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Experts Question U.S. Emphasis on Nuclear Weapon Detection By Joe Fiorill WASHINGTON — Efforts to improve U.S. chances of detecting a smuggled nuclear device before it can be used in an attack are rapidly gaining steam, despite a tenacious controversy over whether fundamentally better detection is physically or operationally possible (see GSN, May 25). The U.S. Homeland Security and Energy departments broke ground this month for the Radiological/Nuclear Countermeasures Test and Evaluation Complex, housed at Energy’s remote Nevada Test Site. The departments said the complex will test detectors in realistic reproductions of roads, border crossings and airport checkpoints, in a bid for better monitoring of moving automobile traffic, passenger luggage and international mail. “The testing area will help evaluate the latest technology to detect radiological dispersal devices, improvised nuclear devices or nuclear weapons smuggled across a U.S. border for use by terrorists within the United States,” they said in a release last week as they broke ground for the complex. “The Department of Homeland Security is implementing a comprehensive system approach that emphasizes early detection and effective intervention capabilities at the federal, state and local levels.” Through testing at the site and other activities, Homeland Security’s new Domestic Nuclear Detection Office is aiming for big improvements to what many experts agree are currently inadequate detection capabilities (see GSN, June 6). Those experts who support a greater focus on locking down nuclear materials where they lie, however, are questioning whether any amount of research can yield basic improvements in detection, given the difficult physics involved. They say the relatively weak radiation emitted by highly enriched uranium — a particular focus of nuclear terrorism worries, because HEU stocks are more plentiful, less secure and easier to use than plutonium — constitutes a fundamental limit on detection that underscores the need for preventing nuclear materials from being stolen or diverted in the first place. “I hope they’re right,” Homeland Security Associates founder Randall Larsen said of those who are optimistic about improvements, “but I think there’s a lot of people that have too much faith in technology.” Detection of nuclear materials can be done in two ways. The more common of the two, called “passive” detection, senses radiation naturally emitted by weapon-usable nuclear material and by many other objects. The less common “active” approach induces fission — and, therefore, causes the emission of comparatively strong radiation — in a suspect object using an external stimulant such as a stream of neutrons from an accelerator. For the foreseeable future, only passive detection is likely to be a plausible basis for the wide-range monitoring capabilities that are a main focus of current research: Although active detection can improve capabilities at controlled checkpoints, filling large areas with neutrons or gamma rays to induce detectable radiation is not possible, experts say. Using passive methods, highly enriched uranium — the material that sparks the most concern among experts — is more difficult than plutonium to detect, because the uranium emits radiation at a lower rate and is more easily shielded. Even for plutonium, though, most experts estimate the current range of possible detection only in the hundreds of yards — although they differ over how much better the figure can get. Given such limits, many nonproliferation advocates are questioning the wisdom of spending large amounts of money on programs that may never lead to a detection capability beyond a narrow set of formal checkpoints and roads. “I very much doubt that we’re going to get to a situation where we can do wide-area searches for highly enriched uranium,” said Harvard University nuclear expert Matthew Bunn. Natural Resources Defense Council nuclear head Tom Cochran agreed, “I don’t think it’s going to happen, and I think for your money, and because of the fact that you can’t really detect it readily or reliably, you ought to have a very high — really, really high — priority on rounding it up and eliminating it, particularly at the commercial uses of HEU.” Many approaches to improving detection that are now under consideration involve changing how detectors are used, not sensitivity or range as such. Researchers cite the possibility of networking large numbers of detectors — along a road, for example — and processing the many data points in a way that compensates for background interference. Many also refer to the possibility of putting detectors in shipping containers when they leave for the United States, to extend detection time and mitigate low rates of radiation emission, or of capitalizing on uranium-232 traces present in much of the world’s highly enriched uranium. A report last year by a Defense Science Board task force, however, indicated that detection range and capability can be fundamentally improved. The group called on the United States to dramatically step up funding for research in the area and said such efforts could pay off quickly. “Detection systems with order-of-magnitude better performance can be developed in two to perhaps five years,” wrote the task force. “Detection range can be extended by an order of magnitude, opening new defense operational modes, such as rapid, wide-area airborne and vehicle sweeps and monitoring large remote areas and/or extensive road networks,” the experts wrote. “Shielding around the weapon could reduce performance of the detection systems, but the shielding mass can slow down the attacker and expose him to discovery by other means, e.g., detection of the shielding itself.” Critics of a detection focus concede that such claims are not totally unfounded, given the expected large infusion of funds into the effort, but that such statements neglect to mention the strict conditions that would circumscribe such improvements — large increases in detection range may be possible only for plutonium, they point out, and even those new technological means that are developed may prove impractical because of massive cost and logistical constraints. “If you put Los Alamos Laboratories at Long Beach, you could detect” nuclear materials threatening that port over a relatively wide area, Cochran said. The cost of putting large, sophisticated facilities at an essentially unlimited number of entry points, however, is an inevitable barrier to effective detection, he said — adding that, in any case, the approach does not account for the adaptability of potential attackers, who would probably choose routes with an eye specifically to avoiding detection. Bunn said he supports increased research and development in detection technology but that the fruits of such efforts would be mainly “refinements” — lower costs, easier use, small increases in sensitivity — that would never amount to a “cordon” to keep highly enriched uranium out of the United States. “We have to be realistic about what we’re buying and what we’re not buying,” he said. Meanwhile, he said, there is a risk that “complacency” based on excessive confidence in detection could undermine support for securing materials in the former Soviet Union and around the world. More spending is needed on all fronts, he said. In a report circulated in March to government officials and top experts, Cochran delivered a detailed indictment of current detection capabilities. Hundreds of portal monitors recently installed at U.S. ports, he said this week, “will detect a lot of things, but they do not reliably detect highly enriched uranium.” “So now they’re sort of poised to do another round of improvements with new spectroscopic systems that are going to have the same problem,” he said, referring to detectors that, unlike those currently in use, can reliably distinguish among various kinds of radiation. Cochran said spectroscopic detectors may lose in sensitivity even as they gain in specificity. He expressed doubt about whether detection technology will ever provide a reliable response to the nuclear terrorism threat — “stings,” he said, are the way to catch those with illicit nuclear materials. “The guys that steal it typically don’t know how to get in touch with the guys that want it,” Cochran said. Cochran also blasted “senior officials in customs and Homeland Security” for disseminating “false information” about the capabilities of detectors. He called detection programs a “cash cow.” “Congress is in the pork business, and this is another case,” he said. While refusing to speculate about how good detection might get or what aspects of the effort might see breakthroughs, the new Homeland Security detection unit says that, “committed to both evolutionary and revolutionary progress in detection technology,” it is pursuing improvements across the board. “We do not agree that the limits of improvements have been reached,” Homeland Security spokesman Donald Tighe said this week. “Included in the focus on evolutionary progress,” he said, “are improvements in effectiveness, affordability and deployability, including mobility.” As for the other, “revolutionary” track, the office has been noncommittal about what could be in store — possibly because, as Bunn said, “Nobody has a revolutionary idea.”
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