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INES – The International Nuclear and Radiological Event Scale


What is INES?

INES - is a tool for promptly communicating to the public in consistent terms the safety significance of reported nuclear and radiological incidents and accidents, excluding naturally occurring phenomena such as Radon. The scale can be applied to any event associated with nuclear facilities, as well as the transport, storage and use of radioactive material and radiation sources.


What is the purpose of INES Scale?

The primary purpose of the INES Scale is to facilitate communication and understanding between the technical community, the media and the public on the safety significance of events.

The aim is to keep the public, as well as nuclear authorities, accurately informed on the occurrence and potential consequences of reported events.


How does INES operate? 

The scale was designed by an international group of experts first convened jointly in 1989 by the IAEA and the Nuclear Energy Agency of the Organization for Economic Co-operation and Development (OECD/NEA).

 Since then, the IAEA has managed its development in cooperation with the OECD/NEA and with the support of more than 70 designated INES national officers that officially represent the INES Member States in biennial technical meetings.

Why to use INES?

To facilitate understanding, just like information on earthquakes or temperature would be difficult to understand without the Richter or Celsius scales, INES uses a numerical rating to explain the significance of nuclear or radiological events.

INES applies to any event associated with the transport, storage and use of radioactive material and radiation sources. Such events can include industrial and medical uses of radiation sources, operations at nuclear facilities, or the transport of radioactive material.

Events are classified at seven levels: Levels 1–3 are "incidents" and Levels 4–7 "accidents" by considering three areas of impact: people and the environment, radiological barriers and control, and defence-in-depth. The scale is designed so that the severity of an event is about ten times greater for each increase in level on the scale. Events without safety significance are called “deviations” and are classified Below Scale / Level 0.

The INES User's Manual 2008 Edition is designed to facilitate the task of those who are required to rate the safety significance of events using the scale. It includes additional guidance and clarifications, and provides examples and comments on the continued use of INES.

Who is eligible to participate in INES?

Any IAEA Member States can articipate, as INES covers a wide spectrum of practices, including industrial use such as radiography, use of radiation sources in hospitals, operations at nuclear facilities, and transport of radioactive material.

Participation in the INES system on is voluntary.

Designated INES National Officers participate in developments and discussions related to the application of the Scale.