HOMELAND SECURITY Scientists work on scanners to detect nuclear weapons

One of the obstacles is preventing false alarms.
SAN FRANCISCO CHRONICLE
The recent cancellation of a Dubai company's deal to take over several U.S. ports has stirred anxiety over the larger, more haunting question: Could terrorists sneak a nuclear weapon or radioactive "dirty bomb" into a U.S. port?
For several years, scientists at Lawrence Livermore National Laboratory and other national labs have been struggling to prevent that possibility by developing new super-scanners to do what no scanner can: detect with 100 percent reliability a nuclear weapon concealed within one of the roughly 10 million huge cargo containers that enter the United States every year. Of crucial importance, they want one that can do all of that without generating so many false alarms that port cities are repeatedly thrown into panic and international commerce grinds to a halt.
The scientists say they've made very good progress. If all goes well, the U.S. Department of Homeland Security plans to field-test prototypes of the scanners -- hopefully by next year -- at its desert laboratory under construction near Las Vegas. The Radiological and Nuclear Countermeasures Test and Evaluation Complex, as the lab will be called, is being built at the Nevada Test Site, where the United States detonated nuclear test weapons until 1992, and is expected to be completed by September.
With luck, the winning type of scanner or scanners could be installed in U.S. ports within a few years. Experts say a typical busy port will probably have more than one type of scanner to increase the chances of spotting a bomb.
Progress made
Over the past two years, researchers at Lawrence Livermore have made significant progress in developing a scanner that emits neutron beams to scan cargo containers. Other national labs are developing scanners that employ different techniques.
"I think we've got something that works," said Dennis Slaughter, a top scanner developer at Lawrence Livermore.
Until the super-scanners are in place, U.S. ports are not totally helpless to stop a hidden terrorist bomb. Since the Sept. 11 terror attacks, the government has pushed hard to equip and train officials at Oakland and other U.S. cargo ports with X-ray scanners and other gadgets that can detect radiation from nuclear bombs, their fissionable components (uranium or plutonium), or radioactive "dirty bombs," composed of materials such as americium.
Slaughter recalled a visit to the Port of Oakland when "all of the [radioactivity] scanners went off simultaneously." They had sensed radioactivity from "a big container labeled 'Cobalt 60' on the outside." As it turned out, it was a legal shipment -- from Shanghai to Toronto -- of a radioactive element used in medical scanners and therapies. In other words, it was a false alarm -- exactly the kind of incident that developers of the new scanners hope to avoid.
One step ahead
Officials and experts also want a scanner that can't be fooled by terrorists, something they worry about with today's security systems. For one thing, cargo containers are huge: Weighing up to 27 tons, they're the truck-size objects, stacked like shoe boxes, atop the freighters that cruise daily into San Francisco Bay. Inspectors couldn't possibly examine each one physically.
Even if they could, containers' contents are so densely, irregularly packed -- French wine here, South Korean tennis shoes there -- that any machine scanning them detects all kinds of confusing signals. Some product components, such as wood, are rich in hydrogen atoms, which tend to absorb neutrons and, thus, might confuse a neutron scanner or accidentally shield a hidden bomb.
Still, "at international seaports, every cargo container should be both passively and radiographically scanned," said Vayl Oxford, director of the Domestic Nuclear Detection Office at the Department of Homeland Security, in testimony before a Senate committee March 28.
The potential horrors defy the imagination, say experts. "A nuclear attack by terrorists against the United States has the potential to make the terrorist attacks of Sept. 11, 2001, look like a historical footnote," warns a report by the Council on Foreign Relations, an East Coast think tank.
The report points out that "a 6-foot-long improvised nuclear device could easily fit inside a 40-foot-long standard shipping container, probably the delivery vehicle of choice for many nuclear terrorists." Yet "the U.S. government has yet to elevate nuclear terrorism prevention to the highest priority," the report claims.