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The International Nuclear and Radiological Event Scale (INES) was introduced in 1990 by the International Atomic Energy Agency (IAEA) in order to enable prompt communication of safety significant information in case of nuclear accidents.

The scale is intended to be logarithmic, similar to the moment magnitude scale that is used to describe the comparative magnitude of earthquakes. Each increasing level represents an accident approximately ten times as severe as the previous level. Compared to earthquakes, where the event intensity can be quantitatively evaluated, the level of severity of a human-made disaster, such as a nuclear accident, is more subject to interpretation. Because of this subjectivity, the INES level of an incident is assigned well after the fact. The scale is therefore intended to assist in disaster-aid deployment.

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 defense in depth degradation.

Out of scale

There are also events of no safety relevance, characterized as "out of scale".

Examples:

• 5 March 1999: San Onofre, United States: Discovery of suspicious item, originally thought to be a bomb, in nuclear power plant.
• 29 September 1999: H.B. Robinson, United States: A tornado sighting within the protected area of the nuclear power plant.
• 17 November 2002, Natural Uranium Oxide Fuel Plant at the Nuclear Fuel Complex in Hyderabad, India: A chemical explosion at a fuel fabrication facility.

Criticism

Deficiencies in the existing INES have emerged through comparisons between the 1986 Chernobyl disaster, which had severe and widespread consequences to humans and the environment, and the 2011 Fukushima nuclear disaster, which caused one fatality and comparatively small (10%) release of radiological material into the environment. The Fukushima Daiichi nuclear accident was originally rated as INES 5, but then upgraded to INES 7 (the highest level) when the events of units 1, 2 and 3 were combined into a single event and the combined release of radiological material was the determining factor for the INES rating.

One study found that the INES scale of the IAEA is highly inconsistent, and the scores provided by the IAEA incomplete, with many events not having an INES rating. Further, the actual accident damage values do not reflect the INES scores. A quantifiable, continuous scale might be preferable to the INES.

Three arguments have been made: First, the scale is essentially a discrete qualitative ranking, not defined beyond event level 7. Second, it was designed as a public relations tool, not an objective scientific scale. Third, its most serious shortcoming is that it conflates magnitude and intensity. An alternative nuclear accident magnitude scale (NAMS) was proposed by British nuclear safety expert David Smythe to address these issues.

Alternatives

Nuclear Accident Magnitude Scale

The Nuclear Accident Magnitude Scale (NAMS) is an alternative to INES, proposed by David Smythe in 2011 as a response to the Fukushima Daiichi nuclear disaster. There were some concerns that INES was used in a confusing manner, and NAMS was intended to address the perceived INES shortcomings.

As Smythe pointed out, the INES scale ends at 7; a more severe accident than Fukushima in 2011 or Chernobyl in 1986 would also be measured as INES category 7. In addition, it is discontinuous, not allowing a fine-grained comparison of nuclear incidents and accidents. But the most pressing item identified by Smythe is that INES conflates magnitude with intensity; a distinction long made by seismologists to compare earthquakes. In that subject area, magnitude describes the physical energy released by an earthquake, while the intensity focuses on the effects of the earthquake. By analogy, a nuclear incident with a high magnitude (e.g. a core meltdown) may not result in an intense radioactive contamination, as the incident at the Swiss research reactor in Lucens shows – yet it resides in INES category 4, together with the Windscale fire of 1957, which caused significant contamination outside of its facility.

Definition

The definition of the NAMS scale is:

NAMS = log₁₀(20 × R)

with R being the radioactivity being released in terabecquerels, calculated as the equivalent dose of iodine-131. Furthermore, only the atmospheric release affecting the area outside the nuclear facility is considered for calculating the NAMS, giving a NAMS score of 0 to all incidents which do not affect the outside. The factor of 20 assures that both the INES and the NAMS scales reside in a similar range, aiding a comparison between accidents. An atmospheric release of any radioactivity will only occur in the INES categories 4 to 7, while NAMS does not have such a limitation.

The NAMS scale still does not take into account the radioactive contamination of liquids such as an ocean, sea, river or groundwater pollution in proximity to any nuclear power plant.

The estimation of magnitude seems to be related to the problematic definition of a radiological equivalence between different types of involved isotopes and the variety of paths by which activity might eventually be ingested, e.g. eating fish or through the food chain.

