Nuclear Car Wash

To address the threat of smuggled nuclear materials being brought into the U.S., a Lawrence Livermore National Lab research program is developing a scanner which would examine cargo shipping containers, which now carry up to 90% of the world's trade.

Six million such containers enter the U.S. each year, the bulk arriving through 10 ports, the top three being Los Angeles, Long Beach, and New York-New Jersey. A parcel of radioactive material, intended as part of a terrorist bomb, would presumably be shielded inside the cargo container, precluding passive detection.

The Livermore scanner would work in the following way: the container, on a moving conveyor, would slide past and be exposed to a neutron beam. The neutrons would irradiate all the contents of the container, but would especially activate such dangerous materials such as uranium-235 and plutonium-239. These radioactive species, perturbed by the neutrons, would fission, resulting in the emission of characteristic gamma rays detectable in arrays located downstream of the neutron beam.

Speaking at this week's meeting of the American Physical Society (APS) in Denver, Thomas Gosnell (gosnell1@llnl.gov) said that the goal of the Livermore research is the development of a scanner capable of locating 5 kg of highly enriched uranium or 1 kg of plutonium with a false-positive or false-negative rate of 1% or less. He expects a prototype "nuclear car wash" device would be working within a year and be deployed on a trial basis in a port, such as Oakland, California, a year after that.