Earth-penetrating nuclear bombs would be capable of destroying military targets deep underground, but not without inflicting "massive casualties at ground level," according to a congressionally mandated study released yesterday.
The study's findings reflect a growing scientific consensus that even relatively small nuclear "bunker-buster" weapons -- under study by the Bush administration but strongly opposed by some members of Congress and arms-control advocates -- could not be used without a high cost in human life. Such a bomb could cause more than a million deaths, depending on the yield, the report said.
"You can use a much smaller weapon if you use an earth penetrator, maybe 20 times smaller, but you will kill a lot of people, because it puts out a huge amount of radioactive debris," said John F. Ahearne, chairman of the Committee on the Effects of Nuclear Earth-Penetrator and Other Weapons of the National Research Council, which produced the report. The council, a branch of the National Academy of Sciences, advises the federal government on science and technology.
The study represents an authoritative finding amid a long-standing conflict over whether it is possible to design an earth-penetrating nuclear bomb that would destroy deeply buried targets without killing people aboveground.
The report found that casualties from an earth-penetrator weapon "would be equal to that from a surface burst of the same weapon yield," causing from thousands to more than a million deaths in an urban area, and hundreds to hundreds of thousands in lightly populated areas with unfavorable winds.
In its fiscal 2003 Defense Authorization Act, Congress directed the Pentagon to request the study to examine the health and environmental effects of the bombs.
The Bush administration this spring renewed its push for $8.5 million in funding to resume Pentagon and Energy Department studies of bunker-buster nuclear warheads. Congress killed funding for the study last year, and lawmakers indicated this year they will again question the request.
On Capitol Hill yesterday, Defense Secretary Donald H. Rumsfeld faced incredulity from at least one senator on why the administration is pursuing the weapons.
"It is beyond me as to why you're 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's at 100 kilotons," Sen. Dianne Feinstein (D-Calif.) said in a subcommittee hearing of the Appropriations Committee.
Rumsfeld replied that 70 countries are pursuing "activities underground" using technology that allows them to burrow into solid rock the length of a basketball court in a single day.
"At the present time, we don't have a capability of dealing with that. We can't go in there and get at things in solid rock underground," he said. "The only thing we have is very large, very dirty, big nuclear weapons. So . . . do we want to have nothing and only a large, dirty nuclear weapon, or would we rather have something in between?"
The Pentagon estimates there are 10,000 hardened targets -- above and below ground -- in the territory of potential adversaries. About 20 percent have a "major strategic function" such as housing command-and-control systems or weapons stockpiles, and of that 20 percent, half are near or in urban areas.
The study found that nuclear weapons, if aimed accurately, would be more effective than conventional bombs in destroying hard and deeply buried targets. Such nuclear weapons could work with a yield one-fifteenth to one-twenty-fifth as large if they are detonated a few yards below the earth's surface, causing a shock wave that could destroy bunkers hundreds of yards below.