TRISO nuclear fuel doesn’t look like much at first glance.
Each of the small, dark particles produced at BWX Technologies’ manufacturing facility just outside Lynchburg is about the size of a poppy seed.
It’s what’s inside that counts.
Each particle contains a kernel of nuclear fuel that could one day help power the next generation of advanced nuclear reactors.
That kernel is surrounded by three layers, much like a jawbreaker candy.
These layers are designed to contain radioactive fission, which is the process by which uranium atoms release the huge amounts of energy that nuclear reactors use to generate electricity.
BWXT officials say that’s the key to TRISO fuel: Each tiny kernel has its own containment system, making it safer than older nuclear fuels.
It’s been proven to withstand temperatures of 1,800 degrees Celsius (or about 3,300 degrees Fahrenheit), well above a nuclear reactor’s operating temperature, Clay Richardson, vice president of BWXT Advanced Fuels, said in an interview.
“If you have a reactor upset condition” — when a nuclear reactor isn’t operating normally — “literally you could walk away and the fuel would be able to withstand any temperature that the reactor could get to, and so it would not create an issue where the fuel would be breached,” Richardson said.
Those three ceramic layers are where the “tri” in “TRISO” fuel comes from. It stands for “tri-structural isotropic,” which — also like a jawbreaker candy — can be a bit of a mouthful.
BWXT can take 13,000 of those tiny particles, mix them with graphite and press them into a “compact,” much like a drugmaker presses aspirin pills.
Each compact is a cylinder about an inch tall and with a diameter of about three-quarters of an inch.
The fuel can also be assembled into “pebbles,” which look more like billiard balls.
Put 40,000 compacts together, and you’re getting somewhere.
That’s what BWXT recently delivered to the Idaho National Laboratory for testing in Project Pele, a portable microreactor that the company is designing and building for the U.S. military.
The company also plans to deliver TRISO fuel to the Idaho laboratory for use in a reactor created by California-based Antares Nuclear Inc. as part of a pilot program to accelerate advanced reactor development.
That program, sparked by a May 2025 executive order from President Donald Trump, aims to have at least three reactors achieve “criticality” — essentially, when a reactor is on and stable — by July 4.
Trump said in his executive order that advanced reactors have “revolutionary potential.”
“They will open a range of new applications to support data centers, microchip manufacturing, petrochemical production, healthcare, desalination, hydrogen production, and other industries,” he said.
Ten reactor developers are working under the program, and all anticipate meeting the deadline, according to the news agency Reuters.
One of those 10 is Antares Nuclear. BWXT began fabricating the fuel for Antares’ reactor in October.
“By using a TRISO fuel specification and compact that BWXT knows well through the Pele program, we’re building on an established, high-confidence manufacturing foundation,” Antares President and CEO Jordan Bramble said in a news release.
The U.S. Department of Energy’s pilot program has a relatively speedy timeline in part because Trump’s order gives the department the authority to “eliminate or expedite the Department’s environmental reviews for authorizations, permits, approvals, leases, and any other activity” that a reactor developer requires.
Although TRISO has seen renewed interest in recent years as a potential fuel solution for advanced nuclear reactors, its development dates back to the 1960s. BWXT hopes TRISO’s time has finally come, but challenges — including successful testing and commercial market adoption — remain.
TRISO fuel adoption faces challenges
One challenge that any company in the nuclear power industry faces is public perception.
“There’s still a portion of the population that if you hear the word ‘nuclear,’ they think of [Three Mile Island] or Chernobyl or something like that,” said Charles Graves, director of engineering at the company’s Innovation Campus in Campbell County, referring to perhaps the two most famous nuclear-power disasters in history.
BWXT officials emphasized that TRISO fuel and advanced reactors will be safer than older technologies.
“This alleviates all of that. This, combined with the design of these next-generation reactors — it’s physically impossible for those types of things to happen,” Graves said.