Smythe lists these incidents: Chernobyl, former USSR 1986 (M = 8.0), Three Mile Island, USA (M = 7.9), Fukushima-Daiichi, Japan 2011 (M = 7.5), Kyshtym, former USSR 1957 (M = 7.3).

See also

• Nuclear meltdown
  • Core damage frequency
  • Fuel element failure
  • Loss-of-coolant accident
• Nuclear power
• Nuclear power debate
• Radioactive contamination
• Radioactive waste
• Vulnerability of nuclear plants to attack
• NRC Emergency Classifications
• Nuclear and radiation accidents and incidents
  • Lists of nuclear disasters and radioactive incidents
  • List of civilian nuclear accidents
  • List of civilian radiation accidents
  • List of military nuclear accidents
    • United States military nuclear incident terminology
• Lists of nuclear reactors
• Nuclear safety and security
• Criticality accident
• List of hydroelectric power station failures

Notes and references

1. "Event scale revised for further clarity". World-nuclear-news.org. 6 October 2008. Retrieved 13 September 2010.
2. Parfitt, Tom (26 April 2006). "Opinion remains divided over Chernobyl's true toll". The Lancet. pp. 1305–1306. Retrieved 8 May 2019.
3. Ahlstrom, Dick (2 April 2016). "Chernobyl anniversary: The disputed casualty figures". The Irish Times. Retrieved 8 May 2019.
4. Mycio, Mary (26 April 2013). "How Many People Have Really Been Killed by Chernobyl? Why estimates differ by tens of thousands of deaths". Slate. Retrieved 8 May 2019.
5. Ritchie, Hannah (24 July 2017). "What was the death toll from Chernobyl and Fukushima?". Our World in Data. Retrieved 8 May 2019.
6. Highfield, Roger (21 April 2011). "How many died because of the Chernobyl disaster? We don't really know (Article updated May 7, 2019)". New Scientist. Retrieved 10 May 2019.
7. "Japan: Nuclear crisis raised to Chernobyl level". BBC News. 12 April 2011. Retrieved 12 April 2011.
8. "Japan's government downgrades its outlook for growth". BBC News. 13 April 2011. Retrieved 13 April 2011.
9. McCurry, Justin (12 April 2011). "Japan upgrades nuclear crisis to same level as Chernobyl". The Guardian. Retrieved 14 December 2020.
10. "Kyshtym disaster | Causes, Concealment, Revelation, & Facts". Encyclopedia Britannica. Retrieved 11 July 2018.
11. ^ "The world's worst nuclear power disasters". Power Technology. 7 October 2013.
12. Canadian Nuclear Society (1989) The NRX Incident by Peter Jedicke Archived 21 May 2015 at the Wayback Machine
13. The Canadian Nuclear FAQ What are the details of the accident at Chalk River's NRX reactor in 1952?
14. Richard Black (18 March 2011). "Fukushima – disaster or distraction?". BBC. Retrieved 7 April 2011.
15. Black, Richard (18 March 2011). "Fukushima – disaster or distraction?". BBC News. Retrieved 30 June 2020.
16. Ahlstrom, Dick (8 October 2007). "The unacceptable toll of Britain's nuclear disaster". The Irish Times. Retrieved 15 June 2020.
17. Highfield, Roger (9 October 2007). "Windscale fire: 'We were too busy to panic'". The Telegraph. Archived from the original on 15 June 2020. Retrieved 15 June 2020.
18. Spiegelberg-Planer, Rejane. "A Matter of Degree" (PDF). IAEA Bulletin. IAEA. Retrieved 24 May 2016.
19. Webb, G A M; Anderson, R W; Gaffney, M J S (2006). "Classification of events with an off-site radiological impact at the Sellafield site between 1950 and 2000, using the International Nuclear Event Scale". Journal of Radiological Protection. 26 (1). IOP: 33–49. Bibcode:2006JRP....26...33W. doi:10.1088/0952-4746/26/1/002. PMID 16522943. S2CID 37975977.
20. Сафонов А, Никитин А (2009). Ядерная губа Андреева (PDF).
21. Lermontov, M.Yu. "The death of officer Kalinin S. V. from radiation overdose at Andreev Bay". Archived from the original on 2 June 2016. Retrieved 20 February 2020.
22. Brian, Cowell. "Loss of Off Site Power: An Operator's Perspective, EDF Energy, Nuclear Generation" (PDF). The French Nuclear Energy Company (SFEN). Retrieved 14 May 2019.
