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Experts Question Effectiveness Of Nuclear Weapons over Time

By Ralph Vartabedian
Los Angeles Times
LOS ALAMOS, N.M.

President Clinton laid down U.S. nuclear weapons policy in July 1994, saying: "We will continue to maintain nuclear forces of sufficient size and capability to hold at risk a broad range of assets valued by such (hostile) political and military leaders."

The problem is how to assure the reliability and safety of these forces without testing, and how to retain the expertise of scientists when nuclear weapons are neither being designed nor produced.

A nuclear bomb contains roughly 6,000 parts, including 50 pounds of high explosives wrapped around a radioactive plutonium sphere. Jas Mercer-Smith, a Los Alamos National Laboratory scientist, compares nuclear bombs to a 747 jetliner in terms of technical sophistication.

Is it possible, Mercer-Smith asks, to park a 747 for two or three decades and have 100 percent confidence that the engines would start and the plane would fly at a moment's notice? Some nuclear weapons are more than 20 years old, and experts say the bombs can go no more than 30 years without being torn apart and updated.

Scientists are increasingly worried that plastic explosives in the bombs will chemically change over decades, plutonium pits will corrode and electronic components will degrade during exposure to radioactivity.

The archive now being compiled by weapons experts - the Knowledge Preservation Project - will preserve know-how that should help to assuage these doubts. The library, for example, will allow scientists to compare bomb components as they age to the original design and examine old test data to see how anomalies may have affected bomb performance.

In addition, the Energy Department's $40-billion "stockpile stewardship" program will construct massive testing machines, including the $1-billion National Ignition Facility laser at the Lawrence Livermore National Laboratory in Livermore, Calif., and the $124-million Dual-Axis Radiographic Hydrotest Facility at Los Alamos.

Despite 50 years of research, scientists say they have only a primitive understanding of the precise physics that occur in a nuclear detonation. These machines will conduct high-energy experiments that simulate conditions in a nuclear bomb, allowing scientists to refine computations that are central to weapon science.