The technology also makes possible just-in-time production, allowing engineers to produce toxic chemicals when and where they require them.
Besser points to phosgene, a nerve agent that was used as a chemical weapon in World War II and is important to the production of plastics. "Why not just make it at the moment you need it, right at the reactor where you are making plastic, rather than making and storing large quantities of a toxic material?"
Although micro-reactors produce only small quantities of a given chemical, they can be linked together to produce larger volumes. This flexibility, along with the micro-reactors' efficiency, also makes them economically attractive.
A Pandora's Box?
At present micro-reactor technology is relatively inaccessible to people outside the field. But as training and production become more widespread, the danger could increase.
"There are some complicated systems, but there are also very simple reactors that wouldn't require too much sophistication," Nguyen, the study author, said. "So in terms of who might be able [to produce dangerous chemicals with such systems], we really can't say."
"It's still an emerging technology, so as of today it probably wouldn't be available to terrorist groups," NJCMS's Besser said. "But 20 years ago you couldn't run out and buy a cell phone for 20 bucks and use it to detonate a roadside bomb. It's all about technology becoming cheaper and more available."
The rapidly developing field poses special challenges for agencies that enforce agreements like the international Chemical Weapons Convention.
"This is a new technology to make chemicals, so the [signs] we've always looked at [to track] chemical production will be different," Nguyen said. "Now instead of looking for large batches, you might be looking at small reactors. This is an example of a technology that will make compliance verification more difficult and also make it more difficult to tell what these reactors are being used for."
Attractive Option for Terrorists?
Many toxic gasses are unstable or tend to break down quickly, and dispersing chemicals for a maximum terror impact is difficult.
"Chemical weapons on the whole are generally not something that terrorists employ, for a number of reasons," said Michael Stebbins, director of biology policy at the Federation of American Scientists in Washington, D.C. "That's not to say that they won't, or that they aren't planning to.
"But generally these weapons are less effective to employ, because they are often technically difficult to make and very dangerous to work with, not to mention distribute, in an attack."
Stebbins cites the example of the 1995 sarin-gas attack in the Tokyo subway by members of the Aum Shinrikyo cult. "Pound for pound, in the same package, they would have hurt a lot more people with dynamite than with sarin."
Stebbins doubts that terrorist groups, at least at present, can take advantage of emerging micro-reactor technologies.
"It's not an easy thing to do, and it's extremely dangerous," he said. "You have to have access to the technology, access to the raw materials, and you also need advanced expertise to deal with this kind of technology. All these are factors that go into making it very difficult to make these things."
But Nguyen, the study author, hopes to focus international attention on the rapidly spreading technology to head off trouble before it begins.
"The first step is to get the policy and science communities together to have a better understanding of the technology," he said. "Looking at these science and technology advancements at an early stage allows us to better deal with problems before they arise."
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