There are only 3 things wrong with nuclear reactors: design, construction, and operation. It appears that the atomic energy community considers fission reactors as versions of thermal power plants, only more powerful. They are wrong. They are wrong in the same way that the people in the military and political establishments who thought of nuclear bombs as stronger dynamite were wrong. Top scientists such as Feynman and Oppenheimer knew better, and were terrified of the bomb.
Nuclear energy is completely different from the energy that comes from chemical reactions which combine carbon with oxygen. The underlying nuclear forces are more powerful, longer-lasting, and more destructive to chemical-based lifeforms by orders of magnitude. A quantitative change means a qualitative change.
Because fissile nuclear material can release so much energy and can keep releasing it over long periods of time, it is not possible to design, build, and operate fissions reactors safely - certainly not with the technological and managerial level we currently employ, which is appropriate for burning gas, oil, and coal. This fact was demonstrated by experience: if the Japanese cannot use their reactors safely, then who can? Neither the richest and freest country in the world could; nor the most secretive, militarized, and centrally planned; now we see that the best organized and most disciplined people in the world aren't able to design, construct, and operate nuclear reactors in a safe manner.
Supporters of nuclear power will say that Japan suffered an earthquake. Yes, they have earthquakes and tsunamis more often then most other countries, and therefore are better prepared for them. In the time scales of atomic power, every place will suffer natural disasters for which even the Japanese haven't prepared. Anyone who thinks they can operate a nuclear power plant safely is like a drunkard who thinks only bad drivers get into accidents.