By Cindy Moffett
“I have an idea,” Howard Hall said to nuclear engineering graduate student Mike Willis in 2011. “Can you figure out the location of a radiation source if it’s moving?”
To help find the answer, Hall presented Willis with an unassembled toy train, a computer, and some radiation detectors. “Make it work,” he said with encouragement and a smile.
As UT-ORNL Governor’s Chair for Nuclear Security and director of UT’s Institute for Nuclear Security, Hall is constantly investigating new avenues of protection against malicious uses of nuclear and radiological materials. The ability to pinpoint and track the movement of a “dirty bomb”—a device that combines conventional explosives and radioactive material—could save hundreds or even thousands of lives by eliminating the threat before it reaches the target.
Heartily accepting the challenge, Willis set up the toy train with one car carrying a small radiation source. He placed a cluster of sodium iodide radiation detectors in the center of the track and started collecting data. After a good deal of trial-and-error research, Willis settled on a method known as fuzzy logic to interpret the information gathered by the detectors. Work continued over the next several months to scale up and refine the equipment.
Things started to pick up speed when Steve Skutnik joined the effort in 2013, becoming principal investigator and primary pitchman. But, as is the case with many good ideas, funding became a barrier. “Given an infinite amount of money, we could develop the most sophisticated radiation detector in the world,” said Skutnik, assistant professor of nuclear engineering. “But we don’t live in a world of infinite resources.”
An early prototype—cobbled together from marine batteries, a desktop computer, an oversized data acquisition system (DAQ), forty feet of excess cable, and other surplus electronics—was about the size of an office credenza. Since then, Hall and Skutnik’s startup research funding has allowed the team to replace the DAQ with more compact and sophisticated electronics about half the size of a shoebox.
The device features four radiation detectors massed together like a four-leaf clover. The detector closest to the source receives the greatest amount of radiation. The others receive lesser amounts depending on their nearness to the source.
Each detector includes a sensor that creates pulses of light when struck by a radioactive isotope. A photomultiplier turns the light into electrical voltage that indicates the specific isotope, such as cobalt-60 or cesium-137. A unique algorithm analyzes the counts from the DAQ in real time, allowing the source to be pinpointed.
Not only is the package now blessedly less cumbersome, its processing speed has significantly increased. “In our original system everything was post-processed,” Willis said. “That’s the way a lot of systems are. You gather the data, then look at it later. I have been improving the data processing in order to provide live feedback to the user.”
“So now we’re reading directly off the electronics,” Skutnik said. “This makes the system robust and commercial-ready, something with a swift response time.” The user sees the results as a compass with an arrow pointing to the radiation source. Whether the user or the radiation source moves, the compass arrow responds. This development inspired the team to the name the device RadCompass.
In 2014, the investigators received a patent for the RadCompass multiplicity detector. They mounted a prototype mobile unit in the bed of a pickup truck and prowled a parking lot to find a radiation source several car lengths away. This first real-world test was recorded and featured on Discovery Channel’s Daily Planet.
Then grants appeared. “The UT Research Foundation gave us $15,000 to purchase the signal processing electronics, which we can now fit into a car rooftop carrier,” Skutnik said. The UT Institute for Nuclear Security also supplied about $10,000 in seed money funding.
The team has been remarkably tenacious in their journey to create a low-cost mobile directional sensor that can pinpoint radiation sources within a few degrees. With a projected price tag of around $40,000, RadCompass will cost only a fraction of comparable systems, which can run close to $200,000. “Our hope is to put these devices in patrol cars so they can locate the source in a matter of seconds,” Skutnik said.
A program of continual testing and refinement has included several field tests on moving sources at a federally owned ghost town in Fort Indiantown Gap, Pennsylvania. The team expects to have a demonstration unit ready by early 2016. RadCompass works so well that Skutnik sees other potential applications, such as monitoring ports and borders for radiation smuggling. It could also be useful in illicit source detection or for nuclear accident cleanup. A smaller wearable device might even be possible.
Similar devices are under development elsewhere, so Skutnik and Willis feel pressure from competitors. Willis jokes that he is particularly driven by the need to get his PhD. What really motivates them, though, is being able to locate unsecured radiological materials. “It’s kind of scary to think that if somebody called a police station and said ‘I have a dirty bomb and I’m going to blow it up in your city,’ the city probably wouldn’t have the technology to locate it,” Willis said.
“I know this is a good idea—I know it will work, and it’s something that has practical real-world applications. It’s just a matter of seeing it through,” Skutnik added. What began with a question and a toy train five years ago may soon be providing protection from potential radiation catastrophes.