Fueling the future of fusion

Tritium is a rare radioactive isotope of hydrogen that is perhaps best known for illuminating watch faces and exit signs. When combined with deuterium, a nonradioactive isotope of hydrogen, tritium also plays a key role in nuclear fusion—both for weapons applications and for possible production of fusion energy. 

For many decades, Los Alamos National Laboratory scientists have researched the process of using tritium to power nuclear fusion reactors. The Lab’s expertise in understanding this fusion fuel cycle could play a crucial role in bringing fusion energy to the electrical grid.

Los Alamos chemical engineer Scott Willms has dedicated his career to studying tritium processing and the fusion fuel cycle. He recently returned to the Lab after spending 14 years at ITER, a collaborative international effort to build the world’s largest tokamak (magnetic confinement device) and explore the feasibility of nuclear fusion as an energy source. Now, Willms is focusing on Los Alamos–designed systems for fueling fusion reactors. He says that understanding the fusion fuel cycle is a key component of creating viable fusion energy.

“In both magnetic and inertial confinement fusion reactor systems, you are not going to burn more than 3 percent of the tritium each time it passes through the reactor,” Willms says. “Tritium is extremely limited, so, for fusion reactors to be effective, we must understand how to clean up tritium and put it back in.” 

Willms says this work first began in the early 1980s with Los Alamos’ Tritium Systems Test Assembly (TSTA), a facility dedicated to the development and demonstration of technologies needed for developing fusion powered reactors. Los Alamos scientists used TSTA to separate isotopes and remove impurities using a process called cryogenic distillation along with a specially designed membrane. “We demonstrated all the systems that you need to clean up the fuel quickly and get it back in the reactor.”

The Department of Energy decommissioned TSTA in 2004, but fusion fuel cycle research continues at Los Alamos’ Hydrogen Processing Lab (HPL). Today at HPL, scientists test new technologies related to the fusion fuel cycle. 

David Dogruel is one of the scientists leading that research. “We are developing and testing the technology using hydrogen and deuterium instead of the fusion fuel of tritium and deuterium because hydrogen behaves identically to tritium but is not radioactive,” Dogruel says. “We can validate the evolving technology and integrate computer modeling to guide and refine both future experimental work and the design of fusion fuel-processing systems. One of the next steps will be to conduct experiments using tritium.”

Dogruel points out that Los Alamos scientists have the benefit of experience working with tritium since the Manhattan Project and have the necessary facilities, such as the Lab’s Weapons Engineering Tritium Facility, the nation’s primary tritium research institution. “You can’t go to Tritium Mart, pick up some tritium, and start playing with it,” he says. “The U.S. national labs have the scientific leadership in tritium and are the only place we can do this.” 

Willms says that the Lab’s expertise and its commitment to working with private companies to support fusion research are a big part of what brought him back to Los Alamos. He and Dogruel say they are excited about the future of their work. 

“Los Alamos has an incredible history of doing very hard things,” says Dogruel, adding, “Many of those things are related to fusion and the fusion fuel cycle.” ★