Nevada "mushroom cloud" blast plan abandoned

WASHINGTON (Reuters) - The Pentagon has abandoned plans for a massive test explosion in the Nevada desert, the first time a mushroom cloud would have been seen near Las Vegas since a nuclear test in the 1960s, officials said on Thursday.

The detonation of conventional explosives had been designed to test the effectiveness of weapons against deep underground targets but critics had expressed concern that dust containing background radiation could be spread into the air.

"I have become convinced that it's time to look at alternative methods that obviate the need for this type of large-scale test," said James Tegnelia, director of the Pentagon's Defense Threat Reduction Agency.

The test, dubbed "Divine Strake," had been scheduled to take place last year over a tunnel at the U.S. Energy Department's Nevada Test Site, about 65 miles northwest of Las Vegas.

But it was postponed indefinitely in May after the National Nuclear Security Administration said it was withdrawing its finding that the detonation of 700 tons of ammonium nitrate and fuel oil would cause no significant environmental impact.

Tegnelia told reporters last March the test would be "the first time in Nevada that you'll see a mushroom cloud over Las Vegas since we stopped testing nuclear weapons." The last above-ground nuclear test at the site was in 1962.

In Thursday's statement, the Defense Threat Reduction Agency said it would try to develop other methods for obtaining data the test would have provided, using scientific analysis and much smaller experiments.

"DTRA remains committed to help develop nonnuclear means to defeat underground targets. I am optimistic that we will succeed," Tegnelia said.