The Fukushima Daiichi nuclear power plant was today put on the maximum alert warning.

The rating is the same as that of the 1986 Chernobyl incident, although the Japanese Nuclear and Industrial Safety Agency estimate that the amount of radioactive material released into the atmosphere is only 10% that of Chernobyl.

The IAEA International Nuclear and Radiological Event Scale describes an event of level seven as “a major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures”.

The Fukushima plant’s reactor was damaged during the tsunami that took place following an earthquake of 8.9 magnitude on March 11. There have been several aftershocks since, including one yesterday of 7.1 richter.