Improving the INES Scale

The INES Scale as it might look like after a graphic revamp currently under way is completed.

Originally developed in the 1990s, the International Nuclear Event Scale (INES) is being revised to become a more versatile and informative tool. Its aim is to consistently communicate the severity of reported nuclear and radiological incidents and accidents.

Ms. Rejane Spiegelberg-Planer, the IAEA´s Incident Reporting Coordinator and INES officer, explains that the revision aims to consolidate the use of the scale to all events associated with radiation and radioactive material, including transport related events.

"We´ve brought INES into the world of nuclear and radiological events surfacing in the 21st century," she says. "Our aim is to consolidate the old INES manual and the additional guidance documents and clarifications that had been issued over the past 15 or more years."

The revised scale is designed to better address areas and activities such as the transportation of radioactive material, or human exposure to sources of radiation. The underlying methodology has not changed. However, the previous procedures were not detailed enough to consistently rate events related to radiation sources and transport, and they have been considerably improved.

The criteria used for rating radioactive sources and transport events have been reviewed and consolidated according to additional guidance which was in pilot use for almost two years and then approved by IAEA Member States in 2006.

The revised scale considers that the impact on people and the environment may be localized, i.e. radiation doses to one or a few people close to the location of the event, or widespread, as with the release of radioactive material from an installation.

The impact on facilities covers unplanned increased radiation fields, due for example to loss of shielding, and the spillage of significant quantities of radioactive material resulting from failures of barriers. These events can threaten the safety of people and the environment within facilities. It was formerly known as on-site criterion.

Degradation in defence-in-depth covers those events without direct impact on people or facilities but for which the measures put in place to prevent accidents did not function as intended.

In the revision, issues such as the use of terminology and wording are addressed, and more examples are added to the manual. Ms. Spiegelberg-Planer says: "A more consistent terminology has been adopted to better address the many areas of coverage."

The revision of INES is the culmination of a lengthy and complex process. Since the early 1990s, several additions have been made to the methodology originally developed for nuclear power plants, while the last complete INES manual was published in 2001.

The process has engaged IAEA experts, as well as the INES Advisory Committee and consultants in nuclear safety and radiological protection. Once reviewed by INES members, the target date for officially issuing the new and improved scale is the end of 2008.

Last update: 11 November 2014