The International Atomic Energy Organisation has prepared an International Nuclear Event Scale (INES) for important events in nuclear installations

IAEA Member States use INES to provide a numerical rating that indicates the significance of nuclear or radiological events. Events are rated at seven levels. The scale is logarithmic – that is, the severity of an event is about ten times greater for each increase in level of the scale. Events are considered in terms of impact on people and the environment, impact on radiological barriers and control and impact on defence in depth.

Events without safety significance are rated as Below Scale/Level 0, while events with no safety relevance with respect to radiation or nuclear safety are not rated on the scale.

Almost 80 IAEA Member States have designated INES National Officers. Member States are encouraged to share information on events rated at Level 2 and above and events attracting international public interest through the IAEA-supported Nuclear Events Web-based System (NEWS), which lists publicly events that were reported in the past 12 months.

INES scale to classify events in nuclear installations