How a new imaging technique could make detecting nukes easier

If proven under real inspection conditions, the technique could significantly improve the ability to prevent the smuggling of dangerous nuclear materials.

Kazem Ghane/AP/File
Unidentified International Atomic Energy Agency (IAEA) inspectors and Iranian technicians cut the connections between the twin cascades for 20 percent uranium enrichment at Natanz facility, some 200 miles (322 kilometers) south of the capital Tehran, Iran, in this January 2014 file photo.

A new imaging technique that relies on neutrons and high-energy photons can detect the presence of "special nuclear materials" carried in cargo containers.

The method, developed by scientists from the Georgia Institute of Technology, the University of Michigan, and Pennsylvania State University, can simultaneously measure the suspected material's density and atomic number using mono-energetic gamma-ray imaging, while minimizing the amount of radiation entering the container itself, thus reducing the likelihood of harming electronics and other items inside.

"This provided proof that the physics works, and that we can use these particles to actually distinguish among various materials, including special nuclear materials," said Igor Jovanovic, professor of nuclear engineering and radiological sciences at University of Michigan.

The technique has not yet been tested in the real-world conditions of a steel cargo container, but researchers hope to one day employ it in real-world detection of cargos arriving at US ports. If proven under real inspection conditions, the technique could significantly improve the ability to prevent the smuggling of dangerous nuclear materials, the researchers say.

The research, published Monday on Nature journal Scientific Reports, is the first successful effort to identify and image uranium using the technique. 

The method employs an ion accelerator to generates the deuterons, which are then dashed against boron to produce the neutrons and high-energy photons. Next, the researchers focus those particles into a fan-shaped beam, which scans the cargo. 

The photons and neutrons excite nuclear materials present in the cargo, which results in the emission of gamma rays and neutrons that can be detected outside the container. A fission reaction, indicating that fissile materials are inside, produces both "prompt" and "delayed" neutrons. A reaction with non-fissionable materials, on the other hand, does not create a delayed reaction. 

"The gamma rays of different energies interact with the material in very different ways, and how the signals are attenuated will be a very good indicator of what the atomic number of the hidden material is, and its potential density," Anna Erickson, an assistant professor in Georgia Tech's George W. Woodruff School of Mechanical Engineering, said in a statement. "We can observe the characteristics of transmission of these particles to understand what we are looking at."

"If you have something benign, but heavy – like tungsten, for instance – versus something heavy and shielded like uranium, we can tell from the signatures of the neutrons," Erickson said. "We can see the signature of special nuclear materials very clearly in the form of delayed neutrons. This happens only if there are special nuclear materials present."

Earlier methods used to detect cargos with radioactive materials used X-rays, which proved difficult because of the containers' heavy shielding. High levels of X-ray radiation also harmed electronics and other materials inside the cargo. The new method, however, minimizes the amount of radiation entering the container, making it more feasible for use at US ports. 

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to