International Nuclear Event Scale
After the Chernobyl accident, the International Nuclear Event Scale (INES) has enhanced reporting on events at nuclear power plants.
In the INES the events are roughly divided into deviations, incidents and accidents. The events are classified on the Scale at seven levels. The lower levels (1-3) are termed incidents. The upper levels (4-7) are termed accidents. The events which have no safety significance are classified as level 0/below scale. They are termed deviations. The lower levels consists of anomalies, incidents and serious incidents. The upper levels are comprised of accidents without significant off-site risk, accidents with off-site risk, serious accidents and major accidents.
The IAEA maintains an information exchange network between the countries participating in the use of the Scale. Reports on the events belonging to the level 2 or above it are submitted to the IAEA through the NEWS (Nuclear Event Web-based System). The IAEA should have information on the level of the event in its disposal within 24 hours.
The event level is defined in the country where the event takes place.