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Pushing fusion energy technology forward

Trey Gebhart. Image credit: Genevieve Martin, ORNL

Trey Gebhart traces his interest in fusion energy back to his experiences as an undergraduate engineering student at Virginia Tech.

“When I was an undergrad, my senior design project was to build a Farnsworth fusor, a benchtop-scale device for generating nuclear fusion reactions,” he said. “That sort of opened my eyes to fusion and the possibility that it holds for generating clean energy to curb our pending climate crisis.”

His latest foray into fusion energy is his research proposal “Solutions for a More Efficient and Economical Fusion Fuel Cycle,” which received an ECRP award from DOE’s Office of Science. His studies will be focused on improving the handling of tritium, a rare isotope of hydrogen that is needed, along with deuterium, to fuel fusion reactors.

“Tritium is very expensive,” Gebhart said, “about $30,000 per gram, and that price is only going to go up. So, in order for a fusion power plant to truly be economical, the tritium inventory of the plants must be kept as low as possible.”

He noted that the groundbreaking ITER fusion device currently under construction in France is designed to send tritium-containing exhaust through an extensive, external recovery and separation process before feeding recovered tritium back into the device’s fuel system. Future fusion power plants will not need to isotopically separate their fuel stream as long as the isotope ratios can be monitored in real time.

“My research is focused on developing a direct, internal recycling loop that will separate both tritium and deuterium from fusion exhaust and send it immediately back into the fueling system,” Gebhart said. “If we can largely bypass the tritium plant in future power plants, we can minimize power plants’ size and increase their economic viability and overall safety.”

Gebhart plans to reach that goal by developing a series of cryogenic pumps that can handle these separations.

“The exhaust from fusion devices has a handful of impurities that are pretty well known,” he said. “We have the background needed to develop pumps that can separate impurities from the fuel to make the fusion fuel cycle more efficient.”

“We could just design these pumps and determine whether they would be efficient enough to reduce the overall tritium inventory of the plant,” Gebhart said, “but the real deliverable isn’t just knowing whether or not this approach is viable; it’s developing the tools and hardware that makes it possible at reactor-relevant conditions.”