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X Energy, LLC
IndustryNuclear power
FounderKam Ghaffarian
Key people
Clay Sell

X-energy is an American private nuclear reactor and fuel design engineering company. It is developing a Generation IV high-temperature gas-cooled pebble-bed nuclear reactor design. Since its founding in 2009, it has received various government grants and contracts, notably through the Department of Energy's (DOE) Advanced Reactor Concept Cooperative Agreement in 2016 and its Advanced Reactor Demonstration Program (ARDP) in 2020.


The company was founded in 2009 by Kam Ghaffarian.[1] In January 2016, X-energy was awarded a five-year $53-million award as part of the DOE's Advanced Reactor Concept Cooperative Agreement to advance elements of their reactor development.[2][3][4] In 2019, X-energy received funding from the United States Department of Defense to develop small military reactors for use at forward bases.[5] Former Deputy Secretary of Energy of the DOE, Clay Sell, was appointed CEO of X-energy in 2019.[6]

In October 2020, the company was chosen by the DOE as a recipient of a matching grant totaling between $400 million and $4 billion over the next 5 to 7 years for the cost of building a demonstration reactor of their Xe-100, helium-cooled pebble-bed reactor design. This is part of the DOE's Advanced Reactor Demonstration Program, which also awarded the same grant to TerraPower.[7]

In 2022 Curtiss-Wright agreed to act as the preferred supplier of 3 critical components of the Xe-100 reactor. The initial installation of the reactor is projected to be for Energy Northwest in Washington State.[8]

Reactor design[edit]

The Xe-100 is a pebble bed high-temperature gas-cooled nuclear reactor design that is planned to be smaller, simpler and safer when compared to conventional nuclear designs. Pebble bed high temperature gas-cooled reactors were first proposed in 1944. Each reactor is planned to generate 200 MWt and approximately 76 MWe. The fuel for the Xe-100 is a spherical fuel element, or pebble, that utilizes the tristructural isotropic (TRISO) particle nuclear fuel design, with Uranium enriched to 20%, to allow for longer periods between refueling.[7] X-energy claims that TRISO fuel will make nuclear meltdowns virtually impossible.


  1. ^ Fehrenbacher, Katie (February 4, 2016). "Meet a Startup Making a New Kind of Safer, Smaller Nuclear Reactor". Fortune. Retrieved November 21, 2021.
  2. ^ Fountain, Henry (January 19, 2016). "U.S. Acts to Spur Development of High-Tech Reactors". The New York Times. ISSN 0362-4331. Retrieved April 2, 2017.
  3. ^ Fehrenbacher, Katie (February 16, 2016). "Meet a Startup Making a New Kind of Safer, Smaller Nuclear Reactor". Fortune. Retrieved November 9, 2017.
  4. ^ Conca, James (March 27, 2017). "X-Energy Steps Into The Ring With Its Advanced Pebble Bed Modular Nuclear Reactor". Forbes. Retrieved November 9, 2017.
  5. ^ Harper, John (April 27, 2020). "Safety Concerns Could Stymie Nuclear Reactor Plans". National Defense.
  6. ^ Bernton, Hal (November 8, 2021). "This next-generation nuclear power plant is pitched for Washington state. Can it 'change the world'?". The Seattle Times. Retrieved November 21, 2021.
  7. ^ a b Cho, Adrian (October 16, 2020). "Department of Energy picks two advanced nuclear reactors for demonstration projects". Science. Retrieved October 20, 2020. DOE will split the total cost of building each plant with private industry. Each project receives $80 million this year and could receive a total of between $400 million and $4 billion in funding over the next 5 to 7 years. ... In contrast, the Xe-100 design from X-Energy would use pressurized helium gas to cool its uranium-based fuel. That fuel would be packaged not in the conventional metal-clad rods, but in "pebbles"—spheres of graphite infused with countless ceramic kernels that contain the uranium. Like a giant gumball machine, the reactor would hold 220,000 pebbles, which would slowly descend through the core and, as their fuel was spent, would exit from a port at the bottom. Heated to 750°C, the helium would generate steam in a secondary circuit to produce electricity. In principle, the pebbles can't melt, eliminating the risk of a meltdown. ... The Natrium and Xe-100 reactors would use fuel enriched to 20%, which would enable them to run longer on a batch of fuel and extract more energy from it.
  8. ^ "Curtiss-Wright, X-energy Sign Supplier Plan". Nuclear Street. September 2022. Retrieved September 26, 2022. Under the terms of the agreement, Curtiss-Wright has been selected as a preferred supplier to develop and provide three of the most critical systems for the Nuclear Steam Supply System (NSSS). These include the Helium Circulator System, which transfers heat generated in the reactor core to a steam generator, where steam is produced to generate electricity or provide process heat for industrial applications, as well as the Fuel Handling System, which performs continuous defueling and refueling of the reactor; loading fresh, recirculating used, and discharging spent fuel as required; and the Reactivity Control and Safe Shutdown System, which controls the outlet temperature of the reactor and provides a redundant shut down mechanism when required.

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