Level 7: Major accident
Impact on people and environment
Major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures
There have been two such events to date:
Chernobyl disaster, 26 April 1986. A power surge during a test procedure resulted in a criticality accident, leading to a powerful steam explosion and fire that released a significant fraction of core material into the environment, resulting in a death toll of 56 as well as estimated 4,000 additional cancer fatalities among people exposed to elevated doses of radiation. As a result, the city of Chernobyl (pop. 14,000) was largely abandoned, the larger city of Pripyat (pop. 49,400) was completely abandoned, and a 30 km exclusion zone was established.
Fukushima Daiichi nuclear disaster, a series of events beginning on 11 March 2011. Rated level 7 on 11 April 2011 by the Japanese government's nuclear safety agency.[2][3] Major damage to the backup power and containment systems caused by the 2011 T?hoku earthquake and tsunami resulted in overheating and leaking from some of the Fukushima I nuclear plant's reactors. Each reactor accident was rated separately; out of the six reactors, three were rated level 5, one was rated at a level 3, and the situation as a whole was rated level 7.[4] An exclusion zone of 20 km was established around the plant as well as a 30 km voluntary evacuation zone.[5] See also 2011 Japanese nuclear accidents.
Huh. Media had me thinking this was a minor event, but it's rated the same as Chernobyl. Huh...