unit
of measure
conversions
equivalences
|
|
|
|
italiano
 |
english
 |
|
|
|
INES
international nuclear event scale
|
The International Nuclear Event Scale (INES) was introduced
by the International Atomic Energy Agency (IAEA) and the
Nuclear Energy Agency (NEA) of the Organization for Economic
Cooperation and Development (OECD) in 1990 as a tool to
communicate the safety significance of reported events at
nuclear installations
or involving nuclear materials to the international community.
Use of the INES by IAEA and OECD Member States (a number
of whom have their own nuclear event classification scales)
serves to promote a common understanding of the significance
of reported
events among governments, the nuclear community, the media
and the public.
La The INES consists of a 7-level event classification system.
Events of greater safety significance (levels 4-7) are termed
"accidents,"
events of lesser safety significance (levels 1-3) are termed
"incidents,"
and events of no safety significance (level 0 or below scale)
are termed "out-of-scale deviations."
INES scale
|
ACCIDENT
|
7
|
MAJOR
ACCIDENT
|
|
ACCIDENT
|
6
|
SERIOUS
ACCIDENT
|
|
ACCIDENT
|
5
|
ACCIDENT
WITH OFF-SITE RISK
|
|
ACCIDENT
|
4
|
ACCIDENT
WITHOUT SIGNIFICANT OFF-SITE RISK
|
| |
|
|
|
INCIDENT
|
3
|
SERIOUS
INCIDENT
|
|
INCIDENT
|
2
|
INCIDENT
|
|
INCIDENT
|
1
|
ANOMALY
|
|
DEVIATION
|
0
|
NO
SAFETY SIGNIFICANCE
|
The becquerel (Bq) 1 Bq = 2.7x10E-11 Ci.
The sievert (Sv) 1 Sv = 1 J/kg.
|
|
LEVEL
DESCRIPTOR
|
NATURE
OF THE EVENTS
|
EXAMPLES
|
|
ACCIDENTS
7
MAJOR
ACCIDENT
|
•
External release of a large fraction of the radioactive material
in a large facility (e.g. the
core of a power reactor). This would typically involve a mixture
of short and long-lived
radioactive fission products (in quantities radiologically
equivalent to more than tens of
thousands of terabecquerels of iodine-131). Such a release
would result in the possibility of
acute health effects; delayed health effects over a wide area,
possibly involving more than
one country; long-term environmental consequences. |
Chernobyl
NPP, USSR
(now in Ukraine), 1986
|
|
6
SERIOUS
ACCIDENT
|
•
External release of radioactive material (in quantities radiologically
equivalent to the order
of thousands to tens of thousands of terabecquerels of iodine-131).
Such a release would
be likely to result in full implementation of countermeasures
covered by local emergency
plans to limit serious health effects. |
Kyshtym
Reprocessing
Plant, USSR
(now in Russia), 1957
|
|
5
ACCIDENT WITH
OFF-SITE RISK
|
•
External release of radioactive material (in quantities radiologically
equivalent to the order
of hundreds to thousands of terabecquerels of iodine-131).
Such a release would be likely
to result in partial implementation of countermeasures covered
by emergency plans to
lessen the likelihood of health effects.
• Severe damage to the installation. This may involve
severe damage to a large fraction of
the core of a power reactor, a major criticality accident
or a major fire or explosion releasing
large quantities of radioactivity within the installation. |
Windscale
Pile, UK, 1957
Three Mile Island, NPP,
USA, 1979
|
|
4
ACCIDENT
WITHOUT
SIGNIFICANT
OFF-SITE RISK
|
•
External release of radioactivity resulting in a dose to the
critical group of the order of a
few millisieverts.* With such a release the need for off-site
protective actions would be
generally unlikely except possibly for local food control.
• Significant damage to the installation. Such an accident
might include damage leading to
major on-site recovery problems such as partial core melt
in a power reactor and comparable
events at non-reactor installations.
• Irradiation of one or more workers resulting in an
overexposure where a high probability of
early death occurs. |
Windscale
Reprocessing
Plant, UK, 1973
Saint-Laurent NPP, France, 1980
Buenos Aires Critical
Assembly, Argentina, 1983
|
|
INCIDENTS
3
SERIOUS
INCIDENT
|
•
External release of radioactivity resulting in a dose to the
critical group of the order of
tenths of millisievert.* With such a release, off-site protective
measures may not be needed.