Another challenge: market adoption. It remains to be seen how quickly advanced commercial nuclear reactors will come online in the U.S.
Most of the country’s nuclear power plants were built between 1970 and 1990. Few new ones started up after that.
In recent years, smaller advanced nuclear reactors have been much discussed but slow to come to market, in large part due to cost, regulations and public concerns about nuclear power.
Last month, the U.S. Nuclear Regulatory Commission approved its first-ever construction permit for a commercial non-light-water power advanced reactor: TerraPower’s 345-megawatt Natrium project in Kemmerer, Wyoming, which is expected to be complete by 2030. It would use a metallic nuclear fuel of a different type than TRISO.
BWXT is designing its own small reactor, the 20-megawatt BWXT Advanced Nuclear Reactor, which would use TRISO fuel.
Meanwhile, BWXT is getting some new competition in the TRISO fuel space.
Framatome, a French nuclear services company with North American headquarters in Lynchburg, formed a joint venture last year with Oak Ridge, Tennessee-based Standard Nuclear to produce TRISO fuel at Framatome’s Richland, Washington plant beginning next year.
TRISO-X, a subsidiary of Rockville, Maryland-based X-Energy, received a federal license in February to produce its fuel.
BWXT officials believe their company has an advantage due to its 20-year history of working with TRISO.
It also has a Nuclear Regulatory Commission Category 1 license, which allows it to handle various uranium enrichments under tight regulations.
“We have the experience and know-how to operate under license conditions that our competitors don’t,” Richardson said.
Project Pele aims to build microreactor for military
In a separate but related project, work is underway to assemble the Project Pele microreactor at BWXT’s Campbell County campus outside Lynchburg.
The company’s site there houses both its Nuclear Operations Group manufacturing facility and the headquarters of its Advanced Technologies division.
In all, the Lynchburg-based firm employs about 2,850 people in the region.
The idea behind Pele is that the military would have a small, portable nuclear reactor generating at least 1.5 megawatts of electricity that it could deploy wherever it needs power, such as remote bases or disaster sites.
It would be powered by BWXT’s TRISO fuel.
“Pele is really the first time that an active reactor is going to use this fuel and demonstrate its success,” Richardson said.
The package of the reactor and its associated systems is designed to fit in four standard shipping containers, like the kind carried by 18-wheeler trucks. The reactor itself will fit in just one of those containers and will be light enough that it could be transported by airplane.
“It’s a much, much smaller footprint than what today’s existing technologies are. If you were to go to a commercial light water reactor, you’d see a big site, and that’s not what this is,” Graves said.
“Light water reactor” is the term for the reactors used in nuclear power plants today — think Dominion Energy’s North Anna Power Station in Louisa County, for example, which has two reactors, each contained within massive domes.
[Disclosure: Dominion is one of our donors, but donors have no say in news decisions; see our policy.]
BWXT plans to finish the Pele assembly in the next couple of years and send it to the Idaho National Laboratory for testing.
There, the microreactor will be put through the paces, from startup to full power operations.
“The easiest way to think about this is we’re testing not only a reactor but an overall plant, which has a lot of different systems in it,” Graves said.
TRISO fuel’s history goes back decades
Comparing TRISO fuel to poppy seeds and candy makes it seem deceptively simple. In fact, it’s the product of decades of research and development.
The general concept began in the United States and the United Kingdom in the 1960s. Germany advanced the technology in the 1980s.
In the early 2000s, the U.S. Department of Energy began looking at the fuel as a way to boost the development of advanced reactors.
That’s when BWXT came in. In 2003, the company and the DOE added carbon to the uranium and oxygen fuel core.
“That provided a much higher benefit to how this fuel performed and its safety,” Richardson said.
In 2009, BWXT’s TRISO fuel underwent a three-year irradiation test at the Idaho National Laboratory.
After that, the fuel was checked for safety by heating it to 1,800 degrees Celsius for 300 hours. It passed the test.
