Pakistani's Nuclear Black Market Seen as Offering Deepest Secrets of Building Bomb

William J. Broad & David E. Sanger, NY Times:

Nuclear investigators from the United States and other nations now believe that the black market network run by the Pakistani scientist A. Q. Khan was selling not only technology for enriching nuclear fuel and blueprints for nuclear weapons, but also some of the darkest of the bomb makers' arts: the hard-to-master engineering secrets needed to fabricate nuclear warheads. READ MORE

Their suspicions were initially raised by the discovery of step-by-step instructions, some of which appear to have come from China and Pakistan, among the documents recovered last year from Libya. More recently, investigators have found that the Khan network had offered similar materials to Iran.

The secrets range from how to cast uranium metal into the form needed at the core of a bomb to how to build the explosive lenses that compress the core and start the detonation.

The discoveries have set off a debate in the intelligence community about whether those technological skills made their way to North Korea and Iran. President Bush has vowed he will not tolerate either country's obtaining a nuclear weapon.

Iran was a customer of the Khan network, and while it appears to have turned down the offer of the engineering secrets in 1987, some intelligence officials are concerned that it picked up the technology elsewhere. North Korea, which is believed to have two separate bomb projects under way, also did business with the Khan network, although precisely what it obtained is not clear. ...

The inability of intelligence officials to track down the whereabouts of the bomb-making instructions underscores the fact that more than a year since Mr. Khan's arrest and pardon by Pakistan's president, Gen. Pervez Musharraf, there are still many mysteries about what exactly the Khan network was selling, and to whom.

The United States has not been allowed to interview Dr. Khan, and Ms. Rice raised concerns about cooperation in the nuclear investigation when she met with General Musharraf last week. But American officials and the International Atomic Energy Agency are beginning to extract information from Dr. Khan's chief deputy, Buhari Sayed Abu Tahir, who is in jail in Malaysia. "It's becoming clearer to us that Khan was selling a complete package," said a senior American official involved in the setting of nuclear strategy. "Not a turnkey operation - that would be overstating it - but close to it."

To investigators and other experts, the discovery that Dr. Khan was selling step-by-step directions for making crucial parts of a bomb was startling.

"The real secrets are in the details of the metallurgy, the manufacturing and the engineering," said Siegfried S. Hecker, director of the Los Alamos weapons laboratory from 1986 to 1997 and now a senior fellow there.

Intelligence officials in the United States and European diplomats said documents from Libya and Iran showed the Khan network had offered for sale instructions on such tricky manufacturing steps as purifying uranium, casting it into a nuclear core and making the explosives that compress the core and set off a chain reaction. Unlike bomb designs themselves, these manufacturing secrets can take years or even decades for a country to learn on its own.

Thomas B. Cochran, a senior scientist at the Natural Resources Defense Council in Washington, a private group that tracks nuclear arms, said having the manufacturing instructions was a tremendous leap beyond rudimentary bomb designs. "I can show you the schematic of an automobile that has a engine and a transmission, and go to a book that describes how the pistons work," he said. "But if you actually want to build a car, you need the details and step-by-step procedures for everything from casting the components, to machining them, to assembling them."

Dr. Khan is a metallurgist and an expert at making both centrifuges that enrich uranium and nuclear warheads. Investigators say that in the early 1980's, he obtained the detailed blueprints for a Chinese atomic bomb.

The first public hint that Dr. Khan's network traded in bomb designs and engineering instruction emerged in 1995 after United Nations inspectors in Iraq found a set of documents describing an offer made to Baghdad before the Persian Gulf war of 1991. An internal Iraqi memorandum, dated June 10, 1990, told of an unidentified middleman saying that Dr. Khan could help Iraq "establish a project to enrich uranium and manufacture a nuclear weapon" and that he was "prepared to give us project designs for a nuclear bomb."

The Iraqis never took up the proposal, which they judged a scam or a sting operation. Western experts also questioned its authenticity.

But the apparent validity of the offer became clear in late 2003 when Libya showed investigators blueprints for a 10-kiloton atomic bomb that it got from the Khan network. The International Atomic Energy Agency reported that the documents included information on both nuclear design and fabrication, calling it of "utmost concern."

The Libya disclosure touched off a global hunt for more Khan documents. Officials in the United States and Europe said the trail recently led to Dubai, where Mr. Tahir, the Sri Lankan businessman who was Dr. Khan's deputy, ran a front company, SMB Computers. They said reliable network sources had told of seeing bomb documents there that contained step-by-step instructions on how to fabricate components for nuclear arms. Intense searches in Dubai, they added, had so far failed to turn up the documents.

The latest development in the hunt came March 1 with the disclosure of the network's 1987 offer to Iran of centrifuge machines and materials, as well as "uranium reconversion and casting capabilities," according to an I.A.E.A. report.

While investigators have determined that Tehran paid precious hard currency to the Khan network for nuclear equipment, it appears to have turned down the offer of the engineering secrets necessary to build the core of a nuclear weapon.

European and American officials said they considered the 1987 transaction some of the best evidence that Iran sought, starting at least 18 years ago, to assemble the technologies needed to build a nuclear arsenal.

"It adds a piece to the puzzle that makes the whole thing more incriminating," a European official said. "But is this a smoking gun? No. Does this make people more suspicious? Yes."