The INES Scale is a worldwide tool for communicating to the public in a consistent
way the safety significance of nuclear and radiological events.
Just like information on earthquakes or temperature would be difficult to understand
without the Richter or Celsius scales, the INES Scale explains the significance of
events from a range of activities, including industrial and medical use of radiation
sources, operations at nuclear facilities and transport of radioactive material.
Events are classified on the scale at seven levels: Levels 1–3 are called "incidents"
and Levels 4–7 "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 without safety
significance are called “deviations” and are classified Below Scale / Level 0.
Chernobyl, 1986 — Widespread health and
effects. External release of a significant
fraction of reactor core inventory.
Kyshtym, Russia, 1957 — Significant release of
to the environment from explosion
of a high activity waste tank.
Windscale Pile, UK, 1957 — Release of radioactive
material to the environment following a fire in a reactor
Three Mile Island, USA, 1979 —
Severe damage to the reactor core.
4 Tokaimura, Japan, 1999 — Fatal overexposures of
workers following a criticality event at a nuclear facility.
Saint Laurent des Eaux, France,
1980 — Melting of one channel of
fuel in the reactor with no release
outside the site.
3 No example available
Sellafield, UK, 2005 — Release
of large quantity of radioactive
contained within the
Vandellos, Spain, 1989 — Near accident caused by
fire resulting in loss of safety systems
at the nuclear
2 Atucha, Argentina, 2005 — Overexposure of a worker
at a power reactor exceeding the
Cadarache, France, 1993 — Spread
of contamination to an area not
expected by design.
Forsmark, Sweden, 2006 — Degraded safety functions
for common cause failure in the emergency power supply
system at nuclear power plant.
1 Breach of operating limits at a nuclear facility.
INES Level People and Environment Radiological Barriers
and Control Defence-in-Depth
• Major release of radioactive
with widespread health and
implementation of planned and
• Significant release of radioactive
material likely to require
• Limited release of radioactive material
likely to require implementation
some planned countermeasures.
• Several deaths from radiation.
• Severe damage to reactor core.
• Release of large quantities of
material within an
with a high probability of
significant public exposure. This
could arise from a major criticality
accident or fire.
• Minor release of radioactive material
unlikely to result in implementation of
planned countermeasures other than
local food controls.
• At least one death from radiation.
• Fuel melt or damage to fuel resulting
in more than 0.1% release of core
• Release of significant quantities of
material within an
with a high probability
• Exposure in excess of ten times the
statutory annual limit for workers.
• Non-lethal deterministic health effect
(e.g., burns) from radiation.
• Exposure rates of more than 1 Sv/h in
an operating area.
• Severe contamination in an area
not expected by design, with a
• Near accident at a nuclear power plant
with no safety provisions remaining.
• Lost or stolen highly radioactive
• Misdelivered highly radioactive
sealed source without adequate
procedures in place to handle it.
• Exposure of a member of the public
in excess of 10 mSv.
• Exposure of a worker in excess of the
statutory annual limits.
• Radiation levels in an operating area
of more than 50 mSv/h.
• Significant contamination within the
facility into an area not expected by
• Significant failures in safety provisions
but with no actual consequences.
• Found highly radioactive sealed
orphan source, device or transport
package with safety provisions intact.
• Inadequate packaging of a highly
• Overexposure of a member of the
in excess of statutory annual
• Minor problems with safety
• Low activity lost or stolen radioactive
source, device or transport package.
Hope this clarifies you a bit.
on 12-3-2011 by FraternitasSaturni because: Added INES PDF Factsheet