LIVERMORE, CALIF. — In response to a secret order from President Bush, the nation's nuclear weapons laboratories are developing technology to make the weapons virtually impossible to use if they fall into the wrong hands.
The security system will be part of a new generation of nuclear weapons, approved formally last week by a special panel of the Defense and Energy departments.
A nuclear bomb equipped with such safeguards could theoretically be left on the streets of Los Angeles or Manhattan and terrorists would be unable, even given months of tinkering, to detonate it. Scientists say they are working on technology that would destroy every component inside -- including the plutonium and uranium -- if anyone tampered with it.
But the 3-year-old effort, known as National Security Presidential Directive 28, has drawn strong criticism from many nuclear weapons experts, who doubt that absolute safeguards are necessary or even possible. Instead, they say, the federal government should fix known security weaknesses at bomb labs and factories.
The nation has 6,000 nuclear warheads, on missiles and in military depots in places as disparate as Texas, North Dakota and Europe. They all have electronic locks or other safeguards, known as use controls, that pose a tough challenge to terrorists.
But the new plan aims for a dramatic improvement.
The big leap would involve the self-destruction of the weapon without dispersing radioactivity or causing an explosion. The new system would be able to destroy the electronic and mechanical components and to render the plutonium and uranium materials unusable in any crude improvised device.
How? That's secret. But one possibility is that the bomb would contain a powerful acid or other chemical that would poison the uranium and plutonium. The resulting sludge theoretically could be reprocessed, but only in a highly specialized chemical-processing factory.
And, the thinking goes, terrorists who had access to such a factory probably wouldn't need to steal a bomb.
The nation's two nuclear weapons laboratories -- Lawrence Livermore in California and Los Alamos in New Mexico -- are competing to design the new generation of bomb, known as the reliable replacement warhead. The Nuclear Weapons Council, a panel of top Defense and Energy officials, could select a winner as soon as this week.
