TCS Daily

Hell in a Suitcase

By Ralph Kinney Bennett - April 1, 2004 12:00 AM

I will never forget the image. An unassuming looking man walking the streets of London with a bulging briefcase. Inside it, an atomic bomb.

It was back in 1950. I was just a kid, and I sat immobilized in my seat at the Manos Theater in Latrobe, Pa., watching a British film "Seven Days to Noon." In it, a leading British atomic scientist, played by now-forgotten actor Barry Jones, posts a letter to the Prime Minister saying he has taken a small nuclear weapon and will detonate it in the center of London in seven days unless the government agrees to abandon its atomic weapons program.

The story of how the police track down "Professor John Willoughby," meanwhile evacuating the city of London, was absolutely riveting. And the scenes of a deserted London as the last day approached were eerie and unforgettable.

I'm pretty sure this Boulting Brothers movie -- filmed in black and white with an almost documentary feel to it -- was the first to introduce the idea of carrying a nuclear weapon around in some sort of case. Very little was publicly known about nuclear weapons at that time. People had little sense of their size or shape. There was only a vague understanding that something relatively small had caused horrendously big explosions at Nagasaki and Hiroshima. So the idea of an atomic bomb in a suitcase was not implausible.

We now know how really big and heavy the first atomic bombs, Fat Man and Little Boy, were. But within a few years of the appearance of this movie the U.S. had developed not only artillery shell-sized nuclear munitions but also an 11- by 16- inch oval warhead, the W-54. Dubbed the Davy Crockett, it weighed as little as 51 pounds and could be fired by a soldier from a recoilless rifle!

The closest the U.S. is known to have come to a "suitcase" or hand-carried weapon was a variation of the W-54 called, interestingly enough, the SADM (small atomic demolition munition). This device -- officially the Mk-54 -- would have required a mighty big suitcase. It was a fat cylinder, 15 inches (diameter) by 24 inches, not unlike one of those big plastic buckets you can buy bulk paint in at Home Depot, and it weighed 150 pounds.

Since the deployment (and eventual retirement) of these weapons, more ingenious designs and advances in explosives, structural materials and microelectronics, have brought relative miniaturization of nuclear weapons to a multi-billion dollar high art, making possible the stuffing of warheads by the half-dozens into missile nose cones

"Relative" is the key word here. How small can a nuclear bomb be? What are the downscale physical limits to making one? It is important to have some concept of these limits as we consider the occasional alarms in the media regarding terrorists and "suitcase" or (lately) "backpack" nuclear bombs. Last week were heard al-Qaeda claims that it has a couple of suitcase bombs it bought from Russians years ago. Chechnyan rebels have made similar claims in the past, as have Palestinian terrorists.

The infamous Soviet-made suitcase bombs that supposedly disappeared from inventory sometime after the break-up of the Soviet Union have been the subject of numerous investigations and much fevered speculation. It is known that the Soviets, like the United States, developed small nuclear munitions, small enough to be fired in artillery shells or to be hand-carried (by one or more soldiers) as a demolition device. If they designed and built one that could actually fit in a large brief case, one of them has not shown up anywhere, nor has an official photograph or blueprint of it.

The ones described by Soviet General Alexander Lebed, in sensational Congressional hearings back in 1997, were supposedly in suitcases approximately 24 x 16 x 8 inches. A mock-up of such a bomb, using the warhead of an American nuclear artillery shell, was constructed and, indeed, all the necessary items -- neutron generators, batteries, arming mechanism etc. -- were successfully stuffed in around the cylindrical device itself. (For a photo of the mock-up and more see This is an excellent site thanks to the expository writing of Carey Sublette.)

There continue to be disturbing rumors, and in some cases evidence of fissile material and dangerous nuclear byproducts (strontium, cesium etc.) floating around the international underworld. And while nothing should be considered beyond the scope of determined terrorists with enough money, building a hand carried nuclear weapon "from scratch," so to speak, would be very difficult.

