Researchers from Purdue University have found mechanisms that are vital to interactions between surfaces inside a thermonuclear fusion reactor and hot plasma, which could lead to the development of coatings capable of tolerating radiation damage and ultimately, fusion power plants. 

The inner lining of a fusion reactor often faces horrific conditions leading to radiation damage due to the hot plasma. With the use of nanotechnology, nuclear engineers are looking to "define" small features in the coating as a way to understand and develop a new material that can come in contact with plasma and not be harmed. Finding a material durable enough to withstand such harsh conditions has been difficult, until now. 

Along with researchers at Princeton University in the Princeton Plasma Physics Laboratory, Purdue researchers are using the National Spherical Torus Experiment to test materials, which is the country's only spherical tokamak reactor. They will also study materials in a special "plasma-materials interface probe," then transfer these materials to an "in situ surface analysis facility laboratory."

"We will bring the samples in and study them right there, and will be able to do the characterization in real time to see what happens to the surfaces," said Jean Paul Allain, an assistant professor of nuclear engineering at Purdue University. "We're also going to use computational modeling to connect the fundamental physics learned in our experiments and what we observe inside the tokamak."

One of the tested linings is lithiated graphite, which consists of lithium being added to the inner graphite wall, and when it diffuses into the reactor wall. Then deuterium atoms and the lithiated graphite bind together in the fuel inside these tokamaks, which are what the fusion reactors are called. A magnetic field inside the tokamaks encloses a circular-shaped plasma of deuterium, which is an isotope of hydrogen. 

When a fusion reaction occurs, deuterium atoms hit the inner lining of the fusion reactor and can be sent back to the core and recycled back to the plasma, or they're "pumped," which causes them to bind with the lithiated graphite. 

"We now have an understanding of how the lithiated graphite controls the recycling of hydrogen," said Allain. "This is the first time anyone has looked systematically at the chemistry and physics of pumping by the lithiated graphite. We are learning, at the atomic level, exactly how it is pumped and what dictates the binding of deuterium in this lithiated graphite. So we now have improved insight on how to recondition the surfaces of the tokamak."

The use of a fusion power plant could cut exhaust completely because the deuterium fuel is in seawater. Also, it could produce 10 times more energy than a nuclear fission reactor. Plants like these would be an endless supply of clean energy.

This study was led by Chase Taylor, a doctoral student, Bryan Heim, a graduate student, and Allain. Two papers have been written on the topic, and one will be presented at the Fusion Nuclear Science and Technology/Plasma Facing Components meeting in August.