TerraPower’s bid to start energy island construction gets EA/FONSI
The Nuclear Regulatory Commission staff has concluded—with an assist from a Department of Energy environmental assessment released in February—that no environmental impact statement is needed for an exemption request from TerraPower that would allow the company to begin construction of the energy island of its planned Natrium sodium fast reactor in Kemmerer, Wyo. The NRC’s EA and finding of no significant impact (EA/FONSI), published on May 7, could clear the way for significant construction to begin while the NRC continues to review TerraPower’s construction permit application.
In a May 8 statement, TerraPower president and CEO Chris Levesque welcomed the decision. “Our innovative design that decouples the nuclear reactor from the energy generating facilities allows us to shorten construction schedules and reduce material costs, making the Natrium technology one of the fastest and most cost-effective solutions to deploy to help meet growing energy demand,” he said. “We look forward to continuing to work with the NRC on our construction permit application for the nuclear island and ultimately bringing America’s next nuclear power plant to market.”
Defining construction: TerraPower, on behalf of its subsidiary US SFR Owner (USO), first requested an exemption in September 2024. It was replaced by a new, more limited exemption request submitted in February 2025 (later supplemented by letters dated April 7, 2025,and April 29, 2025).
At issue is the definition of “construction” that is prohibited without an NRC license or limited work order. TerraPower’s requested exemption would change the definition of construction in 10 CFR 50.10(a)(1)(iv) from “SSCs [structures, systems, and components] whose failure could cause a reactor scram or actuation of a safety-related system” to “SSCs whose failure could cause a reactor scram or actuation of a safety-related system, excluding Natrium [Energy Island] SSCs classified as non-safety-related with no special treatment (NST).”
An issued exemption would allow USO to proceed with driving piles; subsurface preparation; placement of backfill, concrete, or permanent retaining walls within an excavation; installation of foundations; or the in-place assembly, erection, fabrication, or testing of covered non-safety-related SSCs on the energy island. Construction of the nuclear island would await a construction permit.
Avoiding cost and delay: In a supplement to the exemption request submitted April 7 by George Wilson, senior vice president of regulatory affairs for TerraPower, TerraPower made the case that compliance with existing definitions of construction would result in “undue hardship and costs.”
“The Natrium reactor design incorporates several features that support independence of the Nuclear Island (NI) and Energy Island (EI),” the supplement states. “Independence is supported by EI SSCs classified as non-safety-related with no special treatment (NST) not having a reasonable nexus to radiological health and safety or security. . . . The approach, having independence between an NI and EI, and the opportunity it presents for alternative approaches to construction of nuclear power production facilities, was not considered when [the NRC’s definitions on construction] were adopted.”
Without an exemption, energy island construction could not proceed until a construction permit is issued. As stated in the supplement: “Substantial schedule delays for the Natrium Demonstration Project, as supported by a public-private partnership with the Department of Energy (DOE) Advanced Reactor Demonstration Program (ARDP), would be incurred. This delay will not serve the underlying purpose of the rule because EI SSCs classified as NST do not have a reasonable nexus to nuclear safety or security. The cost of any delay of the commercial operation of Kemmerer Unit 1 would depend upon a number of uncertain factors but is expected to be substantial.”
An assist from the DOE: In February 2025, the DOE’s Office of Clean Energy Demonstrations issued a final EA before authorizing the expenditure of federal funds to conduct preliminary activities for Kemmerer Unit 1. The DOE’s EA determined that the environmental impacts of those activities would be minor, and the DOE issued a FONSI.
The DOE’s EA discussed activities that would require NRC authorization, and that relate to TerraPower’s energy island exemption request.
According to the NRC, “the NRC staff reviewed the analysis in the DOE EA and determined that, because it already considered work that this exemption would approve, despite the different proposed actions, the DOE EA bounds those aspects of the work. Therefore, the NRC incorporates the DOE EA by reference into this EA.” Referencing the DOE EA, the NRC concluded the impacts of the proposed exemption on the environment would be minor, with no significant non-radiologic environmental impacts associated with the proposed action.
More information: TerraPower submitted a construction permit in March 2024, and in May 2024 the NRC staff accepted it for docketing. As part of its review of that application, the NRC is preparing an environmental impact statement.
An exemption permitting energy island construction does not “constitute a commitment by the NRC to issue a CP for Kemmerer 1,” the NRC stated in its May 7 notice, adding, “If approved, USO would install the SSCs assuming the risk that its CP application may later be denied.”
More information about some of TerraPower’s recent actions is available here.
