As far as nuclear weapons are concerned, I already explained why countries should try to create or possess as much nuclear weapons as it can.
Now for the power thing. Yes. It has a certain disadvantage of radioactivity. But its advantages far outweigh the SOLE disadvantage of radioactivity. As coal, oil and natural gas becomes exhausted, it will be a valuable source of energy. It will be necessary to maintain our current standard of living. To do that, we will HAVE to use nuclear power.