The starting point would be a critical mass of plutonium or U-233. This would be a sphere about 4 or 5 inches in diameter and weighing roughly 28 to 30 pounds. Since the carriers of the weapon would presumably be in close quarters with it for some period of time, the critical mass would have to be of "supergrade" plutonium, which would be relatively safe to handle because it gives off lower neutron emissions. Beyond that, design variations (neutron reflector, high explosive, trigger type etc.) and the packaging for the device would add to size and weight depending on materials used, ingenuity of layout and other factors.

Part of the design of U.S. and probably Soviet small atomic munitions was to insure maximum safety to handlers and enough robustness to preclude accidental damage. These might not be particularly acute considerations for some terrorists, who would be thinking more about portability and concealment.

There can be little doubt that next to the acquisition of an actual contained nuclear munition (in a suitcase or whatever) the acquisition of an artillery-type nuclear warhead would be the ticket for terrorists -- a sort of advanced starter kit. The smallest one the U.S. ever deployed in its arsenal was the M-45, which could be fired from a 155 mm cannon. It was 6.1 inches in diameter (caliber) and 34 inches long. It weighed up to 128 pounds. Remove the conical tip and fuse from one of those and you reduce the length enough to barely fit diagonally in the Soviet-sized suitcase.

But, hey, why not a larger suitcase? Or a crate, or a strong cardboard box? How about the trunk of a car? The possibilities for concealing or disguising a nuclear weapon are endless. Take a look, for instance, at one of those high-capacity air compressors you can buy in any Sears hardware department.

The big question is the shelf-life and availability of nuclear artillery shells. The U.S. shells are apparently accounted for and secure. Whether all the Soviet era mini-warheads can be accounted for is another story.

The shelf-life issue is important. If there is a nuclear munition or more than one "out there," its condition could be in question. A nuclear weapon involves the melding of a variety of materials in close proximity -- metals, plastics, ceramics, exotic high explosives and, of course plutonium and uranium. Things happen inside a nuclear weapon even when it is just sitting.

The plutonium core gives off quite a bit of heat. This will warm the other parts of the weapon up to as much as 100 degrees Fahrenheit. Uranium "rusts" in much the same manner as steel when exposed to the air. And even though warheads are sealed in airtight metal containers, the materials inside -- the explosives and plastic, for instance -- give off trace amounts of oxygen, hydrogen and water vapor that can eventually cause oxidation and corrosion, both of which are abetted by the weapon's intrinsic heat. The high explosives in the detonating "lenses" of a weapon also have been known to deteriorate.

So, unless the purloined (or purchased) warhead was regularly monitored and, if necessary, refurbished by experts it might become dangerously unstable or perhaps not work at all. It's conceivable that the conventional explosives might detonate incompletely and that the nuclear core might be scattered rather than being "assembled" to cause a nuclear explosion. Thus a "dirty bomb" incident, spreading radioactive material, would be the result.

Of course a nuclear weapon gives off a significant signature in the form of both gamma rays and neutrons. A huge effort is being made to employ a variety of gamma and neutron spectrometry devices at ports of entry and the perimeters of potential targets. But these devices (and more sophisticated ones are now being worked on at the national laboratories) are not foolproof. Distance, shielding of various types (tungsten, lead, steel of a given thickness) and the problem of false positives and false negatives are some of the challenges now being wrestled with by detection experts.

In the end, an atomic bomb in a suitcase is really just a metaphor, not only for the portability of nuclear weapons but for the new and ominous possibility of who might be carrying them. The fictional tweedy professor who terrorized London in "Seven Days to Noon" was a misguided idealist with a bomb in a satchel. Those who now seek to terrorize the West and particularly the United States are hate-filled killers who have glorified suicide as a virtue and are bending every effort to secure and use "the bomb," be it in a suitcase, a packing crate, a car or whatever will surreptitiously deliver it to target. "If" is not the question. Where and when are.

Ralph Kinney Bennett recently wrote for TCS about the military's efforts to reduce collateral damage.


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