Summary

X-energy is a Rockville, Maryland advanced nuclear company founded by Kam Ghaffarian, developing the Xe-100 — a pebble-bed high-temperature gas-cooled reactor (HTGR) that produces 80 MWe per unit. Four units are typically deployed together as a 320 MWe “4-pack” plant. The Xe-100 uses TRISO fuel pebbles in a helium-cooled core operating at 750°C — high enough to provide industrial process heat as well as electricity, making it the only SMR design explicitly targeting industrial decarbonization (chemical plants, refineries, industrial campuses). Dow Chemical is the anchor deployment partner: Dow and X-energy submitted a NRC construction permit application in March 2025 for a 4-pack (320 MW) at Dow’s Seadrift, Texas chemical complex, docketed by the NRC in May 2025 with an 18-month review schedule. Amazon anchored a $500M Series C-1 in October 2024; X-energy raised $700M in Series D in November 2025. X-energy’s TRISO-X subsidiary is constructing the TX-1 HALEU fuel fabrication facility in Oak Ridge, Tennessee — the first commercial-scale HALEU fuel plant in the US, which is a critical supply chain dependency for the entire HALEU-dependent SMR sector.

Key Facts

  • Founded: ~2009
  • HQ: Rockville, MD
  • Type: Private
  • Founder / Executive Chairman: Kam Ghaffarian
  • Reactor design: Xe-100 — pebble-bed high-temperature gas-cooled reactor (HTGR)
  • Output: 80 MWe per unit; 320 MWe for standard 4-unit plant
  • Coolant: Helium gas (inert; no water; no sodium); operates at atmospheric pressure
  • Core temperature: 750°C outlet (highest operating temperature of any Western SMR in deployment); enables industrial process heat
  • Fuel: TRISO fuel pebbles (same TRISO particle as Kairos but in a different form factor — pebbles vs. Kairos’s FLiBe-bath); HALEU enrichment (~15% U-235)
  • Total raised: ~$1.5B+ (Series C-1 $500M + Series D $700M + prior rounds + DOE ARDP)
  • Series C-1: ~$500M, October 2024; anchored by Amazon
  • Series D: $700M, November 2025
  • DOE ARDP award: $1.2B (2020) — cost-share for Xe-100 development
  • Flagship deployment — Seadrift, TX:
    • Partner: Dow Chemical (wholly-owned subsidiary Long Mott Energy LLC is applicant)
    • Site: Dow’s UCC Seadrift chemical complex, Texas Gulf Coast
    • Configuration: 4 × Xe-100 = 320 MWe
    • NRC application: Construction permit application submitted March 2025; NRC docketed May 2025; 18-month NRC review schedule
    • First industrial-site advanced nuclear deployment in North America
    • Commercial operation target: ~2030
  • Fuel facility — TRISO-X TX-1:
    • Location: Oak Ridge, TN
    • Status: Site development ongoing; Geiger Brothers as site developer
    • Significance: First commercial-scale US HALEU fuel fabrication facility; will supply fuel for Seadrift deployment and beyond
    • DOE HALEU Availability Program: TRISO-X allocated initial HALEU tranche (April 2025)
  • Amazon broader partnership: Agreed framework to standardize deployment and financing model for future Xe-100 projects with infrastructure and utility partners; Amazon targeting 5 GW of advanced nuclear capacity by 2040
  • Additional customers: Multiple unnamed utility and industrial partners

What It Is / How It Works

Pebble-bed HTGR physics: The Xe-100 core is a graphite-moderated, helium-cooled reactor where the fuel itself is in the form of spherical “pebbles” — tennis ball–sized graphite spheres each containing thousands of TRISO fuel particles. During operation, pebbles slowly circulate through the core by gravity, are extracted at the bottom, inspected, and either returned to the top of the core or set aside as spent fuel. This “online refueling” means the reactor never needs to shut down for refueling — unlike LWRs that typically refuel during planned outages every 18–24 months.

