Lauren Garrison: Testing materials for the future of fusion
August 7, 2018 – The materials inside a fusion reactor must withstand one of the most extreme environments in science, with temperatures in the thousands of degrees Celsius and a constant bombardment of neutron radiation and deuterium and tritium, isotopes of hydrogen, from the volatile plasma at the heart of the device.
Conventional materials cannot endure such punishing conditions, requiring tougher novel materials to be researched and designed before fusion reactors can move from basic science to potential future energy sources. One of the fusion materials researchers looking to find a possible candidate is Lauren Garrison, a Weinberg Fellow in the Nuclear Materials Science and Technology Group at the Department of Energy’s Oak Ridge National Laboratory.
“I’m drawn to plasma facing materials because it is such a challenging environment, so unique and complex, trying to understand how we can have a material that can withstand all of these very difficult conditions,” Garrison said.
Working with plasma-facing materials is especially tricky, as the environment inside a fusion reactor is like no place on Earth, so the long, arduous process of testing new materials can sometimes feel like assembling a puzzle with no edge pieces to provide a helpful framework.
“Many of the structural and cooling components have some comparable materials that would be used in a fission reactor, so there is some sort of jumping-off point,” Garrison said. “But the plasma-facing region, which is extremely hot and fusing on one side and connected to structural materials on the other side, has nothing comparable in fission, so it is very specific to this application.”
Garrison first studied nuclear engineering during her time as an undergrad at the University of Illinois and had several diverse research internship experiences before finding nuclear materials, which she found distinctly interesting and wished to pursue as a career.
She interned at the university’s Center for Plasma-Materials Interaction, researching plasma processing and plasma modification of surfaces. It was the first research area that caught her attention and gave her experience with lab testing that she hadn’t previously seen in her other classes.
She then interned at a chemistry lab at the National Polytechnic Institute of Lorraine in Nancy, France, which provided an incredible opportunity to branch out into other subjects and gain a perspective on science culture in another country.
“As an engineering or science student, having internship experiences is crucial for both getting the hands-on work and getting a sense for the field, for the actual work environment and for different companies or labs,” Garrison said.
She worked for a short time in the Cryogenic Dark Matter Search research group at Fermi National Accelerator Laboratory before being selected for the DOE Office of Science graduate fellowship program, where she first got to visit ORNL and learn how it supported many nuclear materials projects, especially in fusion materials, that were relevant to her interests.
“No other national lab had the same range of capabilities as ORNL, matched with these amazing materials analysis techniques,” Garrison said. “Whereas smaller labs or universities might be experts in one specific technique, what we have here is the combined benefit of expert scientists in many subareas and the tools to perform all the tests together and compare everything.”
Garrison had found a place that aligned with her interests and would allow her to push the boundaries of her knowledge. ORNL, as a leader in the field of neutron irradiated materials, enabled her to collaborate with other research groups from around the world to test new materials and processes on a wider scale than was possible at other facilities.
Garrison is currently collaborating with Japanese researchers on Project PHENIX, an experiment designed to evaluate tungsten and tungsten-based materials for possible use in future fusion reactors. The team built a specially instrumented capsule with four different temperature zones to hold more than 1,100 material samples for irradiation in the High Flux Isotope Reactor, a DOE Office of Science User Facility. After exposing the capsule to several fuel cycles in HFIR and a cooldown period in a hot cell, Garrison and the project team are now examining the materials to gauge the effects of high heat flux and neutron damage on their microstructures and physical properties.
The goal of her work is to use the results of these varied tests and create a more well-rounded database of potential fusion materials, connect new information together and fill in the knowledge gaps in the field.
“At this point, we’re not going to find a magic material that’s perfect in every different condition it needs to withstand, so we are going to have to make a compromise or understand where the weaknesses are,” Garrison said. “The only way we can move towards building something successful is with the broad testing of materials on many different axes to be able to compare them to each other.”
Garrison would love to see a working fusion reactor in her lifetime and hopes that her work will help contribute to its creation. For now, though, fusion research is still based in basic science, which allows her to pursue questions without specific constraints or a final product in mind.
“It’s very rewarding for me to be able to think creatively and have some freedom to investigate different avenues,” she said.
As time goes on and more of the big questions in plasma science are answered, Garrison hopes the public will come to recognize the potential of fusion energy and how the current investments will pay off in the future.
“I love the big picture of fusion and I think it is easy to get people excited about how great it is for energy,” she said. “Every time I get to talk about it, I get inspired and remember why I’m writing these long reports and doing all this work, because it has really cool applications that it is going towards.”
ORNL is managed by UT-Battelle for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. DOE’s Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/. – By Sean Simoneau