The generating process with the reactor on line also causes thermal pollution with the secondary loop cooling water absorbing heat energy from the primary reactor cooling loop and being circulated into an outdoor pond or through the parabolic cooling towers that have become an immediately recognizable emblem of the industry. Cooling ponds of many acres area can have temperatures above seventy degrees Fahrenheit in the dead of a northern states' winter.
Worst of all is the question of the disposition of spent fuel and the decommissioning of these plants. More than sixty years into the commercial nuclear age, we still have no clear concept of how to guarantee safe, permanent disposal of these materials to maintain containment of the radioactivity that remains deadly for thousands of years.
Our search for geologically stable places to dispose of these materials has yielded little but the knowledge that Earth has no geologically stable areas on the required time scales. Then there is the problem of how to communicate with people ten thousand years along, when we have no idea of what their language or culture will be, except that it is likely to be very different from ours.
This is also the technology that yields byproducts that may be enriched to weapons grade. Such enriched uranium and plutonium are the critical components of nuclear weapons, and we already have as much of that as we can stand.