Amid the bustle of big rigs and forklifts at the Port of Oakland stand 26 rigid yellow scanning devices that officials say form one of the country's best lines of defense against a catastrophic terrorist attack.
The scanners, known as radiation portal monitors, are now in full operation in Oakland, which means that all international cargo arriving at the nation's fourth largest seaport is now scanned for the presence of radioactive substances.
The goal is simple: to prevent terrorists from smuggling a nuclear weapon or radioactive "dirty bomb" into the country, hidden in the stream of thousands of cargo containers that arrive at the Oakland port each day.
"Any container that gives a positive alert upon screening is more closely examined to make sure the contents are safe and can be released onto the streets of our country," said Nat Aycox, director of field operations in San Francisco for U.S. Customs and Border Protection.
Aycox and other officials turned out for a news briefing Tuesday to announce that the port is the first such facility in the country to be fully on board with a homeland security screening program outlined by President Bush at the end of 2003. Scanners now operate at all eight of Oakland's international terminals.
By next year, customs officials plan to have the scanners operating at each of the more than 300 seaports along the nation's periphery. They also are working to install the devices, which cost about $280,000 each, at all land border crossings and major mail distribution centers.
The Oakland scanners are the centerpiece of a $4 million security project at the Port of Oakland, which was funded entirely through federal homeland security grants.
Unlike X-ray devices used to check some shipping containers, the radiation scanners act like radio receivers that respond to certain types of energy. They do not emit radiation.
Steve Baxter, chief customs officer in Oakland, said the devices are so sensitive that natural background radiation sources such as sunlight have been known to trigger their alarms.
That's why any shipments that activate the scanner's alarm are directed to drive through a second scanner. If a second alarm is activated, a more thorough inspection is performed using hand-held scanners, including one device that can identify through spectrum analysis what kind of substance is emitting radiation. Officers then compare these findings with items listed on a container's manifest to see if the source can be explained.
Officers in the past month, for instance, have responded to alarms activated by a load of bananas, because the fruit contains large amounts of potassium, and shipments of ceramic goods, which sometimes are coated with glazing that contains a small amount of radioactive substance.
Officials said the scanners should help reassure the public about the safety of seaports, which have been subjected to pointed criticism in the years since the attacks of Sept. 11, 2001.