The International Nuclear and Radiological Event Scale (INES) was introduced in 1990 [1] by the International Atomic Energy Agency (IAEA) in order to enable prompt communication of safety significant information in case of nuclear accidents.
The scale is intended to be logarithmic, similar to the moment magnitude scale that is used to describe the comparative magnitude of earthquakes. Each increasing level represents an accident approximately ten times as severe as the previous level. Compared to earthquakes, where the event intensity can be quantitatively evaluated, the level of severity of a human-made disaster, such as a nuclear accident, is more subject to interpretation. Because of this subjectivity, the INES level of an incident is assigned well after the fact. The scale is therefore intended to assist in disaster-aid deployment.
A number of criteria and indicators are defined to assure coherent reporting of nuclear events by different official authorities. There are seven nonzero levels on the INES scale: three incident -levels and four accident -levels. There is also a level 0.
The level on the scale is determined by the highest of three scores: off-site effects, on-site effects, and defense in depth degradation.
Level | Classification | Description | Examples |
---|---|---|---|
7 | Major accident | Impact on people and environment:
| To date, there have been two Level 7 accidents:
|
6 | Serious accident | Impact on people and environment:
| To date, there has been one Level 6 accident:
|
5 | Accident with wider consequences | Impact on people and environment:
Impact on radiological barriers and control:
|
|
4 | Accident with local consequences | Impact on people and environment:
Impact on radiological barriers and control:
|
|
3 | Serious incident | Impact on people and environment:
Impact on radiological barriers and control:
Impact on defence-in-depth:
|
|
2 | Incident | Impact on people and environment:
Impact on radiological barriers and control:
Impact on defence-in-depth:
|
|
1 | Anomaly | Impact on defence-in-depth:
(Arrangements for reporting minor events to the public differ from country to country.) |
|
0 | Deviation | No safety significance. |
|
There are also events of no safety relevance, characterized as "out of scale". [37]
Deficiencies in the existing INES have emerged through comparisons between the 1986 Chernobyl disaster, which had severe and widespread consequences to humans and the environment, and the 2011 Fukushima nuclear disaster, which caused one fatality and comparatively small (10%) release of radiological material into the environment. The Fukushima Daiichi nuclear accident was originally rated as INES 5, but then upgraded to INES 7 (the highest level) when the events of units 1, 2 and 3 were combined into a single event and the combined release of radiological material was the determining factor for the INES rating. [43]
One study found that the INES scale of the IAEA is highly inconsistent, and the scores provided by the IAEA incomplete, with many events not having an INES rating. Further, the actual accident damage values do not reflect the INES scores. A quantifiable, continuous scale might be preferable to the INES, in the same way that the antiquated Mercalli scale for earthquake magnitudes was superseded by the continuous physically-based Richter scale. [44]
The following arguments have been proposed: firstly, the scale is essentially a discrete qualitative ranking, not defined beyond event level 7. Secondly, it was designed as a public relations tool, not an objective scientific scale. Thirdly, its most serious shortcoming is that it conflates magnitude and intensity. An alternative nuclear accident magnitude scale (NAMS) was proposed by British nuclear safety expert David Smythe to address these issues. [45]
The Nuclear Accident Magnitude Scale (NAMS) is an alternative to INES, proposed by David Smythe in 2011 as a response to the Fukushima Daiichi nuclear disaster. There were some concerns that INES was used in a confusing manner, and NAMS was intended to address the perceived INES shortcomings.
As Smythe pointed out, the INES scale ends at 7; a more severe accident than Fukushima in 2011 or Chernobyl in 1986 would also be measured as INES category 7. In addition, it is not continuous, not allowing a fine-grained comparison of nuclear incidents and accidents. But then, the most pressing item identified by Smythe is that INES conflates magnitude with intensity; a distinction long made by seismologists to describe earthquakes. In that area, magnitude describes the physical energy released by an earthquake, while the intensity focuses on the effects of the earthquake. In analogy, a nuclear incident with a high magnitude (e.g. a core meltdown) may not result in an intense radioactive contamination, as the incident at the Swiss research reactor in Lucens shows – but yet it resides in INES category 4, together with the Windscale fire of 1957, which has caused significant contamination outside of the facility.
The definition of the NAMS scale is:
with R being the radioactivity being released in terabecquerels, calculated as the equivalent dose of iodine-131. Furthermore, only the atmospheric release affecting the area outside the nuclear facility is considered for calculating the NAMS, giving a NAMS score of 0 to all incidents which do not affect the outside. The factor of 20 assures that both the INES and the NAMS scales reside in a similar range, aiding a comparison between accidents. An atmospheric release of any radioactivity will only occur in the INES categories 4 to 7, while NAMS does not have such a limitation.
The NAMS scale still does not take into account the radioactive contamination of liquids such as an ocean, sea, river or groundwater pollution in proximity to any nuclear power plant.
An estimation of its magnitude seems to be related to the problematic definition of a radiological equivalence between different type of involved isotopes and the variety of paths by which activity might eventually be ingested, [46] e.g. eating fish or through the food chain.
Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes. The amount and spread of fallout is a product of the size of the weapon and the altitude at which it is detonated. Fallout may get entrained with the products of a pyrocumulus cloud and fall as black rain. This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.
