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Written Statement
of Stephen M. Younger
Associate Laboratory Director for Nuclear Weapons
Los Alamos National Laboratory

before the
Senate Judiciary Subcommittee
on Administrative Oversight and the Courts

"A Continuation of Oversight of the Wen Ho Lee Case"

October 3, 2000

Thank you, Chairman Specter, for the opportunity to discuss facts related to the case of Dr. Wen Ho Lee.

The United States developed the most advanced nuclear arsenal in the world through a combination of complex computer calculations, laboratory experiments, and nuclear tests. Key to the design process was a set of sophisticated computer codes, supported by databases that describe the behavior of materials under extreme temperatures and pressures. These codes allowed us to make reasonably accurate predictions of the performance of nuclear devices, predictions that were validated by nuclear tests. I can say based on my review of the contents of the tapes made by Dr. Lee that he systematically collected a set of nuclear weapons design tools that would enable the possessor to perform sophisticated calculations of nuclear explosives. Further, Dr. Lee's tapes contained the actual designs of a number of nuclear explosives, including some weapons currently in the U.S. arsenal.

It has been said that much of the information contained on the tapes made by Dr. Lee is available in the open literature. This is misleading. First, while much of the fundamental physics used in nuclear explosives design is unclassified, the specific combination of physics required to produce an adequate approximation of nuclear weapons performance is a secret. Indeed, one of the most sensitive pieces of knowledge in nuclear weapons design is what is "good enough" to adequately model a weapon. It is always better to put in more detail, to be more accurate, but even the largest computers in the world cannot handle all of the complexities involved in a nuclear explosion. Experienced physicists could waste a great deal of time trying various approximations before they found ones that were sufficiently accurate and sufficiently fast for practical calculations. U.S. design codes are the result of decades of work involving hundreds of people who had access to data from over one thousand nuclear tests.

Second, some of the information on plutonium and uranium and other materials contained on the tapes was obtained through nuclear testing. It is not found in the open literature. Some of the data contained on the tapes cannot be obtained by any means other than nuclear testing.

Third, the tapes that Dr. Lee made contained the designs of actual nuclear devices, some of which have been successfully tested. These designs are certainly not available in the open literature. Providing unauthorized persons with the designs of our nuclear weapons could enable them to advance their own weapons program and identify and exploit weaknesses in our nuclear defenses.

Based on my knowledge of foreign nuclear weapons program, I think that I can say with confidence that our computer codes and databases are the finest in the world. No other country had the technology base that was necessary to perform some of the measurements that we made in nuclear tests, measurements that were used in the calibration and validation of the computer codes downloaded by Dr. Lee. In my opinion it would be impossible at least on a time scale yielding strategic surprise for any country in the world to duplicate information contained on those tapes without nuclear testing, regardless of how much money they were willing to spend or the intelligence of their scientists. There are simply too many unknowns that cannot be resolved without extensive nuclear testing.

During my testimony at Dr. Lee's detention hearing in December 1999 I stated that the information that he downloaded could, if placed in the wrong hands, change the global strategic balance. Although the information itself does not convey all of the technology necessary to build deliverable weapons, it could advance the design effort enormously. Production of a weapon that would be a realistic threat still requires special nuclear materials, special engineering and fabrication skills, and a capable scientific cadre.

Nuclear weapons are the most destructive weapons ever created by humankind. They are the only devices that can threaten the conventional military superiority of the United States. In the wrong hands the information downloaded by Dr. Lee could enable a proliferant nation to design relatively crude but effective nuclear weapons without nuclear testing. Those weapons would certainly not be as sophisticated as the weapons contained in the U.S. arsenal but they would be credible enough to influence other nations, including our own. A nation that already had nuclear weapons could use the codes to help maintain their weapons or to improve them. The information contained on the tapes could also be used to find and exploit potential vulnerabilities in U.S. weapons.

The United States expects our existing nuclear weapons to last a long time. As other countries advance in their military capabilities, we must be careful that our nuclear deterrent is not placed at risk by the compromise of our designs.

In summary, it is my opinion that the information contained on the tapes made by Dr. Lee could, in the wrong hands, pose a grave danger to the national security of the United States.

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