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‘Mini-blasts’ test plutonium power

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BERKELEY, Calif. — Full-fledged nuclear tests are off-limits, but scientists quietly continue to test plutonium's power by exploding small, potent packages 1,000 feet beneath the Nevada desert.

Since 1997, scientists at Livermore Lawrence National Laboratory have unleashed a series of tests — called Bagpipe, Oboe, Clarinet — attempting to gain new insight into how plutonium behaves under extreme conditions.

Next in the series is Piano, a test so powerful scientists may abandon their cost-cutting measure of confining the explosives to a 55-gallon barrel lowered into an underground alcove. They suspect Piano would tear through the inch-thick steel skin of a barrel, so the experiment may be detonated directly in the alcove, which then would be sealed.

The tests are allowed under the Comprehensive Test Ban Treaty because they are subcritical, meaning no critical mass is formed and there is no chain reaction.

The plutonium, some of which comes from old weapons, is "shocked" by a high-explosive detonation that reproduces the pressures and temperatures that occur when a nuclear device is detonated.

Data obtained through high-speed cameras and laser holography are used to refine the supercomputer codes that simulate full explosions.

Tests so far have used less than 65 grams, about two ounces, of plutonium. Livermore spokesman David Schwoegler said the amount of plutonium being used in Piano is classified, but it will not be enough to reach critical mass.

At the Nuclear Resources Defense Council in Washington, Thomas Cochran, director of the watchdog group's nuclear program, criticized the tests. He said they are part of an effort to keep the Energy Department's Nevada Test Site running and available for full-blown underground testing if the 1992 moratorium is lifted.

"The United States and Russia both continue to maintain a breakout capability at these nuclear test sites and to maintain that breakout capability they have to keep the folks there occupied and employed," Cochran said.

Energy Department spokesman Derek Scammell said President Clinton has ordered that the test site be kept ready.

The test site, about 65 miles northwest of Las Vegas, includes a complex of tunnels and alcoves, which are about the size of a two-car garage and are known as zero rooms from the expression "ground zero."

An article from this month's edition of Livermore's in-house "Science and Technology Review" describes the "downhole environment" as "surprisingly comfortable, with well-lit rooms, concrete floors, tall ceilings and lunchrooms."

Scientists with the Los Alamos National Laboratory in New Mexico also have a designated testing area at the Nevada Test Site and conduct experiments about every 15 months.

Livermore scientists have been testing more frequently, since the barrels allow several shots in the same alcove, reducing costs from $20 million to $2 million. The Piano test is scheduled for next year.


On the Net: Lab: www.llnl.gov

Energy Department: home.doe.gov