A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility. Examples include lethal effects to individuals, large radioactivity release to the environment, reactor core melt." The prime example of a "major nuclear accident" is one in which a reactor core is damaged and significant amounts of radioactive isotopes are released, such as in the Chernobyl disaster in 1986 and Fukushima nuclear disaster in 2011.
Nuclear safety is defined by the International Atomic Energy Agency (IAEA) as "The achievement of proper operating conditions, prevention of accidents or mitigation of accident consequences, resulting in protection of workers, the public and the environment from undue radiation hazards". The IAEA defines nuclear security as "The prevention and detection of and response to, theft, sabotage, unauthorized access, illegal transfer or other malicious acts involving nuclear materials, other radioactive substances or their associated facilities".
The Onagawa Nuclear Power Plant genshiryoku hatsudensho, Onagawa NPP) is a nuclear power plant located on a 1,730,000 m2 site in Onagawa in the Oshika District and Ishinomaki city, Miyagi Prefecture, Japan. It is managed by the Tohoku Electric Power Company. It was the most quickly constructed nuclear power plant in the world.
The Fukushima Daiichi Nuclear Power Plant is a disabled nuclear power plant located on a 3.5-square-kilometre (860-acre) site in the towns of Ōkuma and Futaba in Fukushima Prefecture, Japan. The plant suffered major damage from the magnitude 9.1 earthquake and tsunami that hit Japan on March 11, 2011. The chain of events caused radiation leaks and permanently damaged several of its reactors, making them impossible to restart. The working reactors were not restarted after the events.
These are lists of nuclear disasters and radioactive incidents.
The Fukushima nuclear accident was a major nuclear accident at the Fukushima Daiichi nuclear power plant in Ōkuma, Fukushima, Japan which began on March 11, 2011. The proximate cause of the accident was the 2011 Tōhoku earthquake and tsunami, which resulted in electrical grid failure and damaged nearly all of the power plant's backup energy sources. The subsequent inability to sufficiently cool reactors after shutdown compromised containment and resulted in the release of radioactive contaminants into the surrounding environment. The accident was rated seven on the INES by NISA, following a report by the JNES.
Fukushima Daiichi is a multi-reactor nuclear power site in the Fukushima Prefecture of Japan. A nuclear disaster occurred there after a 9.0 magnitude earthquake and subsequent tsunami on 11 March 2011. The earthquake triggered a scram shut down of the three active reactors, and the ensuing tsunami crippled the site, stopped the backup diesel generators, and caused a station blackout. The subsequent lack of cooling led to explosions and meltdowns, with problems at three of the six reactors and in one of the six spent-fuel pools.
The radiation effects from the Fukushima Daiichi nuclear disaster are the observed and predicted effects as a result of the release of radioactive isotopes from the Fukushima Daiichii Nuclear Power Plant following the 2011 Tōhoku 9.0 magnitude earthquake and tsunami. The release of radioactive isotopes from reactor containment vessels was a result of venting in order to reduce gaseous pressure, and the discharge of coolant water into the sea. This resulted in Japanese authorities implementing a 30-km exclusion zone around the power plant and the continued displacement of approximately 156,000 people as of early 2013. The number of evacuees has declined to 49,492 as of March 2018. Radioactive particles from the incident, including iodine-131 and caesium-134/137, have since been detected at atomospheric radionuclide sampling stations around the world, including in California and the Pacific Ocean.
To date, the nuclear accidents at the Chernobyl (1986) and Fukushima Daiichi (2011) nuclear power plants, are the only INES level 7 nuclear accidents.
Unit 3 of the Fukushima Daiichi Nuclear Power Plant was one of the reactors in operation on 11 March 2011, when the plant was struck by the tsunami produced by the Tohoku earthquake. In the aftermath, the reactor experienced hydrogen gas explosions and suffered a partial meltdown, along with the other two reactors in operation at the time the tsunami struck, unit 1 and unit 2. Efforts to remove debris and coolant water contaminated with radiation are ongoing and expected to last several decades.
The Fukushima Daiichi nuclear accident genshiryoku hatsudensho jiko) was a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tōhoku earthquake and tsunami on 11 March 2011. It was the largest nuclear disaster since the Chernobyl disaster of 1986, and the radiation released exceeded official safety guidelines. Despite this, there were no deaths caused by acute radiation syndrome. Given the uncertain health effects of low-dose radiation, cancer deaths cannot be ruled out. However, studies by the World Health Organisation and Tokyo University have shown that no discernible increase in the rate of cancer deaths is expected. Predicted future cancer deaths due to accumulated radiation exposures in the population living near Fukushima have ranged in the academic literature from none to hundreds.
Investigations into the Fukushima Daiichi Nuclear Disaster (or Accident) began on 11 March 2011 when a series of equipment failures, core melt and down, and releases of radioactive materials occurred at the Fukushima Daiichi Nuclear Power Station from the 2011 off the Pacific coast of Tohoku Earthquake and tsunami on the same day.
The Fukushima Daiichi nuclear disaster genshiryoku hatsudensho jiko) was a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tōhoku earthquake and tsunami on 11 March 2011. It is the largest nuclear disaster since the Chernobyl disaster of 1986.
Nuclear labor issues exist within the international nuclear power industry and the nuclear weapons production sector worldwide, impacting upon the lives and health of laborers, itinerant workers and their families.