August 17, 2004
By Earl Lane
Washington Bureau
Washington -- The federal government is putting hundreds of new radiation detection machines at ports and border crossings, but experts say the devices are far from perfect and stress the need to prevent dangerous nuclear materials from being stolen in the first place.
Detectors called radiation portal monitors, pillar-like arrays through which trucks and shipping containers can pass, already are in place at northern border crossings and are being deployed at major ports as well. Several are operating at a container shipping facility in New Jersey and others are being deployed at all container facilities in the port of New York and New Jersey.
The devices can screen the contents of a truck or shipping container for emissions from radioactive material that terrorists might use in a "dirty" bomb to contaminate an area, specialists said in recent interviews.
But the chances are low, they said, that such detectors, which scan for gamma rays and neutrons, can pick up emissions from a well-shielded cache of highly enriched uranium -- material that could be used in a devastating nuclear bomb.
The portal machines also are prone to nuisance alarms on shipments of many materials with low levels of radioactivity, from kitty litter to bananas, and can be triggered by a person who has recently received radioactive tracers in a medical procedure.
The detectors, which must be calibrated to take into account the natural background radiation from rocks, soil and cosmic rays, can be set to minimize nuisance alarms.
"They adjust the detectors so the alarms are tolerable," said Page Stoutland, head of a program for radiological and nuclear countermeasures at Lawrence Livermore National Laboratory in California. "In doing that, have they made the detector such that it will miss legitimate threats? That's the concern."
One study of monitoring systems installed at an Austrian border crossing reported about 13 nuisance alarms a day at a truck lane during January to June 2000 due to materials such as fertilizer and ceramics. About 900 trucks a day passed through the checkpoint.
A federal government expert on radiation detection, who asked not to be identified, said the newly deployed detectors at U.S. sites "are definitely getting nuisance alarms regularly." He said the rates for such machines typically are about one alarm per several thousand vehicles or containers.
Specialists said the alarms typically are cleared quickly when inspectors check the manifest for products that might trigger them or do more elaborate scans with portable monitors that can identify the species of radioactive isotope triggering the signal.
"We have not had any backlogs as a result of these so-called nuisance alarms," said Beth Rooney, manager of port security for the Port Authority of New York and New Jersey.
Federal authorities also are quick to note that radiation portal monitors are but part of a multilayered detection strategy that includes other technology, such as machines that use gamma rays to give an X-ray-like image of the interior of a shipping container. The strategy also emphasizes increased vigilance at ports abroad where shipping containers originate, close scrutiny of shipping manifests and input from intelligence agencies.
Still, taking all aspects of port security into account, including radiation monitors, a mathematical analysis last year by a Stanford University group concluded there is only a 9.75 percent chance of detecting a shielded nuclear weapon made of either plutonium or highly enriched uranium in a container from an untrusted shipper. For a certified shipper, the study estimates a probability of 24 percent.
Lawrence Wein, lead author of the study, said the United States relies too heavily on a tracking system to identify shipping containers that will be given the closest scrutiny by customs authorities.
Stephen Flynn, a former Coast Guard commander who is now with the nonprofit Council on Foreign Relations, said targeting of at-risk containers often depends on cargo manifests that contain errors and do not fully reflect all of the movements of a particular container. "The cargo manifest is the weakest document in the process," said Flynn, a co-author of the Stanford study.
Steven Fetter, a specialist on nuclear proliferation at the University of Maryland, was skeptical about the precision of the probability estimates in the Stanford study, but said the study's finding on the difficulty of detecting a shielded nuclear weapon, particularly highly enriched uranium, is well taken. "The marginal effort should be put into locating and locking up" highly enriched uranium, Fetter said. "That's where the dollar should be spent."
The many tons of the material still being stored at sites in the former Soviet Union remain a major concern. Matthew Bunn, a specialist on nuclear trafficking at Harvard University's Kennedy School of Government, said only about 22 percent of some 600 tons of bomb-grade material stored in the former Soviet Union is currently under the strict security sought by the United States. For the 2005 budget, the Bush administration asked for less money to help tighten security of Russian nuclear materials: $238 million compared with the $258.5 million currently appropriated by Congress.
As of December 2003, an International Atomic Energy Agency database listed 540 confirmed incidents during the previous decade of illicit trafficking in nuclear and other radioactive materials, mostly from the former Soviet Union and neighboring states. Of those cases, 17 involved highly enriched uranium. Since 1995, none of the cases involved more than 1 or 2 percent of the amount needed to construct a bomb, but the agency says that is little reason for complacency.
While there are many ways terrorists might try to smuggle radioactive materials into the United States, critics have complained that only about 2 percent of the more than 6 million cargo containers that enter U.S. ports each year are scanned, even by conventional X-ray machines or other imaging devices (which might detect a suspiciously shielded package), much less by detectors specifically designed to find radioactive materials.
Bill Anthony, a spokesman for U.S. Customs and Border Protection -- an arm of the Department of Homeland Security -- said the percentage of containers scanned by imaging devices now is approaching 6 percent and that represents containers selected as high risk for potential problems. Under the new initiative to deploy radiation monitors, he said, the goal is to be able eventually to scan 100 percent of incoming "goods, people and conveyances" at U.S. ports.
Experts say the quality of portal detectors has been improving since a 2000 Austrian study found half of the machines tested failed to meet minimum requirements.
A team at Brookhaven National Laboratory has been testing off-the-shelf portal monitors since April 2003. Carl Czajkowski, head of the program, said many of monitors tested in the early months did not operate correctly, whether for faulty wiring or other correctable manufacturing problems. Problems have declined in recent tests, he said.
Data processing methods can reduce the number of nuisance alarms for portal detectors and new models can give more clues on the possible contents of a container, experts said. But readily detecting well-shielded highly enriched uranium awaits a new generation of devices, they said, such as detectors under development that would actively interrogate containers by bombarding them with neutrons.
Richard Oxford, director of strategic accounts for Thermo Electron, a maker of radiation detection equipment, called such neutron screening "the Holy Grail" for spotting highly enriched uranium. But he said it will be costly.
Dennis Slaughter, a nuclear physicist at Lawrence Livermore National Laboratory who is on a team that is developing a neutron scanner, agrees. He said the machines could initially cost as much as $3 million compared with as little as $50,000 for a standard portal monitor. Researchers must show the devices can scan a cargo container quickly without risk to personnel or illegal immigrants who might stow away in a container.
The neutrons also can cause fleeting radioactivity in cargo, including foodstuffs, but Slaughter said such activation dies away in minutes. Still, acceptance of the scanners could be an issue for shippers and port officials who fear even brief effects on cargoes.
Another approach is to scan the containers with high-energy, dual-beam X-rays that can distinguish the heavy nuclei of materials such as uranium, according to Dolan Falconer, chief executive officer of ScanTech, a Georgia-based company. His company is developing such a device, which he says should be able to detect a few kilograms of highly enriched uranium.
Flynn argues that "rather than the super, high-end stuff, the money would be better spent putting radiological devices in the boxes." Small sensors, if made cheaply enough, could be placed in every shipping container to monitor for radiation and relay data in real time as the ship is still at sea, he said.
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