False Fears About a Test Ban

By Ray Kidder, Lynn Sykes and Frank von Hippel
Sunday, October 10, 1999; Washington Post Page B07

More than 80 percent of the American people want a permanent ban on nuclear weapons tests, and support outside the United States is at least as high. This public support, sustained over 45 years, has powered the movement that persuaded the governments of 154 nations to sign a Comprehensive Test Ban Treaty, now awaiting ratification in the U.S. Senate.

The arguments against the test ban treaty today are the same as those that opponents used to slow its progress for 40 years: the fear that other countries will cheat and be able to reap advantages from small clandestine tests, and the belief that the only way to make sure that a nuclear weapon works is to test it.

The first argument is illustrated by a continuing controversy within the U.S. intelligence community as to whether Russia is conducting small underground nuclear tests on its Arctic test site. There have been repeated leaks, based on spy satellite images, that Russia is continuing to carry out activities on the island of Novaya Zemlya identical to those that used to accompany underground tests. Russian spy satellites are presumably detecting similar activities at the U.S. Nevada test site. The U.S. government says that we are carrying out permitted and essential zero-nuclear-yield ("sub-critical") tests with plutonium. Russia says it is doing the same.

If the United States and other key countries ratify the test ban and the treaty comes into force, we can request an on-site inspection by the international Test Ban Treaty Organization. Inspectors will be able to go to the site where the suspicious activity took place and drill into the test chamber. If the drilling yields fresh fission products, a cheater will be exposed.

Still there is a possibility that a small nuclear test, carried out secretly away from monitored test sites, might escape detection. But what could be gained from such a test? Very little could be gained below the threshold for the "boosting" of fission explosives. And allegations about Chinese nuclear spying to the contrary, boosting the yield of a fission explosive with the fusion of a small amount of tritium-deuterium gas was the key step in the development of modern compact warheads, a "secret" that has been officially declassified for decades.

Testing boosting requires a nuclear explosion with a power of at least a few hundred tons of TNT, and full boosting gives yields of thousands of tons. This is beyond the level that could plausibly be concealed from U.S. seismic monitoring stations. The detection threshold would be lowered further if the treaty came into force and more seismic stations in other countries could be used.

The United States has done almost no testing for nuclear weapons development below 1,000 tons of TNT, so we can be comfortable with a ban on nuclear tests of all sizes.

What about the reliability argument? Here the most powerful counter would be to make public the statistical record of the remarkable success of U.S. nuclear tests. Nearly all of them were developmental tests. The analyzed classified record shows that since the U.S. nuclear establishment mastered the art of designing boosted thermonuclear weapons more than two decades ago, there have been virtually no failures. Except for tests that were exploring new design concepts or testing sensitivity to extreme environmental conditions, the deviations from theoretically predicted yields were remarkably small.

Given this level of understanding and the availability of non-nuclear means, such as sub-critical tests, to confirm the key properties of nuclear materials, there is no question that U.S. nuclear weapons can be maintained without nuclear testing.

On the surface, the debate over the nuclear test ban is about technical uncertainties. Below the surface, it is about competing priorities. Many test ban opponents care only that the United States be unconstrained in the development of nuclear weapons. If this country resumed testing, however, other countries would as well. They would improve their nuclear weapons much more than we would and the world would be pushed back closer to nuclear weapons use.

Ray Kidder, a senior nuclear weapons physicist, retired from the Lawrence Livermore National Laboratory in 1990. Lynn Sykes, a seismologist, is professor of earth and environmental sciences at Columbia University. Frank von Hippel is a professor of public and international affairs at Princeton University.