As Congress moves closer to a vote on repealing a ban against developing smaller, more usable nuclear warheads, a group of prominent scientists issued a letter Monday urging that the prohibition be kept in place.

The Senate Armed Services Committee has already voted in favor of a total repeal of the prohibition, passed 10 years ago as a means of preventing the use or proliferation of nuclear weapons. But the House Armed Services Committee voted on a compromise version that would permit design work but stop short of production of low-yield warheads.

The Bush administration and many Republicans in Congress have said the law should be repealed because, in a world of dangerous new threats, the U.S. needs a new generation of low-yield weapons for pinpoint strikes, largely against deeply buried caches of weapons of mass destruction. Democrats have fought bitterly to retain the law, saying that a new nuclear program would just provoke other nations to build their own.

In a letter organized by the Union of Concerned Scientists, the eight scientists -- all of whom had been closely involved in the weapons program, argued in favor of the compromise version of the bill. The scientists argued that the proposed weapons:

-- Are unlikely to work as proposed.

-- Would create dangerous plumes of radioactive dust.

-- Would be more likely to disseminate chemical or biological agents in bunkers than to incinerate them.

The bigger objection, though, was on political grounds.

"It is counter to U.S. interests for the United States to pursue new nuclear weapons at a time when the highest U.S. priority is preventing other countries or groups from obtaining them," the authors said. "The perception that the United States is pursuing these weapons and considering their use would give legitimacy to the development of similar weapons by other countries. "

They added, "The United States should be seeking to increase the barriers to using nuclear weapons, not decreasing them."

A low-yield weapon refers to a warhead with a force of five kilotons or less, about a third the force of the warhead that killed 140,000 when dropped on Hiroshima in 1945.

The eight scientists are Hans Bethe, Sidney D. Drell, Richard L. Garwin, Marvin Goldberger, John P. Holdren, Albert Narath, Wolfgang K.H. Panofsky and Bob Peurifoy.

In an interview, Drell, professor emeritus at Stanford University's Linear Accelerator Center, emphasized that he favors a strong nuclear arsenal and maintaining a strong weapons design complex. What he objects to, he said, is creation of more usable low-yield weapons, which he believes will weaken rather than strengthen U.S. security by encouraging other countries to follow suit.

"The military value of these weapons would be very limited," he said, because of the likelihood that a bomb would just spread the chemical or biological weapons it targets.

The biggest impact would be a dangerous erosion of long-standing U.S. efforts to prevent the spread of nuclear weapons, through the Non- Proliferation Treaty.

A number of Republicans have countered that a number of countries are already attempting to develop nuclear weapons, such as North Korea and Iran, and that the treaty has done little to deter them. They add that the only effective deterrent would be a warhead that a foe believes the United States would really use in an attack.

The huge nuclear warheads now in the arsenal are so destructive that an enemy might calculate that the United States would never unleash them.

Drell said that any erosion in the Non-Proliferation Treaty is far more dangerous to the United States and that the Bush administration's efforts might just legitimize the start of a new nuclear arms race. Worse, the scientists said in the letter, the development of a new weapon might require a resumption of testing, which was halted in 1992, and that could also trigger a wave of tests by other countries.

"If that happens, it would make us less secure, not more," Drell said.

©2003 San Francisco Chronicle

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