A low-energy nuclear reaction imaging technique designed to detect the presence of weapons-grade uranium and plutonium in cargo containers arriving at U.S. ports was demonstrated. The method relies on a combination of neutrons and high-energy photons to detect shielded radioactive materials inside the containers.
The transmission of high-energy photons can be used to image materials inside the cargo container, while both photons and neutrons excite the special nuclear material – which then emits gamma rays and neutrons that can be detected outside the container. Transmission imaging detectors located in the line of sight of the interrogating fan beam of photons create the image of the cargo.
Researchers demonstrated that the technique works in a laboratory setting by detecting uranium plates and rods. The technique has not yet been tested under the real-world conditions of a steel cargo container, but such demonstration may take place in the near future.