The AQ guys allegedly purchased these devices from disillusions Russians. They did not make them.
It would not be impossible to make one. There are numerous reports of fissionable material missing from railroad freight yards. The tools available to common people of today are highly more sophisticated that those that were available to the Manhattan project of the 1940s. Never assume that any enemy lacks the technical knowhow to accomplish anything. The time required to stage impressive attacks is generally consumed in preparations, including attendance at schools. Flight schools, or engineering schools. Any real difference?
It would not be impossible to make one. There are numerous reports of fissionable material missing from railroad freight yards. The tools available to common people of today are highly more sophisticated that those that were available to the Manhattan project ...How often do you suppose that certain areas are 'scanned' from street level (via drive bys) with sensitive radiation detectors/Geiger counters?
Are the border crossings into Mexico equipped with the appropriate sensors (DON'T even suggest that a practical-sized device (non-suitcase sized) is going to be dragged across the desert into the US!)
The number of times this topic has been covered on FR is in the hundreds. There is simply no technical possibility that the foot-locker sized transportable atomic weapons that the USSR produced in the late 70's through mid '80's remain serviceable and usable today. If you possessed one you'd been in a world of hurt trying to get it do anything other than give you a bad case of radiation poisoning.
Where are the numerous credible reports of missing fissionable material? It's always brought up, but the amounts missing always end up being trivial, or the actual missing material of the wrong type.
There are clearly Pakistanis and Iraqis with the requisite knowledge to build a bomb. To succeed they would need series of unlikely events, not to mention plenty of time and advanced facilities to build the bomb. It will, of course, not be a suitcase sized bomb, but a large, crude, poorly shielded (and therefore easily detected) device. It will throw off radition, sicken and even kill those who work on it and transport, and likely become unstable or unusuable during transport.
You people think that building a servicable, transportable nuclear weapon is something that a few Islamists with an engineering degree can pull off. If so, how did Sadaam not get the job done in 20 years of trying? Why did it take the North Koreans so long as well? The odds of such a weapon working is slim to none.
As for purchasing these devices from disaffected Russians, this story has been hyped and discredited a thousand times.