Minamata and Bhopal were chemical plants, not power generation plants. Dam failures are always ugly, but they are rather predictable and preventable. And the Great Smog of London killed more people than Chernobyl but was caused by low-grade coal burning in low-tech furnaces. Even if we buy the suspicious number of 12 million, it's not a coal power plant accident.
Don't get me wrong. I like nuclear. I just know it's dangerous and the consequences of one accident can be pretty scary and long lasting.
Chernobyl, an INES-7 killed 56 people. Plus another 4000 from radiation.
As previously linked, check these out: http://en.wikipedia.org/wiki/Great_Smog http://en.wikipedia.org/wiki/Bhopal_disaster http://en.wikipedia.org/wiki/Banqiao_Dam http://en.wikipedia.org/wiki/Minamata_disease
The Great Smog of London killed twelve million people. Banqiao Dam killed 171 000 and destroyed homes for another eleven million people.