TAB, I just got back to this thread, I know how easy it is to build a nuke.
Basically all you have to do is drop 1/2 of your critical mass on the other 1/2 and you get your boom.
The only thing that is a challenge to aspiring countries is acquiring the nuclear material, that is why countries like Iran and NK first build a legitimate power plant, then they build the centrifuge cascade to "Enrich" the uranium from spent fuel rods.