International Nuclear Event Scale

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Impression of the 1986 exploded Chernobyl NPP unit 4

After the Chernobyl accident, the International Nuclear Event Scale (INES) has enhanced reporting on events at nuclear power plants[1]. It was implemented in 1990[2]. The UN's International Atomic Energy Agency (IAEA) describes INES as a tool for "promptly communicating to the public in consistent terms" what a nuclear episode means[2]. It has three factors: radioactivity releases to the public; barriers against radiation at a nuclear site; and civil-defence measures[2].

In the INES the events are roughly divided into deviations, incidents and accidents[1]. The events are classified on the Scale at seven levels[1]. Each increase in level on the scale indicates a roughly 10-fold increase in severity[2].

The lower levels (1-3) are termed incidents[1]. The upper levels (4-7) are termed accidents[1]. The events which have no safety significance are classified as level 0/below scale[1]. They are termed deviations[2][1]. The lower levels consists of anomalies, incidents and serious incidents[1]. The upper levels are comprised of accidents without significant off-site risk, accidents with off-site risk, serious accidents and major accidents[1].

Contents

Description of INES levels

  • INES 0: Events known as "deviations" that have no safety significance[2]
  • INES 1: Anomaly[2]
Minor problem with safety components at a nuclear facility, but significant safety margin remaining
  • INES 2: Incident[2]
Radiation levels in an operating area of a nuclear facility of more than 50 millisieverts (mSv) per hour. Exposure of a member of the public to radiation in excess of 10 mSv, exposure of a worker in excess of statutory annual limits.
  • INES 3: Serious Incident[2]
Severe contamination in an area of a facility, with non-lethal injuries such as radiation burns. Low probability of significant public exposure.
  • INES 4: Accident with local consequences[2]
Partial meltdown or damage to fuel, release of significant quantities of radioactive material within an installation. No counter-measures likely to be needed other than local food controls.
  • INES 5: Accident with wider consequences[2]
Severe damage to reactor core, large quantities of radioactive material released within a site. Limited release of material to the wider environment, requiring implementation of some planned countermeasures.
  • INES 6: Serious accident[2]
Significant release of radioactive material likely to require implementation of planned countermeasures.
  • INES 7: Major accident[2]
Major release of radioactive material with widespread health and environmental effects, requiring implementation of planned and extended countermeasures.


Examples of INES accidents

INES 7:

  • 1986 Chernobyl (Pripyat) (UA)[2] - meltdown and explosion
  • 2011 Fukushima (J)[3] - several meltdowns and explosions

INES 6:

  • 1957 Mayak (Kyshtym) (RUS) - explosion at a waste tank[2]
  • 1959 Simi Valley (USA) - meltdown (classified to INES 5-6)[4]

INES 5:

  • 1952 Chalk River (CDN) - meltdown[4]
  • 1957 Windscale/Sellafield (UK) - fire nuclear plant[2]
  • 1969 Lucens (CH) - meltdown (classified to INES 4-5)[4]
  • 1969 Rocky Flats (USA) - fire (classified to INES 4-5)[4]
  • 1974 Leningrad (Soviet Union) - several accidents with radiation release/partial meltdown (classified to INES 4-5)[5]
  • 1977 Belojarsk (Soviet Union) - meltdown[4]
  • 1979 Three Mile Island (Harrisburg) (USA) - meltdown[2]
  • 1982 Chernobyl unit 1 (Pripyat) (UA) - meltdown[6][7]
  • 1985 Vladivostok (Soviet Union) - explosion in an atomic submarine[4]
  • 1987 Goiânia (BR) - radiological incident/contamination accident[8]
  • 1999 Tokaimura (J) - explosion in a reprocessing plant (classified by authorities to INES 4[9], by some scientist to INES 5[4])

INES 4:

