INES The international nuclear and radiological event scale
he INES Scale is a worldwide tool for communicating to the public in a consistent Tway the safety significance of nuclear and radiological events.
Just like information on earthquakes or temperature would be difficult to understand without the Richter or Celsius scales, the INES Scale explains the significance of events from a range of activities, including industrial and medical use of radiation sources, operations at nuclear facilities and transport of radioactive material.
Events are classified on the scale at seven levels: Levels 1–3 are called "incidents" and Levels 4–7 "accidents". The scale is designed so that the severity of an event is about ten times greater for each increase in level on the scale. Events without safety significance are called “deviations” and are classified Below Scale / Level 0. C A
7 MAJOR
ACCIDENT I C 6 SERIOUS ACCIDENT E D 5 ACCIDENT WITH WIDER CONSEQUENCES T N 4 ACCIDENT WITH LOCAL CONSEQUENCES N I 3 SERIOUS INCIDENT D I C
2 INCIDENT T N E
1 ANOMALY
Below Scale / Level 0 NO SAFETY SIGNIFICANCE OECD Nuclear Energy Agency
For more information: www-news.iaea.org Major Accident Level 7 INES classifies nuclear and radiological event may occur from media or from public accidents and incidents by considering three speculation. In some situations, where not all Serious Accident areas of impact: the details of the event are known early on, a Level 6 provisional rating may be issued. Later, a final People and the Environment considers the rating is determined and any differences Accident with radiation doses to people close to the location of explained. Wider Consequences the event and the widespread, unplanned release Level 5 of radioactive material from an installation. To facilitate international communications for events attracting wider interest, the IAEA main- Accident with Radiological Barriers and Control covers tains a web-based communications network Local Consequences events without any direct impact on people or that allows details of the event to immediately Level 4 the environment and only applies inside major be made publicly available. facilities. It covers unplanned high radiation levels Serious Incident and spread of significant quantities of radioactive The two tables that follow show selected Level 3 materials confined within the installation. examples of historic events rated using the INES scale, ranging from a Level 1 anomaly to Incident Defence-in-Depth also covers events without a Level 7 major accident; a much wider range Level 2 any direct impact on people or the environ- of examples showing the rating methodology ment, but for which the range of measures put is provided in the INES Manual. Anomaly Level 1 in place to prevent accidents did not function as intended. Scope of the Scale No Safety INES applies to any event associated with Significance Communicating Events the transport, storage and use of radioactive (Below Scale/ Level 0) Nuclear and radiological events are promptly material and radiation sources, whether or not communicated by the INES Member States, the event occurs at a facility. It covers a wide otherwise a confused understanding of the spectrum of practices, including industrial use
Examples of events AT nuclear facilities
Radiological Barriers People and Environment Defence-in-Depth and Control
Chernobyl, 1986 — Widespread health and 7 environmental effects. External release of a significant fraction of reactor core inventory.
Kyshtym, Russia, 1957 — Significant release of 6 radioactive material to the environment from explosion of a high activity waste tank.
Windscale Pile, UK, 1957 — Release of radioactive Three Mile Island, USA, 1979 — material to the environment following a fire in a 5 Severe damage to the reactor core. reactor core.
Saint Laurent des Eaux, France, Tokaimura, Japan, 1999 — Fatal overexposures of 1980 — Melting of one channel of 4 workers following a criticality event at a nuclear facility. fuel in the reactor with no release outside the site.
Sellafield, UK, 2005 — Release Vandellos, Spain, 1989 — Near accident caused by of large quantity of radioactive No example available fire resulting in loss of safety systems at the nuclear 3 material, contained within the power station. installation.
Cadarache, France, 1993 — Spread Forsmark, Sweden, 2006 — Degraded safety functions Atucha, Argentina, 2005 — Overexposure of a worker of contamination to an area not for common cause failure in the emergency power supply 2 at a power reactor exceeding the annual limit. expected by design. system at nuclear power plant.
1 Breach of operating limits at a nuclear facility. Examples of events involving Radiation SourceS and Transport
People and Environment Defence-in-Depth
7 INES 6
Goiânia, Brazil, 1987 — Four people died and six 5 received doses of a few Gy from an abandoned and ruptured highly radioactive Cs-137 source.
Fleurus, Belgium, 2006 — Severe health effects for a 4 worker at a commercial irradiation facility as a result of high doses of radiation.
Yanango, Peru, 1999 — Incident with radiography Ikitelli, Turkey, 1999 — Loss of a highly radioactive 3 source resulting in severe radiation burns. Co-60 source. in t erna The
USA, 2005 — Overexposure of a radiographer exceeding France, 1995 — Failure of access control systems 2 the annual limit for radiation workers. at accelerator facility.
