At the Y-12 National Security Complex in Oak Ridge, Tennessee, scientists are quietly assembling what they hope will be the world’s most radioactive library. The idea behind the National Uranium Materials Archives is to create the equivalent of a fingerprint database that will help scientists sleuth out the origins of nuclear materials on the black market or detonated in an attack.

Nuclear-GlobeThe archive, launched last spring, is part of the rapidly advancing field of nuclear forensics, which aims to trace clandestine nuclear material to the nation and even the reactor it came from. Authorities seize black market nuclear samples each year, including byproducts of nuclear power generation and weapons-grade uranium left over from the cold war. “The basic principle is to read what we call ‘signatures’ in the nuclear material,” explains Klaus Mayer, head of nuclear forensics at the Institute for Transuranium Elements, in Karlsruhe, Germany. “We then analyze these signatures to learn about its origin.”

Enriched uranium—the fuel for nuclear weapons and power plants—has distinctive chemical signatures (such as the concentration of radioactive isotopes) as well as physical ones (the size of grains or pellets, the presence of impurities). “We use the exclusion principle,” Mayer says. “So if the pellet diameter is bigger than such and such, we can exclude Western-type reactors. If the enrichment is above 5 percent, we can exclude material intended for use in power reactors. We try to narrow down the possible origins as much as possible.” Over the past seven years, Mayer says, his lab has helped to identify samples in some 20 different incidents involving unauthorized possession of nuclear material.

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Source: Joseph Stromberg | Smithsonian Magazine | February 2013