'Dirty bomb' Tops Europe's Threat List, But Who Could Build It?

Detectors probe for radioactive materials while security experts consider 'dirty bombs'

Truckloads of vegetables, dishware, even cranberry juice are setting off the radiation alarms at Europe's biggest port, as thousands of shipping containers bound for America pass through Rotterdam's new "dirty bomb" detectors.

"They talk about our 'false' or 'innocent' alarms," Dutch Customs' Bert Wiersema said of his equipment, sensitive to even traces of radioactivity. "It doesn't matter. We want to detect everything."

And so far, over 18 months, they've detected everything but bombs.

The Dutch are learning daily lessons in a 21st-century school of counterterrorism, pioneering use of technology Washington would like to see deployed at shipping hubs around the world, a forward defense against any terrorist bid to sneak a radiation dispersal device, or dirty bomb, into an American port.

Such hypothetical weapons, pairing ordinary explosives with radioactive material, are seen as the likeliest "weapon of mass destruction" terrorists might use. They topped the list in a U.S. Senate survey in June of 85 government officials and other U.S. and international experts. From Siberia to the U.S. heartland, teams are busy locking down potential sources of dirty-bomb material, such as disused radiation therapy equipment.

But how serious is the threat?

Only 40 percent in that survey thought such an attack likely in the next 10 years. Many experts note that, unlike a nuclear bomb, a radiological device wouldn't cause tens of thousands of casualties or "mass destruction." Some complain the news media overplay the potential and underplay the difficulty of assembling such a weapon.

An example from Russia's rebellious Chechnya illustrates that difficulty: In 1999 three looters tried to steal rods of highly radioactive cobalt-60 from an abandoned chemical factory. All three died of radiation exposure, one reportedly within 30 minutes.

"It's not a trivial thing to do, build a dirty bomb. It's not simply a matter of tying a rod of cesium to a couple of sticks of dynamite and running away," said physicist Benn Tannenbaum, who has studied the question for the American Association for the Advancement of Science.

The rods, powders and pellets of cesium-137, cobalt-60 and other radioactive isotopes are housed in tens of thousands of heavily shielded pieces of equipment worldwide - for cancer radiation therapy, in industrial gauges, in food irradiators, among other uses.

Old portable generators from Soviet days, powering Arctic beacons and other remote instruments, are among the most dangerous, each holding the equivalent of the strontium-90 radioactivity released by the 1986 Chernobyl nuclear plant accident.

The Russians, with U.S. aid, have recovered 72 strontium generators and about 1,000 other disused or abandoned radioactive sources. In the United States itself, the Energy Department has recovered about 11,000 of these "orphan" sources, under a program greatly accelerated since the Sept. 11 attacks. Thousands more remain out there worldwide, including hundreds more old generators.

In former Soviet republics, from Estonia to Tajikistan, the International Atomic Energy Agency has helped secure about 100 sources. But IAEA program chief Vilmos Friedrich said those were "the highest priority only. The job is not complete by any means."

If a cache of iridium-192 or thulium-170 does fall into the wrong hands, U.S.-bound smugglers would have to evade almost 500 radiation monitors installed at U.S. land crossings, seaports and mail facilities in recent years.

Washington is working to extend that line of defense abroad, to container ports of origin. But thus far only Rotterdam and Piraeus, Greece, participate in the "Megaports" network. Others have been slow to accept the added expense and the risk of delaying cargo traffic.

Customs manager Wiersema says he's heard few complaints from shippers about delays, and Dutch Customs has ordered 30 more monitors - at a total cost of at least $18 million - to add to the four on loan from the Americans.

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