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The Bush Administration's Misguided Quest for Low-Yield Nuclear Bunker Busters

Contact: Christopher Paine, 434-244-5013 or Matthew McKinzie, 202-289-2363
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The Bush administration is provoking a political confrontation over repealing an obscure restriction on nuclear weapons research and development that has been on the books for nearly a decade. Why? It wants to develop new low-yield nuclear weapons and improved nuclear earth-penetrating bombs to hit hardened and deeply buried targets.

The restriction, called the Spratt-Furse Amendment after its original House cosponsors, was enacted in November 1993. It bars the secretary of energy from conducting "research and development which could lead to the production by the United States of a new low-yield nuclear weapon," defined in the statute as a weapon with a yield less than 5 kilotons.

To encourage lawmakers to repeal the restriction, senior Defense Department officials have testified in Congress that they interpret the law as requiring them to refrain from even "research leading to development" of such weapons, a phrase that appears nowhere in the statute. They suggest that the only remedy for the "chilling effect" of the restriction on "scientific inquiry" at the nation's defense laboratories is to get rid of it.

The House and Senate are now debating this issue in their respective versions of the FY 2004 Defense Authorization bill. Under the leadership of Republican Sens. John Warner (Va.) and Wayne Allard (Colo.), the Senate Armed Services Committee has reported a version of the bill that would repeal the Spratt-Furse ban and devote $15 million to develop a high-yield "robust nuclear earth penetrator" weapon capable of attacking deeply buried nuclear command centers in Russia and China. The House Armed Services Committee recently amended its version of the same bill to loosen, but not repeal, the Spratt-Furse restriction. If upheld by the Republican-dominated House, a bipartisan compromise crafted by Reps. John Spratt (D-S.C.) and Curt Weldon (R-Pa.) would allow studies of new low-yield nuclear weapons, but not full-scale engineering development or production of such weapons. Opponents of Bush's "revitalized" nuclear weapons program are expected to offer amendments in the Senate to reinstate the ban, and in both houses to cut funding for the robust nuclear earth penetrator.

A recent analysis by the Nuclear Program at NRDC (Natural Resources Defense Council) found that developing a new low-yield nuclear weapon with improved penetration characteristics is politically, technically and militarily unjustifiable (for the analysis, go to http://www.nrdc.org/nuclear). Such a weapon would hamper the United States' ability to curb nuclear proliferation, legitimize the use of nuclear weapons in battlefield situations, and strengthen the Pentagon's ability to destroy underground sites only at the cost of generating significant fallout, which would imperil civilian populations. Meanwhile, developing a high-yield robust nuclear earth penetrator would bolster U.S. capability to strike deeply buried targets, but it would produce even more fallout than a low-yield version.

Undoing His Father's Legacy

There is considerable irony in President George W. Bush's apparent zeal to overturn this law, given that the political-military consensus favoring it was largely forged during his father's administration, when the current secretary of state, Colin Powell, was chairman of the Joint Chiefs of Staff. In September 1991, when the Soviet empire was falling apart, the first President Bush announced that all U.S. tactical nuclear weapons deployed with land forces and surface fleets worldwide would be removed from overseas storage sites and surface ships, retired from the stockpile, and ultimately destroyed, and he challenged the Soviet Union to do the same. Russia reciprocated with a substantial removal effort of its own, securing thousands of nuclear warheads in the newly independent states of the former Soviet Union and shipping them back to Russia, where they destroyed a large but indeterminate number of them. The United States assisted these efforts under the aegis of the Nunn-Lugar program.

In July 1992, President Bush went a step further, issuing an executive order stating that in the changed security environment, the United States had no military requirements for new nuclear weapons, and would henceforth limit its efforts to evaluating and improving the safety and reliability of the U.S. nuclear stockpile. Following this White House directive, new warhead development efforts not already terminated by Congress were scrubbed, and shortly thereafter Congress cut off funding for nuclear test explosions. According to the current administration's testimony on April 8, 2003, this situation remains true today: The Pentagon does not have any approved military requirements for new nuclear weapons.

In the current political context of heightened global concern about nuclear weapons proliferation in East Asia, South Asia and the Middle East, the current Bush administration's sudden resurgence of interest in tactical nuclear weapons could hardly be more anomalous and discordant, or more damaging politically to the credibility and moral standing of the United States as its pursues the indispensable task of shoring up the global nonproliferation regime.

No Technical Advantage

Administration officials claim that they support developing nuclear earth penetrators and low-yield weapons because they would provide a more discriminate capacity to destroy hardened and deeply buried targets, and thus a more "credible" deterrent military posture. However, NRDC's technical analysis found improved earth penetrators could not penetrate deeply enough to substantially contain the radioactive debris they would generate. While shallow penetration -- below 5 meters -- would produce roughly the same amount of radioactive fallout as a surface burst, fallout would actually increase the deeper the weapon penetrated because the blast would throw up a greater volume of earth.