  • 1945 Los Alamos (USA) - radiation accident[10]
  • 1946 Los Alamos (USA) - criticality accident[10]
  • 1955 Idaho Falls (USA) - meltdown[4]
  • 1955-1979 Sellafield (UK) - five incidents[3]
  • 1958 Los Alamos (USA) - criticality accident[11]
  • 1959 Knoxville (USA) - explosion (classified to INES 3-4)[4]
  • 1961 Idaho Falls (USA) - explosion[4]
  • 1964 Rhode Island/Charlestown (USA) - radiation accident[12]
  • 1966 Monroe (USA) - meltdown[4]
  • 1966 Enrico Fermi (USA) - partial meltdown[7][13][14]
  • 1966 Melekess (Soviet Union) - radiation accident[12]
  • 1969/1980 Saint-Laurent (F) - meltdown[4]
  • 1973 Windscale/Sellafield (UK) - radiation accident[5]
  • 1975 Greifswald/Lubmin (GDR) - fire leading to station blackout & loss of most feedwater pumps[7]
  • 1977 Jaslovské Bohunice (SK) - overheating and damage in reactor core[15]
  • 1978 Belojarsk (Soviet Union) - collapse of the building and radiation accident[5]
  • 1983 Buenos Aires RA-2 facility (RA) - accidental criticality[16]
  • 1986 Kerr-McGee/Gore (USA) - radiation accident[17]
  • 1993 Tomsk-7 - radioactive gas release after tank explosion[18]
  • 2006 Fleurus (B) - radiation accident[19]


Other concepts

In Germany accidents up to INES level 4 are called GAU (German for größter anzunehmender Unfall) refering to the US-American concept of the maximum credible accident a nuclear plant needed to be prepared for. Accidents of higher level are called Super-GAU as their impacts are even bigger than the biggest accidents the plant concepts necessarily have to deal with.[20].


Atomic catastrophe information network

The IAEA maintains an information exchange network between the countries participating in the use of the Scale. Reports on the events belonging to the level 2 or above it are submitted to the IAEA through the NEWS (Nuclear Event Web-based System). The IAEA should have information on the level of the event in its disposal within 24 hours.[1]

The event level is defined in the country where the event takes place.[1]


Further information


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 http://www.stuk.fi/ydinturvallisuus/ydinvoimalaitokset/vakavuusasteikko/en_GB/asteikko/ as at December 10, 2010
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 http://www.smh.com.au/environment/energy-smart/world-scale-for-rating-nuclear-accidents-20110412-1dc3m.html as at April 12, 2011
  3. 3.0 3.1 http://en.wikipedia.org/w/index.php?title=International_Nuclear_Event_Scale&oldid=423691959 as at April 13, 2011
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 http://de.wikipedia.org/wiki/Liste_meldepflichtiger_Ereignisse_in_deutschen_kerntechnischen_Anlagen as at February 26, 2013
  5. 5.0 5.1 5.2 http://www.atomunfall.de/atomunfaelle-1970-1979.shtml as of November 28, 2014
  6. http://en.wikipedia.org/w/index.php?title=Chernobyl_Nuclear_Power_Plant&oldid=588749513 as at January 7, 2014
  7. 7.0 7.1 7.2 http://www.ines7.info/ines-7/ as of May 4, 2016
  8. http://de.wikipedia.org/w/index.php?title=Goi%C3%A2nia-Unfall&oldid=125210766 as at January 7, 2014
  9. http://www.world-nuclear.org/info/inf37.html as at February 26, 2013
  10. 10.0 10.1 http://www.atomunfall.de/atomunfaelle-1945-1949.shtml as of November 28, 2014
  11. http://www.atomunfall.de/atomunfaelle-1950-1959.shtml as of November 28, 2014
  12. 12.0 12.1 http://www.atomunfall.de/atomunfaelle-1960-1969.shtml as of November 28, 2014
  13. http://news.blogs.cnn.com/2011/03/29/u-s-nuclear-plant-had-partial-meltdown-years-before-three-mile-island/ as of May 4, 2016
  14. http://mragheb.com/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Fermi%20I%20Fuel%20Meltdown%20Incident.pdf as of May 4, 2016
  15. http://en.wikipedia.org/w/index.php?title=KS_150&oldid=505733444 as of November 27, 2014
  16. http://en.wikipedia.org/w/index.php?title=List_of_civilian_nuclear_accidents&oldid=635202869 as of November 27, 2014
  17. http://www.atomunfall.de/atomunfaelle-1980-1989.shtml as of November 28, 2014
  18. http://en.wikipedia.org/w/index.php?title=Nuclear_and_radiation_accidents_and_incidents&oldid=635503778 as of November 27, 2014
  19. http://www.atomunfall.de/atomunfaelle-seit-1990.shtml as of November 28, 2014
  20. http://de.wikipedia.org/w/index.php?title=Auslegungsst%C3%B6rfall&oldid=86847110 as at March 24, 2011

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