A proposed 100 MWe sodium cooled fast reactor is moving into a more detailed development phase in the United States, as ARC Clean Technology and Battelle Energy Alliance, the operator of Idaho National Laboratory, establish a framework covering the engineering, testing and potential first of a kind deployment of ARC’s ARC-100 reactor.
The agreement is significant because the project would place a commercial advanced reactor design within the U.S. national laboratory system, giving ARC access to capabilities spanning materials testing, fuel research, computational modeling, manufacturing and reactor operations. However, the framework is not itself a construction or operating license, and the project remains subject to the technical, regulatory and deployment work required for a first commercial unit.
The ARC-100 is designed as a 286 MWth, approximately 100 MWe sodium cooled fast reactor using metallic uranium alloy fuel. The design is intended to provide electricity as well as industrial heat, potentially allowing the technology to target applications beyond conventional grid generation.
Its technical lineage is important. ARC bases the reactor concept on the Experimental Breeder Reactor II, a sodium cooled fast reactor developed at Argonne National Laboratory that operated from 1961 until 1994. That heritage gives ARC a substantial body of historical operating experience to draw upon, although translating a research reactor design lineage into a modern commercial system still requires extensive validation.
The new framework with Battelle Energy Alliance is structured around the entire development cycle, including engineering and design, advanced materials and manufacturing, high performance computing, irradiation testing, commissioning, operation and site development.
That breadth reflects one of the central challenges facing advanced nuclear developers: moving from a reactor concept with established technical principles to a repeatable, licensable and economically deployable commercial product.
Idaho National Laboratory is one of the U.S. Department of Energy’s principal centers for nuclear technology research. Its role in the ARC-100 program could therefore extend beyond conventional engineering support.
For a sodium cooled fast reactor, materials performance, fuel behavior and long duration operating characteristics are particularly important. The ARC-100’s metallic fuel system and fast neutron spectrum require validation under conditions that cannot be fully established through computer modeling alone.
INL also has historical expertise with metallic uranium alloy fuels and sodium cooled fast reactor technology. That experience is directly relevant to ARC’s technology and could reduce some of the technical development burden associated with a first deployment.
The partnership therefore represents more than a site arrangement. It potentially links ARC’s commercial development program with a U.S. research infrastructure designed specifically to address advanced reactor technologies.
ARC has also made progress in Canada, where the Canadian Nuclear Safety Commission completed a Phase 2 pre licensing vendor design review of the ARC-100.
The regulator concluded that it had identified no fundamental barriers to licensing the design at that stage. However, the CNSC explicitly noted that the ARC-100 remained in preliminary engineering and that additional technical work was required before the design could demonstrate compliance with all applicable Canadian regulatory expectations.
That distinction matters because a vendor design review does not constitute reactor certification or a construction license. The CNSC describes the process as an opportunity to identify regulatory and technical issues before a formal licensing application, while licensing decisions remain subject to separate, more detailed reviews.
For ARC, the Canadian assessment nonetheless provides regulatory feedback that can inform further engineering as the company pursues deployment in both Canada and the United States.
ARC has been developing the ARC-100 with New Brunswick Power since 2018. The Canadian utility and ARC submitted an environmental assessment registration document and an application for a site preparation license for a proposed reactor at the Point Lepreau site in 2023.
The Canadian project has therefore provided an important parallel pathway for the technology, while the proposed Idaho deployment would give ARC an opportunity to work with U.S. nuclear research infrastructure and advance the design toward first deployment.
The two efforts also illustrate the regulatory complexity of advanced nuclear development. A reactor design can progress through pre licensing assessment while still requiring significant engineering, site specific analysis, safety documentation and licensing work before construction can begin.
The commercial proposition for ARC-100 ultimately depends on whether the reactor can move beyond technical validation to construction and operation on an economically credible schedule.
That challenge is shared across the advanced reactor industry. First of a kind projects must simultaneously establish the technology, supply chain, manufacturing processes, regulatory basis and construction methodology. Each unresolved issue can add cost or delay, while the absence of multiple operating units makes it difficult to establish the economies of repetition that underpin the SMR business model.
ARC’s decision to involve INL across the reactor’s development lifecycle addresses part of that problem by connecting design development with testing and operational expertise. It does not, however, eliminate the commercial risks associated with first deployment.
The ARC-100’s sodium cooled fast reactor configuration also places it in a different technical category from the light water SMRs now being pursued by several developers. Its potential advantages include high temperature operation and the ability to support both electricity generation and industrial heat, while its fuel, coolant and fast spectrum introduce their own engineering and licensing requirements.
For ARC, the Idaho agreement therefore represents an effort to convert decades of sodium fast reactor research into a commercial deployment pathway. The more consequential milestones will be the completion of detailed engineering, resolution of remaining regulatory issues, demonstration of fuel and materials performance, site development and ultimately authorization to construct and operate a reactor.
