Three leading nuclear energy startups—TerraPower, X-energy, and Kairos Power—have reached critical development milestones in 2024, including groundbreaking and regulatory approvals for next-generation reactor designs. While these advances signal a shift toward Small Modular Reactors (SMRs), systemic challenges in fuel supply chains and regulatory timelines mean these companies are not yet delivering energy at a meaningful scale to the power grid.
The progress comes amid a surge in demand for carbon-free baseload power, driven largely by the energy requirements of artificial intelligence data centers. TerraPower, founded by Bill Gates, broke ground on its first commercial-scale Natrium reactor in Kemmerer, Wyoming, on June 20, 2024, according to a TerraPower official announcement. This event marks the first time a next-generation advanced reactor has moved into the construction phase in the United States in decades.
Simultaneously, Kairos Power has advanced its Hermes low-power demonstration reactor in Tennessee, having secured construction permits from the Nuclear Regulatory Commission (NRC). X-energy continues to refine its Xe-100 reactor design, focusing on the deployment of TRISO fuel, which is designed to be inherently safe by trapping radioactive fission products within ceramic layers.
How these nuclear energy startups milestones change the energy landscape
The shift toward SMRs represents a departure from the massive, multi-billion-dollar light-water reactors that have dominated the industry since the Cold War. SMRs are designed to be built in factories and transported to sites, which theoretically reduces construction time and financial risk. According to the International Atomic Energy Agency (IAEA), these reactors can be scaled to fit the needs of a specific community or industrial site, making them more flexible than traditional plants.
The immediate catalyst for this renewed interest is the energy crisis facing the tech industry. Hyperscalers like Microsoft, Google, and Amazon have committed to net-zero goals while simultaneously expanding AI clusters that require constant, high-density power. Unlike wind and solar, which are intermittent, the advanced designs from TerraPower and X-energy provide a steady “baseload” of electricity. This has led to a strategic pivot where tech firms are no longer just buying credits but are actively partnering with nuclear developers to secure future power.
TerraPower’s Natrium technology is particularly notable because it uses liquid sodium as a coolant rather than water. This allows the reactor to operate at higher temperatures and lower pressures, which increases efficiency and enhances safety by reducing the risk of a pressure-driven explosion. The Wyoming project is designed to provide roughly 345 megawatts of electricity, with the ability to store energy in molten salt to meet peak demand spikes on the grid.
Why the progress may not lead to immediate grid impact
Despite the groundbreaking ceremonies and permit approvals, a critical bottleneck exists: the fuel. Most of these advanced reactors require High-Assay Low-Enriched Uranium (HALEU), which is enriched between 5% and 20%. Until recently, the primary commercial supplier of HALEU was Russia’s TENEX. The geopolitical fallout from the invasion of Ukraine has left U.S. startups facing a precarious supply chain for the very fuel their reactors need to operate.
To address this, the U.S. Department of Energy (DOE) has allocated funds to establish a domestic HALEU supply chain. According to the U.S. Department of Energy, the government is working with private companies to build enrichment facilities on American soil, but these plants will take years to reach full capacity. Without a steady stream of HALEU, the reactors being built today cannot move from “demonstration” to “commercial production.”
Regulatory hurdles also remain a significant drag on the timeline. The NRC’s licensing process is rigorous and historically slow, designed for large-scale water reactors. Startups using molten salt or liquid sodium are essentially asking the NRC to approve entirely new safety frameworks. While the Hermes project by Kairos Power serves as a “test case” to streamline this process, the transition from a permit to a fully operational, grid-connected plant typically takes a decade or more.
Comparing the three leading SMR technologies
The three companies are pursuing different physics to solve the same problem. TerraPower uses sodium-cooling to maximize heat transfer; X-energy utilizes high-temperature gas-cooled reactors with TRISO fuel to prevent meltdowns; and Kairos Power employs fluoride salt-cooled technology to operate at low pressures.
The primary difference lies in the intended application. X-energy’s design is highly suited for industrial heat—such as chemical processing or hydrogen production—because of its high operating temperatures. TerraPower’s Natrium is more focused on grid stability and energy storage. Kairos Power is prioritizing a faster, iterative “learn-by-doing” approach with its Hermes reactor to prove the molten salt concept before scaling up.
Financial viability remains the final question. The “first-of-a-kind” (FOAK) cost for any new reactor is notoriously high. While SMRs promise lower costs through modularity, the first few plants will likely be expensive and heavily subsidized by the government. The industry must prove that the “nth” reactor is significantly cheaper than the first to attract the massive private investment required for a nationwide rollout.
What happens next for advanced nuclear power
The success of these startups now depends on three variables: the speed of domestic HALEU production, the NRC’s willingness to adapt licensing for non-light-water designs, and the continued appetite of Big Tech to fund the initial capital expenditures. The industry is moving out of the “whiteboard phase” and into the “concrete phase,” but the gap between breaking ground and flipping a switch remains wide.
The next major checkpoint will be the completion of the non-nuclear components of the Natrium plant in Wyoming and the first criticality tests of the Kairos Power Hermes reactor. These events will determine if the theoretical safety and efficiency gains of SMRs hold up under real-world conditions.
Do you believe SMRs are the answer to the AI energy crisis, or is the fuel supply chain too great a risk? Share your thoughts in the comments below.