Nuclear power plant accidents: listed and ranked since 1952
How many nuclear power plants have had accidents and incidents? Get the full list and find out how they're ranked
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The explosions and nuclear fuel rods melting at Japan's Fukushima nuclear power plant, following the Sendai earthquake and tsunami last week, have caused fears of what will happen next. Today Japan's nuclear safety agency has raised the nuclear alert level for Japan from four to five - making it two levels lower than the Chernobyl disaster in 1986.
So far, the Japanese authorities have maintained that there is "no cause to fear a major nuclear accident".
We have identified 33 serious incidents and accidents at nuclear power stations since the first recorded one in 1952 at Chalk River in Ontario, Canada.
The information is partially from the International Atomic Energy Authority - which, astonishingly, fails to keep a complete historical database - and partially from reports. Of those we have identified, six happened in the US and five in Japan. The UK and Russia have had three apiece.
Using Google Fusion tables, we've put these on a map, so you can see how they're spread around the globe:
But how serious are they? The International Atomic Energy Authority ranks them using a special International Nuclear Events Scale (INES) - ranging from 'anomaly' to 'major accident', numbered from 1 to 7.
The events at Fukushima are level 5, so far and there has only been one 7 in history: Chernobyl in 1986. You can see the full ranking system below and on the attached spreadsheet
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|2011||Fukushima||5||Japan||Reactor shutdown after the 2011 Sendai earthquake and tsunami; failure of emergency cooling caused an explosion|
|2011||Onagawa||Japan||Reactor shutdown after the 2011 Sendai earthquake and tsunami caused a fire|
|2006||Fleurus||4||Belgium||Severe health effects for a worker at a commercial irradiation facility as a result of high doses of radiation|
|2006||Forsmark||2||Sweden||Degraded safety functions for common cause failure in the emergency power supply system at nuclear power plant|
|2006||Erwin||US||Thirty-five litres of a highly enriched uranium solution leaked during transfer|
|2005||Sellafield||3||UK||Release of large quantity of radioactive material, contained within the installation|
|2005||Atucha||2||Argentina||Overexposure of a worker at a power reactor exceeding the annual limit|
|2005||Braidwood||US||Nuclear material leak|
|2003||Paks||3||Hungary||Partially spent fuel rods undergoing cleaning in a tank of heavy water ruptured and spilled fuel pellets|
|1999||Tokaimura||4||Japan||Fatal overexposures of workers following a criticality event at a nuclear facility|
|1999||Yanangio||3||Peru||Incident with radiography source resulting in severe radiation burns|
|1999||Ikitelli||3||Turkey||Loss of a highly radioactive Co-60 source|
|1999||Ishikawa||2||Japan||Control rod malfunction|
|1993||Tomsk||4||Russia||Pressure buildup led to an explosive mechanical failure|
|1993||Cadarache||2||France||Spread of contamination to an area not expected by design|
|1989||Vandellos||3||Spain||Near accident caused by fire resulting in loss of safety systems at the nuclear power station|
|1989||Greifswald||Germany||Excessive heating which damaged ten fuel rods|
|1986||Chernobyl||7||Ukraine (USSR)||Widespread health and environmental effects. External release of a significant fraction of reactor core inventory|
|1986||Hamm-Uentrop||Germany||Spherical fuel pebble became lodged in the pipe used to deliver fuel elements to the reactor|
|1981||Tsuraga||2||Japan||More than 100 workers were exposed to doses of up to 155 millirem per day radiation|
|1980||Saint Laurent des Eaux||4||France||Melting of one channel of fuel in the reactor with no release outside the site|
|1979||Three Mile Island||5||US||Severe damage to the reactor core|
|1977||Jaslovské Bohunice||4||Czechoslovakia||Damaged fuel integrity, extensive corrosion damage of fuel cladding and release of radioactivity|
|1969||Lucens||Switzerland||Total loss of coolant led to a power excursion and explosion of experimental reactor|
|1967||Chapelcross||UK||Graphite debris partially blocked a fuel channel causing a fuel element to melt and catch fire|
|1966||Monroe||US||Sodium cooling system malfunction|
|1964||Charlestown||US||Error by a worker at a United Nuclear Corporation fuel facility led to an accidental criticality|
|1959||Santa Susana Field Laboratory||US||Partial core meltdown|
|1958||Chalk River||Canada||Due to inadequate cooling a damaged uranium fuel rod caught fire and was torn in two|
|1958||Vinča||Yugoslavia||During a subcritical counting experiment a power buildup went undetected - six scientists received high doses|
|1957||Kyshtym||6||Russia||Significant release of radioactive material to the environment from explosion of a high activity waste tank.|
|1957||Windscale Pile||5||UK||Release of radioactive material to the environment following a fire in a reactor core|
|1952||Chalk River||5||Canada||A reactor shutoff rod failure, combined with several operator errors, led to a major power excursion of more than double the reactor's rated output at AECL's NRX reactor|