U.S. Sets Off A-Weapon in Nevada : Nuclear: The test is the third since Iraq’s invasion of Kuwait triggered the Mideast crisis.

The United States detonated a nuclear weapon 2,000 feet beneath the Nevada desert Friday, the third such test since the Iraq-Kuwait crisis.

The blast registered 5.7 in magnitude at the Earthquake Center in Golden, Colo., and was felt in Las Vegas, 105 miles away, less than one minute after the 10:30 a.m. detonation.

Some Las Vegas residents reported feeling a slight swaying in the wake of the blast.

U.S. Department of Energy spokesman Jim Boyer, speaking from a control point 34 miles from ground zero, said no radiation leaked into the atmosphere.

Airplanes and helicopters equipped with cameras and radiation detection equipment circled ground zero at blast time.

“The test was successful. Everything went well,” Boyer said.

The test of the nuclear weapon, with a yield of 20 to 150 kilotons, was code named “Tenabo” and was the seventh announced nuclear detonation by the United States this year. It was the third U.S. nuclear weapons test in the last four weeks.

The atomic bomb dropped on Hiroshima during World War II was a 13-kiloton weapon.

The nuclear weapon detonated Friday was positioned in a mined-out chamber at the bottom of a vertical shaft sunk into Pahute Mesa, a 5,000-foot-high volcanic plateau located deep within the boundaries of the Nevada Test Site.

The test shaft was plugged with grout and cement to prevent radioactive material and gasses from escaping into the atmosphere.

The detonation, originally scheduled for 7 a.m. Thursday, has been delayed several times--once because of a technical difficulty and other times because adverse winds would have carried an accidental leak of radiation toward Las Vegas.

Since the Nevada Test Site became operational in 1951, a total of 706 nuclear tests have been conducted at the facility, including 501 since the signing of the Limited Test Ban Treaty with the Soviets in 1963. The treaty, in effect, requires that nuclear weapons tests be conducted underground to prevent accidental radiation releases from drifting across international borders.

The Nevada Test Site, the heart of the country’s nuclear weapons testing, is a 1,350-square-mile outdoor nuclear testing laboratory the size of Rhode Island.