North Korea’s nuclear weapons program. Likewise, as the United States continues to work with Russia to ensure that nuclear materials are adequately protected and accounted for, the partners will continue to require transparency measures to facilitate the process, as has been the case in the implementation of the 1993 Highly Enriched Uranium Purchase Agreement.

The study has addressed the technical and institutional approaches and capabilities in transparency and monitoring that could be applied to any or all of these purposes. It has not tried to analyze or make recommendations about the choices in U.S. nuclear weapon and nonproliferation policies and priorities that will continue to shape the context within which such approaches and capabilities might be applied. The pros and cons of different policy choices in these domains have been and continue to be extensively explored both inside and outside of government,2 and we did not want to detract from this study’s primary focus on technical and institutional capabilities by revisiting this policy terrain here.

We address the challenges and possibilities of increased transparency and monitoring largely in the context of the U.S. and Russian arsenals of nuclear weapons and stockpiles of nuclear-explosive materials (NEM).3 Those two countries have by far the largest inventories of nuclear weapons and NEM, and they also have the most extensive, varied, and sustained experience with the possibilities and pitfalls of transparency, monitoring, and verification. It is reasonable to assume that solutions to the problems of


For U.S. government policy statements see, for example, “The National Security Strategy of the United States of America” (Washington, DC: The White House, September 2002). Available as of January 2005, at: and “National Strategy to Combat Weapons of Mass Destruction” (Washington, DC: The White House, December 2002). Available as of January 2005, at: This committee’s studies include Committee on International Security and Arms Control, The Future of U.S. Nuclear Weapons Policy (Washington, DC: National Academy Press, 1997) and Committee on International Security and Arms Control, Management and Disposition of Excess Weapons Plutonium (Washington, DC: National Academy Press, 1994). Bibliographies and links to other government and nongovernment publications may be found at a number of Web sites, in particular those of the Nonproliferation Project of the Carnegie Endowment for International Peace, available as of January 2005, at: and the Nuclear Threat Initiative, available as of January 2005, at:


A nuclear-explosive material” is a mixture of fissionable nuclides in which the proportions of these are such as to support an explosively growing fission chain reaction when the material is present in suitable quantity, density, configuration, and chemical form and purity. Uranium containing more than 20 percent U-235 or more than 12 percent U-233 (or an equivalent combination of proportions of these two nuclides) is considered NEM, as are all mixtures of plutonium isotopes containing less than 80 percent Pu-238. See Chapter 3 and Appendix A for more detail.

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