Helium coolant: Helium is chemically inert and does not become radioactive under neutron bombardment (unlike water, which produces tritium). This means the secondary steam circuit has essentially no radioactive contamination risk, simplifying maintenance. Helium also doesn’t change phase (it stays gaseous) — eliminating the loss-of-coolant accident risk associated with boiling/condensing coolants.

High temperature = industrial process heat: The Xe-100’s 750°C helium outlet temperature is significantly higher than LWR steam temperatures (~300°C) or even sodium fast reactor temperatures (~500°C). Many industrial chemical processes require heat at 600–800°C — steam cracking, hydrogen production, ammonia synthesis. The Xe-100 can supply this heat directly, making it unique among SMRs in its ability to decarbonize hard-to-abate industrial processes. The Dow Seadrift deployment is explicitly designed to provide both electricity and process heat to Dow’s chemical complex.

TRISO safety: Like Kairos’s fuel, TRISO particles retain fission products up to ~1800°C — far above any temperature the Xe-100 can reach. The pebble-bed design also has an inherently negative temperature coefficient: as the reactor heats up, the neutron chain reaction slows down naturally. Combined, these properties make the Xe-100 genuinely walk-away safe — no operator action, AC power, or coolant is needed to prevent fuel damage in any postulated accident.

The Dow strategic logic: Dow’s Seadrift site produces polyethylene, ethylene oxide, and other chemicals requiring large amounts of both electricity and 600°C+ steam. Natural gas currently provides both. Decarbonizing these processes with a single nuclear plant that provides firm, 24/7 electricity and process heat is a compelling industrial economics case. Dow committed to being the first US industrial Xe-100 deployment before the technology is proven at commercial scale — a significant vote of confidence.

TRISO-X and the HALEU supply chain solution: Most SMR developers identify HALEU supply as a critical risk but don’t own the solution. X-energy is vertically integrating into fuel production through TRISO-X, its fuel fabrication subsidiary. TX-1 in Oak Ridge will be the first commercial-scale US HALEU fuel plant. This is strategically important not just for X-energy — if TX-1 succeeds, it becomes a potential HALEU fuel supply source for Kairos Power and other TRISO-dependent designs.

Notable Developments

  • 2025-11: Series D — $700M raised. (Neutron Bytes)
  • 2025-05: NRC formally dockets Dow / Long Mott Energy construction permit application for Seadrift Xe-100 project; 18-month NRC review schedule published. (ANS Nuclear Newswire; DOE)
  • 2025-04: TRISO-X allocated initial HALEU tranche via DOE HALEU Availability Program for TX-1 fuel facility.
  • 2025-03: Dow and X-energy submit construction permit application to NRC for Seadrift site. (Dow IR)
  • 2024-12: TRISO-X selects Geiger Brothers for TX-1 site development in Oak Ridge, TN.
  • 2024-10: Series C-1 — ~$500M anchored by Amazon; partnership to develop 5 GW of Xe-100 capacity.
  • 2020: DOE ARDP award — $1.2B cost-share for Xe-100 development and TRISO-X fuel fabrication.

Key People

Kam Ghaffarian — Founder and Executive Chairman

  • LinkedIn: linkedin.com/in/kamghaffarian
  • Role: Founder and Executive Chairman
  • Background: Serial entrepreneur in government/defense and space sectors; founder of KGS Group (government services, sold for ~$1B), Stinger Ghaffarian Technologies (sold to Jacobs Engineering), and Axiom Space (commercial space stations); Iranian-American immigrant; long-standing advocate for nuclear energy as climate solution
  • Notes: Ghaffarian’s background is in government services and contracting, not nuclear engineering — X-energy’s technical foundation comes from acquired expertise and DOE partnerships rather than a founder-scientist origin

J. Clay Sell — CEO

  • LinkedIn: Search “Clay Sell X-energy”
  • Role: CEO
  • Background: Former Deputy Secretary of Energy under President George W. Bush (2005–2008); long career in energy policy and nuclear advocacy; brings deep DOE and regulatory relationships

