International Nuclear Event Scale (INES) is being revised

A staff reporter of the IAEA reported that the INES scale, originally developed for nuclear power plants in the 1990s, is being revised to make it more versatile and informative tool. Its aim is to consistently communicate the severity of nuclear and radiological incidents and accidents in nuclear industry in the scale 1-3 (incidents) and 4 to 7 (accidents). The scale will now cover all events associated with radiation and radioactive material, including transport related events and human exposure to sources of radiation. The underlying methodology of assessment originally planned for the events rating has not changed. However, the previous procedures were not detailed enough to consistently rate events related to all radiation sources and transportation of the radioactive materials. Over the years, the procedures employed for rating the events have been considerably improved /modified.

The revised scale considers the impact on people and the environment of localized events of exposure of a few people close to the location of the event, or widespread impact, as with the release of radioactive material from an installation. The impact on facilities covers unplanned increased radiation fields due to breach in shielding and spillage of significant quantities of radioactive material resulting from failure of barriers. Degradation in defense-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.

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