Just as earthquakes are rated on the Richter scale, the International Nuclear Event and Radiological Scale (INES) is used to assess the safety significance of nuclear and radiological events. Seven levels are used to classify events on the INES. The goal is to provide the public with information that is objective and easy to understand.

The description of an earthquake would be incomplete without its classification on the Richter scale. Similarly, precise data is necessary to communicate weather information. The International Nuclear and Radiological Event Scale (INES) was created to describe the risks associated with a nuclear event, from an anomaly to a reactor core meltdown.

Promoting consistency and transparency

In use since 1991, the INES was created by the International Atomic Energy Agency (IAEA) in collaboration with the Organization for Economic Cooperation and Development (OECD). It can be used quickly to communicate with the public on anything related to nuclear facility safety. In 2006, itwas adapted to take into account the growing need for communications related to the transport, storage and use of radioactive materials and radiation sources, whether or not the event occurs in a facility. The INES also covers industrial uses, such as radiography or the use of radiation sources in hospitals, using a specific classification system.

Seven levels for three types of impact

The French nuclear safety authority ASN classifies events according to the seven levels of the scale: Levels 1, 2 and 3 correspond to incidents, while Levels 4 through 7 correspond to accidents. The scale is designed so that the severity of an event is about ten times greater for each increase in level on the scale. Events with no safety significance are called “deviations” and are classified as Level 0 on the scale.

The INES classifies nuclear events in regulated nuclear facilities according to three criteria:
1. Off-site consequences, evaluated in terms of radioactive releases with a potential impact on the public;
2. On-site consequences with a potential impact on workers and facilities;
3. The deterioration of the facility’s defense-in-depth, consisting of a series of barriers that separate radioactivematerials from the environment.

Each country decides how it will communicate

As noted by Rejane Spiegelberg Planer, who coordinates notices of events to the IAEA, “Each country has its own reporting criteria. The INES is not intended for use in rating the safety-related performance of facilities, organizations or countries.” A high number of events reported at Levels 0 or 1 should be viewed as a sign of transparency rather than a sign of a poor safety record. In the IAEA bulletin, Rejane Spiegelberg Planer compares the scale to a thermometer. Level 0 corresponds to normal body temperature. Level 1 indicates a low fever calling for an aspirin. In other words, the anomaly serves as a warning to prevent more serious events. “You don't go to the emergency room when an aspirin is sufficient,” she explains. “But at Level 7, you’re already in the hospital.”