PARIS, Nov 6: US plans to build a bunker-busting mini-nuclear bomb have triggered alarm among scientists, who warn the weapons could spray radioactive fallout in a wide radius around the impact site.

President George Bush’s administration has earmarked 15 million dollars in the draft 2003 defence budget for research into a so-called Robust Nuclear Earth Penetrator (RNEP).

The bomb could be used in pre-emptive strikes to destroy hardened underground targets such as as command bunkers or weapons of mass destruction squirrelled away by rogue stakes, according to leaked documents.

The idea is that the RNEP would be dropped from high altitude and hit the ground with such speed that it would penetrate like a knife deep into the surface before detonating.

Fallout would — theoretically — be negligible as the debris would be contained by the thick lid of earth, rock and concrete above.

But, according to experts quoted by New Scientist, even the smallest warheads are likely to spew up thousands of tonnes of highly radioactive dust and debris.

“Even for a 0.3-kiloton explosion, you would need a burial depth of about 70 metres in dry soil and about 40 metres in dry, hard rock to contain the blast,” David Wright, a nuclear-weapons specialist at the Union of Concerned Scientists in Washington, told the British weekly.

The likely design for the RNEP will be an existing nuclear bomb, the B61, whose explosive yield can be set from anything between 0.3 kilotons equivalent of TNT and 340 kilotons, New Scientist said. By comparison, the Hiroshima bomb had a yield of 12 kilotons.

In any case, said Wright, a 0.3-kiloton bomb would not be powerful enough to destroy a hardened target buried more than 20 metres beneath the ground.

Some Iraqi facilities are said to be buried to a depth of 60 metres under rock. To destroy those targets would therefore require a bigger warhead, in the hundreds of kilotons. —AFP