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 risks associated with the world’s stockpiles of nuclear weapons, nuclear-explosive components of weapons, and nuclear-explosive materials (NEM)1 include:

  • the dangers in the potential for use of existing arsenals, including the possibilities of deliberate use of nuclear weapons by their authorized possessors and also the possibilities of accidental, inadvertent, or unauthorized use;

  • the risks that the existing arsenals and perceptions about their characteristics and intended uses will provoke further, potentially destabilizing nuclear weapon developments and deployments either by the countries already possessing such weapons or by additional countries; and

  • the danger that the existing stockpiles of weapons, components, and NEM will be the enablers rather than merely one of the motivators of proliferation, through illicit transfer to or theft by (or on behalf of) proliferant states or terrorist groups.

The risks posed by nuclear weapons are exacerbated in many respects by the size of the current arsenals and by the magnitude of the worldwide stockpiles of NEM. The United States and Russia possess about 95 percent of the approximately 30,000 existing nuclear weapons, with the remainder held by the United Kingdom, France, China, Israel, India, Pakistan, and possibly North Korea. Enough additional NEM exists in military and civil nuclear facilities worldwide to make something like 100,000 additional nuclear weapons. These stockpiles of NEM, in addition to presenting a


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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