Even though nuclear power plants do not give off carbon dioxide, they do create radioactive waste as part of the process. These spent fuel rods must be stored somewhere to prevent them from releasing the radioactive waste from seeping into the environment. Even if a single, well-protected location is agreed upon, the nuclear industry still faces the problem of safely transporting the spent fuel from the plant to depository without it leaking, or worse, falling into the wrong hands.
Even most skeptics of nuclear power will admit that the chance of a meltdown has decreased over the years since Three Mile Island and Chernobyl. However, the chance still exists and the consequences would be devastating. During a nuclear meltdown, the radioactive waste is released into the environment, exposing people in the general vicinity to potentially lethal levels. In addition, the exposed land would become contaminated for decades if not centuries.
During the refining process, uranium mined for nuclear power plants can be converted to use for nuclear weapons. In addition, spent fuel can be refined to separate out the weapons-grade plutonium, a byproduct of the process, and uranium for use in weapons. Only a small amount is needed for a nuclear weapon, and the consequences of this material falling into the wrong hands would be disastrous. Even if you thought that nuclear reactors in one country, such as the United States, would be safe, reactors in other countries, especially less developed nations, may not be so well guarded.