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The Pakistani scientist Abdul Qadeer Khan has been described as a man who sold more nuclear secrets than anyone else in history. So there's enormous concern among U.S. nuclear experts over his release after five years of house arrest in Pakistan. Pakistan says it will keep a close eye on Khan, but there's still fears he could try to resume his old activities. NPR's national security correspondent Jackie Northam reports.
JACKIE NORTHAM: It was a sight that many people in the non-proliferation community hoped they'd never see. On a sunny afternoon late last week, A.Q. Khan stepped out of his home in Islamabad essentially a free man - after Pakistan's high court lifted restrictions against him.
The 73-year-old Khan is considered the father of Pakistan's nuclear weapons program and is hailed there as a national hero. He also headed up a vast black market nuclear weapons network, selling technology to North Korea, Iran and Libya.
Leonard Spector, the director of the D.C. office of the James Martin Center for Nonproliferation Studies, says Khan was unique because he was a great networker and he had access to the technology.
LEONARD SPECTOR: He had not only knowledge and know-how about uranium enrichment centrifuges and a nuclear weapon design, but he had access to physical objects. He could distribute to customers actual centrifuges that had worked in Pakistan that were no longer being used.
NORTHAM: In 2004, after a long international investigation, Khan admitted to illicitly spreading nuclear technology. His network was broken up, and several key operatives in countries such as Switzerland and South Africa were arrested. But there have been lingering questions over whether Khan's network was fully disrupted. Spector says virtually all of the operatives who were arrested have since been released. And now so too has Khan.
It's possible that Khan - who is ill with cancer - will live a quiet, uneventful life. But David Albright, the president of the Institute for Science and International Security, says Khan still represents a risk. He might sell off assets such as nuclear weapon designs or centrifuge designs that might be held by the Khan network and remain outside Pakistan.
DAVID ALBRIGHT: And if Khan is feeling vindictive or feeling that there's more money to be made, then he could actually try to activate some of these old relationships. I don't think he would be in a position to restart a network or anything like what he had, but he could sell off the surplus inventory.
NORTHAM: Albright says there are potential customers: countries such as Syria, Burma or Sudan, or terrorist organizations or individuals who want the weapons and have the money to pay for them. Albright says one major concern is not knowing what information Khan still possesses - in his head or elsewhere. Albright points to three sets of nuclear weapons designs - two of them partial - that were discovered on a computer in Switzerland in 2006. He says those designs link back to Khan.
ALBRIGHT: Two of the designs where drawings were found are for warheads that are relatively small and would be just the type that could solve some of Iran's problems. They have to miniaturize their nuclear warhead to fit it on missiles.
NORTHAM: The U.S. has pushed the Pakistani government to reverse its high court's decision. Pakistani officials say that there will be complete vigilance when it comes to Khan, that his calls will be monitored, his travel curtailed, and his guests vetted.
When asked if the State Department was satisfied with Pakistan's assurances, spokesman Robert Wood sounded less than fully confident.
ROBERT WOOD: Well, certainly we have to take them at their word. But of course we'll have to see how things play out with regard to these assurances.
NORTHAM: Clark Murdock, a nuclear strategy specialist and a senior adviser at the Center for Strategic and International Studies, says at the moment the U.S. can put only so much pressure on Pakistan to hold Khan.
CLARK MURDOCK: Why would the United States be making a big deal about A.Q. Khan - whether he's under house arrest or not - when you consider we've got a lot more problems with al- Qaida leaders, when they're in sanctuary in northern - the northern territories. I mean, that's something that we really care about.
NORTHAM: Leonard Spector says Khan and his former operatives will be likely be under very tight surveillance by everyone. He says he's more worried about the signal Khan's release sends - that Pakistan doesn't take nuclear weapons smuggling seriously.
SPECTOR: To me the more damaging outcome was the symbolism, the fact that Pakistan did not stand by a tough nonproliferation commitment.
NORTHAM: Not a good sign for a nuclear armed country.
Jackie Northam, NPR News, Washington.
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