one of these (South Africa’s) led to the development of nuclear weapons. Iran, Iraq, and North Korea are believed to have active weapons development programs at present, and these countries probably have the technical capabilities to develop nuclear weapons but may not have sufficient quantities of SNM (plutonium or HEU).
The weapons arsenals of Britain, China, France, Israel, and the United States are probably well protected. Indian and Pakistani nuclear weapons are also thought to be adequately protected at present, but the near-term (1- to 5-year) security of Pakistani weapons may be problematical. Theft or diversion of Russian nuclear weapons for terrorist use may represent a significant near-term threat to the United States, especially the theft or diversion of smaller, manportable weapons. Table 2.1 and the classified annex provide additional details on these threats.3
Improvised nuclear devices are nuclear weapons fabricated by terrorists, with or without state assistance, using stolen or diverted SNM. The basic technical information needed to construct a workable nuclear device is readily available in the open literature. The primary impediment that prevents countries or technically competent terrorist groups from developing nuclear weapons is the availability of SNM, especially HEU.
HEU could potentially be obtained by terrorists from several sources. There are large stockpiles of excess HEU and weapons-grade plutonium in both the United States and Russia, and other countries with nuclear weapons may have smaller stockpiles of these materials. HEU also exists in nuclear fuel from naval reactors, and large stocks of reactor-grade plutonium are contained in commercial spent fuel. Spent-fuel reprocessing programs and separated stocks of reactor-grade plutonium also exist in several countries, and these stocks are routinely transported across national borders. Reactor-grade plutonium can be used to fabricate workable nuclear devices.
Theft or diversion of excess Russian HEU for terrorist use represents a significant near-term threat to the United States. There are estimated to be about 150 metric tons of separated plutonium and 1,200 metric tons of HEU in Russia. The United States has been working with Russia over the past 7 years to secure this material and has made major progress. These safeguards are effective against casual thefts but may not be effective against higher-level threats, especially sophisticated insider threats. Moreover, a complete inventory of Russian materials is not available, so it is impossible to confirm that diversions of materials have