The U.S. Department of Energy has awarded $160 million to X-energy and TerraPower with the potential for billions more in federal funding, as the companies strive to build a working model of their smaller scale, more flexible advanced nuclear reactor designs by 2027. TerraPower is partnered with the GE Hitachi Nuclear Energy, a nuclear industry joint venture formed in 2007.

DOE’s Advanced Reactor Demonstration Program will provide $80 million to each award winner, DOE Secretary Dan Brouillette said Tuesday. DOE intends to invest about $3.2 billion over the next seven years into advanced nuclear, subject to future congressional appropriations, he said.

The remainder of the $230 million appropriated for the program in the fiscal 2020 budget is meant to support additional nuclear demonstration projects. But Tuesday's grant winners “stand out for advancing the technology,” as well as for the financial wherewithal to match DOE's grants and complete their work within seven years, Brouillette said. 

“These awards are a critical first step in a program that will strengthen our country’s nuclear industry,” Brouillette said. “It’s absolutely vital that we make progress on this technology now, so as to ensure we don’t lose access to new markets before access to infrastructure and supply chains in the United States is lost.” 

Brouillette's comments are a nod to the United States’ relatively slow progress in advanced nuclear power compared to countries like Russia, which has the world’s only full-scale testing platform for smaller-scale nuclear reactors, and China, which is building units today, albeit with less modern designs.

Smaller reactors are critical to rejuvenate an industry that’s struggling to finance and build the massive, gigawatt-plus power plants that make up the world’s existing nuclear fleet. In the U.S., several of these have been canceled, and Southern Company’s Plant Vogtle expansion is behind schedule and over budget.

Meanwhile, existing reactors in Pennsylvania and Illinois are facing the threat of closure due to challenging energy market economics, and California’s sole remaining nuclear reactor is set to close by mid-decade.

TerraPower and X-energy’s designs, by contrast, “should be more efficient, they should be cheaper, they should be easier for utilities to bring online,” Brouillette said. Many of the utilities setting net-zero carbon goals by midcentury are relying on advanced nuclear reactors to provide carbon-free energy to replace closing coal and natural gas plants. 

These advanced reactors are also far more flexible than traditional reactors designed to run at maximum output, a critical capability to balance the rising share of intermittent wind and solar power being built to reduce electricity generation carbon emissions, Brouillette said. “Both of the designs we’ve mentioned today have the ability to load follow, to go up and down in power very efficiently and very easily.” 

TerraPower’s molten salt reactor with thermal storage  

TerraPower, founded in 2008 and backed by Microsoft billionaire Bill Gates, is partnering with GE-Hitachi Nuclear Energy to use molten salt energy storage to provide such flexibility. The Bellevue, Wash.-based company has worked with partners including engineering giant Bechtel, DOE’s Oak Ridge National Laboratory and utilities Energy Northwest, Duke Energy, Southern Company and PacifiCorp, and won a $40 million DOE matching grant in 2016.  

TerraPower’s sodium fast reactor design*, dubbed Natrium, generates more heat than needed to drive the steam turbines used to generate electricity. That heat can be captured in molten salt and used to increase the output of the 345-megawatt units to as much as 500 MW for up to about five hours at a time. 

The design also uses sodium as a coolant in the reactor core, differentiating it from traditional reactors that use deuterium oxide, or “heavy water” with a greater atomic weight that’s expensive to make and has limited production sources today. 

TerraPower’s initial plans for what it calls a traveling wave reactor drew investment from Gates and Sun Microsystems billionaire Vinod Khosla with its promise of using depleted uranium rather than enriched uranium-235. But that project was abandoned last year after the Trump administration imposed limits on U.S.-China technology transfer forced it to cancel its partnership with China National Nuclear Corp. 

X-energy’s advanced pebble-bed reactor

X-energy, founded in 2009, is developing a modular “pebble-bed” reactor, so named for the balls of graphite, embedded with radioactive materials such as uranium, that are used for fuel. They’re designed to operate at very high temperatures, with inert gases used both as a coolant and as a heat transfer medium to generate steam to power turbines. 

This design offers passive safety features that differentiate it from water-cooled and steam-powered reactors. But it has yet to be proven in commercial form. A 15 MW demonstration reactor in Germany operated for two decades, but a second, larger-scale version was shut down after only four years of operation. China has built a 10 MW demonstration reactor, and a 250 MW unit began construction in 2012, but plans to start operations in 2019 have been pushed back, with no new completion date announced. 

X-energy’s XE-100 is an 80 MW modular reactor, meant to be built in a factory to reduce construction cost and complexity, and can be combined to a four-unit, 320 MW power plant or larger. The Rockville, Md.-based company has also designed its own tri-structural isotropic fuel pellets, meant to avoid pellet degradation or melting, a core safety concern for pebble-bed designs. 

Like TerraPower’s Natrium design, X-energy’s reactor can use its heat for high-temperature industrial processes as well as for generating electricity. The company won a five-year, $53 million DOE grant in 2016, and has partnered with Southern Company’s nuclear business, BWX Technology, Oregon State University, Teledyne-Brown Engineering, SGL Group, Idaho National Laboratory, and Oak Ridge National Laboratory, the birthplace of the pebble-bed concept. 

New nuclear reactor designs must undergo decades of testing and certification before they can be put into operation. NuScale Power, founded in 2007 to develop a light water modular reactor, received a key approval from the Nuclear Regulatory Commission last month and hopes to deliver its first 50 MW Power Module units in 2027. Other companies pursuing small nuclear reactor designs include Hyperion Power GenerationTerrestrial Energy, and the now-defunct Transatomic


*Correction: A previous version of this article mistakenly described details of TerraPower's molten chloride fast reactor. It has been corrected to provide details of its Natrium sodium fast reactor.