International Nuclear Event Scale
Encyclopedia
The International Nuclear and Radiological Event Scale (INES) was introduced in 1990 by the International Atomic Energy Agency
International Atomic Energy Agency
The International Atomic Energy Agency is an international organization that seeks to promote the peaceful use of nuclear energy, and to inhibit its use for any military purpose, including nuclear weapons. The IAEA was established as an autonomous organization on 29 July 1957...

 (IAEA) in order to enable prompt communication of safety
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,...

 significance information in case of nuclear accidents.

The scale is intended to be logarithmic
Logarithmic scale
A logarithmic scale is a scale of measurement using the logarithm of a physical quantity instead of the quantity itself.A simple example is a chart whose vertical axis increments are labeled 1, 10, 100, 1000, instead of 1, 2, 3, 4...

, similar to the moment magnitude scale
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...

 that is used to describe the comparative magnitude of earthquakes. Each increasing level represents an accident approximately ten times more severe than the previous level. Compared to earthquakes, where the event intensity can be quantitatively evaluated, the level of severity of a man-made disaster, such as a nuclear accident, is more subject to interpretation. Because of the difficulty of interpreting, the INES level of an incident is assigned well after the incident occurs. Therefore, the scale has a very limited ability to assist in disaster-aid deployment.

As INES ratings are not assigned by a central body, high-profile nuclear incidents are sometimes assigned INES ratings by the operator, by the formal body of the country, but also by scientific institutes, international authorities or other experts which may lead to confusion as to the actual severity.

Details

A number of criteria and indicators are defined to assure coherent reporting of nuclear events by different official authorities. There are seven nonzero levels on the INES scale: three incident-levels and four accident-levels. There is also a level 0.

The level on the scale is determined by the highest of three scores: off-site effects, on-site effects, and defence in depth
Defence in depth
Defence in depth is a military strategy; it seeks to delay rather than prevent the advance of an attacker, buying time and causing additional casualties by yielding space...

 degradation.

Level 7: Major accident

Impact on people and environment: Major release of radio­active ­material with widespread health and environmental effects requiring implementation of planned and extended ­countermeasures
There have been two such events to date:
  • 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...

    , 26 April 1986. A power surge during a test procedure resulted in a criticality accident
    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...

    , leading to a powerful steam explosion and fire that released a significant fraction of core material into the environment, resulting in a death toll of 56 as well as estimated 4,000 additional cancer fatalities among people exposed to elevated doses of radiation. As a result, the city of Chernobyl (pop. 14,000) was largely abandoned, the larger city of Pripyat (pop. 49,400) was completely abandoned, and a 30 km exclusion zone was established.

  • 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 ,...

    , a series of events beginning on 11 March 2011. Rated level 7 on 11 April 2011 by the Japanese government's nuclear safety agency. Major damage to the backup power and containment systems caused by 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...

     resulted in overheating and leaking from some of the Fukushima I nuclear plant's reactors. Each reactor accident was rated separately; out of the six reactors, three were rated level 5, one was rated at a level 3, and the situation as a whole was rated level 7. An exclusion zone of 20 km was established around the plant as well as a 30 km voluntary evacuation zone. See also 2011 Japanese nuclear accidents
    2011 Japanese nuclear accidents
    This is a list of articles describing aspects of the nuclear shut-downs, failures, and nuclear meltdowns triggered by the 2011 Tōhoku earthquake and tsunami.-Fukushima nuclear power plants:* Fukushima I Nuclear Power Plant...

    .

Level 6: Serious accident

Impact on people and environment: Significant release of radioactive material likely to require implementation of planned countermeasures.
There has been only one such event to date:
  • 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...

     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...

    , Soviet Union, 29 September 1957. A failed cooling system at a military nuclear waste reprocessing facility caused a steam explosion that released 70–80 tons of highly radioactive material into the environment. Impact on local population is not fully known. This is the only accident to go over 5 on the scale besides Chernobyl and Fukushima.

Level 5: Accident with wider consequences

Impact on people and environment: Limited release of radioactive ­material likely to require i­mplementation of some planned­ countermeasures.
Several deaths from ­radiation.


Impact on radiological barriers and control: Severe damage to reactor core.
Release of large quantities of radioactive material within an installation with a high probability of significant public exposure. This could arise from a major criticality accident or fire.

