The University of Illinois Urbana-Champaign (U of I) has submitted a Construction Permit Application (CPA) to the US Nuclear Regulatory Commission (NRC) for US-based start-up NANO Nuclear’s KRONOS MMR microreactor. The CPA was formally submitted by The Grainger College of Engineering at U of I.
The KRONOS MMR Energy System is a high-temperature, gas-cooled microreactor that uses helium coolant and TRISO particle fuel. Its compact, modular architecture is intended to support flexible deployment and scalable power output, from single-unit configurations to gigawatt-class multi-reactor clusters capable of powering large industrial and civil campuses as well as other applications, including governmental requirements.
In January NANO Nuclear signed a memorandum of understanding with the Board of Trustees of the University of Illinois on behalf of U of I to collaborate on the development, construction, and operation of its KRONOS MMR on campus as an advanced research reactor. This extended NANO’s existing research agreement with U of I providing for support in design and regulatory licensing of the KRONOS MMR.
NANO said the CPA submission “represents the achievement of a critical milestone for the KRONOS MMR on the pathway from engineering design to construction on the campus of the U of I, to reactor licensing, to ultimate commercial deployment”.
Unlike early-stage conceptual work, a CPA requires: advanced engineering and safety analysis; site-specific evaluation and environmental considerations; demonstration of compliance with NRC regulatory frameworks; extensive documentation developed through ongoing engagement with NRC staff.
The preparation of a CPA represents the culmination of years of engineering development, thousands of pages of technical documentation, coordinated input across reactor design, safety analysis, environmental review, and regulatory compliance disciplines, and establishment of a viable supply chain.
Advancing to the CPA stage signals that the intellectual property protected KRONOS MMR is no longer just a design, but an energy system being actively moved into construction, licensing, and eventual commercial deployment at scale. Insights gained through the CPA process are expected to play a critical role in refining NANO Nuclear’s assembly, siting, and deployment strategies, enabling the Company to move efficiently through future licensing and through multi-unit deployment projects.
Florent Heidet, Chief Technical Officer of NANO Nuclear said the CPA application represents years of engineering, regulatory engagement, and disciplined execution. “It is where advanced nuclear projects begin to separate into those that are ready for execution and those still requiring significant R&D efforts. We are now firmly on the path toward constructing, demonstrating, and ultimately deploying our reactor technology at scale.”
Jay Yu, Founder and Chairman of NANO Nuclear Energy said reaching the CPA stage places NANO Nuclear in a small group of companies that are advancing toward commercial deployment at scale. “This process demands a significant level of technical maturity, regulatory alignment, and operational readiness. It is a powerful validation of our technology and our strategy. With this milestone achieved, our engineering teams are now laser focused on building out a reduced-scaled KRONOS MMR™ non-nuclear engineering demonstration unit in our newly renovated Oak Brook, Illinois technical and demonstration facility.”
Caleb Brooks, Professor and Donald Biggar Willett Faculty Scholar of Nuclear, Plasma and Radiological Engineering at The Grainger College of Engineering, said: “By submitting the Construction Permit Application to the NRC, we are taking the next step in signifying that the work will be done correctly and precisely. And we continue to look forward to the possibilities of what can become the most advanced nuclear research platform on any US campus.”
NRC will begin its formal evaluation process, including safety and environmental assessments. NANO Nuclear estimates the NRC formal review period to take approximately 12 months. Developers capable of navigating the regulatory process today are expected to be well-positioned to deploy reactors in the years to come.
NANO Nuclear is the first commercially-ready microreactor developer and the third commercially-ready Generation IV advanced reactor developer to submit a CPA. The other two are Kairos Power, which received a construction permit (CP) for its Hermes fluoride salt-cooled high-temperature reactor in December 2023; and TerraPower, which received a CP for its Natrium sodium-cooled fast reactor in March. X-energy is also moving through the CPA process toward deployment having submitted a CPA in March 2025 for its Xe-100 high-temperature gas-cooled reactor.
TerraPower and Kairos Power have already broken ground on their demonstration or commercial sites. Kairos Power is targeting 2027–2028 for its first operational units. X-energy is currently focused on building its TRISO-X fuel fabrication facility in Oak Ridge, Tennessee. Vertical construction on the Xe-100 reactor in Texas is not expected to start until later this decade.
