Radiation detection at US ports and borders.

A nuclear or radiological attack on a US port would be devastating. According to a recent study published by the RAND Institute, in a worst-case scenario, up to 1 million people could be killed by the detonation of a 10-20-kiloton bomb. Aside from the human cost, the economic effects of such an

Over 11 million shipping containers pass through the US' 361 ports each year, and the government is faced with the difficult task of making sure that none of them contains illicit radioactive or nuclear material. The same screening must be done at the northern and southern land borders. Technologies that can detect radiation are at the forefront of this effort, and developments in these technologies have a direct effect on national and global security.

Instruments used to detect nuclear and radioactive material are generally placed into the following categories: personal radiation detectors (PRDs), radioactive isotope identification devices (RIIDs), radiation portal monitors (RPMs) and non-invasive imaging (NII) systems.

PRDs are small devices that can be worn on a bolt or in a pocket. PRDs detect gamma rays and can give information about radiation strength. More than 14,000 PRDs are deployed at US ports of entry. Vendors of PRDs include Berkeley Nucleonics, SAIC, Canberra Industries and RAE Systems.

RIIDs not only react to radiation, they use gamma-ray spectrometry to read the spectrographic "fingerprint" of radiation produced In order to determine isotopic identity. RIIDs are larger than PRDs, varying in size from half a pound to backpack-based systems weighing up to 25 pounds. Some RIIDs are equipped with helium-3 tubes to detect neutrons. According to the March 2006 testimony of Jayson Ahem, assistant commissioner in the Office of Field Operations in US Customs & Border Protection (CBP), 491 RIIDs are being used at US entry points. Makers of RIIDs include Ortec, Berkeley Nucleonics, Thermo Electron and Canberra Industries.

RPMs are large portals through which a truck or a train can pass. RPMs contain plastic-based (frequently polyvinyltuolene) scintillators to detect gamma rays, and many of them also use helium-3 tubes to detect neutrons. As of the end of March, 740 RPMs are being used at US entry ports. RPMs are made by Canberra Industries and SAIC, among others.

NII systems do not detect radiation; rather, they are used to scan the insides of containers with x-rays or gamma rays. This can be useful because radioactive or nuclear material can be shielded by materials such as lead. Particularly dense materials will attract attention on being scanned. These units can be driven through or installed In vehicles for mobile applications. Some makers of NII systems include OSI, American Science and Engineering, SAIC and L-3 Communications.