NRDC also found that the expected increase in an earth penetrator's radius of destruction tails off rapidly after the first 8 to 12 feet of penetration, for yields between 1 and 100 kilotons. For example, the current U.S. nuclear earth-penetrating weapon, the B61-Mod 11, with an estimated explosive power of 300 kt, can penetrate roughly 10 feet of frozen tundra before detonating. Employing a reduced-yield robust nuclear earth penetrator in the 1-10 kt range, and doubling its nominal penetration depth to 20 feet of hard rock, increases its destruction radius against a hard buried target by only about 25 feet. Tripling the penetration depth to its likely physical limit of about 33 feet in hard rock would produce a damage zone that is only about 50 foot deeper.

Even at this probable maximum limit of penetration, a 10-kt robust penetrator would not cause severe damage to hard targets buried below about 275 feet and protected by intervening layers of hard rock. To severely damage such a target buried at 1,000 feet, for example, one would need a weapon in the megaton range, about 70 times larger than the Hiroshima bomb.

In sum, there would appear to be little military justification for replacing or augmenting the current B61-11 capability with a lower-yield enhanced penetrator. With a 10-kt yield, it would create relatively less, but still very substantial levels, of lethal fallout over a wide area while failing to produce the deeper damage zone generated by the B61-11. A 1-kt enhanced penetrator could not destroy any targets below 150 to 250 feet, depending on the geology of the site. Its low yield would require placing it directly above its intended buried target, with little margin for error, but it would still produce substantial local fallout.

Perhaps most significant, an improved low-yield penetrator weapon would encourage military planners to identify shallower targets, and a wider range of circumstances, for "credibly" threatening the use of nuclear weapons, while ignoring the global political, moral and legal consequences, and increased proliferation risks, that ensue from legitimizing nuclear threats to preemptively attack another nation's nuclear, biological, chemical, command and control, and leadership facilities.

Conversely, a weapon like the proposed robust nuclear earth penetrator, having both improved penetration capability and nuclear yields in the range of 300-1,000 kt -- equal to or higher than the current B61-11 -- would increase the U.S. capability to strike deeply buried command and control and leadership targets. But the resulting high number of wounded and dead civilians presumably would limit the United States to using such a weapon only to preempt or retaliate against a nuclear attack by another state with the military resources to construct deeply buried targets and threaten the survival of the United States.>1 The only two countries that fit that profile are China and Russia.

The robust nuclear earth penetrator proposal is symptomatic of an increasingly disconnected nuclear weapons establishment in search of a mission. On the one hand, the weapon is strategically, legally and morally unsuitable for preemptive or retaliatory counterproliferation warfare, and should not be developed with that mission in mind. On the other hand, the alternative justification -- improved nuclear "deterrence" against Russia and China -- seems gratuitously provocative politically, and militarily unnecessary.

What Should Congress Do?

If the Bush administration is sincere in its recent assurances that it has no plans to develop new low-yield nuclear weapons, then there should be no difficulty for Congress to reach a bipartisan agreement on minor modifications of the Spratt-Furse restriction that would remove the ambiguities that are ostensibly causing scientific paralysis at our nation's defense laboratories. For example, by merely replacing the more open-ended "could lead" to development with the more definitive "leading," the restriction would be revised to more clearly bar "research and development leading to production" of a low-yield nuclear weapon, and therefore not earlier stages of research.

This simple fix would take care of the issue until this or a future administration had assessed the technical feasibility of alternative design concepts and wanted to proceed to the next stage of estimating full-scale engineering development and production costs and schedule -- in other words, to "research and development leading to production." A subsequent, and required, congressional funding authorization to develop a new low-yield nuclear warhead design -- a step that NRDC believes is technically unwarranted and politically unwise -- would effectively repeal the Spratt-Furse restriction. So NRDC perceives no rationale, beyond a misguided ideological zeal for more nuclear "warfighting" capability, for further alarming the world now and discrediting U.S. nonproliferation objectives, merely to pave the way politically for a full-scale development decision that must be revisited by Congress in any event.

As for the ongoing development of a high-yield robust nuclear earth penetrator warhead, it is nothing more than "workfare" for federal nuclear weapons laboratories, and a retread of the very Cold War policies the Bush administration pledged to jettison. Congress should deny all funding for it.


1. For example, NRDC calculates that a 300-kt earth-penetrator attack on an underground facility west of Pyonyang, North Korea, would result in more than half a million civilian casualties.

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