International_Nuclear_Event_Scale
International Nuclear Event Scale
The scale is inspired on the Richter scale for earthquakes, each increasing level representing an accident ten times more severe than the previous level. However, compared to earthquakes, where ground elevation is relatively easy to assert, the level of severity of a Man made disaster, such as a nuclear accident, is more subject to interpretation, and often the INES level of an incident is only assigned well past the incident occurrence. Therefore the scale cannot aid immediate appropriate disaster-control deployment.
A number of criteria and indicators are defined to assure coherent reporting of nuclear events by different official authorities. There are 7 levels on the INES scale; 3 incident-levels and 4 accident-levels
7 – Major Accident6 – Serious Accident5 – Accident With Wider Consequences4 – Accident With Local Consequences3 – Serious Incident2 – Incident1 – Anomaly0 – Deviation (No Safety Significance)
Details
The level on the scale is determined by the highest of three scores: Off site effects, on site effects, and Defence in depth degradation.
Level 7
A large off-site impact with widespread health and environmental effects. So far, the Chernobyl disaster is the only accident to reach level 7. An example of a non nuclear accident of roughly the same magnitude would be the Bhopal disaster which resulted in thousands of off-site deaths.
Level 6
Significant off-site release, likely to require full implementation of planned countermeasures. Example: Mayak accident (former Soviet Union) - 1957.
Level 5
Limited off-site release, likely to require partial implementation of planned countermeasures. Example: Windscale fire (United Kingdom)- 1957
or
Severe damage to a reactor core/radiological barriers. Example: Three Mile Island accident (United States) - 1979.
Level 4
Minor off-site impact resulting in public exposure of the order of the prescribed limits.
or
Significant damage to a reactor core/radiological barriers or the fatal exposure of a worker.
Examples:
- Sellafield (United Kingdom) - 5 incidents 1955 to 1979
- Saint-Laurent Nuclear Power Plant (France) - 1980
- Buenos Aires (Argentina) - 1983
- Tokaimura nuclear accident (Japan) - 1999.
Level 3
A very small off-site impact, public exposure at levels below the prescribed limits.
or
Severe spread of contamination on-site and/or acute health effects to one or more workers.
or
It is a "near accident" event, when no safety layers are remaining.
Examples:
- THORP plant Sellafield (United Kingdom) - 2005.
- Paks Nuclear Power Plant (fuel rod damage in cleaning tank) (Hungary) - 2003.
Level 2
This is an incident with no off-site impact, a significant spread of contamination on-site may have occurred.
or
Overexposure of a worker.
or
Incidents with significant failures in safety provisions.
Examples:
- Ascó Nuclear Power Plant, (Catalonia, Spain) April 2008; radioactive contamination
- Forsmark Nuclear Power Plant (Sweden); backup generator failure.
Level 1
This is an anomaly beyond the authorized operating regime.
Example:
- Tricastin Nuclear Power Center (Drôme, France), July 2008; leak of 6000 litres of water containing 75 kg of Uranium into the environment.
Level 0
This is a "below-scale event" of no safety significance.
There are also events of no safety relevance, characterized as "out of scale".
See also
- Chernobyl disaster
- Three Mile Island accident
- Windscale fire
- Nuclear meltdown
- Nuclear debate
- Nuclear power
- Nuclear and radiation accidents
- List of civilian nuclear accidents
- List of civilian radiation accidents
- List of military nuclear accidents
- List of nuclear reactors
- Nuclear safety
- Radioactive contamination
- Radioactive waste
References
External links
- Nuclear Events Web-based System (NEWS), IAEA
- International Nuclear Event Scale factsheet, IAEA
- International Nuclear Event Scale, User's manual, IAEA, 2001
This article is licensed under the GNU Free Documentation License.
Last updated on Friday October 10, 2008 at 02:05:12 PDT (GMT -0700)
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