From: Kurt Feltenberger

> 
> With the resources of a solar system similar to ours, how many nuclear
> weapons would it be possible to construct?

Well, the molar abundance of Uranium is about 1/10^12 that of hydrogen for a mass abundance that is somewhere around 1/10^10, most of it can in principle be processed into bombs via breeder reactors, the mass of the solar system is around 2e+30 kg, so there's around 10^20 kg of uranium that can be processed into Pu-239 and around 10^18 kg of U-235. Critical mass is 52 kg of U-235 or 10 kg of Pu-239, which can be reduced somewhat by compression, so figure a lower theoretical limit of around 10^19 nuclear weapons.

Of course, much of that is totally inaccessible. The fraction of U in asteroids and planetary crusts will be on the order of 1/10^8, the mass of the asteroid belt is maybe 10^20 kg, so asteroid mining might only allow building on the order of 10^11 weapons.

In any case, it's high enough to probably be a nonfactor; it's mostly an issue of 'how much money are you willing to spend/