Terrestrial Energy Inc. (Nasdaq: IMSR) has submitted a Thermal and Electric Facility (TEF) Topical Report to the U.S. Nuclear Regulatory Commission (NRC), according to a company press release.

The report asks the NRC to confirm that the TEF — which houses the generators, turbines, and steam supply systems of the Integral Molten Salt Reactor (IMSR) Plant — does not constitute nuclear construction under federal regulations. If approved, the TEF could be built and operated before the plant's nuclear construction permit and operating license are obtained.

The TEF could enter commercial service ahead of the nuclear portion of the plant using an auxiliary heat source such as natural gas. The submission argues that the IMSR Plant's nuclear systems do not rely on the TEF for safe operation, and that any failure originating in the TEF is isolated from the nuclear systems.

"This submission can change how an IMSR Plant is regulated, built and financed," said Simon Irish, CEO of Terrestrial Energy. "With its NRC approval, only the nuclear portion of the plant would follow the nuclear licensing timeline. The rest of the plant would become a conventional industrial project, giving customers earlier power and heat and giving financing partners a bankable construction phase."

The TEF Topical Report is the company's third such submission in 2026. The NRC previously approved the company's Postulated Initiating Events and Principal Design Criteria Topical Reports in 2026 and 2025, respectively. A fourth report seeking approval of a methodology for graphite regulatory qualification was submitted in September.

Approved Topical Reports establish foundational elements of the IMSR licensing basis that may be referenced in future applications without re-evaluation, reducing the scope of subsequent technical review.