INES Classification and What it Means
March 18, 2011
- What is the purpose of the INES scale?
- Who uses the INES scale?
- What does it mean?
- Who classifies the event?
- What are examples of events classified on the INES scale?
What is the purpose of the INES scale?
The International Nuclear and Radiological Event Scale (INES), like the scales developed to classify natural events such as earthquakes and hurricanes, is a worldwide tool used to communicate the safety significance of nuclear and radiological events to technical communities, the media, and the public.
Who uses the INES scale?
The INES scale allows the CNSC and regulatory agencies in the 60 member countries of the International Atomic Energy Agency (IAEA) to classify events involving radioactive materials.
Since its inception in 1990, INES has been adapted to meet the growing needs for communicating all significant events associated with nuclear reactors, processing facilities, the transport, storage and use of radioactive material and radiation sources for medical, industrial and research applications.
The current version of the INES manual was adopted on July 1, 2008.
What does it mean?
Events are classified at seven levels: Levels 1–3 are “incidents” and Levels 4–7 are “accidents”.
These levels consider three areas of impact:
- people and the environment
- radiological barriers and controls
- defence in depth
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 without safety significance are called “deviations” and are classified Below Scale/Level 0.
Source : IAEA (click to enlarge)
Consequences in terms of people and the environment are measured by assessing the amounts and types of radioactive releases that can impact members of the public in general and the environment.
Consequences relating to radiological barriers and controls are assessed by looking at impacts on both workers and facilities.
Degradation to the defence in depth of the facilities is measured by assessing the successive barriers between radioactive material and the environment, such as safety systems and technical and administrative procedures.
General Discription Levels
Source : IAEA (click to enlarge)
Who classifies the event?
In Canada, the CNSC is responsible for assigning INES ratings to Canadian events.
This is the case for each IAEA member country, where an organization designated by the local government is responsible for assigning INES ratings to events which may occur in that country.
The IAEA provides tools and training to help each country’s designated agency discharge this responsibility.
The IAEA also manages a database of events and distributes the information at the international level.
What are examples of events classified on the INES scale?
Some examples of events at nuclear facilities are:
Source : IAEA (click to enlarge)