Examples:
  • Windscale fire
    Windscale fire
    The Windscale fire of 10 October 1957 was the worst nuclear accident in Great Britain's history, ranked in severity at level 5 on the 7-point International Nuclear Event Scale. The two piles had been hurriedly built as part of the British atomic bomb project. Windscale Pile No. 1 was operational in...

     (United Kingdom), 10 October 1957. Annealing
    Annealing (metallurgy)
    Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...

     of graphite moderator at a military air-cooled reactor caused the graphite and the metallic uranium fuel to catch fire, releasing radioactive pile material as dust into the environment.
  • Three Mile Island accident
    Three Mile Island accident
    The Three Mile Island accident was a core meltdown in Unit 2 of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg, United States in 1979....

     near Harrisburg, Pennsylvania
    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...

     (United States), 28 March 1979. A combination of design and operator errors caused a gradual loss of coolant, leading to a partial 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...

    . Radioactive gases were released into the atmosphere although no deaths have been attributed to this accident.
  • First Chalk River accident, Chalk River, Ontario (Canada), 12 December 1952. Reactor core damaged.
  • Lucens partial core meltdown
    Lucens reactor
    The Lucens reactor at Lucens, Vaud, Switzerland, was a small pilot nuclear reactor destroyed by an accident in 1969.In 1962 the construction of a Swiss-designed pilot nuclear power plant began. The heavy-water moderated, carbon dioxide gas-cooled, reactor was built in an underground cavern and...

     (Switzerland
    Switzerland
    Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

    ), 21 January 1969. A test reactor built in an underground cavern suffered a loss-of-coolant accident during a startup, leading to a partial core meltdown and massive 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...

     of the cavern, which was then sealed.
  • Goiânia accident
    Goiânia accident
    The Goiânia accident was a radioactive contamination accident that occurred on September 13, 1987, at Goiânia, in the Brazilian State of Goiás after an old radiotherapy source was taken from an abandoned hospital site in the city...

     (Brazil
    Brazil
    Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

    ), 13 September 1987. An unsecured caesium chloride
    Caesium chloride
    Caesium chloride is the inorganic compound with the formula CsCl. This colorless solid is an important source of caesium ions in a variety of applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chlorine ions...

     radiation source left in an abandoned hospital was recovered by scavenger thieves unaware of its nature and sold at a scrapyard. 300 people were contaminated and 11 died.

Level 4: Accident with local consequences

Impact on people and environment: Minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls.
At least one death from radiation.


Impact on radiological barriers and control: Fuel melt or damage to fuel ­resulting in more than 0.1% release of core inventory.
Release of significant quantities of radioactive material within an installation with a high ­probability of significant public exposure.

Examples:
  • 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...

     (United Kingdom) – five incidents 1955 to 1979
  • SL-1 Experimental Power Station
    SL-1
    The SL-1, or Stationary Low-Power Reactor Number One, was a United States Army experimental nuclear power reactor which underwent a steam explosion and meltdown on January 3, 1961, killing its three operators. The direct cause was the improper withdrawal of the central control rod, responsible for...

     (United States) – 1961, reactor reached prompt criticality
    Prompt critical
    In nuclear engineering, an assembly is prompt critical if for each nuclear fission event, one or more of the immediate or prompt neutrons released causes an additional fission event. This causes a rapid, exponential increase in the number of fission events...

    , killing three operators.
  • 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....

     (France) – 1969, partial core meltdown; 1980, graphite overheating.
  • 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...

    ) – 1983, criticality accident during fuel rod rearrangement killed one operator and injured 2 others.
  • Jaslovské Bohunice
    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...

     (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...

    ) – 1977, contamination of reactor building.
  • Tokaimura nuclear accident
    Tokaimura nuclear accident
    The Tokaimura nuclear accident , which occurred on 30 September 1999, resulted in two deaths. At that time, it was Japan's worst civilian nuclear radiation accident. The criticality accident occurred in a uranium reprocessing facility operated by JCO , a subsidiary of Sumitomo Metal Mining Co...

     (Japan) – 1999, three inexperienced operators at a reprocessing facility caused a criticality accident
    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...

