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Sceptics detect flaws in US nuclear monitor plan

Nature volume 443, pages 890891 (26 October 2006) | Download Citation


Can North Korea's nuclear advances be contained?

Washington DC

Now that North Korea has joined the nuclear club, the United States is intent on preventing it from extending membership perks to others.

Secretary of State Condoleezza Rice visited the region last week to meet leaders from neighbouring countries and discuss ways to detect and intercept illicit nuclear stocks. But proliferation experts disagree about whether such a screening regime is practical or even possible. Spotting radioactive material aboard ships, trucks and aircraft is technically difficult and would require unprecedented regional cooperation.

North Korea's nuclear test on 9 October (see Nature 443, 883–884; 2006 10.1038/443883b) renewed fears about nuclear proliferation. Last week, Mohamed ElBaradei, head of the United Nations' nuclear watchdog, the International Atomic Energy Agency, warned that another 20 to 30 states could soon have the capacity to develop nuclear weapons.

A particular concern is that North Korea might smuggle nuclear material to other states or terrorist groups, says Michael Burns, principal deputy for threat reduction at Los Alamos National Laboratory in New Mexico. Burns says that before leaving for her trip, Rice's team consulted Los Alamos on the possibility of detecting nuclear materials leaving North Korea.

“This is not something you can do from a mile away. You have to get as close as possible.”

Detection is possible, says Burns, but only by integrating a lot of information: “Detection of nuclear material needs a systems-wide approach.” The most important tactic will be to create bottlenecks for goods travelling in and out of North Korea. These ports and border crossings will then need a variety of detection equipment. Passive detectors catch flashes of gamma radiation from the decay products of uranium or plutonium, or neutrons from the decay of certain radioactive isotopes, notably plutonium-240. In addition, active detectors use X-rays or neutrons to scan shipping containers and trucks for dense masses. “That will be an immediate indication to a customs agent to take it aside and look at it by eye,” says Burns.

If nuclear material were found entering or leaving the country, it would also be important to establish where it came from — which is difficult without international cooperation, says Burns: “We have to establish information-sharing through diplomatic channels.” One proposal is to create an international database of nuclear samples (see description on page 907). It's hoped that the ability to trace the origin of illicit stocks would also deter states from selling their nuclear material.

But others disagree about whether such a detection scheme could work. “It's not feasible,” says Steve Fetter, dean of public policy at the University of Maryland in College Park. “The problem is that the radiation signature from the nuclear materials you use in weapons is quite small.” It would be relatively easy to shield the radiation with lead, plastic and other materials, he says. Gaining access to North Korean cargo is also complicated. “This is not something you can do from a mile away,” Fetter says. “You have to get as close as possible.”

Shipping news: plan to step up detection amid fears that North Korea may smuggle nuclear material. Image: K. SASAHARA/AP

Daniel Pinkston, director of the East Asia non-proliferation programme at the Monterey Institute of International Studies in California, agrees, adding that borders are porous and difficult to monitor. “And boarding ships on the high seas is basically an act of war.” Beyond the technical difficulties, Pinkston thinks North Korea would be unlikely to surrender its limited plutonium stocks. “Why would North Korea give up its fissile material? It's priceless to them,” he says. A more real concern, he believes, is that North Korea may export nuclear knowledge: “Data sets or design plans can't be interdicted at all.”

Burns declined to comment on the ability to detect nuclear material remotely, but says he believes a perimeter around North Korea can be built. “Nothing is 100% effective,” he says. “But a system that increases our confidence that we are deterring the movement of nuclear material can be established.”

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