The Department of Homeland Security is spending a bundle to install new radiation detectors at ports and border crossings. Too bad the things don't work all that well, Newsday reports.
The devices can screen the contents of a truck or shipping container for emissions from radioactive material that terrorists might use in a "dirty" bomb to contaminate an area, specialists said in recent interviews.But the chances are low, they said, that such detectors, which scan for gamma rays and neutrons, can pick up emissions from a well-shielded cache of highly enriched uranium -- material that could be used in a devastating nuclear bomb.The portal machines also are prone to nuisance alarms on shipments of many materials with low levels of radioactivity, from kitty litter to bananas, and can be triggered by a person who has recently received radioactive tracers in a medical procedure.The detectors, which must be calibrated to take into account the natural background radiation from rocks, soil and cosmic rays, can be set to minimize nuisance alarms."They adjust the detectors so the alarms are tolerable," said Page Stoutland, head of a program for radiological and nuclear countermeasures at Lawrence Livermore National Laboratory in California. "In doing that, have they made the detector such that it will miss legitimate threats? That's the concern..."Stephen Flynn, a former Coast Guard co mmander who is now with the nonprofit Council on Foreign Relations, argues that "rather than the super, high-end stuff, the money would be better spent putting radiological devices in the boxes." Small sensors, if made cheaply enough, could be placed in every shipping container to monitor for radiation and relay data in real time as the ship is still at sea, he said.