Pocket nuke
The term pocket nuke is slang that describes a very small nuclear weapon which could cause considerable damage in densely populated areas. The possibility of such weapons existing is often considered an urban legend due to physical difficulties and costs involved. However, weapons suitable for this purpose have been developed, such as the W54. In 1994 the United States Congress passed The National Defense Authorization for Fiscal Year 1994, preventing the government from developing nuclear weapons with a yield of less than 5 kilotons, thereby making the official development of these weapons in the U.S. unlikely. This law was, however, repealed in the National Defense Authorization Act for Fiscal Year 2004.
Californium-251 is famous for having a small critical mass creating speculation about possible use in pocket nukes.
"Pocket nukes" in literature
The concept of pocket nukes appears frequently in contemporary spy novels and thriller fiction and films. Plot techniques often involve terrorists smuggling a nuclear device into a crowded city or releasing a dirty bomb against civilian targets. With the rising fear of terrorism in the West, fiction of this type is expected to become more common, particularly in the wake of current terrorist attacks against civilian targets.