    ; two of them died.


Level 3: Serious incident

Impact on people and environment: Exposure in excess of ten times the statutory annual limit for workers.
Non-lethal deterministic health effect (e.g., burns) from radiation.


Impact on radiological barriers and control: Exposure rates of more than 1 Sv/h in an operating area.
Severe contamination in an area not expected by design, with a low probability of ­significant public exposure.


Impact on defence-in-depth
Defence in depth
Defence in depth is a military strategy; it seeks to delay rather than prevent the advance of an attacker, buying time and causing additional casualties by yielding space...

: Near accident at a nuclear power plant with no safety provisions remaining.
Lost or stolen highly radioactive sealed source.
Misdelivered highly radioactive sealed source without adequate procedures in place to handle it.

Examples:
  • THORP 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...

     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...

     (United Kingdom) – 2005.
  • 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...

     (Hungary), 2003; fuel rod damage in cleaning tank.
  • Vandellos Nuclear Power Plant
    Vandellòs Nuclear Power Plant
    The Vandellòs Nuclear Power Plant is a nuclear power station in Vandellòs located close to the Coll de Balaguer pass in Catalonia, Spain....

     (Spain), 1989; fire destroyed many control systems; the reactor was shut down.
  • San Onofre Nuclear Generating Station
    San Onofre Nuclear Generating Station
    The San Onofre Nuclear Generating Station is a nuclear power plant located on the Pacific coast of California. The site is in the northwestern corner of San Diego County, south of San Clemente, and surrounded by the San Onofre State Park and next to the I-5 Highway.Unit 1 is no longer in service...

     (United States), 2011; Ammonia leak. No evacuation called for.

Level 2: Incident

Impact on people and environment: Exposure of a member of the public in excess of 10 mSv.
Exposure of a worker in excess of the statutory annual limits.


Impact on radiological barriers and control: Radiation levels in an operating area of more than 50 mSv/h.
Significant contamination within the facility into an area not expected by design.


Impact on defence-in-depth: Significant failures in safety ­provisions but with no actual ­consequences.
Found highly radioactive sealed orphan source, device or transport package with safety provisions intact.
Inadequate packaging of a highly radioactive sealed source.

Examples:
  • Blayais Nuclear Power Plant flood
    1999 Blayais Nuclear Power Plant flood
    The 1999 Blayais Nuclear Power Plant flood was a flood that took place on the evening of December 27, 1999. It was caused when a combination of the tide and high winds led to the sea walls of the Blayais Nuclear Power Plant in France being overwhelmed...

     (France) December 1999
  • Ascó Nuclear Power Plant
    Ascó Nuclear Power Plant
    Ascó Nuclear Power Plant is a nuclear power station located in Ascó, Catalonia, in Spain.It consists of two PWRs of 933 and 943 MWe.-2007 leak:...

     (Spain) April 2008; radioactive contamination.
  • Forsmark Nuclear Power Plant
    Forsmark Nuclear Power Plant
    Forsmark Nuclear Power Plant is a nuclear power plant in Forsmark, Sweden, and also the site of the Swedish Final repository for radioactive operational waste...

     (Sweden) July 2006; backup generator failure.

Level 1: Anomaly

Impact on defence-in-depth: Overexposure of a member of the public in excess of statutory ­annual limits.
Minor problems with safety components with significant defence-in-depth remaining.
Low activity lost or stolen radioactive source, device or transport package.


(Arrangements for reporting minor events to the public differ from country to country. It is difficult to ensure precise consistency in rating events between INES Level-1 and Below scale/Level-0)
Examples:
  • Gravelines
    Gravelines Nuclear Power Plant
    The Gravelines Nuclear Power Station is the fifth largest nuclear power station in the world. It is located in Nord, France, approximately from Dunkerque and Calais. Its cooling water comes from the North Sea. The plant houses 6 nuclear reactors. Two entered service in 1980, two in 1981, and two...

     (Nord, France), 8 August 2009; during the annual fuel bundle exchange in reactor #1, a fuel bundle snagged on to the internal structure. Operations were stopped, the reactor building was evacuated and isolated in accordance with operating procedures.
  • TNPC
    Tricastin Nuclear Power Center
    The Tricastin Nuclear Power Plant is a collection of sites run by Areva and EDF located in 4 different communes Saint-Paul-Trois-Châteaux and Pierrelatte in Drôme, Bollène and Lapalud in Vaucluse, and four departments on right bank of the Channel of Donzère-Mondragon between Valence The Tricastin...

