Xe-100 SMR plant (Seadrift site)

Executive Overview

The Xe-100 SMR plant at Seadrift, Texas — formally the Long Mott Generating Station — is a 320 MWe / 800 MWth advanced nuclear facility comprising four Xe-100 high-temperature gas-cooled reactor (HTGR) modules, developed by X-energy for Dow's wholly owned subsidiary Long Mott Energy at Dow's Seadrift Operations site in Calhoun County. X-energy and Dow submitted a construction permit application to the U.S. Nuclear Regulatory Commission in March 2025 — the first NRC construction permit application for a commercial advanced nuclear reactor in the United States — and the NRC announced an 18-month review schedule in June 2025. The DOE's Advanced Reactor Demonstration Program (ARDP) provided $80 million in initial funding in 2020, with a potential total DOE investment of up to $1.23 billion over the project's duration. When operational, Long Mott is expected to be the first grid-scale advanced nuclear reactor deployed to serve an industrial site in North America.

How It Works & Differentiation

Each Xe-100 module is a pebble-bed HTGR: over 200,000 spherical TRISO fuel pebbles (each containing 18,000 ceramic-coated uranium fuel particles) continuously cycle through a graphite core cooled by helium, with helium outlet temperatures of 750°C and steam output at 565°C. The fuel design contains over 99.99% of radioactive byproducts within the TRISO particles, making the reactor inherently meltdown-proof — no operator action or active cooling is required under adverse conditions. Spent fuel transfers directly to dry storage without a cooling pool, and all spent fuel can be stored on-site for the reactor's 60-year operational life. The operational plan for Seadrift allocates two modules to deliver process steam to Dow's chemical manufacturing operations, one to deliver electricity internally, and one to sell electricity to the local grid, with enough redundancy that any single module shutdown does not interrupt production. The Seadrift site spans 4,700 acres and produces more than 4 billion pounds of materials per year; the four reactor modules will occupy approximately 30 acres.

Commercialization & Traction

Dow's primary commercial motivation is replacement of an ageing natural gas plant currently supplying process steam and electricity to the Seadrift site. The project is expected to eliminate most of the site's Scope 1 and 2 emissions — approximately 500,000 tonnes of CO₂e per year. The TRISO-X fuel fabrication facility at Oak Ridge, Tennessee (215,000 sq ft, targeting up to 714,000 fuel pebbles per year) is under site development, with the DOE allocating an initial tranche of HALEU fuel for the first Xe-100 core load in April 2025. X-energy has raised approximately $1.1 billion in private capital, including a $500 million Amazon Series C-1. Amazon separately backs X-energy for up to 5 GW of Xe-100 deployment by 2039, anchored by an initial 320 MWe plant in central Washington state, giving the Xe-100 commercial pipeline two major anchor customers.

Scalability & Strategic Context

Seadrift is the highest-profile demonstration of the thesis that advanced nuclear can decarbonise industrial process heat at commercial scale — a market that is technically inaccessible to most clean energy technologies due to the continuous, high-temperature steam requirements. Successful NRC licensing and construction at Seadrift would establish the Xe-100 as the first demonstrated pebble-bed HTGR in the western hemisphere, complementing China's HTR-PM 1 which entered commercial operation in December 2023. X-energy's pre-application NRC engagement dates to 2018 and has accumulated 117,000 hours of regulatory interaction, positioning the Xe-100 licensing dossier as substantially more mature than competing advanced reactor designs. The construction permit review outcome — expected in late 2026 — is the next critical milestone on the project's path to a final investment decision.