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Date: July 31, 2002
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Academy Addresses Technical Issues in Nuclear Test Ban Treaty:
Verification Capabilities Are Good, Cheating Possibilities Are Limited, and Safety and Reliability of U.S. Weapons Can Be Maintained Without Nuclear Tests

WASHINGTON -- The main technical concerns raised about the Comprehensive Nuclear Test Ban Treaty when the Senate refused to ratify it in 1999 are all manageable, says a new report from the National Academies' National Academy of Sciences. It concludes that verification capabilities for the treaty are better than generally supposed, U.S. adversaries could not significantly advance their nuclear weapons capabilities through tests below the threshold of detection, and the United States has the technical capabilities to maintain confidence in the safety and reliability of its existing weapons stockpile without periodic nuclear tests.

The Committee on Technical Issues Related to Ratification of the Comprehensive Nuclear Test Ban Treaty, which wrote the report, was formed in mid-2000 at the request of Gen. John Shalikashvili, former chair of the Joint Chiefs of Staff and then special adviser to the president and secretary of state for the CTBT. Committee members included former directors of the Los Alamos, Sandia, and Oak Ridge national laboratories; other experts on nuclear-weapon design, testing, and maintenance; a leading expert on seismic verification of nuclear explosions; and a former commander in chief of U.S. forces in the Pacific.

The chair of the committee -- Harvard professor John P. Holdren, who also chairs the Academy's Committee on International Security and Arms Control -- emphasized that the group was not asked to reach a conclusion on the overall question of whether the United States should ratify the treaty. "Answering that question requires taking into account a wider array of issues -- not just the technical ones we addressed but also military and political issues that were outside our mandate," he said. "But understanding of the technical issues is certainly an essential ingredient of the informed public and policy-maker discussion that must precede a ratification decision, and we hope our report will help provide this."

Verification of the CTBT would be accomplished through a combination of the International Monitoring System (IMS) established under the treaty, publicly available geophysical data collected for other purposes, and information gathered by U.S. military and intelligence agencies, the report says. Together these assets would provide a high probability of detection of nuclear tests with explosive yields down to about a kiloton in all locations and environments -- the atmosphere, the oceans, underground, and in near-Earth outer space. A kiloton is equivalent to 1,000 tons of chemical high explosive. A small nuclear weapon, like those that devastated Hiroshima and Nagasaki, would typically yield 10 to 20 kilotons. Today's strategic thermonuclear weapons are typically 100 kilotons or more.

Conducting nuclear tests at the smaller yields that might be concealable is technically difficult and produces limited insights, the group said. Only highly experienced nuclear-weapon states -- notably the United States, Russia, the United Kingdom, France, and China -- would be likely to succeed at concealment. Such constrained nuclear testing, however, would not add significantly to the nuclear-weapon capabilities these states already have, according to the committee.

Less experienced nuclear-weapon states and those aspiring to develop nuclear-weapon capabilities would not be able to reliably test below the threshold of detection, unless aided by one of the more experienced states. If they managed to do so, they would not learn much that would help them develop advanced nuclear weapons unless they subsequently conducted higher-yield tests that would be detected, the committee said.

Certain types of simple and relatively heavy and inefficient fission weapons can be developed without any nuclear testing at all, the committee cautioned. What a treaty blocks is independent development of efficient and compact fission weapons -- and thermonuclear weapons of any kind -- by countries that have not already done so. It also would block development of advanced new designs by the more experienced nuclear-weapon states.

While some limited amount of cheating on a ban can never be completely ruled out, the committee concluded that "the worst-case scenario under a no-CTBT regime poses far bigger threats to U.S. security interests -- sophisticated nuclear-weapons systems in the hands of many more adversaries -- than the worst-case scenario of clandestine testing in a CTBT regime, within the constraints posed by the monitoring system."

The United States has the technical capabilities to maintain confidence in the safety and reliability of the weapons in its existing nuclear stockpile without periodic nuclear explosive tests, provided that adequate resources are focused on the essential ingredients of a strategy for achieving this, the committee said. Those ingredients include attracting and retaining a high-quality work force in the nuclear-weapons complex, maintaining a rigorous stockpile surveillance program, maintaining the capacity to remanufacture aging nuclear weapons to the original specifications, and conducting rigorous reviews of any proposed changes to those specifications. Testing of the thousands of non-nuclear components that a nuclear weapon contains is not restricted under the treaty.

