Bunkers, Bombs, Radiation

A myth is emerging that we can develop low-yield nuclear weapons that will destroy hardened, deeply buried targets of military interest without contaminating the atmosphere with deadly radioactivity. Such weapons, delivered by bombers, must penetrate below the Earth’s surface before detonating in order to create the maximum destructive ground shock.

There are problems with this myth: Its validity is doubtful and its consequences are dangerous.

Low-yield nuclear weapons have limited effectiveness against buried targets and they would disperse significant amounts of radioactivity.

Perhaps more important, however, the deployment of such weapons would likely have an extremely harmful effect on ongoing efforts to slow--if not prevent--the proliferation of nuclear weapons.

First, some technical facts. Yields greater than 1 kiloton are required to damage hard targets deeper than about 200 feet. Much larger yields--in the range of 100 kilotons or more--are needed to create enough ground shock to destroy a hardened structure at a 1,000-foot depth.

Taking into account realistic limits on material strengths, 50 feet is about the maximum depth a warhead can dig and maintain its integrity in dry, hard soil, the likely locations for buried targets. Even a 1 kiloton warhead--1/20th the yield that destroyed Hiroshima--detonated at a depth of 20 feet would eject about 1 million cubic feet of radioactive debris from a crater about the size of ground zero at the World Trade Center.

The U.S. has produced a high-yield weapon capable of destroying a number of underground targets of interest. Such an explosion would dig a much larger crater and create substantially larger amounts of radioactive debris.

The U.S. capability against a reportedly growing number of military targets buried at relatively shallow depths--less than 100 feet--can be greatly enhanced by delivering several conventional bombs on the same target with precision guidance. If nuclear weapons are used to attack buried targets, however, there is no possibility of a so-called “clean” attack, free of extensive radioactive contamination spreading in the atmosphere.

Actions by the U.S. to deploy new designs of nuclear warheads for new military missions would also strike at the heart of the current worldwide effort to prevent the proliferation of nuclear weapons. Currently, 185 nations have endorsed this effort by signing on to the indefinite extension of the Nonproliferation Treaty, or NPT, agreed to in 1995.

Many of the NPT signatories based their support on the explicit assumption that the nuclear-armed powers would honor a commitment to cease all underground nuclear explosive tests and continue efforts to reduce their reliance on nuclear weapons, rather than to create new missions for new ones. This commitment is supported by the Comprehensive Test Ban Treaty, which the U.S. has signed--along with more than 160 other nations--but not yet ratified.

A ban on all nuclear testing enhances our national security for the foreseeable future. The U.S. should ratify the test ban treaty, joining the 89 other nations that have already done so, because the U.S. is the natural and necessary leader for advancing the cause of nuclear nonproliferation.

Already, three nuclear powers--Russia, England and France--and many of our NATO allies plus Japan have ratified the test ban. China has declared its intent to sign once the U.S. does, while India has also expressed interest.

Bringing the test ban treaty into force requires U.S. ratification, which would then trigger the completion of an international monitoring system to enhance our ability to verify worldwide compliance.

Attaching false hopes to low-yield nuclear weapons for destroying buried targets is no reason to undermine the so-far-successful efforts to limit the proliferation of nuclear weapons. And resumption of underground nuclear explosions in the quest for these so-called “more usable” nuclear weapons would harm the nonproliferation treaty and, thus, our national security.