Sarah Scoles reports that nuclear security researcher Rodney Ewing left the University of Michigan for Stanford in 2014, he left some of his belongings back in the Midwest. Hundreds of his belongings, actually. All of them radioactive. He wasn't trying to poison anybody: It was a collection of minerals from around the world—some unearthed himself, some donated—each with uranium enmeshed inside. And soon, scientists would use this legacy in a novel Department of Homeland Security project—one that aims to hunt down the source of illegal nuclear material that could end up in bombs.
Ewing bequeathed the samples to his former postdoc, Peter Burns, then a professor at Notre Dame. And along with his colleague Antonio Simonetti, he set off to build a global forensic database of uranium ore to help the DHS identify the perps. Each sample has its own chemical and isotopic fingerprints, unique to the geological and geochemical forces that formed it. That way, if authorities find someone trafficking radioactive material, they can figure out where it came from. And a dirty bomb goes off somewhere, they can analyze the fallout’s fingerprint to determine the source of the original material—and so, perhaps, who took it. For much of his career, Simonetti, a geochemist, had stayed in the scientific realm, researching Earth's upper mantle. But around 2011, he heard about a program starting at an organization called the National Nuclear Security Administration. “Essentially, they were looking for a materials scientist who could investigate blast material in very fine detail,” says Simonetti—in particular, the leftovers from the first-ever nuclear blast.
There are two basic ways to find out the composition of radioactive material. “The conventional way is by destroying the sample,” says Simonetti. You dissolve it into solution, creating a kind of nuclear-chemical Kool-Aid. Then, you send that solution into a specific kind of mass spectrometer, which picks apart its individual chemical constituents. If you particularly want to know about the details of one element—like uranium—you purify the solution and pull out just that one thing. Then, you run it through the spectrometer to find out which isotopes show up how often. It’s kind of like text-searching a book to find out how many times the poorly edited author wrote “bookeeper” versus “bookkeeper.”
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