If unforeseen problems emerged in the stockpile that could not be resolved without nuclear tests, the committee noted, the United States would have the option of withdrawing from the treaty. The group recommended periodic independent reviews of "the acceptability of age-related changes relative to original specifications and the cumulative effect of individually small modifications" in stockpiled weapons -- as well as formal reviews of any large-quantity replacement of nuclear components in stockpiled weapons -- to determine whether a need to resume testing has materialized.

The tools and approaches that the United States has developed and is developing to ensure the safety and reliability of its stockpile in the absence of nuclear-explosive tests are collectively known as the Stockpile Stewardship Program. This program will not provide this country with the ability to develop and certify the performance of new weapon designs without nuclear tests, the committee said, "unless by accepting a substantial reduction in the confidence in weapon performance associated with certification up until now, or a return to earlier, simpler, single-stage design concepts, such as gun-type weapons." This conclusion rebuts a concern, expressed by some other countries, that sophisticated stewardship tools and this country's extensive prior nuclear-test experience would enable the United States to develop new nuclear-weapon types while observing a treaty, while other countries could not.

Negotiations resulting in the Comprehensive Nuclear Test Ban Treaty were completed in 1996, 38 years after President Eisenhower initiated negotiations for a test ban with the Soviet Union and the United Kingdom. The treaty has been signed by 165 nations, including the United States. The pact, which would prohibit nuclear test explosions in all environments, would establish a network of monitoring stations to help monitor compliance and provide for inspections of suspected tests. It would permit research, development, and design activities by the nuclear-weapon states, but experiments producing a nuclear yield are forbidden.

The treaty would enter into force after ratification by the 44 countries that either already possess nuclear weapons or have nuclear reactors. To date, 31 have done so, including Russia, the United Kingdom, and France. The U.S. Senate failed to give its advice and consent to ratification in 1999. The Bush administration has stated that it will not seek ratification, although it has also indicated that it does not see any need to resume testing and does not intend to do so. The United States has observed a testing moratorium since October 1992.

The study was sponsored by the U.S. Department of Energy, U.S. Department of State, Carnegie Corporation of New York, John D. and Catherine T. MacArthur Foundation, and the William and Flora Hewlett Foundation. The National Academy of Sciences is a private, nonprofit institution that provides science advice under a congressional charter. A roster of the committee that conducted the study follows.

Copies of Technical Issues Related to the Comprehensive Nuclear Test Ban Treaty are available from the National Academy Press; tel. (202) 334-3313 or 1-800-624-6242 or on the Internet at The cost of the report is $18.00 (prepaid) plus shipping charges of $4.50 for the first copy and $.95 for each additional copy. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).

Division on Policy and Global Affairs
Committee on International Security and Arms Control

Committee on Technical Issues Related to Ratification of the Comprehensive Test Ban Treaty

John P. Holdren1,2 (chair)
Program on Science, Technology, and Public Policy
Belfer Center for Science and International Affairs
John F. Kennedy School of Government
Harvard University
Cambridge, Mass.

Harold M. Agnew 1,2
General Atomics (retired), and
Los Alamos National Laboratory (retired)
Los Alamos, N.M.

Richard L. Garwin 1,2,3
Emeritus Fellow
IBM T.J. Watson Research Center, and
Phillip D. Reed Senior Fellow for Science and Technology
Council on Foreign Relations
New York City

Raymond Jeanloz
National Security Panel
President's Council, and
Department of Earth and Planetary Science and
Department of Astronomy
University of California

Spurgeon M. Keeny Jr.
Senior Fellow
National Academy of Sciences, and
Deputy Director
U.S. Arms Control and Disarmament Agency (retired)
Washington, D.C.

Charles R. Larson
Admiral (USN retired), and
Former Commander in Chief
U.S. Pacific Command, and
U.S. Naval Academy (retired)
Annapolis, Md.

Albert Narath 2
Sandia National Laboratories (retired)
Albuquerque, N.M.

Wolfgang K.H. Panofsky 1
Professor and Director Emeritus
Stanford Linear Accelerator Center
Stanford University
Stanford, Calif.

Paul G. Richards
Mellon Professor of the Natural Sciences
Lamont-Doherty Earth Observatory
Columbia University
Palisades, N.Y.

Seymour Sack
Laboratory Associate
Lawrence Livermore National Laboratory
Livermore, Calif.

Alvin W. Trivelpiece 2
Lockheed Martin Energy Research Corp. (retired), and
Oak Ridge National Laboratory (retired)
Oak Ridge, Tenn.


Jo Husbands
Study Director

1 Member, National Academy of Sciences
2 Member, National Academy of Engineering
3 Member, Institute of Medicine