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Securing the Bomb 2007
Slide Show
Simple "Gun-Type" Nuclear Bomb
Unfortunately, if terrorists could get the needed highly enriched uranium (HEU) or plutonium, making a crude nuclear bomb is not as difficult as is sometimes thought. A "gun-type" bomb, shown here, requires little more than slamming two pieces of HEU together at high speed with conventional explosives. The bomb that obliterated the Japanese city of Hiroshima, for example, was a cannon that fired a shell of HEU into rings of HEU. A gun-type bomb requires approximately 50 kilograms of HEU; if a terrorist group had less HEU, or had plutonium, it would have to try to make a more difficult "implosion-type" bomb, in which explosives arranged around a ball of nuclear material crush it to a smaller size, setting off the nuclear chain reaction. Government studies have repeatedly concluded that it is plausible that a sophisticated terrorist group could make a crude nuclear bomb. As an Office of Technology Assessment study warned: "A small group of people, none of whom have ever had access to the classified literature, could possibly design and build a crude nuclear explosive device... Only modest machine-shop facilities that could be contracted for without arousing suspicion would be required."
For more information, see Chapter 1 of Securing the Bomb 2007, or check out "A Tutorial on Nuclear Weapons and Nuclear-Explosive Materials" .
The Securing the Bomb section of the NTI website is produced by the Project on Managing the Atom (MTA) for NTI, and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, agents. MTA welcomes comments and suggestions at atom@harvard.edu. Copyright 2007 by the President and Fellows of Harvard College.