[zizee]

Is it much worse than the Banqiao Dam disaster where an estimated 90-230k people died? What would happen if there was a catastrophic failure of the Hoover dam?

This is not to say nuclear failure isn't bad news, just that many large scale electricty generating schemes have a big downside and it's going to be a big ask to find 100% benign alternatives.

http://en.m.wikipedia.org/wiki/Banqiao_Dam