Clemson Scientist Seeks to Repurpose Nuclear Waste

CLEMSON – From the mining of uranium ore to the storage of used fuel, radioactive waste is generated at every stage of the nuclear fuel cycle, and a Clemson University scientist is pursuing research that could help in handling it.

In a collaboration with the Savannah River National Laboratory (SRNL) in Aiken, College of Science professor Stephen Creager of the department of chemistry is working on ways to clean water contaminated by radioactive tritium.

Tritium is an isotope, or form, of hydrogen with a nucleus that has one proton and two neutrons. It differs from hydrogen in that the element’s most common form – protium – has a lone proton and no neutrons. The other isotope of hydrogen – deuterium – falls in the middle of the three, having one proton and one neutron.

Because tritium is an unstable, radioactive isotope, it’s the rarest form of hydrogen, produced mostly as a byproduct of nuclear reactors rather than as a naturally occurring isotope. The Savannah River National Laboratory is one of two facilities in the United States that stores the majority of the country’s nuclear waste, prompting the desire for SRNL to better understand how to dispose of or repurpose tritium. Creager might have a way to do it using the world’s thinnest material: graphene.

“In 2010, the Nobel Prize in physics was awarded for studies on graphene,” Creager said. “At the time, I thought it was trivial because graphene is just a layer of graphite – the lead of pencils – but just that single layer has all of these interesting properties, one of which is that it’s an excellent barrier. It’s thin, but it’s also very impenetrable, and people are doing things like putting it in batteries because it’s got a very high surface area and it’s electronically conductive.”

The researchers who won the Nobel Prize continued to work with graphene and discovered in 2014 that under certain conditions the material is permeable to hydrogen ions, also called protons.

Two years later, in the publication that caught Creager’s attention, the same researchers found that not only did graphene allow protons to flow through it, but it let them through 10 times faster than deuterons, the nuclei of deuterium atoms. In other words, graphene allows 10 times more protons to be separated from deuterium in a single step, an enrichment factor that trumps conventional methods.

One of those conventional methods – electrochemical hydrogen pumping – provides a way to separate mixtures of gases composed of hydrogen isotopes. Schematically, a hydrogen pump is an electrochemical cell that has a cathode on one end, an anode at the other and is connected to a power source.

The team’s idea is to build an electrochemical cell that can clean tritium out of contaminated water by means of water electrolysis – useful to SRNL in the event that its storage facilities ever leak tritium into the groundwater and useful to Creager for his miniature cell specialty.

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