I interpret the "worse than worst case" as "What the designers thought was the worst case in reality was not" so we are now faced with a case that wasn't predic

I interpret the "worse than worst case" as "What the designers thought was the worst case in reality was not" so we are now faced with a case that wasn't predicted and the outcome is unknown. I can see the sense, this reactor was designed 50 years ago even with upgrades it's old technology and there have been huge improvements in the past 50 years. So this shows that the designers 50 years ago didn't do a perfect job. This is what the author means I believe. And a "major nuclear accident" is defined as a level 7 accident in the International Nuclear Event Scale[1], I have no idea if the author refers to it when he talks about major nuclear events but probably not since there has been only one level 7 accident and that's Chernobyl. [1]: http://en.wikipedia.org/wiki/International_Nuclear_Event_Scale http://en.wikipedia.org/wiki/International_Nuclear_Event_Sca...