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.
At a container terminal at the heart of Rotterdam's vast harbor, the routine looks smooth. Trucks hauling 40-foot seagoing containers toward their cargo ships first roll slowly between two 20-foot-high white pillars, housing detectors that profile any gamma or neutron radiation on computer screens in a nearby command post.
Manning those screens, Wiersema's agents are now expert readers of the distinctive "signatures" of vegetables, ceramics and other items with slightly radioactive minerals. If anything's suspicious, they order the container to an enclosure where powerful X-rays probe for material that is extremely dense, like radioisotopes.
None has turned up, and that's fine, Wiersema said. "This isn't cocaine or cigarettes," his agents' usual smuggling haul. "There aren't a million bombs. But it's important for prevention. They know we're here."
The greatest deterrent to would-be bombers remains the radiation itself. How would novices extract, handle, transport such material?
"Very quickly," Tannenbaum said dryly. "You'd wear lead underwear and a lead apron. You'd use tongs to keep yourself separated from it." Some experts even theorize, improbably, that relay teams of "suicide technicians" would be needed.
An official U.S. planning scenario envisions a worst case: a bomb laden with powerfully radioactive cesium chloride powder, whose blast kills relatively few people, but whose long-term contamination keeps many blocks of a city uninhabitable for years.
A dirty bomb, if not a mass killer, would be "an economic weapon and a fear weapon," said Carolyn MacKenzie, an IAEA radiation source specialist. "Spreading radioactive materials around can shut down an area for a very, very long time."
But is a highly lethal load of radioactivity necessary? Some suggest a dirty bomber could achieve his goal, terrorizing a population, with a small amount of low-level radioactivity, posing little threat - as long as Geiger counters go off in New York, Washington or whichever city.
The IAEA urges governments to plan carefully to keep the public well informed in such an emergency. Then, said MacKenzie, "it is up to the press not to inspire fear."
NEXT: Part IV - Nuclear terrorism.
On the Net:
Proceedings of the 2003 IAEA conference "Security of Radioactive Sources":