Nuclear experiment held beneath US desert

SCIENTISTS from the US and Britain performed an underground nuclear experiment, short of a nuclear blast, in Nevada, the National Nuclear Security Administration said.

It involved detonating explosives around radioactive material in a vault about 1,000 feet below ground at a remote part of the desert testing range 85 miles north-west of Las Vegas.

No radioactivity was released, said Nancy Tufano, the spokeswoman for Bechtel Nevada, a contractor at the nuclear security administration in Las Vegas.

She described the material tested as specially processed nuclear plutonium, but said she could not disclose the isotope for security reasons.

Scientists posted a video weblog of preparations for Thursday's experiment, which was designed to examine the effects of the explosion on the nuclear material. It was the 22nd "subcritical test" at the site since 1997.

Anti-nuclear groups criticise such experiments as contrary to the spirit of the 1996 Comprehensive Test Ban Treaty on nuclear arms. The US has had a moratorium on full-scale nuclear testing since 1992, but has not ratified the treaty.

Federal officials say subcritical experiments are essential to maintain the safety and reliability of the US nuclear arsenal.