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ARC Clean Technology and the contractor running Idaho National Laboratory have signed a multi year framework to advance the ARC 100 — a 100 megawatt sodium cooled fast reactor, one that uses molten sodium instead of water to carry heat with
ARC Clean Technology and the contractor that runs Idaho National Laboratory have signed a multi-year framework to advance the ARC-100, a 100-megawatt sodium-cooled fast reactor whose design traces to Argonne National Laboratory's Experimental Breeder Reactor-II (EBR-II), a sodium-cooled prototype that ran at what is now INL from 1961 to 1994. The agreement, announced July 28, formalizes first-of-a-kind (FOAK) deployment planning for the reactor at the lab site.
The actual counterparty is not INL itself but Battelle Energy Alliance, LLC (BEA), the management-and-operating contractor that runs the lab for the U.S. Department of Energy. The American Nuclear Society reported the deal on July 31, calling the framework "a pivotal step" — a phrase ARC itself uses. The agreement covers engineering and design, advanced materials and manufacturing, high-performance computing and modeling, irradiation testing, reactor commissioning and operation, and site development.
The ARC-100 belongs to a class of compact nuclear plants known as small modular reactors (SMRs) — a category defined less by wattage than by the goal of being factory-built and sited flexibly, including for industrial heat. A 100-megawatt unit is roughly enough to power about 80,000 homes. "Sodium-cooled" means the reactor uses molten sodium instead of water to carry heat away from the core, and "fast" means neutrons keep most of their energy as they split uranium atoms, which lets the design burn nuclear fuel more efficiently than today's water-cooled fleet. The metallic uranium-alloy core is unusual among U.S. commercial reactor designs but well-studied in research settings.
That research base is the EBR-II inheritance. Argonne operated EBR-II as a sodium-cooled fast-reactor prototype for more than three decades before shutting it down in 1994. The ARC-100 is not a brand-new idea being scaled up; it is an old idea being retooled for commercial deployment, which is both its engineering argument and its political one. INL has previously supported ARC under the Department of Energy's Advanced Reactor Concepts 2020 (ARC-20) program, with prior work spanning fuel design and analysis, probabilistic risk assessment, and related areas.
The company's July 28 release argues that a successful first reactor at INL "would establish the ARC-100 as a compelling export opportunity," letting the U.S. offer allies a domestic advanced reactor and, in ARC's words, "counter the growing influence of state-sponsored nuclear programmes from geopolitical competitors." That is company framing, not a settled U.S. policy position, and it should be read as such: the export pitch is real, but the geopolitical language is ARC's, not Washington's.
advanced-reactor field. ANS notes that ARC was founded in 2006, making it older than peer developers TerraPower (2008), X-energy (2009), and Oklo (2013), though the company's early years are not well documented and are obscured by several name changes. The DOE's Advanced Reactor Demonstration Program (ARDP), which promotes accelerated SMR development, has backed ARC, though the specific ARDP track and award value are not spelled out in the announcement.
The honest counterweight is the long record of SMR economics and FOAK deployment timelines slipping. The early-2000s Clinch River cancellation, the more recent NuScale Carbon Free Power Project retreat, and repeated licensing stumbles all show how hard it is to move from a signed framework to reactors actually running on the grid. The ARC-100 is closer to a paper reactor with a research pedigree than to a working plant, and the new agreement is a planning instrument, not a construction commitment.
What the framework does add is a concrete execution channel: BEA's engineering, materials, computing, irradiation, commissioning, and site-development work now has a defined multi-year home, and INL's prior ARC-20 collaboration gives the parties a working relationship. ARC's CEO Irfan Ali called the agreement "a pivotal step forward for the ARC-100 program and for the United States' advanced reactor future," per the company's release. Whether that step becomes a reactor on the grid, or another entry in the SMR-delay file, is the question the next two to three years of design, licensing, and site work will answer.