Radiation portal monitors have indirect benefit, Flynn says

Radiation portal monitors have indirect benefit, Flynn says    In addition to problems distinguishing between types of nuclear material, radiation detection machines used to screen trucks and containers at U.S. ports and borders cannot detect nuclear bombs or a shielded dirty bomb, homeland security expert Stephen Flynn said Monday.
   Several major daily newspapers and weekly magazines have recently reported that the drive-through radiation portal monitors are flawed because they can’t distinguish between naturally occurring radiation found in some kinds of household items and nuclear bomb material.
   Flynn said the $400,000 machines cannot detect highly enriched uranium, which doesn’t give off much radiation, when it is shielded in a metal casing or a nuclear bomb that has a built-in shield.
   “So other than that it’s a great system,” he said during a question-and-answer session at the American Association of Exporters and Importers conference in New York.
   The radiation portal monitors can provide some benefit, though, because they force terrorists to use shielding, which then can be picked up by gamma-ray images taken of containers and trailers considered to contain high-risk cargo. The large-scale scanning devices can show a very dense object that allows inspectors to take a closer look at the shipment, he said, previewing testimony he is scheduled to give today before the Senate Homeland Security and Governmental Affairs Committee.
   “So in combination, they are showing some benefit,” he said.