Non-nuclear experiment conducted

For the first time in four years, scientists conducted a non-nuclear experiment at the government's Nevada desert proving ground, an official with the federal National Nuclear Security Administration said Thursday.

There was no nuclear reaction and no release of radioactivity from the so-called subcritical test at 5:35 p.m. Wednesday at the recently renamed Nevada National Security Site, NNSA spokesman Darwin Morgan said.

Scientists from the government's Los Alamos National Laboratory in New Mexico detonated explosives around radioactive material in a specially designed sphere in a vault some 1,000 feet beneath the surface, Morgan said.

The experiment, dubbed Bacchus, was the 24th subcritical test since 1997 at the vast federal reservation 85 miles northwest of Las Vegas. The last was Unicorn on Aug. 30, 2006.

Subcritical experiments test the properties of plutonium but stop short of critical mass, the point at which a self-sustaining nuclear reaction occurs.

Officials call the experiments essential to test and maintain the safety and reliability of the U.S. nuclear arsenal.

Anti-nuclear groups criticize the experiments as contrary to the spirit of a 1996 Comprehensive Test Ban Treaty on nuclear arms.

The U.S. Senate in 1999 rejected the treaty, but officials have said President Barack Obama plans to resubmit it for ratification.

The test site hosted 928 full-scale nuclear tests involving 1,021 nuclear detonations from 1951 to 1992, when the U.S. agreed to a moratorium on full-scale nuclear testing.