International Nuclear and Radiological Event Scale (INES)

The International Nuclear and Radiological Event Scale (INES) is a tool for communicating the safety significance of nuclear and radiological events to the public. Member States use INES on a voluntary basis to rate and communicate events that occur within their territory. It is not a notification or reporting system to be used in emergency response.

Scope

INES covers events at facilities and activities involving radiation sources. It is used for the rating of events that result in a release of radioactive material into the environment and in the radiation exposure of workers and the public. It is also used for events that have no actual consequences but where the measures put in place to prevent them did not function as intended. The scale is also  applied to events involving the loss or theft of radioactive sources and the discovery of uncontrolled radioactive sources in scrap metal. INES should not be used to rate events resulting from procedures where people are intentionally exposed to radiation as part of a medical treatment.  

INES is intended for use in non-military applications and only relates to the safety aspects of an event.

INES should not be used to assessing or comparing safety performance between facilities, organizations or countries. It also should not be used to trigger emergency response actions.

INES Rating Descriptions

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
    • Impact on defence in depth
  • Events without safety significance are rated as Below Scale/Level 0.
  • Events that have 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.

Background

INES was developed in 1990 by the IAEA and the Nuclear Energy Agency of the Organization for Economic Co-operation and Development (OECD/NEA). Initially the scale was applied to classify events at nuclear power plants, then extended and adapted to enable it to be applied to all installations associated with the civil nuclear industry. It has subsequently been extended and adapted further to meet the growing need for communication of the significance of all events associated with the use, storage and transport of radioactive material and radiation sources.

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