How Easy Is It to Produce Nuclear Weapons?
The major challenge in all nuclear weapon designs is to ensure that a significant fraction of the nuclear fuel is consumed before the weapon destroys itself. Of course, no nuclear weapon can be built without the requisite nuclear material. Highly enriched uranium is uranium whose isotope U-235 has been artificially concentrated to a high degree (more than 90 percent is considered best, but lower concentrations can also be used in weapons). By contrast, naturally occurring uranium has a concentration of only 0.7 percent U-235, and nuclear power plants require uranium with only a low level of enrichment (generally 3 to 5 percent). The process of increasing the concentration of U-235 takes place in a uranium enrichment plant, which typically uses either the gaseous diffusion method or the high-speed gas centrifuge method. The latter method is more efficient and uses less energy than the former method. Gas centrifuges are linked together in what is referred to as a cascade to achieve the enrichment desired. Pakistan (and possibly North Korea) has used this method, and this is also what Iran appears to be intent on developing.
Producing plutonium requires additional, expensive facilities, such as a plutonium reactor or a reprocessing plant. Such facilities are difficult to hide. This has been the primary means of producing weapons by India, North Korea, presumably Israel, and to some extent Pakistan.
Nonmilitary nuclear power reactors may also be used to produce plutonium. Most power reactors use uranium fuel enriched to 3 to 5 percent, and various countries have commercial uranium enrichment plants to fuel these power reactors. Gas centrifuge enrichment facilities that produce low-enriched uranium for fuel can be reconfigured to produce highly enriched uranium for weapons. This points to an inherent weakness in traditional nonproliferation measures designed to stop the production of highly enriched uranium, and is part of the concern about Iran obtaining a uranium enrichment capability. Also, conventional commercial nuclear fuel produces “reactor grade” plutonium in its spent fuel as a result of operations. It has been demonstrated that reactor-grade plutonium can be used in a workable nuclear weapon.1 Experts believe that 25 kilograms (55 pounds) of highly enriched