Revision planned for UN-backed system to inform public of severity of nuclear accidents

The United Nations-sponsored system to enhance international safety by promptly communicating to the public the significance of nuclear and radiological accidents and incidents is being upgraded to make it even more versatile and informative.

Originally developed in the 1990s by the UN International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency of the Organisation for Economic Co-operation and Development, the International Nuclear Event Scale (INES) aims to consistently communicate the severity of reported nuclear and radiological events, with a scale ranging for 1 (anomaly) to 7 (major accident).

“We’ve brought INES into the world of nuclear and radiological events surfacing in the 21st century,” IAEA Incident Reporting Coordinator and INES officer Rejane Spiegelberg-Planer said. “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.”

Under the INES scale, the 1986 accident at the Chernobyl nuclear power plant in the Soviet Union (now in Ukraine) had widespread environmental and human health effects and was classified as Level 7, while the 1979 Three Mile Island accident in the United States, with very limited off-site radioactivity although the reactor core was severely damaged, was rated as Level 5, based on the on-site impact.

The improvements are designed to better address areas such as the transportation of radioactive material, or human exposure to sources of radiation. The underlying methodology has not changed, but previous procedures were not detailed enough to consistently rate events related to radiation sources and transport. Terminology has also been standardized.

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

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.