manhattan Project physicist Louis Slotin performed a risky experiment known as "tickling the dragon's tail" which involved two hemispheres of neutron-reflective beryllium being brought together around a plutonium core to bring it to criticality. Against operating procedures, the hemispheres were separated only by a screwdriver. The screwdriver slipped and set off a chain reaction criticality accident filling the room with harmful radiation and a flash of blue light (caused by excited, ionized air particles returning to their unexcited states). Slotin reflexively separated the hemispheres in reaction to the heat flash and blue light, preventing further irradiation of several co-workers present in the room. However Slotin absorbed a lethal dose of the radiation and died nine days afterwards. The infamous plutonium mass used in the experiment was referred to as the demon core.

Lost source

Lost source accidents, also referred to as an orphan source are incidents in which a radioactive source is lost, stolen or abandoned. The source then might cause harm to humans. For example, in 1996 sources were left behind by the Soviet army in Lilo, Georgia. Another case occurred at Yanango where a radiography source was lost, also at Samut Prakarn a phosphorus teletherapy source was lost and at Gilan in Iran a radiography source harmed a welder. The best known example of this type of event is the Goiânia accident which occurred in Brazil.

The International Atomic Energy Agency has provided guides for scrap metal collectors on what a sealed source might look like. The scrap metal industry is the one where lost sources are most likely to be found.

Trafficking in radioactive and nuclear materials

Information reported to the International Atomic Energy Agency (IAEA) shows "a persistent problem with the illicit trafficking in nuclear and other radioactive materials, thefts, losses and other unauthorized activities".

From 1993 to 2006, the IAEA confirmed 1080 illicit trafficking incidents reported by participating countries. Of the 1080 confirmed incidents, 275 incidents involved unauthorized possession and related criminal activity, 332 incidents involved theft or loss of nuclear or other radioactive materials, 398 incidents involved other unauthorized activities, and in 75 incidents the reported information was not sufficient to determine the category of incident. Several hundred additional incidents have been reported in various open sources, but are not yet confirmed.

Comparisons

Comparing the historical safety record of civilian nuclear energy with other forms of electrical generation, Ball, Roberts, and Simpson, the IAEA, and the Paul Scherrer Institute found in separate studies that during the period from 1970 to 1992, there were just 39 on-the-job deaths of nuclear power plant workers worldwide, while during the same time period, there were 6,400 on-the-job deaths of coal power plant workers, 1,200 on-the-job deaths of natural gas power plant workers and members of the general public caused by natural gas power plants, and 4,000 deaths of members of the general public caused by hydroelectric power plants. In particular, coal power plants are estimated to kill 24,000 Americans per year due to lung disease as well as causing 40,000 heart attacks per year in the United States. According to Scientific American, the average coal power plant emits more than 100 times as much radiation per year than a comparatively sized nuclear power plant in the form of toxic coal waste known as fly ash.

Journalist Stephanie Cooke says that it is not very useful to make accident comparisons just in terms of number of immediate deaths, as the way people's lives are disrupted is also relevant, as in the case of the 2011 Japanese nuclear accidents, where 80,000 residents were forced to evacuate from neighborhoods around the Fukushima plant:

You have people in Japan right now that are facing either not returning to their homes forever, or if they do return to their homes, living in a contaminated area... And knowing that whatever food they eat, it might be contaminated and always living with this sort of shadow of fear over them that they will die early because of cancer... It doesn't just kill now, it kills later, and it could kill centuries later... I'm not a great fan of coal-burning. I don't think any of these great big massive plants that spew pollution into the air are good. But I don't think it's really helpful to make these comparisons just in terms of number of deaths.

In terms of energy accidents, hydroelectric plants were responsible for the most fatalities, but nuclear power plant accidents rank first in terms of their economic cost, accounting for 41 percent of all property damage. Oil and hydroelectric follow at around 25 percent each, followed by natural gas at 9 percent and coal at 2 percent. Excluding Chernobyl and the Shimantan Dam, the three other most expensive accidents involved the Exxon Valdez oil spill (Alaska), the Prestige oil spill (Spain), and the Three Mile Island nuclear accident (Pennsylvania).

Nuclear safety

Main article: Nuclear safety

Nuclear safety covers the actions taken to prevent nuclear and radiation accidents or to limit their consequences. This covers nuclear power plants as well as all other nuclear facilities, the transportation of nuclear materials, and the use and storage of nuclear materials for medical, power, industry, and military uses.

The nuclear power industry has improved the safety and performance of reactors, and has proposed new safer (but generally untested) reactor designs but there is no guarantee that the reactors will be designed, built and operated correctly. Mistakes do occur and the designers of reactors at Fukushima in Japan did not anticipate that a tsunami generated by an earthquake would disable the backup systems that were supposed to stabilize the reactor after the earthquake. According to UBS AG, the Fukushima I nuclear accidents have cast doubt on whether even an advanced economy like Japan can master nuclear safety. Catastrophic scenarios involving terrorist attacks are also conceivable.

An interdisciplinary team from MIT have estimated that given the expected growth of nuclear power from 2005 – 2055, at least four serious nuclear accidents would be expected in that period. To date, there have been five serious accidents (core damage) in the world since 1970 (one at Three Mile Island in 1979; one at Chernobyl in 1986; and three at Fukushima-Daiichi in 2011), corresponding to the beginning of the operation of generation II reactors. This leads to on average one serious accident happening every eight years worldwide.

Nuclear weapon safety, as well as the safety of military research involving nuclear materials, is generally handled by agencies different from those that oversee civilian safety, for various reasons, including secrecy.

See also

• Lists of nuclear disasters and radioactive incidents
  • List of military nuclear accidents
  • List of civilian nuclear accidents
• Acute radiation syndrome
• Fuel element failure
• Genpatsu-shinsai
• Ionizing radiation
• International Nuclear Event Scale
• Nuclear debate
• Radioactive contamination
• United States military nuclear incident terminology

External links

• U.S. Nuclear Accidents (lutins.org) most comprehensive online list of incidents involving U.S. nuclear facilities and vessels, 1950–present
• US Nuclear Regulatory Commission (NRC) website with search function and electronic public reading room
• International Atomic Energy Agency website with extensive online library
• Nuclear Disasters - slideshow by Life magazine
• Chernobyl Children's Project International
• 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
• Radiological Incidents Database Extensive, well-referenced list of radiological incidents
• A Review of Criticality Accidents (Template:Wayback)
• Nuclear Files.org List of nuclear accidents
• Annotated bibliography for civilian nuclear accidents from the Alsos Digital Library for Nuclear Issues
• Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security. Albert J. Fritsch, Arthur H. Purcell, and Mary Byrd Davis (2005).Updated edition, June 2006