ABSTRACT
Fissile fuels are required for the operation of nuclear weapons. Although there are some relatively exotic materials that can be used for this purpose (e.g., 233U), the most likely fuels for weapons applications are Pu and Uhighly enriched in 235U (HEU or Oralloy). Plutonium and HEU were –rst produced in the 1940s by the United States and the Soviet Union atthe inception of their nuclear weapons programs (see Chapter 1). Since that time, large quantities of both have been produced in many countries-including some without acknowledged weapons programs. Plutonium and HEU are dif–cult to produce, requiring a large initial investment in facilities and the mastery of dozens of engineering and scienti–c disciplines. Both fuels require extensive physical protection and safeguarding, in part to prevent criticality accidents and (in the case of Pu) the accidental release of a highly toxic substance.
