Nuclear forensics: New method traces plutonium to original source

Video: Dwight Look College of Engineering

Investigators can now track any sample of weapons-grade plutonium to its source, thanks to a new method in nuclear forensics created by researchers at Texas A&M University.

The method is the work of the Nuclear Security and Science Policy Institute, the Department of Nuclear Engineering in the Dwight Look College of Engineering, and Charles M. Folden III, an assistant professor and head of the Heavy Elements Group, an interdisciplinary collaboration between the College of Science and the Dwight Look College of Engineering .

“The goal is forensics,” said Sunil Chirayath, the Institute’s interim director and a research assistant professor in the Department of Nuclear Engineering. “If somebody is smuggling plutonium to the United States and if it is confiscated, we need to attribute who did this and we have to put together several pieces of this puzzle. One of the pieces of the puzzle we specifically deal with is determining which type of nuclear reactor produced the confiscated plutonium.”

In the neutron spectrum of nuclear reactors, Chirayath said, there are two extremes: thermal reactors and fast reactors, with some variants between.

Based on a number of variables, different reactor types leave different signatures in the plutonium that is created from spent nuclear fuel. Once investigators are able to determine what kind of reactor the material came from, it becomes a game of elimination between the different countries where these reactor types operate.

Using this information, government agencies will look at possible countries in which the material could have been produced and attempt to track how the plutonium may have been transported and illegally acquired.

According to Chirayath, the method for tracing the source of the nuclear material shares some similarity with modern criminal forensics. In the same way criminals might leave fingerprints or DNA evidence at a crime scene, the process for creating the weapons grade plutonium leaves its own type of characteristics on the nuclear material.

“Some specific elements, when you separate plutonium, go with that plutonium as trace contaminants,” Chirayath said. “When you touch something you don’t leave just your fingerprint behind, you leave some characteristics behind with that print that leaves an indelible mark. We want to know if there is any trace contamination in that plutonium where these specific elements are, and we can then tell through that element where this material was created.”

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