Announcement • Sep 10

Terrestrial Energy Submits Graphite Topical Report to U.S. Nuclear Regulatory Commission, Advancing IMSR Plant Regulatory Program

Terrestrial Energy Inc. has submitted its Graphite Topical Report to the U.S. Nuclear Regulatory Commission (NRC). The submission supports the regulatory basis for qualifying graphite, a central component of the IMSR Core-unit, for use in commercial plant operations. The IMSR is a graphite-moderated molten salt reactor, a configuration previously demonstrated at national laboratories in the United States. Graphite has served as a reactor moderator over decades of commercial operations, however regulators require its performance to be demonstrated for each specific reactor design — in Terrestrial Energy’s case, the IMSR Core-unit — through a process known as qualification. Terrestrial Energy’s graphite qualification program is already well advanced. Over the last several years, the Company has been collecting graphite performance data at the NRG High Flux Reactor in Petten, the Netherlands, from tests of multiple nuclear graphite grades from multiple suppliers. This testing program will support the graphite qualification methodology described in the Graphite Topical Report. The Graphite Topical Report seeks NRC approval of the Company’s methodology to complete qualification of graphite for the IMSR Plant. The methodology establishes the Company’s systematic approach to graphite selection, identification and resolution of information requirements, and qualification activities necessary to demonstrate graphite performance under intended IMSR Core-unit operating conditions. In March 2026, the Company stated that it expected to submit at least three additional Topical Reports to the NRC during the year covering key and consequential areas that increase readiness for the license submissions required to construct and operate an IMSR Plant. Each report is intended to address important regulatory matters during the pre-application phase and establish elements of the licensing basis that can support future applications. The submission is one component of a deliberately sequenced program of engineering, licensing, supply chain development, testing, and commercial project development supporting the Company’s planned first commercial IMSR deployment in the early 2030s. The Graphite Topical Report follows the Company’s Postulated Initiating Events methodology Topical Report, approved by the NRC in 2026, and its Principal Design Criteria Topical Report, approved in 2025. Together, these activities demonstrate continued execution of the Company’s regulatory strategy as the IMSR progresses toward commercial deployment. 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. The replaceable IMSR Core-unit is central to Terrestrial Energy’s capital-light business model. Planned sequential Core-unit replacements on a seven-year cycle over the operating life of the IMSR Plant underpin recurring, post-construction component supply, which the Company expects to account for the majority of estimated lifetime revenue per IMSR Plant.

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