• On-site events resulting in doses to workers sufficient
to cause acute health effects
and/or an event resulting in a severe spread of contamination
for example a few thousand
terabecquerels of activity released in a secondary containment
where the material can be
returned to a satisfactory storage area.
• Incidents in which a further failure of safety systems
could lead to accident conditions, or
a situation in which safety systems would be unable to prevent
an accident if certain initiators
were to occur. |
Vandellos
NPP, Spain,
1989
|
|
2
INCIDENT
|
•
Incidents with significant failure in safety provisions but
with sufficient defence
remaining to cope with additional failures. These include
events where the actual
would be rated at level 1 but which reveal significant additional
organisational inadequacies
or safety culture deficiencies.
• An event resulting in a dose to a worker exceeding
a statutory annual dose limit
an event which leads to the presence of significant quantities
of radioactivity in the installation
in areas not expected by design and which require corrective
action. |
|
|
1
ANOMALY
|
•
Anomaly beyond the authorised regime but with significant
defence in depth remaining.
This may be due to equipment failure, human error or procedural
inadequacies and may
occur in any area covered by the scale, e.g. plant operation,
transport of radioactive material,
fuel handling, waste storage. Examples include: breaches of
technical specifications or
transport regulations, incidents without direct safety consequences
that reveal inadequacies
in the organisational system or safety culture, minor defects
in pipework beyond the expectations
of the surveillance programme. |
|
|
DEVIATIONS
0
BELOW SCALE
|
•
Deviations where operational limits and conditions are not
exceeded and which are
properly managed in accordance with adequate procedures. Examples
include: a single
random failure in a redundant system discovered during periodic
inspections or tests, a
planned reactor trip proceeding normally, spurious initiation
of protection systems without
significant consequences, leakages within the operational
limits, minor spreads of contamination
within controlled areas without wider implications for safety
culture. |
NO
SAFETY SIGNIFICANCE
|
|
Examples
of Rated Nuclear Events
|
The 1986 accident at the Chernobyl nuclear power plant
in the Soviet Union (now in Ukraine) had widespread environmental
and human health effects. It is thus classified as Level 7.
The 1957 accident at the Kyshtym reprocessing plant
in the Soviet Union (now in Russia) led to a large
off site release. Emergency measures including evacuation
of the population were taken to limit serious health
effects. Based on the off-site impact of this event it is
classified as Level 6.
The 1957 accident at the air-cooled graphite reactor pile
at Windscale (now Sellafield) facility in the United
Kingdom involved an external release of radioactive fission
products. Based on the off-site impact, it is
classified as Level 5.
The 1979 accident at Three Mile Island in the United
States resulted in a severely damaged reactor core. The off-site
release of radioactivity was very limited. The event is classified
as Level 5, based on the on-site impact.
The 1973 accident at the Windscale (now Sellafield)
reprocessing plant in the United Kingdom involved a release
of radioactive material into a plant operating area as a result
of an exothermic reaction in a process
vessel. It is classified as Level 4, based on the on-site
impact.
The 1980 accident at the Saint-Laurent nuclear power
plant in France resulted in partial damage to the reactor
core, but there was no external release of radioactivity.
It is classified as Level 4, based on the on-site impact.
The 1983 accident at the RA-2 critical assembly in
Buenos Aires, Argentina, an accidental power excursion due
to non-observance of safety rules during a core modification
sequence, resulted in the death of the operator, who was probably
3 or 4 metres away. Assessments of the doses absorbed indicate
21 Gy for the gamma dose together with 22 Gy for the neutron
dose. The event is classified as Level 4, based on the on-site
impact.
The 1989 incident at the Vandellos nuclear power plant
in Spain did not result in an external release of radioactivity,
nor was there damage to the reactor core or contamination
on site. However, the damage to the plant’s safety systems
due to fire degraded the defence in depth significantly. The
event is classified
as Level 3, based on the defence in depth criterion. |
  
|
| Copyright ©
1999 -2010 THEmeter.net - All Rights Reserved - |
(ver.
#
23.03.08
)
|
|
