However, such "earth-penetrating" nuclear weapons cannot go deep enough to avoid massive casualties at ground level, and they could still kill up to a million people or more if used in heavily populated areas, said the committee that wrote the report.

"Using an earth-penetrating weapon to destroy a target 250 meters deep - the typical depth for most underground facilities - potentially could kill a devastatingly large number of people," said John F. Ahearne, committee chair and director of the ethics program at the Sigma Xi Center of Sigma Xi, The Scientific Research Society, Research Triangle Park, N.C.

Many countries use underground facilities to conceal and protect military personnel, weapons, and equipment. Most of these facilities are beyond the reach of conventional explosive weapons and can be destroyed only by nuclear weapons.

Earth-penetrating weapons have been considered as an alternative to conventional nuclear weapons because they could destroy such targets with up to 25 times less energy than weapons detonated at the surface.

The weapons' lower power would produce two to 10 times fewer surface casualties, but they still would lead to a large number of deaths and injuries, the report says.

Fatalities could be further reduced if military commanders warned of an attack in time for people to evacuate. Commanders could also take advantage of wind conditions to minimize civilians' exposure to fallout.

But a nuclear weapon burst in a densely populated urban area will always result in a large number of casualties, the committee emphasized.

Most of the weapons' destructive effect on a target is achieved at a depth of three meters. Beyond that depth, the weapon may fail, the committee said. Significant explosive power is needed to destroy targets located as deep as 400 meters, the report notes.

For example, a 300-kiloton earth-penetrating nuclear weapon has a high probability of destroying a target 200 meters below, but a 1-megaton weapon is needed to destroy a 300-meter-deep facility.

The committee also examined the possible effects of using conventional or nuclear weapons to destroy chemical and biological weapons depots.

Except for the BLU-118B thermobaric bomb - a conventional bomb that can target a shallowly buried facility and destroy it with high pressure and heat - conventional weapons are not likely to be effective in destroying chemical or biological agents, the report says.

In a nuclear attack on a chemical weapons facility, far more civilian deaths will likely be caused by the nuclear blast itself than by the resulting dispersal of chemical agents.

In contrast, the release of as little as 0.1 kilogram of anthrax spores, for example, would result in a number of fatalities similar to those caused by a 3-kiloton earth-penetrating nuclear weapon.

Rumsfeld: Study Of Earth Penetrating Nukes Makes "All The Sense In The World"
Washington (AFP) Apr 27, 2005 US Defense Secretary Donald Rumsfeld said Thursday it makes "all the sense in the world" to study the feasibility of designing a nuclear weapon capable of penetrating deeply buried targets.

Rumsfeld defended the proposed 8.5 million-dollar study of a "robust nuclear earth penetrator" at a Senate hearing after it came under fire from Senator Diane Feinstein, a California Democrat.

Feinstein noted that Energy Secretary Samuel Bodman has acknowledged in previous hearings that no missile could bore deep enough into the earth to trap all fallout from a nuclear explosion.

"It is beyond me as to why you are proceeding with this program when the laws of physics won't allow a missile to be driven deeply enough to retain the fallout which will spew in hundreds of millions of cubic feet if it is a hundred kilotons," Feinstein said.

Rumsfeld said more than 70 countries have programs to build facilities underground, and have available to them equipment that can dig chambers the size of a basketball court from rock in a single day.

"We can't go in there and get at things in solid rock underground," Rumsfeld said.

"The only thing we have is very large, very dirty nuclear weapons. So the choice is: do we want to have nothing and only a large, dirty nuclear weapon, or would we rather have something in between. That is the issue," he said.

He said the administration wanted see if it is feasible to develop weapons casings hard enough to penetrate "not with a large nuclear weapon but with either a conventional capability or a very small nuclear capability in the event that the United States of America at some point down the road decided they wanted to undertake that type of project."

"It seems to me studying it makes all the sense in the world," he said.

The proposal has been attacked by arms control advocates as a step toward developing a weapon that would lower the threshhold for the use of nuclear weapons.

Congress last year killed funding for the study, but the administration has requested resumed funding in its 2006 budget proposal.

Besides 8.5 million dollars in 2006, the proposal calls for another 14 million dollars to complete the study in 2007.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.

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