1 Theft of a moisture-density gauge. scale even t radiological and nuclear t ional
such as radiography, use of radiation sources organizations or countries. The statistically small Examples of events AT nuclear facilities in hospitals, activity at nuclear facilities, and numbers of events at Level 2 and above and the transport of radioactive material. differences between countries for reporting more Radiological Barriers People and Environment Defence-in-Depth minor events to the public make it inappropriate and Control It also includes the loss or theft of radioactive to draw international comparisons. sources or packages and the discovery of Chernobyl, 1986 — Widespread health and orphan sources, such as sources inadvertently History 7 environmental effects. External release of a significant fraction of reactor core inventory. transferred into the scrap metal trade. Since 1990 the scale has been applied to classify events at nuclear power plants, then
Kyshtym, Russia, 1957 — Significant release of When a device is used for medical purposes extended to enable it to be applied to all 6 radioactive material to the environment from explosion (e.g., radiodiagnosis or radiotherapy), INES is installations associated with the civil nuclear of a high activity waste tank. used for the rating of events resulting in actual industry. By 2006, it had been adapted to exposure of workers and the public, or involv- meet the growing need for communication of Windscale Pile, UK, 1957 — Release of radioactive ing degradation of the device or deficiencies the significance of all events associated with Three Mile Island, USA, 1979 — material to the environment following a fire in a 5 Severe damage to the reactor core. in the safety provisions. Currently, the scale the transport, storage and use of radioactive reactor core. does not cover the actual or potential con- material and radiation sources. sequences for patients exposed as part of a Saint Laurent des Eaux, France, medical procedure. The IAEA has coordinated its development in 4 Tokaimura, Japan, 1999 — Fatal overexposures of 1980 — Melting of one channel of workers following a criticality event at a nuclear facility. fuel in the reactor with no release cooperation with the OECD/NEA and with the outside the site. The scale is only intended for use in civil support of more than 60 Member States through Sellafield, UK, 2005 — Release (non-military) applications and only relates their officially designated INES National Officers. Vandellos, Spain, 1989 — Near accident caused by of large quantity of radioactive No example available fire resulting in loss of safety systems at the nuclear to the safety aspects of an event. INES is 3 material, contained within the power station. installation. not intended for use in rating security-related The current version of the INES manual was events or malicious acts to deliberately expose adopted 1 July 2008. With this new edition, it people to radiation. is anticipated that INES will be widely used by Cadarache, France, 1993 — Spread Forsmark, Sweden, 2006 — Degraded safety functions Atucha, Argentina, 2005 — Overexposure of a worker of contamination to an area not for common cause failure in the emergency power supply the Member States and become the world- 2 at a power reactor exceeding the annual limit. expected by design. system at nuclear power plant. What the Scale is Not For wide scale for putting into the proper It is not appropriate to use INES to compare perspective the safety significance of nuclear safety performance between facilities, and radiation events. 1 Breach of operating limits at a nuclear facility. INES The international nuclear and radiological event scale
general description of ines levels
Radiological Barriers INES Level People and Environment Defence-in-Depth and Control
• Major release of radioactive material Major Accident with widespread health and environmental effects requiring Level 7 implementation of planned and extended countermeasures.
• Significant release of radioactive Serious Accident material likely to require Level 6 implementation of planned countermeasures.
• Severe damage to reactor core. • Release of large quantities of • Limited release of radioactive material Accident with radioactive material within an likely to require implementation of installation with a high probability of Wider Consequences some planned countermeasures. significant public exposure. This Level 5 • Several deaths from radiation. could arise from a major criticality accident or fire.
• Fuel melt or damage to fuel resulting • Minor release of radioactive material in more than 0.1% release of core Accident with unlikely to result in implementation of inventory. Local Consequences planned countermeasures other than • Release of significant quantities of Level 4 local food controls. radioactive material within an • At least one death from radiation. installation with a high probability of significant public exposure.
• Near accident at a nuclear power plant • Exposure rates of more than 1 Sv/h in with no safety provisions remaining. • Exposure in excess of ten times the an operating area. • Lost or stolen highly radioactive Serious Incident statutory annual limit for workers. • Severe contamination in an area sealed source. • Non-lethal deterministic health effect not expected by design, with a Level 3 • Misdelivered highly radioactive (e.g., burns) from radiation. low probability of significant public sealed source without adequate exposure. procedures in place to handle it.
• Significant failures in safety provisions • Radiation levels in an operating area but with no actual consequences. • Exposure of a member of the public of more than 50 mSv/h. • Found highly radioactive sealed Incident in excess of 10 mSv. • Significant contamination within the orphan source, device or transport • Exposure of a worker in excess of the Level 2 facility into an area not expected by package with safety provisions intact. statutory annual limits. design. • Inadequate packaging of a highly radioactive sealed source.
• Overexposure of a member of the public in excess of statutory annual limits. Anomaly • Minor problems with safety Level 1 components with significant defence-in-depth remaining. • Low activity lost or stolen radioactive source, device or transport package.
No Safety Significance ( Below Scale/Level 0)
Photo Credits: Chilean Nuclear Energy Commission, International Atomic Energy Agency Genkai Nuclear Power Plant, Genkai, Japan/Kyushu Electric Power Co., Information Series / Division of Public Information J. Mairs/IAEA 08-26941 / E