US Startup X-energy developing innovative Xe-100 “pebble bed” high temperature gas-cooled reactor

X-energy, a Greenbelt-based nuclear engineering company,recently convened a group of world-renowned nuclear experts to discuss best-practices in pebble fuel fabrication. X-energy will use the spherical elements to fuel their Xe-100 gas-cooled nuclear reactor in the mid-2020s. The Xe-100 is a “pebble bed” high temperature gas-cooled reactor

The Xe-100 is a helium-cooled “pebble bed” HTGR that operates at 125MWth and produces approximately 48MWe.

The Xe-100 will benefit from decades of research and safe operation in pebble bed reactors internationally, and X-energy plans to bring the remarkable features and benefits of pebble fuel to the United States for the first time. The Xe-100 will be ultra-safe, small-scale, compact, versatile, and able to respond in real-time to fluctuating grid demands.

The unique properties and benefits of the Xe-100 allow it to solve energy challenges in diverse markets including government application, commercial electrical generation, and combined heat and power (CHP) industries

* A small footprint and reduced water requirement mean the Xe-100 can be installed in a much wider range of potential locations compared to other clean energy solutions

* X-energy estimates the total U.S. market at more than 240 potential locations representing 3,600 reactors (180 GWe market for their 50 MWe reactors)

X-Energy’s technical game-changer is NASA systems engineering coupled with nuclear reactor design. Company leadership includes former NASA executives who bring unique perspectives and experience in simplification, reliability, modularity, and operational efficiency to the nuclear power industry. X-Energy draws on the expertise of its sister company, SGT, Inc. (Stinger Ghaffarian Technologies, Inc.), a prominent engineering services provider with over thirty active contracts with DOT, DOI, DOC, NASA, and DoD. SGT has annual revenues of approximately $500 million and a backlog of nearly $3 billion. (

A Department of Energy Technical Review Panel (TRP) recently completed an evaluation of seven advanced reactor concepts that are currently under development. The TRP noted several of the key benefits of the Xe-100 pebble bed design:

“When deployed for electricity generation, the Xe-100 can be placed in close proximity to the power users due to its intrinsic safety that excludes the possibility of a core melt.”

“Regarding regulatory environment, the TRP noted that the X-energy pebble-bed concept…[has] greater readiness for licensing than other concepts.”

“In evaluating the market attractiveness of the concepts, the members rated all of the concepts similar to the current LWR technology, except for the X-energy reactor which was somewhat more attractive.”

Pebble Bed – A Different Kind of Nuclear Reactor

• Ultra-Safe –Passive cooling design prevents core melt while independent radionuclide barriers virtually eliminate the risk of radionuclide release
• Compact Footprint – Small enough to fit inside the fence at vital national security locations, existing “brown-field” power plants, and other locations
• Small EPZ – Ultra-safe design minimizes the emergency planning zone to within the plant boundary, allowing siting close to population centers
• Secure Site – Reactor units and control facilities are underground in a concrete silo built to withstand seismic events or manmade attacks
• Incremental Growth – Truly modular construction allows incremental growth in installments of 47MWe, lowering upfront capital cost
• Reliable – Xe-100 eliminates refueling shutdowns with automated fueling during active operation, allowing for an availability rate greater than 95%

Load Following. With its unique variable output capability, the Xe-100 will be able to follow power demands in real-time, based on fluctuating energy grid demands—a capability that only fossil fuel plants can claim today and that no other existing nuclear project has.

Uninterrupted Power. The reactor will not shut down for refueling, due to continuous fueling during active operation. Power generation will continue around the clock, regardless of external factors such as sunshine or wind.The Xe-100 will have an availability rate of over 95%.

Reduced Construction Time. Modular reactor installation and innovative site-preparation techniques will reduce contract-to-startup time by an estimated 20%-40% compared to LWR facilities and other small modular reactor projects.