Thorium Atomics Initiates Pre-Application Regulatory Engagement with U.S. Regulators for Tesseract TGR Reactor

On August 7, Thorium Atomics announced that it has initiated pre-application regulatory engagement with the U.S. Nuclear Regulatory Commission (NRC) for its Tesseract TGR advanced reactor project. Prior to this, the company submitted a letter of intent to the NRC outlining the technical and licensing discussions it plans to conduct with regulators in the future.

Thorium Atomics submitted the letter of intent on June 23, 2026. The NRC subsequently responded by letter on July 24, 2026, confirming the assignment of project number 99902174 for the Tesseract TGR project and designating a project manager from the Office of Advanced Reactors to coordinate pre-application activities. This number will be used for the administrative management and tracking of future correspondence, meetings, submissions, and regulatory staff reviews. The relevant notice has been made publicly available in the NRC's Agencywide Documents Access and Management System (ADAMS) under accession number ML26189A392.

The company plans to engage with the NRC under Part 53 of Title 10 of the Code of Federal Regulations. Part 53 is the NRC's risk-informed, performance-based, and technology-inclusive licensing framework for commercial nuclear power plants, which became effective on April 29, 2026. Thorium Atomics stated that it is developing a regulatory engagement plan that will include a description of the Tesseract technology, the proposed licensing strategy, and the sequencing of pre-application submittals.

The Tesseract TGR, or Thorium-Enhanced Gas-Cooled Reactor, is a pebble-bed high-temperature reactor that differs from conventional water-cooled reactors. The design uses helium gas as the coolant, employs coated-particle TRISO fuel, and seeks to achieve advanced safety responses through passive physical characteristics rather than active safety systems and high-pressure water systems. Based on currently available information, the design remains in the research and development stage and has not yet been constructed, licensed, or independently verified.

According to Thorium Atomics, the Tesseract TGR is a small modular reactor with a design thermal power of 250 megawatts, capable of providing approximately 100 megawatts of steady-state electricity or delivering industrial process heat up to approximately 750 degrees Celsius. The company states that such high-temperature heat is currently difficult to replace directly with electricity and remains predominantly dependent on combustion methods in industrial applications.

Regarding the fuel strategy, the Tesseract TGR's initial fission driver fuel is TRISO uranium fuel with uranium-235 enrichment below 10%. The reactor also includes a thorium-containing fertile blanket designed to capture neutrons that would otherwise escape the core and convert thorium-232 into fissile uranium-233 during operation.

Thorium Atomics states that this "uranium-fueled, thorium-enhanced" architecture is intended to diversify the nuclear fuel supply chain, improve the full-lifecycle utilization efficiency of uranium resources, while keeping the fuel and licensing pathway grounded in existing uranium mining and TRISO fuel infrastructure. The company's current analysis estimates that, compared with a comparable second-generation light-water reactor, this architecture could reduce uranium mining requirements per unit of energy by approximately half. However, this estimate still requires further engineering optimization and independent verification through qualified analysis codes.

Thorium Atomics is an advanced nuclear reactor development company with offices in Toronto, Canada, and Knoxville, Tennessee, United States. In addition to its pre-application work with the NRC, the company states that it is maintaining parallel regulatory engagement with the Canadian Nuclear Safety Commission (CNSC).

Jack Vecchiarelli, Chief Science and Regulatory Officer at Thorium Atomics, stated that the project number and designated project manager provide the company with a clear point of contact at the NRC and establish a traceable reference basis for subsequent pre-application work. He believes that Part 53, being risk-informed and capable of accommodating multiple technology pathways, is well suited for high-temperature gas-cooled reactors to conduct regulatory engagement during the design and development phase.

Yong Huang, founder and Chief Executive Officer of Thorium Atomics, stated that the company has also submitted a proposal to Idaho National Laboratory (INL) under the Nuclear Energy Launchpad program and has proposed a plan for independent, qualified-code reactor physics verification at a U.S. national laboratory. He stated that the company is advancing regulatory, engineering, and technical verification records in parallel.