The Beat Goes On
"The Chicago Tribune describes a new method for detecting nuclear material. The Los Alamos-developed detector relies on measuring the interaction between cosmic rays and and the material being scanned. The different materials have interaction signatures which identify them.
...
The system is said to require only 20 seconds to scan a shipping container and because it simply measures cosmic rays which are present in the everyday environment, the method does not pose a risk to users, even illegal immigrants who might be hiding within the container."
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