Enhanced vision

The attacks on the Pentagon and World Trade Center showed how terrorists could turn civilian aircraft into guided missiles. Those attacks also brought home the realization that terrorists might try to turn cargo containers into weapons of mass destruction.

Detecting biological, chemical or nuclear weapons hidden in cargo containers has become an urgent issue at U.S. ports. This mobile X-ray inspection system, produced by Advanced Research and Applications Corp., is capable of inspecting a container in less than a minute.

Such weapons are more likely to arrive in freight containers than via ICBMs (intercontinental ballistic missiles), according to Capt. Jon Helmick, director of the Logistics and Intermodal Transportation Program at the U.S. Merchant Marine Academy. He is an expert on security risks facing U.S. ports.

“Perhaps no sector is more dangerously exposed and woefully underprotected than ports and the intermodal freight transportation systems to which they are connected,” Helmick said.

Oceangoing vessels, mostly containerships, make more than 22,000 calls at America’s nearly 360 ports, carrying roughly 11.4 million TEUs (20-foot-equivalent units, or the equivalent of a 20-foot-long shipping container.) each year.

Other than opening each container — and there may be thousands of them on any given ship — there’s no conventional way to verify whether they contain lawnmowers, as listed on the manifest, or weapons.

“Given the consequences of failure in the new era in which we now find ourselves, the current system of cargo security and contraband interdiction does not offer an acceptable degree of protection,” Helmick said.

This heightened sense of danger is driving the rapid development and adoption of new methods for inspecting and making containers more secure. Since Sept. 11, 2001, ports have spent millions of dollars and undertaken a number of initiatives to enhance and strengthen security. Several new security technologies have emerged.

RFID tags

Radio frequency identification (RFID) tags are a relatively new technology with the potential of tracking anything that moves. The system employs encoded tags containing an integrated circuit or silicon chip with a unique identification code and other data. Readers or interrogators are the center of the RFID system, sending a radio signal that is received by the tag.

Ports using RFID can track cargo containers, manage loading and unloading of ships and trucks, and ensure the accurate transfer of goods between vessels and storage areas.

Thousands of transponders embedded into the ground act as an electronic grid throughout the port. As cranes move about the yard lifting cargo, RFID readers mounted on the lifting arms interrogate each transponder they pass, matching the transponder’s code with the location in the yard. The entire system supplies personnel with real-time information on the location and destination of each container and its contents.

In theory, RFID, in combination with other technologies like electronic container seals, should allow inspectors to be reasonably certain the contents have not been tampered with or that contraband or explosives have not been smuggled aboard.

Others maintain that the delicate electronics involved will not stand up to the rough treatment and weather conditions that containers experience. Most technologies that have been tried in the past to transmit information from containers fail because they rust and break down from the salt in the ocean air, become damaged, or break off during transit.

An X-ray image of a truck carrying a water tank. The X-rays from Aracor’s Eagle system are capable of penetrating almost a foot of steel.

Electronic seals

At least four companies now sell a container lock that combines an RFID tag, an optical seal and, in one case, a global positioning satellite (GPS) receiver. After a container is locked, the tag will record any opening of the optical seal and note the location from the GPS. As the container passes through customs, a receiver senses the data in the tag and transmits it to a computer that can flag any evidence of tampering.

Container locks range in price from $5 for a single-use model to about $200 for one equipped with GPS that can be reused for 10 years or more.

An e-lock pilot program has been initiated for containers at the Blaine, Wash., U.S.-Canada border crossing north of Seattle. Officials there are testing the use of disposable electronic seals to track containers on some of the 900,000 trucks passing through annually and to alert inspectors of any cargo tampering. The idea is, if you can prove the container was safe when it went out and wasn’t tampered with en route, you have positive assurance it does not pose a threat.

X-ray detectors

Several companies are producing detectors capable of peering inside containers to verify that the contents match the manifest. Originally used to detect drugs and other contraband, these detectors have now been enlisted in the war on terrorism to scan for substances such as explosives, weapons and ammunition.

While most X-ray systems may take seven to 15 minutes to scan a container, new mobile units are now able to process a 20-foot container in less than a minute.

The detectors do have certain disadvantages. They are expensive (some of them run as high as $1.4 million), and they slow the handling of cargo. Major seaports and border crossings typically inspect only 5 or 10 percent of all containers based on suspicion or random sampling.


A mini-sub inside a cargo container. The X-rays from Aracor’s Eagle system are capable of penetrating almost a foot of steel.

