Terrestrial Energy Submits Topical Report to NRC to Confirm IMSR Plant’s Thermal and Electric Facility Can Be Built and Operated Ahead of Nuclear Licensing

Approval enables site-specific heat and power systems, expands IMSR Plant access to industrial markets, and supports early commercial operation using natural gas as a bridge to nuclear power

Approval shortens critical path to plant commercial operation and revenue

CHARLOTTE, N.C., October 08, 2026--Terrestrial Energy Inc. (Nasdaq: IMSR) ("Terrestrial Energy" or the "Company"), a leader in Generation IV molten salt nuclear plants supplying electricity and high-temperature industrial heat, today announced that it has submitted its Thermal and Electric Facility (TEF) Topical Report to the U.S. Nuclear Regulatory Commission (NRC). If approved, the TEF, which houses the generators, turbines, and steam supply systems of the Integral Molten Salt Reactor (IMSR) Plant, could be customized for each site and built and operated ahead of the plant's nuclear construction permit and operating license.

"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. As this pathway applies to every IMSR Plant, it is a fleet-wide advantage, not a one-off exemption."

The IMSR Plant is designed in two discrete parts: the Nuclear Facility (NF), containing standardized and modular nuclear systems, and the TEF, containing non-nuclear heat transfer, steam supply and electric systems for commercial power generation and thermal energy supply.

With NRC approval, the TEF could enter commercial service ahead of the NF, using an auxiliary heat source such as natural gas as a bridge to nuclear power.

The report asks the NRC to confirm that building the TEF is not nuclear construction under 10 CFR 50.10(a)(1). The submission incorporates elements of the Company's NRC-approved Postulated Initiating Events (PIE) methodology and shows 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.

The TEF Topical Report is the Company's third Topical Report submission of 2026, delivering on its guidance of submitting at least three reports in calendar 2026. The NRC approved the Company's PIE and Principal Design Criteria Topical Reports in 2026 and 2025, respectively. In September, the Company submitted a Topical Report seeking NRC approval of the Company's methodology to complete regulatory qualification of graphite for the IMSR Plant.