Eli5: Why is it so hard for a country to make a nuclear bomb?

Question

I’m assuming the science of making one is out there. Why then countries like Iran who so want to develop atomic weapons haven’t been able to do so?

In: Physics

Answer 1

I’m sure someone with more knowledge will be along to provide a better answer, but…

Designing the enclosure, primary explosives, and firing mechanism for a nuclear bomb are (relatively) easy. The way they work is reasonably well understood at a conceptual level.

Refining enough fissile material when access to the ingredients is tightly controlled by nuclear-armed countries who want to remain the only nuclear-armed countries… now that’s the tough part.