Three years ago the federal government began passing out pills that may protect against some of the most dangerous effects of radiation. Fourteen states whose residents live near nuclear power plants haven't bothered to accept them.

Never mind that experts say the over-the-counter potassium iodide pills are the cheapest and easiest way to prevent radiation poisoning -- especially in children -- in case of a nuke accident. Last year, a report commissioned by Congress recommended that everyone under 40 near a nuclear power plant should have the pills on hand.

Despite the efforts of nuclear safety advocates and medical associations, the pills' existance remains fairly obscure. "You sit there scratching your head and say, 'Why aren't they giving it out?'" said Alan Morris, president of Anbex, the only potassium iodide pill manufacturer in the United States.

Physicists have discovered a new signature characteristic of radiation that could be used to detect the gamma ray emissions of smuggled illegal nuclear materials, even if they are concealed among large bundles of shipping containers.

The problem of detecting smuggled nuclear weapons or devices presents an enormous challenge for security officials. More than 6 million containers enter U.S. ports annually. West Coast facilities alone process about 11,000 a day, or an average of eight every minute. A single container can hold up to 57,000 pounds.

Officials have been attempting to figure out how to inspect containers for smuggled nuclear materials without disrupting the flow of the nation's commerce.

The physicists, from Lawrence Livermore National Laboratory in Berkeley, Calif., think they have come up with the solution.

"We have identified a new radiation signature, unique to fissionable material, that exploits high-energy, fission-product, beta-delayed, gamma ray emissions," said lead researcher Thomas Gosnell. "Fortunately, this signature is robust in that it is very distinct compared to normal background radiation, where there are no comparable high-energy gamma rays."

To cope with the possibility that terrorists might someday detonate a nuclear bomb on American soil, the federal government is reviving a scientific art that was lost after the cold war: fallout analysis.

The goal, officials and weapons experts both inside and outside the government say, is to figure out quickly who exploded such a bomb and where the nuclear material came from. That would clarify the options for striking back. Officials also hope that if terrorists know a bomb can be traced, they will be less likely to try to use one.

Critics say American 'double standard' will undermine efforts to curb nuclear arms.

Research on a new generation of precision atomic weapons by the Bush administration threatens to undermine international efforts to stop the spread of nuclear arms and to tarnish recent successes, according to diplomats and nonproliferation experts.

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