The INES is an international convention to classify roughly the severity of nuclear and radiological events.
After the events of March 2011 at the Fukushima Daiichi plant, various authorities have provisionally estimated the nuclear events between the levels 4 and 7 of the INES scale, but the IAEA is the only authority to issue a definitive official evaluation.
- On March 12, the Japan Atomic Energy Agency (JAEA) has estimated the emergency as a level 4 on the INES scale.
- On March 14, some Russian experts have classified the incident at level 5 or 6.
- On 15 March the French Nuclear Safety Authority (ASN) and the French Authority for Radiation Protection and Nuclear Safety (IRSN) has estimated a level 6. The Finnish nuclear authority (STUK) has reached the same conclusions.
- On March 24, using the data of the IRSN and of the Austrian Institute of Meteorology (ZAMG), an expert of Greenpeace evaluated the accident as INES 7.
- On April 12, 2011 the Japanese authorities for nuclear and industrial safety (NISA) has announced with a press release that the accident is an INES 7.
The same day, the estimation was officially confirmed by the International Atomic Energy Agency (IAEA). Fukushima Daiichi nuclear events are classified as major accident on the INES scale.
The only nuclear accident rated at Level 7 of the INES scale was the Chernobyl accident in 1987. According to experts, at present the accident in Fukushima has produced a lower radiological contamination than caused by Chernobyl.
Currently the Fukushima Daiichi nuclear crisis is in progress, the reactors No. 1, 2 and 3, and the nuclear fuel storage pool of the reactor No. 4 are not in a stable condition.
Before the Fukushima Daiichi nuclear plant will placed in a cold shutdown condition, it is not excluding that the crippled plant will spread other radioactive substances in the environment.
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Header image: IAEA delegation visit Fukushima Daiichi (Unit 3 building), May 27, 2011. Photo by TEPCO, Flickr.