Forbes.com October 27, 2006
Nuclear Tests
By Elisabeth Eaves
The Elevator Pitch
The United States conducted the world’s first nuclear test in July 1945, secretly exploding a plutonium bomb with a 20 kiloton yield in the New Mexico desert. America’s nuclear monopoly lasted only until the Soviet Union conducted its first test in 1949, setting off the arms race that became the defining feature of the Cold War. In 1952, the U.S. upped the ante when it tested the first hydrogen bomb, capable of massively more destructive power than the first nukes.
The Soviets exploded the biggest nuclear weapon ever tested, a 50 megaton hydrogen bomb, over an Arctic peninsula in 1961. Most historians’ view is that the impractically large “Tsar Bomba” was pure Cold War saber-rattling, never intended for use in warfare.
The Soviet Union conducted its last nuclear test in 1990, and the United States followed suit two years later. The other nuclear powers that have signed the Nuclear Non-Proliferation Treaty (NPT)--France, Great Britain, and China--have also been observing a testing moratorium. But India and Pakistan, neither of which has signed the NPT, both tested nuclear weapons in 1998.
Nuclear tests not only reveal whether bomb designs work, but can provide information on after-effects like nuclear fallout. Obviously, tests now also serve another purpose: “The first nuclear test by any state today is about sending a political message,” says Michael Levi, author of The Future of Arms Control and a fellow at the Council on Foreign Relations. A weapon can’t be a credible threat if no one knows you have it.
Why Now?
North Korea conducted its first nuclear test on Oct. 9, becoming the world’s eighth openly declared nuclear state. Kim Jong Il’s regime, which unilaterally withdrew from the NPT in 2003, has not ruled out another test. On Wednesday President Bush warned North Korea of “grave consequences” if it tried to sell nuclear arms.
The Nitty-Gritty
Nuclear tests have been conducted in and above the atmosphere, underwater and underground, but fears of contamination from nuclear fallout led to the 1963 Limited Test Ban Treaty, which barred all but the last.
To carry out an underground test, the nuclear device is placed in either a tunnel or a deep hole--the higher-yield the bomb, the deeper the hole. When the U.S. conducted tests, scientists would drill a shaft roughly three to ten feet in diameter and from 700 to 2,500 feet deep, or up to nearly a half mile. Radiation detectors were placed some distance back to monitor the escape of any releases into the atmosphere.
Nuclear bombs can be made with either uranium or plutonium, and while it’s cheaper and easier to acquire the basic ingredients--spent fuel rods--for the latter, plutonium bombs are also more difficult to make. They must be detonated by an implosion in which multiple triggers, set around a perfect sphere, fire simultaneously. “If one is off by even a millionth of a second, so that the implosion isn’t spherical, it’s not going to work,” says Lt. Col. (Retired) Edward Corcoran, a senior fellow at GlobalSecurity.org and former strategic analyst at the U.S. Army War College. In August 1945 the U.S. dropped two bombs on Japan, “Little Boy,” a cylindrical uranium bomb, and “Fat Boy,” a round plutonium bomb. It never tested the uranium bomb because it was so sure it would work.
Nations going nuclear don’t necessarily want to keep it secret. If they do, though, scientists can detect explosions in several ways. They can measure seismic shock waves, which occur in a pattern different from those caused by earthquakes. They also can collect and analyze the contents of atmospheric samples from near the test site. And sometimes they can use satellites to look for the distinctive flash of light caused by a nuclear explosion.
North Korea’s plutonium bomb appears to have fizzled, with measurements by South Korea, France and the United States suggesting a size of less than one kiloton. GlobalSecurity.org’s Corcoran thinks it was likely a plutonium bomb that failed to detonate correctly.
On The Other Hand
Maybe some nuclear testing is good. Many U.S. scientists and weapons experts have been pressing to return to the practice. They argue that new warhead designs need to be tried out, and that the older the existing stockpile gets, the less sure they can be of its effectiveness.
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