Gamma-ray detector

Ports looking for a more advanced solution will find that gamma-ray technology often represents a faster, more reliable and less expensive way to identify and deter contraband. The technology, developed by Science Applications International Corporation (SAIC), uses gamma rays emitted by naturally occurring isotopes already used in industrial applications. A radioactive element, such as cesium 137 or cobalt 60, produces gamma rays, which are aimed at the target. The rays interact with the object, are detected and then displayed as an image on a monitor.

Because gamma-ray detectors are inherently more sensitive than X-ray detectors, a gamma-ray system can scan objects faster, making such systems perhaps the best hope for achieving 100 percent inspection rates. Gamma-ray systems can examine a standard 40-foot container in a minute or less. A recent demonstration at the Port of Miami resulted in the inspection of over 1,300 TEUs in an eight-hour shift.

U.S. Customs uses an SAIC mobile system to scan cargo for drugs, weapons and contraband. Commercial truck-mounted scanners can cost between $900,000 and $1.4 million, although the federal government can obtain them at a discount of up to 33 percent.

Vapor/trace detection

Sniffer-type sensors analyze air samples emanating from containers using a variety of spectrographical methods. Alternatively, a physical wipe is used to collect particulate matter from the surface of the container. The wipe is then placed in a device and analyzed. The results are used to determine the molecular signature of the material within the container.


Research is also being done in the use of ultrasound to define a container’s contents. An ultrasonic transducer is put into contact with the container. A sensor then detects the sound reflection from objects inside and forms an image of them. However, this technology is useful only in liquid environments.

Miniature nuclear detector

Other technologies are just coming off the drawing board. One potentially useful anti-terrorism tool is in development at the Princeton Plasma Physics Laboratory. Researchers there are testing a miniature nuclear-detection system to scan containers, vessels, autos and luggage for radioactive materials that could be used in nuclear weapons.

The designers believe this portable system could be installed not only at tollbooths and airports, but in port security vehicles as well.

The Princeton team used off-the-shelf components — a solid-state detector, multichannel analyzer, hand-held computer, pre-amp and amplifier — to build a system that can identify the signatures of radioactive materials. The system can be tuned to flag only suspect signatures, eliminating false positives from “normal” nuclear signatures, like medical isotopes and radiography equipment. This capability to differentiate materials with a high degree of spatial resolution in a device that is light, small, robust and portable makes the device unique.

“We’ve performed two tests demonstrating the effectiveness of the technology for detecting radioactive materials in intermodal cargo containers,” said Charles Gentile, lead engineer on the project. “We hid some very small radioactive sources in lead containers, and within four seconds our detection system not only determined there was radioactive material present, but it could also identify the exact nuclear signature.”

According to Gentile, it’s not difficult to detect radiation. The tricky part is to determine exactly what the radiation source is. Being able to distinguish benevolent from malevolent sources can save time, effort and frustration.

In September 2002, for instance, the Coast Guard ordered the Liberian-flagged container ship Palermo Senator to move from Port Elizabeth, N.J., to a safe security zone when trace amounts of radiation were detected in the cargo. Several days later inspectors determined that the source was a naturally occurring material found in a shipment of clay floor tiles.

Gentile’s portable nuclear detection unit may answer the need for a device that can quickly clear a suspect ship or cargo.

Implementation issues

A major issue for many systems is the amount of space needed to operate them safely. Space is usually at a premium in ports and at border stations.

“Normally, the higher energy used by a system, the more space it needs for radiation safety, although there are some systems on the market now that are low in stray radiation, even at high energies,” said Ralph Sheridan, president of American Science and Engineering, in a report prepared for the U.S. Customs Service. “Also, for normal operation, fixed and relocatable systems must rely on local infrastructure (power, water, sewer, communications, etc.) for support.”

Mobile (vehicle-mounted) versions of these systems are usually self-contained and do not need local infrastructure, although some may require a significant exclusion zone, Sheridan said.

No technology, however, possesses all the characteristics that would make it the ideal inspection system.

The best solution, according to Sheridan, is to have a range of systems, each with its own strengths, permitting an inspector to make the most informed decision possible regarding the threat posed by a container.

“For example, a vapor/trace detection system ($50,000 or less) coupled to an X-ray system ($1 million or less) coupled to a radiation system ($50,000 or less) provides a plethora of information” at a reasonable cost, he said. •

By Professional Mariner Staff