X-energy Reactor Co., a startup developing miniature nuclear reactors, today announced that it has raised $700 million in late-stage funding.

Jane Street led the oversubscribed Series D investment with participation from more than ten other institutional investors. The deal comes about a year after Amazon.com Inc.’s Climate Pledge Fund backed a $500 million Series C-1 round for X-Energy. The investment was made as part of a nuclear energy project that will see the companies develop more than 5 gigawatts of power generation capacity.

X-Energy is developing a miniature nuclear reactor called the Xe-100 (pictured). The system uses a specialized fuel known as TRISO-X that the company plans to manufacture at a plant in Oak Ridge, Tennessee. Construction on the facility began shortly before today’s funding announcement.

The company’s TRISO-X fuel takes the form of silvery spheres that are about the size of a tennis ball. Each sphere comprises a microscopic uranium kernel surrounded by three protective layers. One layer is made of silicon carbide, a compound of silicon and carbon that can withstand high temperatures. It’s sandwiched between two layers of pyrolytic carbon, a sturdy material similar to graphene.

The main purpose of the TRISO-X’s three protective layers is to prevent the release of fission byproducts. According to X-energy, the design of its fuel spheres ensures that 99.99% of those materials stay within the enclosure. Furthermore, the fact that the fuel spheres are made of materials capable of withstanding high temperatures prevents them from melting.

The company’s technology also includes other safety features. X-energy says that only four of its Xe-100’s components must be actively managed by power plant staff, which means there are relatively few opportunities for human error. The company claims that the reactor can operate continuously for two decades.

Each Xe-100 includes 200,000 TRISO-X fuel spheres. Those spheres generate heat that is absorbed by helium circulated through the reactor. X-energy uses the high-temperature helium to heat water, creating jets of steam that rotate a turbine. The turbine can generate up to 80 megawatts of power.

Last year, X-energy teamed up with Amazon to build a nuclear power plant in Washington state. The facility will initially host four Xe-100 reactors that are expected to provide 320 megawatts of power. In the long term, Amazon and X-energy plan to deploy more than 5 gigawatts of power generation capacity by 2039.

The company is also working with Dow Inc. to build a four-reactor power plant next to one of the chemicals giant’s Texas manufacturing campuses. The facility is expected to come online early next decade.

X-energy disclosed today that its sales pipeline comprises a total of 144 reactors. Those systems will have an aggregate power generation capacity of more than 11 gigawatts. X-Energy will use the new funding to expand its supply chain, finance the construction of its fuel manufacturing facility and establish new partnerships. 

Photo: X-energy