International nuclear event scale
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The International Nuclear and Radiological Event Scale, or INES, is a worldwide tool for communicating to the public in a consistent way the safety significance of nuclear and radiological events.
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 following are the INES levels and events from the IAEA.
| INES Level | General Description | Accidents |
| Major Accident Level 7 |
• Major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures |
Chernobyl, Soviet Union (now Ukraine), 1986 |
|
Serious Accident Level 6 |
• Significant release of radioactive material likely to require implementation of planned countermeasures. |
Kyshtym, Soviet Union (now Russia), 1957 – Significant release of radioactive material to the environment from explosion of high-activity waste tank. |
| Accident with Wider consequences Level 5 |
• Limited release of radioactive material likely to require implementation of some planned countermeasures. |
Three Mile Island, USA, 1979 – Severe damage to reactor core. Windscale Pile, UK, 1957 – A release of radioactive material following a fire in a reactor core. Goiania, Brazil, 1987 – Four people died and six people received high doses of radiation. |
| Accident with Local Consequences Level 4 | • Minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls. |
Tokaimura, Japan, 1999 – Fatal overexposures of workers following a criticality event at a nuclear facility. |
| Serious Incident Level 3 |
• Exposure in excess of ten times the statutory annual limit for workers. • Non-lethal deterministic health effect (e.g., burns) from radiation. |
Yanango, Peru, 1999 — Incident with radiography source resulting in severe radiation burns. |
|
Incident Level 2 |
• Exposure of a member of the public in excess of 10 mSv. • Exposure of a worker in excess of the statutory annual limits. |
|
|
Anomaly Level 1 |
• Overexposure of a member of the public in excess of statutory annual limits. |
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