[Teacher317]

Radioactivity is not what makes a nuclear reactor work. The dirty little secret is that, essentially, nuclear power plants do nothing more than boil water. The heat generated by two elements being put together is what boils the water. It just so happens that the most heat is generated by using radioactive elements.

However, once it has been "used up" (ie, it has changed to a new radioactive element after the heat-generating interaction with another element), the fact that they're radioactive does not help. In their new state, they don't help generate heat anymore. Therefore, they're useless as "nuclear fuel". Now they're just really interesting metals that also happen to be rather dangerous to most living things, due to that radioactivity.

(Warning: that is an over-simplified explanation, but hopefully it helps clarify the basics.)

[wizr]

Thanks. Science was not my forte.