     (Drôme
    Drôme
    Drôme , a department in southeastern France, takes its name from the Drôme River.-History:The French National Constituent Assembly set up Drôme as one of the original 83 departments of France on March 4, 1790, during the French Revolution...

    , France), July 2008; leak of 6000 litres (12,680.3 US pt) of water containing 75 kilograms (165.3 lb) of 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...

     into the environment.

Level 0: Deviation

No safety significance.
Examples:
  • 4 June 2008: Krško
    Krško Nuclear Power Plant
    The Krško Nuclear Power Plant is located in Krško, Slovenia. The plant was connected to the power grid on October 2, 1981 and went into commercial operation on January 15, 1983...

    , Slovenia: Leakage from the primary cooling circuit.
  • 17 December 2006, Atucha
    Atucha I nuclear power plant
    Atucha I is one of two operational nuclear power plants of Argentina. It is located in the town of Lima, Zárate, Buenos Aires, about from Buenos Aires, on the right-hand shore of the Paraná de las Palmas River....

    , Argentina: Reactor shutdown due to tritium increase in reactor compartment.
  • 13 February 2006: Fire in Nuclear Waste Volume Reduction Facilities of the Japanese Atomic Energy Agency
    Japan Atomic Energy Agency
    The was formed October 1, 2005 by a merger of two previous semi-governmental organizations. While it inherited the activities of both PNC and JAERI, it also inherited the nickname of JAERI, "Genken" 原研, an abbreviated word for "nuclear research"....

     (JAEA) in Tokaimura.

Out of scale

There are also events of no safety relevance, characterized as "out of scale".
Examples:
  • 17 November 2002, Natural Uranium Oxide Fuel Plant at the Nuclear Fuel Complex
    Nuclear Fuel Complex
    The Nuclear Fuel Complex was established in 1971 as a major industrial unit of Department of Atomic Energy, for the supply of nuclear fuel bundles and reactor core components. It is a unique facility where natural and enriched uranium fuel, zirconium alloy cladding and reactor core components are...

     in Hyderabad, India: A chemical explosion at a fuel fabrication facility.
  • 29 September 1999: H.B. Robinson
    H. B. Robinson Nuclear Generating Station
    The H. B. Robinson Nuclear Generating Station is a nuclear plant located near Hartsville, South Carolina. The plant consists of one Westinghouse 735 MW pressurized water reactor. The site also includes a coal-fired unit that generates 174 MW and a combustion turbine unit that generates...

    , United States: A tornado sighting within the protected area of the nuclear power plant
    Nuclear power plant
    A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...

     (NPP).
  • 5 March 1999: San Onofre
    San Onofre Nuclear Generating Station
    The San Onofre Nuclear Generating Station is a nuclear power plant located on the Pacific coast of California. The site is in the northwestern corner of San Diego County, south of San Clemente, and surrounded by the San Onofre State Park and next to the I-5 Highway.Unit 1 is no longer in service...

    , United States: Discovery of suspicious item, originally thought to be a bomb, in nuclear power plant.

See also

  • Nuclear 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...

    • Core damage frequency
      Core damage frequency
      Core damage frequency is a term used in probabilistic risk assessment that indicates the likelihood of an accident that would cause damage to a nuclear reactor core. Core damage accidents are considered serious because damage to the core may prevent control of the nuclear reaction, which can lead...

    • Fuel element failure
      Fuel element failure
      A fuel element failure is a rupture in a nuclear reactor's fuel cladding that allows the nuclear fuel or fission products in the form of dissolved radioisotopes or hot particles to enter the reactor coolant or storage water....

    • Loss-of-coolant accident
  • Nuclear power
    Nuclear power
    Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

  • Nuclear power debate
    Nuclear power debate
    The nuclear power debate is about the controversy which has surrounded the deployment and use of nuclear fission reactors to generate electricity from nuclear fuel for civilian purposes...

  • 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...

  • Radioactive waste
    Radioactive waste
    Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...




External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK