Oddly enough, nuclear warheads are largely obsolete, aside from being used as weapons of terror. Air-Fuel Explosives deliver about the same destructive capability over roughly the same area, but without the fallout hassles. And are FAR cheaper. You want a source of fissionables for nuclear plants? Decommissioning some of the Cold War era nukes would probably go a long way. After all, it's not like we don't have freeking Rail Gun anti-missile defenses, making the entire concept of ICBMs moot.