23. Information on Japanese criticality accidents,
24. "Statement of civil incidents meeting the Ministerial Reportable Criteria (MRC) reported to ONR – Q1 2017". www.onr.org.uk. Archived from the original on 8 May 2019. Retrieved 8 May 2019.
25. "Sellafield Ltd incident reports and notices". www.gov.co.uk. Retrieved 12 October 2019.
26. River use banned after French uranium leak. The Guardian (10 July 2008).
27. (AFP). "AFP: Incident "significatif" à la centrale nucléaire de Gravelines, dans le Nord". Archived from the original on 16 August 2009. Retrieved 13 September 2010.
28. (ASN) – 5 April 2012. "ASN has decided to lift its emergency crisis organisation and has temporarily classified the event at the level 1". ASN. Archived from the original on 10 May 2012. Retrieved 6 April 2012.{{cite web}}: CS1 maint: numeric names: authors list (link)
29. "Statement of civil incidents meeting the Ministerial Reportable Criteria (MRC) reported to ONR – Q1 2018". www.onr.org.uk. Archived from the original on 14 May 2019. Retrieved 14 May 2019.
30. "Statement of civil incidents meeting the Ministerial Reportable Criteria (MRC) reported to ONR – Q2 2018". www.onr.org.uk. Archived from the original on 14 May 2019. Retrieved 14 May 2019.
31. "Sellafield Ltd incident reports and notices". www.gov.co.uk. Retrieved 19 October 2019.
32. Forepoint (http://www.forepoint.co.uk). "Incident Reports". Sellafield Ltd. Archived from the original on 12 July 2017. Retrieved 9 March 2021.
33. http://www.jaea.go.jp/02/press2005/p06021301/index.html (in Japanese)
34. http://200.0.198.11/comunicados/18_12_2006.pdf (in Spanish)
35. News | Slovenian Nuclear Safety Administration
36. "More information on the plant disturbance at Olkiluoto 2".
37. IAEA: "This event is rated as out of scale in accordance with Part I-1.3 of the 1998 Draft INES Users Manual, as it did not involve any possible radiological hazard and did not affect the safety layers."
38. Discovery of suspicious item in plant | Nuclear power U.S.A.. Climatesceptics.org. Retrieved on 22 August 2013.
39. "NRC: SECY-01-0071 – Expanded NRC Participation in the Use of the International Nuclear Event Scale". US Nuclear Regulatory Commission. 25 April 2001. p. 8. Archived from the original on 27 October 2010. Retrieved 13 March 2011.
40. "SECY-01-0071-Attachment 5 – INES Reports, 1995–2000". US Nuclear Regulatory Commission. 25 April 2001. p. 1. Archived from the original on 27 October 2010. Retrieved 13 March 2011.
41. Tornado sighting within protected area | Nuclear power in Europe. Climatesceptics.org. Retrieved on 22 August 2013.
42. Archived 21 July 2011 at the Wayback Machine
43. Geoff Brumfiel (26 April 2011). "Nuclear agency faces reform calls". Nature. 472 (7344): 397–398. doi:10.1038/472397a. PMID 21528501.
44. Spencer Wheatley, Benjamin Sovacool, and Didier Sornette Of Disasters and Dragon Kings: A Statistical Analysis of Nuclear Power Incidents & Accidents, Physics Society, 7 April 2015.
45. David Smythe (12 December 2011). "An objective nuclear accident magnitude scale for quantification of severe and catastrophic events". Physics Today (12): 1851. Bibcode:2011PhT..2011l1851S. doi:10.1063/PT.4.0509. S2CID 126728258.
46. Smythe, David (12 December 2011). "An objective nuclear accident magnitude scale for quantification of severe and catastrophic events". Physics Today (12): 13. Bibcode:2011PhT..2011l1851S. doi:10.1063/PT.4.0509.
47. "David Smythe - - Nuclear accidents". www.davidsmythe.org. Retrieved 9 May 2024.

External links

• Nuclear Events Web-based System (NEWS), IAEA
• International Nuclear Event Scale factsheet, IAEA
• "International Nuclear Event Scale, User's manual" (PDF). Archived from the original (PDF) on 15 May 2011. Retrieved 19 March 2011. International Nuclear Event Scale, User's manual, IAEA, 2008

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