| A | B | C | D | E | F | ||
|---|---|---|---|---|---|---|---|
1 | Level | Definition | People and environment | Radiological barriers & control | Defence in depth | Example | |
2 | 7 | Major accident | Major release of radio active material with widespread health and environmental effects requiring implementation of planned and extended countermeasures | Chernobyl, Ukraine, 1986 | |||
3 | 6 | Serious accident | Significant release of radioactive material likely to require implementation of planned countermeasures. | Kyshtym, Russia, 1957 | |||
4 | 5 | Accident with wider consequences | Limited release of radioactive material likely to require implementation of some planned countermeasures • Several deaths from radiation | • Severe damage to reactor core. • Release of large quantities of radioactive material within an installation with a high probability of significant public exposure. This could arise from a major criticality accident or fire | Windscale, UK, 1957; Three Mile Island, 1979 | ||
5 | 4 | Accident with local consequences | • Minor release of radioactive material unlikely to result in implementation of planned countermeasures other than local food controls. • At least one death from radiation. | • Fuel melt or damage to fuel resulting in more than 0.1% release of core inventory. • Release of significant quantities of radioactive material within an installation with a high probability of significant public exposure. | FUKUSHIMA 1, 2011 | ||
6 | 3 | Serious incident | • Exposure in excess of ten times the statutory annual limit for workers. • Non-lethal deterministic health effect (e.g., burns) from radiation. | • Exposure rates of more than 1 Sv/h in an operating area. • Severe contamination in an area not expected by design, with a low probability of significant public exposure. | • Near accident at a nuclear power plant with no safety provisions remaining. • Lost or stolen highly radioactive sealed source. • Misdelivered highly radioactive sealed source without adequate procedures in place to handle it. | Sellafield, UK, 2005 | |
7 | 2 | Incident | • Exposure of a member of the public in excess of 10 mSv. • Exposure of a worker in excess of the statutory annual limits | • Radiation levels in an operating area of more than 50 mSv/h. • Significant contamination within the facility into an area not expected by design | • Significant failures in safety provisions but with no actual consequences. • Found highly radioactive sealed orphan source, device or transport package with safety provisions intact. • Inadequate packaging of a highly radioactive sealed source. | Atucha, Argentina, 2005 | |
8 | 1 | Anomaly | • Overexposure of a member of the public in excess of statutory annual limits. • Minor problems with safety components with significant defence-in-depth remaining. • Low activity lost or stolen radioactive source, device or transport package |