Researchers receive $1.75 million grant to improve detection of nuclear materials
A team of University of Wisconsin-Madison scientists and engineers will improve a technology that could detect nuclear materials, including atomic weapons and other hazardous materials in everything from luggage to cargo containers.
Led by Douglass Henderson, a professor of engineering physics at UW-Madison, the researchers received a $1.75 million grant from U.S. Department of Homeland Security’s Domestic Nuclear Detection Office (DNDO) to research ways to increase the sensitivity of systems that can sense the presence of highly enriched uranium (HEU) and other harmful materials.
Researchers are able to detect highly enriched uranium, a substance used in the production of atomic bombs, by hitting it with neutrons and observing the radioactive particles it emits. Yet there is a large incentive to reduce the quantity of neutrons required to detect HEU, in order to protect the human body against radioactivity from the neutrons themselves.
Highly enriched uranium is composed largely of uranium-235, an isotope of the chemical element uranium. Although it can be used for nuclear power generation, it is most widely known as a key ingredient in nuclear weapons. Uranium-235 is not highly detectable, and can be easily shielded with lead or similar materials, since their gamma rays are low energy.
Henderson and UW-Madison colleagues John Santarius, a research professor of engineering physics, and Gerald Kulcinski, the Grainger professor emeritus of nuclear engineering, are assessing ways to develop more versatile and sensitive neutron sources so that they can engineer a detection device to fit a broad range of applications. For instance, this sort of device could more easily fit into tight spaces or between containers, which would be practical for detecting a material, such as highly enriched uranium, hidden among the containers on a cargo ship.
Instead of delivering neutrons from a single-point source into a target in order to detect a hazardous material, the researchers intend to develop a chamber that will expose the material being scanned to more complicated neutron distributions. “If you pattern your source neutrons in time and space, then find the resulting patterns in the detector signals, you can be more sensitive and reliable in detecting highly enriched uranium,” Santarius says.
The research is not just about detecting bombs, however, but rather honing the technology so that it is sensitive to various hazardous materials.
“Think of going through airport security,” says Santarius. "You don’t necessarily have to be looking for a bomb; it takes somewhere on the order of 5 to 10 kilograms of HEU to make a bomb. That’s not a large volume, because it’s very dense. If someone were to bring in a kilogram, it wouldn’t be enough for a bomb itself, but you could assemble a bomb with it. There are also various other materials you could smuggle, like chemical explosives, which you wouldn’t want terrorists to bring in. Neutrons are useful for detecting such materials and also chemical pollutants.”
The researchers received funding through the College of Engineering Research Innovation Committee to conduct preliminary research, which ultimately made their research proposal to the Department of Homeland Security more competitive. Through this initial support, they were able to fund a graduate student to begin setting up an experimental test program.
Now, early in the five-year research project, they are starting to conduct research on the future system: how to configure the neutron sources and the detectors, and how to process the signals. They aim to reduce the amount of time it takes to detect a hazardous material to under a minute, and ultimately build a system that can detect even well hidden hazardous materials of much smaller sizes than is currently possible. “We know if we can hit HEU with enough neutrons, we can get signals above the noise, which is the brute force method. If you can rise above the muck far enough, you can sense HEU,” Santarius says. “The DNDO project aims to use patterned neutron sources as a way to more sensitively separate the HEU signature from the noise.”