To protect nations against weapons of mass destruction, governments have been active in implementing programmes to increase container handling security. Efforts such as the Container Security Initiative, the Secure Freight Initiative, and the SAFE Ports Act represent the leading edge of legislation aimed at eventually screening 100 per cent of high-risk containers loaded in foreign ports for nuclear materials and other potential weapons. These containers will be screened through a combination of two types of nonintrusive inspection technologies: radiographic imaging to view the contents of closed containers, and passive scanning to detect radiation sources inside these containers. Additional legislation will likely be enacted.
While useful in focusing efforts to address container screening challenges, legislation alone is insufficient. It is futile to implement technologies that ignore the realities of modern commerce – high throughput and minimal physical space requirements. Nonintrusive inspection systems must be designed to meet the goals of both security and commerce. Because shipping volumes can reach as high as thousands of containers per hour at the world’s busiest facilities, these systems must be very fast to scan all containers. It only takes one container concealing a threat to create a disaster.
Because they are entirely passive and emit no radiation, radiation detection systems are easily deployed in high-throughput drive-through configurations. The main challenge facing designers is integrating these systems with radiographic imaging technology, which can interfere with radiation detection. X-ray and gamma-ray radiographic imaging systems come in a variety of configurations. Gantry systems, in which the source and detector array move past stationary, unoccupied trucks with containers, provide bumper-to-bumper scanning but have low throughput. Truck-mounted mobile systems offer a compromise between throughput and bumper-to-bumper scanning as well as ease of relocation. No configuration, however, is better suited to scanning containers than fixed-portal systems, which allow trucks to drive through without stopping or requiring the driver to exit the vehicle.