Four Micro Reactors Hit Criticality Milestones Crossing DOE’s Finish Line on July 4th

• Four Micro Reactors Meet Criticality Milestones Crossing DOE’s Finish Line
• TRISO Fuel Delivered to INL for Radiant’s Kaleidos Reactor Experiment
• Quadrant Nuclear & INL Partner on HALEU Fuel 
• Applied Atomics Licenses BWXT’s mPower SMR Design
• Standard Nuclear Announces Launch of its Initial Public Offering 
• NRC Proposes Comprehensive Modernization of Reactor Licensing 
• NRC Proposes Modernization of Radiation Protection Rules

Four Micro Reactors Meet Criticality Milestones

On 07/04/26 as part of the U.S. Department of Energy Reactor Pilot Program, Aalo Atomics’ advanced reactor design, Aalo-X, was the fourth firm to successfully complete a zero-power fueled criticality demonstration.

Earlier in June, Antares Nuclear, Valar Atomics, and Deployable Energy completed a zero-power fueled criticality demonstration.

All of the experiments took place at Idaho National Laboratory. Aalo nosed over the finish line in the early morning hours of July 4th.

DOE Energy Secretary Chris Wright took a victory lap celebrating the accomplishments of all four firms in a press statement. He said that DOE issued a challenge to 11 firms selected for the reactor pilot program expecting at least three of them to meet it.  He said, “I’m pleased to share that through the dedication and hard work of INL and DOE, we have surpassed that ask and delivered four!”

Yasir Arafat, President and CTO, Aalo Atomics, observed that,“The hardest problem in nuclear was never the physics, our country simply forgot how to build. The success of the Department of Energy Reactor Pilot Program is proof America can execute again.” 

“We are proud to play a major role in America’s nuclear renaissance, going from breaking ground to a sustained chain reaction in just eight months, one of the fastest reactor builds in modern American history.”

The Reactor Pilot Program leverages DOE authorization to certify and construct first-of-a-kind advanced reactor designs for demonstration. DOE said in its press statement that “the new authorization pathway is an example of how regulatory reform can accelerate innovation.” 

For a quick review of the technical details of reactor designs of the four firms that crossed the finish line on July 4th, see Steffan Szumowski’s “Nuclear Review” for 07/06/26.

The Challenges Facing Microreactor Developers

A key fact is that the four firms that achieved a zero-power fueled criticality demonstration have also hit a key milestone related to investor interest. These firms have verified that they have a minimum viable product that sets the stage for further investor funding to pay for progress towards commercialization of their reactor designs.

The key success factor for an advanced micro nuclear reactor Minimum Viable Product (MVP) is regulatory validation and a pathway to rapid licensing of the design. Unlike software, a nuclear MVP cannot simply be “buggy” or iterated on in a live, public environment. It must prove safety, transportability, and predictable modular power output to secure market trust and regulatory approval and licensing.

Regulatory Clearance and Licensing

• Licensing framework adaptation: Secure early-stage approvals using tailored pathways, such as the U.S. Nuclear Regulatory Commission’s (NRC) 10 CFR Part 53 risk-informed framework.
• Pre-licensing engagement: Establish formal vendor design reviews with regulators to catch showstoppers before manufacturing.
• Safety case baseline: Define a deterministic safety case focusing on inherent physics rather than active, operator-dependent safety systems.

Inherent and Passive Safety Verification

• Walk-away safety: Demonstrate that the reactor shuts down safely during total power loss without human intervention.
• Negative temperature coefficient: Utilize fuels (like TRISO) and physics layouts where rising temperatures naturally slow down the nuclear reaction.
• Fission product retention: Prove containment boundaries can withstand extreme thermal and physical stress at the MVP scale.

Factory Fabrication and Transportability

• Standardized envelope: Limit physical dimensions to fit within a standard ISO shipping container or standard cargo aircraft.
• Plug-and-play architecture: Design rapid site integration interfaces so the reactor connects easily to local microgrids.
• Modular manufacturing: Avoid custom, site-specific civil engineering by utilizing off-the-shelf industrial components where possible. 

High-Fidelity Non-Nuclear Prototyping

• Thermal-hydraulic testing: Build full-scale electrically heated loops to validate coolant flow behaviors without using actual nuclear fuel.
• Digital twin deployment: Run real-time simulation models parallel to physical testing to predict component degradation and transient responses.
• Fuel surrogate validation: Utilize depleted uranium or surrogate materials to test mechanical handling and core loading mechanisms.

Economics and Supply Chain Viability

• High-assay low-enriched uranium (HALEU): Secure a reliable fuel supply chain or design the MVP to utilize readily available enrichment levels, e.g. LEU at less than 5% U235.
• Targeted minimum output: Optimize power generation (typically 1–20 MW) to match the immediate needs of remote mines, military bases, or data centers.
• Simplified decommissioning: Design the MVP for a “heart swap” model where the entire reactor module is returned to the factory at end-of-life. 

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TRISO Fuel Delivered to INL for Radiant’s Kaleidos Reactor

(WNN) The first shipment of fuel for full-power, full-temperature testing of Radiant’s Kaleidos microreactor technology has been delivered to the National Reactor Innovation Center’s (NRIC) Demonstration of Microreactor Experiments (DOME) facility at Idaho National Laboratory (INL).

