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International Nuclear Event Scale Enhances Public Communications
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International Nuclear Event Scale Facilitates Communications
The need for an international nuclear event scale became clear during the late 1980s when many countries found that the safety significance of events was being exaggerated in the media and they needed a simple means to communicate the true significance of the event.
The IAEA and the Nuclear Energy Agency of the Organization for Economic Co-operation and Development developed the INES in 1989. The scale is intended to ensure that events of the same significance that have occurred in different countries are labeled the same way in communicating with the media and public.
The INES has seven levels. The three lowest levels are considered “incidents”; the four highest levels, “accidents.”
The following explains the seven levels of the INES and provides examples of historical events that would have ranked at the five highest levels had the scale been in use at the time. The two lowest levels account for most of the reported events, according to the IAEA. Nations that participate in the INES have different requirements for reporting low-level events. For this reason, the IAEA cautions against making any comparisons between nations.
Level 1: Anomaly
The incident is outside normal operating parameters but had no on-site or off-site impact.
Level 2: Incident
The incident involves significant failures in safety provisions, and/or there were on-site consequences, such as contamination of part of the facility or worker exposure to radiation levels above regulatory limits.
Level 3: Serious Incident
The incident involves a “near accident” or has an on-site impact, such as widespread contamination with radioactive materials or acute health effects to a worker, and/or there was a very small off-site release of radiation such that public exposure was a fraction of regulatory limits.
Example : A 1983 event at the Vandellos nuclear plant in Spain resulted in significant fire damage to safety systems. There was no fuel damage, on-site contamination or off-site release. The INES classified the event as level three because the fire rendered many safety systems inoperable.
Level 4: Accident Without Significant Off-Site Risk
The accident has on-site effects, such as significant damage to the reactor or a worker fatality resulting from radiation exposure, and/or there was a minor off-site release of radiation that may have reached regulatory limits.
Example : A 1973 event at the Windscale (now Sellafield) reprocessing plant in the United Kingdom caused a significant release of radiation into an operating area of the facility. The INES classified the event as a level four accident because of the on-site impact.
Level 5: Accident With Off-Site Risk
The event has on-site impact such that it severely damaged the reactor, and/or there is a limited off-site release of radiation.
Example : The 1979 accident at Three Mile Island destroyed the reactor, but there was no significant off-site release of radiation. The INES classified that accident as level five because of the severity of the on-site damage.
Level 6: Serious Accident
The accident involves a significant release of radiation such that full implementation of emergency procedures likely will be needed to protect the public and the environment.
Example : A 1957 accident at the Kyshtym reprocessing plant in Russia caused a large off-site release of radioactive material. Emergency responders evacuated people in the area and took other measures to minimize effects on public health. The IAEA considers the event a level 6 accident.
Level 7: Major Accident
The accident involves a major release of radioactivity and has widespread health and environ-mental effects.
Example : The IAEA classified the 1986 accident at Chernobyl as level 7 because of its wide-spread environmental and public health effects.
The IAEA is preparing a revision to the INES user’s manual, scheduled for release in 2008. The revision is primarily intended to bring together the guidance for facilities and the guidance for radiation sources and transport into a single document. It will not significantly change how IAEA or participating nations use the scale.
More detailed information on the international scale is available at the IAEA’s INES Web page . The agency provides information on events reported during the previous six months through its Nuclear Events Web-Based System .
Conclusion
The U.S. nuclear energy industry recognizes the importance of the INES in supporting communications about nuclear power plant events. Knowing more about this tool will give the public, the media and other stakeholders a better understanding of nuclear-related events around the world.
Pages 1 2 3
International Nuclear Event Scale Facilitates Communications
The need for an international nuclear event scale became clear during the late 1980s when many countries found that the safety significance of events was being exaggerated in the media and they needed a simple means to communicate the true significance of the event.
The IAEA and the Nuclear Energy Agency of the Organization for Economic Co-operation and Development developed the INES in 1989. The scale is intended to ensure that events of the same significance that have occurred in different countries are labeled the same way in communicating with the media and public.
The INES has seven levels. The three lowest levels are considered “incidents”; the four highest levels, “accidents.”
The following explains the seven levels of the INES and provides examples of historical events that would have ranked at the five highest levels had the scale been in use at the time. The two lowest levels account for most of the reported events, according to the IAEA. Nations that participate in the INES have different requirements for reporting low-level events. For this reason, the IAEA cautions against making any comparisons between nations.
Level 1: Anomaly
The incident is outside normal operating parameters but had no on-site or off-site impact.
Level 2: Incident
The incident involves significant failures in safety provisions, and/or there were on-site consequences, such as contamination of part of the facility or worker exposure to radiation levels above regulatory limits.
Level 3: Serious Incident
The incident involves a “near accident” or has an on-site impact, such as widespread contamination with radioactive materials or acute health effects to a worker, and/or there was a very small off-site release of radiation such that public exposure was a fraction of regulatory limits.
Example : A 1983 event at the Vandellos nuclear plant in Spain resulted in significant fire damage to safety systems. There was no fuel damage, on-site contamination or off-site release. The INES classified the event as level three because the fire rendered many safety systems inoperable.
Level 4: Accident Without Significant Off-Site Risk
The accident has on-site effects, such as significant damage to the reactor or a worker fatality resulting from radiation exposure, and/or there was a minor off-site release of radiation that may have reached regulatory limits.
Example : A 1973 event at the Windscale (now Sellafield) reprocessing plant in the United Kingdom caused a significant release of radiation into an operating area of the facility. The INES classified the event as a level four accident because of the on-site impact.
Level 5: Accident With Off-Site Risk
The event has on-site impact such that it severely damaged the reactor, and/or there is a limited off-site release of radiation.
Example : The 1979 accident at Three Mile Island destroyed the reactor, but there was no significant off-site release of radiation. The INES classified that accident as level five because of the severity of the on-site damage.
Level 6: Serious Accident
The accident involves a significant release of radiation such that full implementation of emergency procedures likely will be needed to protect the public and the environment.
Example : A 1957 accident at the Kyshtym reprocessing plant in Russia caused a large off-site release of radioactive material. Emergency responders evacuated people in the area and took other measures to minimize effects on public health. The IAEA considers the event a level 6 accident.
Level 7: Major Accident
The accident involves a major release of radioactivity and has widespread health and environ-mental effects.
Example : The IAEA classified the 1986 accident at Chernobyl as level 7 because of its wide-spread environmental and public health effects.
The IAEA is preparing a revision to the INES user’s manual, scheduled for release in 2008. The revision is primarily intended to bring together the guidance for facilities and the guidance for radiation sources and transport into a single document. It will not significantly change how IAEA or participating nations use the scale.
More detailed information on the international scale is available at the IAEA’s INES Web page . The agency provides information on events reported during the previous six months through its Nuclear Events Web-Based System .
Conclusion
The U.S. nuclear energy industry recognizes the importance of the INES in supporting communications about nuclear power plant events. Knowing more about this tool will give the public, the media and other stakeholders a better understanding of nuclear-related events around the world.
Pages 1 2 3
