most urgent unmet national security threat to the United States today is the danger that weapons of mass destruction or weapons-usable materials in Russia could be stolen and sold to terrorists or hostile nations and used against American troops abroad or citizens at home. --Secretary of Energy Advisory Board, January 2001 Political and economic upheavals over the past decade have weakened the ability of Soviet successor states to monitor and control their potentially dangerous nuclear assets. A strong theoretical possibility exists--and has existed for some time--that nuclear material and even complete weapons could be removed from insecure stockpiles, trafficked abroad, and sold to virulently anti-Western states and groups. Several factors underscore the significance of this threat. One is the enormous quantity of former Soviet fissile material stored outside of weapons--some 600 to 650 tons scattered among 300 buildings at more than 50 nuclear facilities. (1) According to standard calculations, only six to eight kilograms of plutonium and 15 to 25 kilograms of highly-enriched uranium (HEU) are needed to make an implosion-type nuclear bomb; hence, even minor leakage episodes could provide the makings of a major proliferation catastrophe. (2) (The required amounts could be greater or less, depending on the design of the device and the engineering skills of the producer.) A second factor relates to reputedly lax physical security and accounting systems at many nuclear weapons enterprises. A third is the depressed economic situation of employees in parts of the nuclear complex, reflected in relatively low pay, a shrinking social safety net, and uncertain professional prospects. These factors are widely believed to constitute a pri me source of proliferation danger on the supply side. A fourth concern, frequently cited by US authorities, is that outside adversaries such as Iraq, Iran, and the al Qaeda organization have made efforts to acquire nuclear weapons or sufficient materials and expertise to make them. There seems little doubt that Russia's vast and troubled nuclear complex has been a target of such attempts, although adversaries also may have looked to other nuclear-armed states (such as Pakistan) to supply their weapons of mass destruction (WMD) requirements. Finally, existing US nuclear security programs have only modestly reduced the nuclear proliferation threat from Russia and other newly independent states (NIS). The basic US approach has been twofold: to contain the threat at the source with technological fixes and procedural norms--to build better fences around nuclear facilities in the words of a former Department of Energy (DOE) official familiar with the programs (3)-and to improve export control regimes, including NIS border defenses against nuclear smuggling. The new systems, though, still do not extend to many facilities, and adversaries with sufficient resources and the right connections could easily exploit the gaps in them. Also, insider corruption and economic hardship can erode the deterrent value of even the advanced safeguards being introduced, possibly paving the way for serious proliferation episodes. Additionally, the extraordinary length of Russia's border with neighboring countries, which runs some 12,000 miles, underscores the immense ch allenge of preventing clandestine exports of nuclear goods from that country. In surveying the condition of nuclear security in the new states, the question arises whether hostile states or groups already have acquired ingredients of nuclear weapons (or the weapons themselves) and from where and in what quantities. No clear answers are available, although there is much speculation. An international black market of sorts for radioactive substances developed in the aftermath of the Soviet collapse, but it provides few clues. Confirmed smuggling cases involving weapons-usable material are few and far between, and traffickers in these instances have had no obvious links to customers. …