Chernobyl, Ukraine 1986 – Level 7
Fukushima, Japan 2011 – Level 7
Kyshtym, Russia 1957 – Level 6
Windscale Fire (Sellafield), UK 1957 – Level 5
http://en.wikipedia.org/wiki/Chernobyl_New_Safe_Confinement
http://iacknowledge.net/unfolding-fukushima-nuclear-disaster-worse-than-chernobyl-meet-the-victims/
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&docid=J-LCxdJ7kZOnzM&tbnid=5gFUWJKOJacEcM:&ved=0CAQQjB0&url=http%3A%2F%2Fwww.parksandlandscapes.org%2Fblog%2Fkyshtym-chelyabinsk-region-russia%2F&ei=mkWNU9LZIYrsoASF_YDwCQ&bvm=bv.68235269,d.cGU&psig=AFQjCNERJSn4zpHKOKhlSq4owRsgnbp1Sg&ust=1401853716087227
http://en.wikipedia.org/wiki/Lists_of_nuclear_disasters_and_radioactive_incidents:/