US-based Terrestrial Energy Proposes Phased Construction Model to Accelerate Deployment of 390 MW Integrated Molten Salt Reactor

Fourth-generation advanced nuclear developer Terrestrial Energy has recently formally submitted to the U.S. Nuclear Regulatory Commission (NRC) a topical report for the “Thermal and Electric Facility” (TEF) of its Integrated Molten Salt Reactor (IMSR) project. The document proposes a dual-track regulatory review model aimed at allowing key non-nuclear power components of the plant to proceed with construction and enter commercial operation before a full nuclear facility license is obtained.

If this regulatory approach is approved by federal regulators, it will effectively break through the economic and approval obstacles that have long constrained the development of the nuclear power industry. In traditional nuclear power projects, because the scope of regulatory safety reviews typically covers both the reactor proper and its main steam power conversion systems, project timelines often face severe delays. Under this new decoupled approval pathway, however, only the core nuclear module must follow the rigorous and detailed nuclear safety licensing process, while conventional power facilities such as turbine generators can proceed entirely on a standard commercial engineering schedule.

This regulatory strategy is being proposed at a time when large institutions and major energy consumers are experiencing surging demand for round-the-clock stable clean electricity. It is understood that the U.S. Army's Aberdeen Proving Ground in Maryland is planning to serve as the host site for a 390 megawatt-electric (MWe) IMSR molten salt reactor power plant, in order to establish a safety barrier against external large-grid failures at this, the oldest active U.S. military test base, and to ensure the energy resilience of critical national defense facilities.

In order to achieve rapid delivery of commercial units in the 2030s, Terrestrial Energy has implemented a clear physical zoning division of the plant site in its engineering design. The entire power plant is divided into two independent areas, with the main module containing only the reactor core, while a physically separated auxiliary building houses the steam system, heat exchangers, and turbine generators and other standard energy conversion equipment. The company hopes to obtain formal recognition from regulators through the topical report, clarifying that the installation and construction work of the turbine building does not fall under the jurisdiction of federal nuclear facility construction regulations.

This distinction in regulatory classification can bring direct economic benefits and financing advantages to nuclear power projects. Constructing non-nuclear facilities according to general industrial building codes enables developers to provide project investors with a more controllable construction timeline, thereby reducing capital-raising risks. Plant operators can not only flexibly customize power modules according to surrounding industrial demand before nuclear fuel arrives, but can even use natural gas as a temporary transitional heat source to drive turbines while waiting for reactor nuclear-grade licensing approval, generating commercial cash flow for the project in advance.

For nuclear safety regulators, the inherent safety of the reactor remains the core prerequisite for approval. In this technical submission, Terrestrial Energy systematically demonstrated that its nuclear core module maintains complete physical independence from the downstream power conversion system under operating conditions. Based on accident assessment methods previously approved by the NRC, the technical team confirmed that even if a severe equipment damage accident occurs inside the conventional island turbine building, its effects would not propagate in reverse toward the nuclear reactor core.

This report is the third formal topical document that Terrestrial Energy has submitted to U.S. federal regulators this year. Prior to this, the NRC had already approved the company's baseline design criteria and its core safety criteria. Meanwhile, another specialized technical report concerning reactor-grade graphite certification for this reactor type is currently under regulatory review. Once these topical reports receive final approval from regulators, they will establish permanent licensing precedents that subsequent commercial construction applications for similar units can directly reference, without the need to repeat lengthy technical demonstrations.

Unlike traditional conventional high-pressure light water reactors (LWRs), the Integrated Molten Salt Reactor uses standard-assay low-enriched uranium (LEU) fuel and operates under near-atmospheric pressure conditions and at extremely high operating temperatures. Its compact and modular system characteristics enable it not only to provide low-cost and highly reliable baseload electricity, but also to directly deliver high-parameter industrial-grade process heat, deeply suited to the decarbonization transition needs of high-energy-consumption sectors such as large data centers, the chemical industry, and petrochemicals.