Because they are unlikely to be able to buy or steal a usable bomb and because they are further unlikely to have one handed off to them by an established nuclear state, the most plausible route for terrorists would be to manufacture the device themselves from purloined materials. That is the course identified by a majority of leading experts as the one most likely to lead to nuclear terrorism.44
The simplest design is a “gun” type of device in which masses of highly enriched uranium are hurled at each other within a tube. Such a device would be, as Allison acknowledges, “large, cumbersome, unsafe, unreliable, unpredictable, and inefficient.“45
The process of making such a weapon is daunting even in this minimal case. In particular, the task requires that a considerable series of difficult hurdles be conquered and in sequence.
To begin with, now and likely for the foreseeable future, stateless groups are incapable of manufacturing the requisite weapons‐grade uranium themselves because the process requires an effort on an industrial scale. Moreover, they are unlikely to be supplied with the material by a state for the same reasons a state is unlikely to give them a workable bomb.46 Thus, they would need to steal or illicitly purchase the crucial material.
A successful armed theft is exceedingly unlikely, not only because of the resistance of guards but also because chase would be immediate. A more plausible route would be to corrupt insiders to smuggle out the necessary fissile material. However, that approach requires the terrorists to pay off a host of greedy confederates, including brokers and money transmitters, any one of whom could turn on them or — either out of guile or incompetence — furnish them with stuff that is useless.47 Moreover, because of improved safeguards and accounting practices, it is decreasingly likely that the theft would remain undetected.48 That development is important because if any missing uranium is noticed, the authorities would investigate the few people who might have been able to assist the thieves, and one who seems suddenly to have become prosperous is likely to arrest their attention right from the start. Even one initially tempted by, seduced by, or sympathetic to, the blandishments of the smooth‐talking foreign terrorists might soon develop sobering second thoughts and go to the authorities. Insiders tempted to assist terrorists might also come to ruminate over the fact that, once the heist was accomplished, the terrorists would, as analyst Brian Jenkins puts it none too delicately, “have every incentive to cover their trail, beginning with eliminating their confederates.“49
It is also relevant to note that over the years, known thefts of highly enriched uranium have totaled fewer than 16 pounds. That amount is far less than that required for an atomic explosion: for a crude bomb, more than 100 pounds are necessary to produce a likely yield of one kiloton. Moreover, none of those thieves was connected to al Qaeda, and, most arrestingly, none had buyers lined up — nearly all were caught while trying to peddle their wares. Indeed, concludes analyst Robin Frost, “There appears to be no true demand, except where the buyers were government agents running a sting.” Because there appears to be no commercial market for fissile material, each sale would be a one‐time affair, not a continuing source of profit such as drugs, and there is no evidence of established underworld commercial trade in this illicit commodity.50
If terrorists were somehow successful in obtaining a sufficient mass of relevant material, they would then have to transport it out of the country over unfamiliar terrain, probably while being pursued by security forces. Then, they would need to set up a large and well‐equipped machine shop to manufacture a bomb and populate it with a select team of highly skilled scientists, technicians, and machinists. The process would also require good managers and organizers. The group would have to be assembled and retained for the monumental task without generating consequential suspicions among friends, family, and police about their curious and sudden absence from normal pursuits back home. Pakistan, for example, maintains a strict watch on many of its nuclear scientists even after retirement.51
Some observers have insisted that it would be “easy” for terrorists to assemble a crude bomb if they could get enough fissile material.52 However, Christoph Wirz and Emmanuel Egger, two senior physicists in charge of nuclear issues at Switzerland’s Spiez Laboratory, conclude that the task “could hardly be accomplished by a subnational group.” They point out that precise blueprints are required, not just sketches and general ideas, and that even with a good blueprint, the terrorist group “would most certainly be forced to redesign.” They also stress that the work, far from being “easy,” is difficult, dangerous, and extremely exacting and that the technical requirements “in several fields verge on the unfeasible.“53
Los Alamos research director Younger makes a similar argument, expressing his amazement at “self‐declared ‘nuclear weapons experts,’ many of whom have never seen a real nuclear weapon,” who “hold forth on how easy it is to make a functioning nuclear explosive.” Information is available for getting the general idea behind a rudimentary nuclear explosive, but none is detailed enough for “the confident assembly of a real nuclear explosive.” Younger concludes, “To think that a terrorist group, working in isolation with an unreliable supply of electricity and little access to tools and supplies” could fabricate a bomb “is far‐fetched at best.“54
Under the best of circumstances, the process could take months or even a year or more, and it would all, of course, have to be carried out in utter secret even while local and international security police are likely to be on the intense prowl. In addition, people, or criminal gangs, in the area may observe with increasing curiosity and puzzlement the constant comings and goings of technicians unlikely to be locals.
The process of fabricating a nuclear device requires, then, the effective recruitment of people who at once have great technical skills and will remain completely devoted to the cause. In addition, a host of corrupted coconspirators, many of them foreign, must remain utterly reliable; international and local security services must be kept perpetually in the dark; and no curious outsider must get wind of the project over the months, or even years, it takes to pull off.
The finished product could weigh a ton or more. Encased in lead shielding to mask radioactive emissions, it would then have to be transported to, as well as smuggled into, the relevant target country. Then, the enormous package would have to be received within the target country by a group of collaborators who are at once totally dedicated and technically proficient at handling, maintaining, and perhaps assembling the weapon. Then, they would have to detonate it somewhere under the fervent hope that the machine shop work has been proficient, that no significant shakeups occurred in the treacherous process of transportation, and that the thing — after all that effort — doesn’t prove to be a dud.
The financial costs of the extended operation in its cumulating entirety could become monumental. There would be expensive equipment to buy, smuggle, and set up, as well as people to pay — or pay off. Some operatives might work for free out of dedication, but the vast conspiracy also requires the subversion of an array of criminals and opportunists, each of whom has every incentive to push the price for cooperation as high as possible. Any criminals who are competent and capable enough to be an effective ally in the project are likely to be both smart enough to see opportunities for extortion and psychologically equipped by their profession to be willing to exploit them.