LOS ALAMOS, N.M. (AP) - A team of Los Alamos National Laboratory scientists has developed a prototype detector that could quickly screen vehicles and cargo crossing U.S. borders for nuclear materials.
The detector would provide border security with a fast way to screen for weapons being smuggled into the United States without interrupting legitimate international trade.
The scientists presented their prototype detector at the Association for the Advancement of Science in Washington, D.C., this weekend.
"We believe we've worked through all of the major obstacles to building a prototype system for a range of security scenarios," Los Alamos lab scientist Chris Morris said.
A recent CIA report noted that the United States is more likely to be attacked by a weapon smuggled into the country than by one delivered by a ballistic missile.
But with more than 7 million sea cargo containers entering U.S. ports each year, as few as 2 percent of them are ever screened.
For the last two years, the team has been looking at ways to develop a technology to screen quickly and effectively without causing delays at border crossings.
The detector they developed uses naturally occurring cosmic radiation to detect nuclear materials, like uranium and plutonium, hidden within cargo, even if protected behind a thick lead shield.
The cosmic radiation - mostly protons - generates a cascade of particles when it hits Earth's atmosphere. One variety of the particles is called muons.
Each minute, more than 10,000 muons hit every square meter of Earth, passing through nearly everything in their path.
But dense materials with a large number of protons, like plutonium and uranium, produce stronger electromagnetic forces that deflect muons from their course.
The lab's system uses two detectors above the target and two below, so that scientists can measure how many muons are deflected.
Then a complex mathematical algorithm translates the data into a three-dimensional image that allows screeners to locate suspicious items.
In some tests, the team pinpointed 800 grams of plutonium in a lead box surrounded by 12 tons of iron parts in a container.
The algorithm also can analyze the data to determine whether a bomb, nuclear material or shielding are present.
The system has a rate of false positives or negatives of less than 3 percent, lab scientist Rick Chartrand said. He said improvement is still possible.
A new prototype now under construction will be able to check large objects, such as auto engines, in one minute. Scientists predict future prototypes will be able to screen most vehicles at border crossings in about 20 seconds.