|Fig. 1: U.S. officials examine a M-388 Davy Crockett nuclear weapon.(Source: Wikimedia Commons)|
Suitcase Nukes have been a fascination of hollywood and spy television shows, as well as a concern for members of Congress throughout the Cold War and after. The premise of a nuclear device with such decimating power in something as inconspicuous and portable as a suitcase has spawned an irrational fear of the term, further heightening the fear of a nuclear mutually assured destruction. However, the probability of danger or misuse by these devices in reality is much less than what Hollywood perceives them to be.
The first creation of a portable nuke was in the 1950s and 1960s by the U.S. in the form of a large backpack called Special Atomic Demolition Munition. For such a portable device, the damage produced is very effective and haunting (Fig 1). The primary objective of these devices were to be carried by a brave two-man team to a particular demolition target such as a dam, tunnel, or bridge. Alternatively, the consequent radiation was also used as a tactical area of denial. Some of these devices could reach the destructive power of the bomb dropped on Hiroshima.  Despite their use in military service and special forces for almost 25 years, not once were they required to be detonated because of the collateral damage they would cause and their highly expensive upkeep.
The primary use case of portable nuclear weapons is their ability to be moved across borders unnoticed by undercover teams or individuals through conventional and widely used civilian systems. This way the distance between target and device is minimized with no suspicions being raised. However, the portability of these nuclear devices comes at a cost of the physical limitations of being so small. In any device, there requires a certain amount of fissile material to reach critical mass. This specific amount of fissile material is needed for a spontaneous nuclear chain reaction to happen by itself. So far, the smallest device to have been made weighed less than 100 pounds with less than a 0.2 kiloton explosion. 
The main reason why these suitcase bombs have not been prevalent in the modern war on terrorism is because the logistics of the bomb itself demand a significant financial and technical infrastructure to create and maintain. Firstly, to create a portable nuclear device that is small enough to be moved by one individual, the main ingredient would have to be plutonium. It would take about 22 pounds of plutonium or 130 pounds of uranium to create a nuclear detonation.  Both would require explosives to set off the blast, but significantly more for the uranium. [3,4] Since the creation and maintenance of plutonium is so extensively difficult and expensive, the only method ill-intentioned actors could create one is by stealing 130 pounds of uranium and creating the device without the fissile material frying the circuitry, both of which are nigh impossible for most non-state actors, not to mention delivering the device.
The miniaturization of nuclear devices remains a risk and danger to all nations. Despite the complex logistics required to support the manufacturing and sustaining of a handheld nuclear device, the inconspicuousness of how easy it is to slip by almost all kinds of security, as well as the looming threat of more than 100 unaccounted-for Russian suitcase bombs, make this archaic cold-war threat still a haunting reality. [2-4]
© Daniar Imanbayev. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for non-commercial purposes only. All other rights, including commercial rights, are reserved to the author.
 C. Schultz, "For 25 Years, U.S. Special Forces Carried Miniature Nukes on Their Backs," Smithsonian Magazine, 10 Feb 14.
 K. Shrader, "Suitcase Nuclear Bomb Unlikely to Exist," Washington Post, 11 Nov 07.
 G. W. Phillips, D. J. Nagel and T. Coffey, "A Primer on the Detection of Nuclear and Radiological Weapons," Center for Technology and National Security Policy, National Defense University, 2005.
 A. J. Keller, "An Increasingly Rare Isotope," Physics 241, Stanford University, Winter 2011.