Before the events of 11 September 2001, some defence policy analysts attempted, in vain, to convince policy-makers that the enemies of the US were much more likely to send a nuclear weapon to North America hidden in a shipboard container rather than in a ballistic missile whose launch site would be easily detectable. The logic was inescapable: a nuclear device hidden in a seaborne container could be detonated remotely, without revealing the identity of the nation (or terrorist group) that built the device - thereby rendering useless the traditional threat of massive retaliation.
In both scenarios, the threat was envisaged to come from a weapon of mass destruction consisting of either highly enriched uranium (HEU) or plutonium, both of which are referred to in the nuclear industry as 'special nuclear materials'. However, most experts believe that the greatest threat at present is not that a foreign government or organisation will ship a fully functional nuclear weapon, but rather that the enemy will try to create a radiological dispersion device (RDD), also known a 'dirty bomb'. This denotes an explosive device that spreads radioactive material over a large area, where the explosion is conventional rather than nuclear.
An RDD could contain highly radioactive materials drawn from medical or industrial sources, such as caesium, cobalt, and iridium. Another possible source is strontium, which was used by the former Soviet Union in batteries to generate power in remote areas. In June 2002 the International Atomic Energy Agency (IAEA) admitted that radioactive materials needed by terrorists to build an RDD are available around the world, and that more than 100 countries may have inadequate programmes in place to prevent, or even detect, the theft of radioactive materials.
A year later a plot was foiled to sell some 70 pounds of caesium-137 in Bangkok, Thailand. In light of this threat, it is essential that all containers entering the US should be screened for radioactivity to try to prevent the entry of uncontrolled radioactive materials that may later be used to construct either a nuclear device or a 'dirty bomb'.
The Bush administration deserves full credit for proposing the Container Security Initiative, which seeks to 'push the border outwards'; that is, to carry out screening of containers before they reach the US. This is important because most of the largest US cities have or are situated near major ports. If there is indeed a radioactive weapon hidden in a container, it could be set off once it reaches a US port - imagine the devastating impact of several devices being detonated simultaneously in the ports of New York, Long Beach, and Baltimore. Screening containers after they reach the US is better than doing nothing, but it defeats the primary purpose of defending the US homeland.
After 11 September 2001, the importance of screening is better appreciated but there remains much misunderstanding as to how to handle the obvious dilemma of effectively screening roughly six million seaborne containers coming into the US each year without bringing trade to a screeching halt. Securing the US or other national borders from the importation of radioactive materials hidden in containers has so far been cast as impossible. The truth is that preventing this doomsday scenario, using current and well-tested technologies, is achievable. In spite of the current focus on airport security, the fact remains that the greatest threat to the US population does not come from terrorist-directed civilian aircraft but from radioactive devices hidden in seaborne containers. This is where the government needs to immediately focus its efforts.
The x-ray screening technologies currently being employed for most cargo applications are insufficient. There are several systems in use that are designed to screen slowly moving trucks and containers for shielding and other anomalous objects. However, a purely visual screening system, such as a standard x-ray machine, has great difficulty spotting one small suspicious object in a standard 40ft container. For example, a kilogram of HEU is less than one inch in radius, below the capabilities of most imaging systems. A more powerful particle accelerator-based technology has sufficient imaging resolution, but the operator is faced with the daunting task of visually scanning a large container, looking at a monitor filled with a bewildering collection of unfamiliar shapes for objects that would only appear as one or two pixels out of several thousand. However, the shielding necessary to hide a radioactive source will require such a degree of density/and or bulk that it should be easily spotted by a competent operator.
Either a radioactive source is sent with minimal shielding, in which case it can be detected by a radiation detection device, or it must be heavily shielded, facilitating detection through the use of an appropriate x-ray screening device. A hand-held radiation detector is not practical because it is both too slow and insufficiently sensitive, requiring each container to be opened up.
An effective solution to the problem of screening shipping containers will therefore require a fully integrated system containing the following elements:
· An active imaging system for the detection and examination of possible radiation shields;
· A portal monitor for the detection of radiation;
· A reliable security seal system to detect any efforts to breach the security of a container after it has been inspected;
· A global tracking system to monitor the movement of each container; and
· An integrated instrumentation and alarm system that will alert a central monitoring facility in the event radiation is detected, and relay a secure CCTV feed of the actual screening facility.
The last element is critical as unless there is a system under which an alarm is automatically sent to a central monitoring facility located in the destination country, there is a high risk that a possible radiological source may, by accident or design, fail to be noticed by the workers carrying out the search. It is for this reason that a remote monitoring capability is a key feature. With such a capability, US government officials in Washington can automatically be alerted when an incident takes place at any site around the world. They can have real-time, secure video coverage of the port facility in question.
This approach minimises a reliance on manual operators. In addition, explosive and biochemical detection equipment could be integrated into this system. One 40ft container could be scanned every 5 seconds. Multiple scanning systems would allow for cargo to be accurately scanned without significantly slowing down the pace of international trade. This last element is essential if the support of the world's shipping companies, a key element to the success of any screening plan, is to be obtained.
Each of the above elements is already in use, albeit separately. Advanced x-ray machines, for instance, are already being used for a variety of industrial and security applications; mature portal monitoring technologies exist for the detection of radioactive materials to prevent the removal of uranium and plutonium from weapons and nuclear fuel fabrication facilities; an intelligent system for sealing containers of radioactive materials has been employed commercially with the approval and participation of IAEA; and the tracking of large containers, such as railroad cars, using the Global Positioning System is common in many nations. Most importantly, data from each of these systems can also easily be securely transmitted to a central processing facility to ensure proper implementation of the programme.
Portal monitors are the key element of radiation detection in an optimal system. Unlike standard radiation detectors, they are designed to screen moving trucks and containers, are optimised for the detection of uranium and plutonium, and can also detect gamma-ray and neutron-ray emitting radioisotopes. (For all practical purposes, only plutonium emits neutron rays.) These units have been successfully used in the US, Europe and the states of the former Soviet Union to detect the illicit transport of radioactive materials. In addition, portal monitors do not require operators and are very cost-effective, with some systems costing as little as US$30,000.
In summary, the US already has in its possession the technologies necessary to prevent the importation of radioactive materials that could be used to construct weapons. What has been lacking - until now - is a decision to implement these technologies as quickly as possible.
Christopher Boucek is a security writer and media analyst with extensive experience in Middle Eastern affairs
Richard Hubbell is a former CIA officer and currently a security consultant