The IAEA describes the activities of Khan and the sophisticated network of black marketers associated with him as "the most serious case of nuclear proliferation in recent times."
Corey Hinderstein, a nuclear nonproliferation analyst at the Institute for Science and International Security (ISIS) in Washington, D.C., says the investigation into the black market has revealed a well-organized network selling nuclear secrets at high profits.
"I think the scope of the nuclear trafficking network that is slowly being uncovered is actually more extensive than many experts might have thought. By more extensive, I mean the level of coordination and cooperation between these people really is an organization, as opposed to random criminals," Hinderstein said.
She continues, saying, "the scale of the type of technology that was being sold is [worrisome]. And by that I specifically refer to actual nuclear weapons designs. I think many people have for years suspected A.Q. Khan in Pakistan of possibly selling off his centrifuge knowledge. But the idea that he is actually selling wholescale weapons designs, some of which have a level of detail that are precise enough for manufacture, is quite scary."
Khan has confessed that he and associates traded nuclear secrets from 1987 to the mid-1990s. According to the IAEA, he sold gas centrifuges that can be used to produce nuclear reactor fuel or for attempts to make weapons-grade material. He also sold nuclear weapons blueprints and designs.
Nuclear experts say the network was first organized by Khan decades ago to secretly procure nuclear technology for Pakistan in its arms race with India. But it was later used by Khan to also organize nuclear transfers to clients in other states for financial gain.
The extent to which the technology transfers to other states was known by previous Pakistani governments remains uncertain. Islamabad -- which pardoned Khan after he confessed and said he acted independently of the government -- has refused any outside investigation into Khan's activities.
The unexpected scope of the black market in nuclear technology is raising concerns that international terrorist groups could have greater access to such materials than previously thought.
IAEA spokesperson Melissa Fleming says her agency is trying to determine whether the black market network sold to underground organizations, as well as to states.
"What has been exposed over recent months through our inspections in Iran and in Libya is that there is a very extensive nuclear black market out there. We are aware of at least two of the customers. We are very concerned that there were other customers, and we are talking about both countries as well as terrorist groups," Fleming said.
But Fleming says there are good reasons to think the network did not include terrorist groups among its clients. One is that the network appears to have been offering technology that would be difficult for terrorist groups to apply without major industrial facilities at their disposal.
"In the case of terrorist groups, we do think that the main product that was on offer from this nuclear network -- which was centrifuge designs, centrifuge components -- would be something that a terrorist group might be unlikely to seek, just because you really would need a state apparatus behind you, a major industrial structure, and large numbers of scientists. It wouldn't be easy for an underground group to put together," Fleming said.
But she says the danger remains that black market networks could enable terrorist groups to pursue at least one way to produce a nuclear bomb. She notes that if terrorists were to buy the kind of weapons blueprints Khan's group sold to Libya, and then could also obtain a stock of already enriched uranium or plutonium, they could conceivably produce a nuclear device by themselves.
So far, there is no evidence that terrorist groups have been able to do that. Nuclear experts say there is no known case to date of someone stealing the amounts of enriched uranium or plutonium required to make a nuclear weapon and no state possessing such materials is known to have offered such amounts for illicit sale. But security at storage sites for nuclear materials in the former Soviet Union and at research reactors in some parts of the world remains a cause for concern, and the IAEA has often called for it to be tightened.
(The second part of this series looks at some of the difficulties of cracking down on the nuclear black market.)