Chernobyl: We don't build plants like that. "It can't happen here."
TMI: A good example of what happens to the environment when a serious accident with multiple screw-ups in succession are done in an American plant: a tiny amount of radiation leaks, no injuries, no fatalities, no serious damage to the environment. Compare that to the cost of a single tanker leak, or a single well fire. Nuclear power is much safer than any other technology, but the environazis just won't have any of it - despite the fact it is the best thing we could possibly do for the environment.
Besides, Post-TMI was used to upgrade existing plants and new plant designs and procedures to address those problems. Present designs are even less suseptable to accidents.