People — Last Reviewed: 2026-03-25

Supply Chain Position

Layer Detail
HALEU fuel (critical) TRISO-X TX-1 (X-energy subsidiary, Oak Ridge TN) — first commercial-scale US HALEU fuel plant; currently under construction; initial DOE HALEU allocation secured; full commercial production timeline TBD
TRISO particle manufacturing BWXT — sole US TRISO manufacturer; BWXT supplies TRISO particles; TRISO-X encapsulates into pebbles at TX-1
Helium coolant Industrial helium supply (Air Products, Linde, Air Liquide); global supply is reasonably constrained but helium is consumed minimally in a closed loop
Reactor pressure vessel Custom HTGR vessel with graphite reflector; limited fabricators with Gen IV HTGR experience
Steam generator / heat exchanger Conventional high-temperature steam systems; multiple qualified vendors
Construction at Seadrift EPC contractor not yet publicly named for Seadrift
Process heat customer Dow Chemical (Seadrift)
Power customer Dow Chemical (Seadrift electricity) + ERCOT grid
Broader offtake Amazon (5 GW framework) + other utility/industrial partners

⚑ BWXT TRISO shared constraint: Both X-energy (through TRISO-X) and Kairos Power rely on BWXT as the TRISO particle manufacturer. BWXT is expanding TRISO capacity at its Lynchburg facility, but the expansion timeline must keep pace with both programs’ schedules. If Darlington (GEH), Kemmerer (TerraPower), Hermes (Kairos), Seadrift (X-energy), and INL Aurora (Oklo) all progress toward construction simultaneously in the late 2020s, BWXT’s TRISO capacity becomes a sector-wide bottleneck.

⚑ TX-1 as a sector-level asset: If TRISO-X’s TX-1 succeeds in producing commercial-scale HALEU fuel, it creates a supply option not just for X-energy but potentially for Kairos (which currently sources TRISO from BWXT under separate agreements). X-energy’s vertical integration into fuel is strategically more important than its proprietary reactor design — whoever controls HALEU fuel production has leverage over the entire advanced reactor sector.

Claim Verification

Claim: 750°C “highest temperature” among Western SMRs providing industrial process heat

Status: Accurate as of Q1 2026 among Western SMRs with active deployment programs

Supporting: LWRs produce ~300°C steam; sodium fast reactors ~500°C; TerraPower Natrium ~550°C; Xe-100 at 750°C helium outlet is the highest temperature of any Western SMR with a filed NRC construction permit application

Summary: Accurate; the industrial process heat application is genuine and differentiated

Claim: NRC 18-month review schedule

Status: Published by NRC — verifiable

Supporting: NRC published the 18-month schedule after docketing the application in May 2025; 18-month review is the NRC’s standard timeline for construction permit applications; the schedule is NRC’s commitment, not X-energy’s claim

Refuting / questioning: NRC review schedules frequently slip when the application has information deficiencies requiring requests for additional information (RAIs); NRC issued extensive RAIs for NuScale’s and other first-of-kind applications; Xe-100 HTGR technology is novel to the NRC

Summary: The 18-month schedule is NRC’s published commitment, not a company claim. Track RAI issuance and response timelines as the leading indicator of whether the schedule will hold.

Claim: Commercial operation ~2030 at Seadrift

Status: Consistent with 18-month NRC review (ending ~late 2026/early 2027) followed by construction; aggressive but not impossible

Supporting: If NRC review completes on schedule (~late 2026), construction permit in early 2027, construction period of 3–4 years → 2030–2031

Refuting / questioning: NRC RAI delays on a first-of-kind HTGR design are highly likely; construction of a novel reactor on an active chemical complex site (Seadrift) introduces operational safety coordination complexity beyond a greenfield nuclear site

Summary: 2030 is the optimistic scenario; 2031–2032 is the realistic central estimate.

Sources