Collapse at Ground Zero

Initially, the test seemed routine. At 9 a.m., Department of Energy(DOE) engineers detonated a nuclear bomb 1,168 ft. beneath the aridlandscape of the Rainier Mesa at the Nevada test site 93 milesnorthwest of Las Vegas. About three hours later, after instrumentsdetected no radiation at the site, workers in white coveralls returnedto trailers near the blast area to begin collecting data. They had juststarted to snip the 150 cables connected to underground sensors whenthe earth gave way. “I felt the earth shake, and before I knew it I wasstanding on my head,” said J. L. Smith, a site supervisor. “We werewalking on the ground, and all of a sudden it wasn’t there.”

Last week’s cave-in left a D-shaped crater about 60 ft. wide, 150 ft.long and between 10 and 30 ft. deep. Although apparently no radiationhad leaked, 14 workers emerged with broken bones and lacerations.Craters from previous underground nuclear tests pock the desert floorelsewhere on the 1,350-sq.-mi. site. But officials said they had had noreason to expect such a result in the mesa because it is made up ofhardened volcanic ash and granite. In the past 20 years, the Governmenthas exploded 45 nuclear devices with no ill effects in the tunnelsbored under the mesa. Indeed, until last week there had been no directinjuries from the more than 600 atomic tests conducted in Nevada since1951.

The Soviet Union promptly denounced the explosion as a violation of a1974 Soviet-American agreement that limits underground detonations to150 kilotons (150,000 tons of TNT). Although the force of the weapontested last week was classified, DOE officials said it was considerablylower than 20 kilotons, the explosive yield of the bomb dropped onNagasaki. The blast registered 4.5 on the Richter scale on seismographsat the University of Nevada, Las Vegas. But DOE officials said theinstruments probably gave a high reading because the test was conductedin hard rock, which sends out a more powerful seismic ripple than doessandy soil. The incident is not expected to interfere with futurenuclear testing.

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