The INES-scale (International Nuclear and Radiological Event Scale), issued by the International Atomic Energy Agency (IAEA), is a classification scale for the safety significance of nuclear and radiological events. This scale is used worldwide and in an event facilitates the communication with the public and the media.

The uniform assessment criteria allow for a consistent description of the type and severity of the event and thus result in a common understanding of incidents and accidents.

INES classifies nuclear and radiological incidents and accidents by considering three areas of consideration:

  • Radiological consequences outside of the plant
  • Radiological consequences within the plant
  • Impact on safety provisions

Apart from Level 0 for events without safety significance, the scale classifies events at seven levels, from Level 1 "Anomaly" to Level 7 "Major Accident".

Graphic representation. A distinction is made between events with little or no safety significance (level 0) and events with significant safety significance (levels 1 to 7). Levels 1 to 3 are referred to as incidents (level 1 as a malfunction, level 2 as an incident and level 3 as a serious incident). Levels 4 to 7 are considered accidents (level 4 as an accident, level 5 as a serious accident, level 6 as a serious accident and level 7 as a catastrophic accident).

Extended image description of the INES scale

Below the scale and level 0: No safety significance

Classification of levels 1 to 3 as an accident:

  • Level 1 "Anomaly"
  • Level 2 "Incident"
  • Level 3 "Serious Incident"

Classification of levels 4 to 7 as an accident:

  • Level 4 "Accident with local consequences"
  • Level 5 "Accident with wider effects"
  • Level 6 "Serious Accident"
  • Level 7 "Major Accident"