I thought the article “Detecting Illicit Radioactive Sources” by Joseph McDonald, Bert Coursey, and Michael Carter (Physics Today, November 2004, page 36) was a good presentation of current and future techniques for detecting radioactive material passing through legal ports of entry. However, passage through legal entry points is not the only pathway for illicit radioactive material to enter the US.
The US–Mexico border is almost 2000 miles (3200 km) long. Hundreds of thousands of illegal aliens cross that border into the US each year. It might be difficult to shield strong gamma emitters to the point where an individual could carry a significant quantity. However, the shielding or containment needed for beta or alpha emitters, including special nuclear materials, is light enough that a few individuals could safely carry enough material for a radioactive dispersal device or an improvised nuclear device.
Hundreds of metric tons of illegal drugs are smuggled into the US each year via land, sea, and air pathways. Larger quantities of illicit radioactive materials could enter the US by these routes.
I fully support the efforts to secure our legal ports of entry. They are a necessary part of our security. But I think this article may give a false sense of security by failing to mention these alternate entry pathways for illicit radioactive sources. Questions about the likelihood of terrorists using legal or illegal entry pathways, and about how illegal entry pathways could be patrolled need to be addressed.
