TerraPower’s Natrium reactor received NRC construction approval in March 2026, the first commercial-scale next-generation nuclear plant to achieve that milestone in the United States, and began major reactor construction at Kemmerer, Wyoming in April.
Within months, TerraPower’s founder Bill Gates is arranging a meeting with South Korean Prime Minister Han Seong-sook to discuss SMR cooperation, with SK Group, which invested $250 million in TerraPower in 2022, expected to help coordinate the agenda and participants. The timing is not coincidental. The Kemmerer construction permit unlocked a project that was previously a regulatory ambition, and the companies now being asked to supply components have moved from a speculative pipeline to a funded, permitted, active construction programme. Korea’s position in that programme is already substantial, and the diplomatic visit reflects an intent to deepen it.
HD Hyundai Heavy Industries was selected in May 2026 as preferred bidder to supply key equipment for the Natrium reactor enclosure system, a contract that draws on Korea’s established heavy manufacturing capacity in large-scale nuclear and industrial equipment. The reactor enclosure for a sodium-cooled fast reactor is not a standard component: it must maintain a hermetically sealed environment around liquid sodium coolant at elevated temperatures, accommodate thermal expansion and seismic requirements, and be built to quality assurance standards that nuclear regulators impose on safety-classified systems. HD Hyundai’s selection as preferred bidder indicates that TerraPower has concluded Korean manufacturing capability meets those standards in a domain where the global supplier base is thin.
The Natrium Design and What Distinguishes It Commercially
The Natrium reactor is a 345 MWe sodium-cooled fast reactor paired with a molten salt thermal storage system that allows the plant to deliver up to 500 MWe of peak output for approximately five and a half hours by drawing down stored thermal energy. The storage integration was designed explicitly to make the reactor economically complementary to variable renewable generation: the reactor runs at constant thermal output while the storage system absorbs surplus thermal energy during periods of low grid demand and discharges it when wind and solar output is insufficient and prices are high. This operational flexibility addresses the principal commercial disadvantage of baseload nuclear in markets with high renewable penetration, where a reactor that cannot follow load earns energy revenue at the average price rather than the peak price.
The sodium coolant choice carries both advantages and challenges relative to conventional light water reactors. Liquid sodium operates at atmospheric pressure, eliminating the high-pressure primary circuit that defines safety and engineering cost in pressurised water reactors, and its thermal conductivity allows passive heat removal in loss-of-coolant scenarios without active safety systems. These characteristics theoretically reduce the size, complexity, and cost of safety systems compared to LWR designs. The challenges are that sodium reacts violently with water and ignites on contact with air, requiring leak-prevention engineering and inert atmosphere containment that add their own complexity to the plant design and maintenance regime.
TerraPower’s fourth-generation fast reactor lineage also enables breeding or burning of spent nuclear fuel, which addresses the long-term waste disposition problem that has constrained nuclear expansion in several jurisdictions. Whether that capability is commercialised in the Natrium design or remains a future option depends on regulatory pathways and fuel cycle policy that are not yet defined for the US commercial nuclear sector.
South Korea’s Nuclear Industrial Position
South Korea’s interest in Natrium cooperation reflects both its domestic nuclear ambitions and its long-standing position as a commercial nuclear equipment manufacturer and operator. Korea operates 26 nuclear reactors providing approximately 30% of national electricity generation, has exported the APR-1400 reactor design to the UAE through the Barakah project, and is developing its own small modular reactor programme under the SMART design. The combination of operating experience, supply chain depth, and engineering workforce makes Korea one of a small number of countries with the industrial capacity to manufacture nuclear components at the quality and scale that new reactor programmes require.
SK Group’s $250 million stake in TerraPower, taken in 2022 when the Natrium design was still in the pre-licensing phase, was an early commitment to a technology that has since validated itself through the regulatory process. The investment gives SK a financial interest in TerraPower’s success and a relationship with the Gates-founded company that creates a natural coordination role for the group in bringing Korean industrial partners into the project. The Gates visit’s use of SK as the organising party for meetings with Korean executives reflects this relationship’s operational utility.
The expected meetings with HD Hyundai and other Korean companies extend beyond the existing reactor enclosure contract. TerraPower’s Kemmerer project is the first unit of what the company intends to develop into a repeatable commercial platform. A single demonstration plant requires a bespoke supply chain that can accept the inefficiencies of first-of-a-kind manufacturing. A commercialised platform requires a supply chain capable of serial production at competitive cost and quality, and establishing Korean suppliers in safety-classified roles in the Kemmerer project creates the regulatory history and quality records that would allow them to supply subsequent units without the full qualification overhead that the first deployment required.
The SMR Market Context in Korea
South Korea’s domestic energy context provides an independent motivation for the conversations Gates is expected to have with the Prime Minister. The government has reversed the previous administration’s nuclear phase-out policy and is pursuing aggressive expansion of nuclear generation as part of its 2050 net zero strategy and its response to electricity demand growth from semiconductor fabrication, data centres, and industrial electrification. The 11th Basic Plan for Electricity Supply and Demand, published in 2024, targets nuclear capacity growth of approximately 5 GW through new unit construction by 2038 alongside the continued operation of existing plants beyond originally planned retirement dates.
Korea Electric Power Corporation and Korea Hydro and Nuclear Power are evaluating SMR options including the domestically developed SMART reactor, international designs such as NuScale’s VOYGR and Rolls-Royce’s SMR, and the Natrium. The Gates visit, if it produces concrete cooperation agreements rather than memoranda of understanding, could position Natrium favourably in that evaluation process. SK Group’s existing shareholder relationship with TerraPower creates a structural alignment of interests that other SMR developers competing for Korean deployment opportunities do not have. Whether that alignment translates into a Korean Natrium deployment or remains focused on Korean supply chain participation in US and international projects depends on the regulatory, financing, and policy framework that the Prime Minister’s discussions are designed to advance.