The tri-structural isotropic (TRISO) fuel was fabricated by Standard Nuclear to Radiant’s specifications earlier this year. It will be used to power Radiant’s Kaleidos reactor to conduct a full-power, full-temperature test this summer. This effort will kick off months of rigorous testing and validation. With fuel now on site, the company said it is “poised to bring Kaleidos online”.

Radiant is to carry out a five-phase reactor development testing programme at the facility to collect critical reactor and fuel performance data, which it says will help accelerate the commercial licensing process with the US Nuclear Regulatory Commission. It will progress through zero-power criticality, 1 MW thermal, full power, and full heat, before operating for a minimum of 150 hours at full power without operator intervention, a crucial milestone in proving commercial readiness. 

The Demonstration of Microreactor Experiments test bed is a 100 feet (30 metres) tall and 80 feet in diameter facility that uses the containment structure of the Experimental Breeder Reactor-II (EBR-II) which operated from 1964 to 1994.

It provides a safe environment to test experimental reactor concepts and gather performance data that can be used to inform future commercial licensing applications, helping to accelerate development timelines and ultimately saving money and reducing project risk. Radiant designed, validated and performed the safety analysis of its own system for transporting the fuel 

“We are de-risking a commercial product that will be manufactured and delivered within 18 months,” Radiant Chief Nuclear Officer Rita Baranwal said.

“Receipt of our freshly fabricated, modern-pedigree, custom-made fuel is a key milestone toward that goal. Radiant has been very disciplined with our testing program at the DOME; we are testing our prototypic fuel, coolant, and power levels to validate our product and ensure success for our customer deployment by 2028.”

Data collected from DOME will also play a key role in supporting Radiant’s Part 70 licence application for its R-50 manufacturing facility in Tennessee, which is in accelerated review by the NRC. Once approved, the licence will enable Radiant to handle and load fuel for its Kaleidos reactors before shipping to customers across the United States, unlocking standardized mass production.

Kaleidos is a high-temperature gas-cooled reactor using TRISO fuel, helium gas coolant, and prismatic graphite blocks. The transportable microreactor will be fully contained in a single shipping container, and is designed to generate 3MW thermal or and around 1MW electrical.

The Nuclear Regulatory Commission has been conducting pre-application activities for the reactor with Radiant since 2022. Kaleidos is one of three microreactor designs selected in 2023 to receive US federal funding or front-end engineering and experiment design at DOME.

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Quadrant Nuclear & INL Partner on HALEU Fuel 

• Collaboration at Idaho National Laboratory will support research and development for advanced fuel recycling and recovery of strategic nuclear materials

Under the Strategic Partnership Project, Quadrant Nuclear and the Idaho National Laboratory  will conduct collaborative research and development at the lab site. A key focus is work associated with INL’s Material Recovery Pilot Plant (MRPP), a research facility supporting front-end processing of used nuclear fuel. QNI’s objective is to develop the design of a privately owned and funded fuel recycling facility intended to recover HALEU from used nuclear fuel currently held by the U.S. Department of Energy.

By leveraging INL’s zirconium removal prior to extraction (ZIRCEX) process, QNI aims to transform this used fuel into a commercially viable domestic HALEU supply that will directly enable the deployment of advanced reactor technologies across the country. QNI’s broader objective is to develop a privately funded fuel-recycling platform that could contribute to the United States’ advanced reactor fuel supply, subject to applicable DOE approvals, site access arrangements, regulatory and environmental review, and definitive agreements.

QNI and INL are testing aluminum and zirconium-clad highly enriched uranium fuels using the hybrid ZIRCEX process to produce HALEU. The project involves initial fuel treatment and use of INL’s solvent extraction modeling capabilities to design a purification process. INL will act as a consultant on QNI’s full-scale plant design.

“QNI is focused on building a practical domestic pathway for advanced nuclear fuel supply,” said Vice Admiral, U.S. Navy (Retired) Dee L. Mewbourne, Ed.D., Chief Executive Officer of QNI. “Our work with INL supports the national imperative to strengthen HALEU availability for advanced reactors while advancing responsible used-fuel recycling and material recovery.”

HALEU, generally defined as uranium enriched between 5% and less than 20% U-235, is expected to be an important fuel source for existing and many advanced reactor designs under development in the United States. Establishing reliable domestic supply pathways is widely viewed as essential to the demonstration and deployment of next-generation nuclear technologies.

About Quadrant Nuclear Industries, Inc.

Quadrant Nuclear Industries, Inc. is a U.S.-based advanced nuclear fuel-cycle company developing domestic capabilities for the recovery of high-assay low-enriched uranium and other strategic isotopes from used nuclear fuel. 

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Applied Atomics Licenses BWXT’s mPower SMR Design

The mPower is a 195-megawatt Generation III+ small modular reactor based on light water reactor design principles. Its entire nuclear steam supply system is integrated into a single pressure vessel measuring seventy-five feet tall by fifteen feet in diameter, sized deliberately to be able to ship by rail on a standard flatcar. It runs on standard commercial nuclear fuel. It does not require river or coastal siting and requires less than less than 1% of water used in conventional plants with cooling towers when producing the same amount of electricity.

Under the agreement, Applied Atomics holds the exclusive commercial rights to deploy the mPower reactor across the United States, Canada, and other jurisdictions with comparable nuclear liability frameworks. BWXT retains ownership of the underlying intellectual property. Applied Atomics holds the deployment rights. BWXT is the exclusive manufacturer of all new, replacement, maintenance, and overhaul components for the reactor, which allows Applied Atomics to leverage its expertise and facilities.

The first work under the agreement is a focus on regulatory progress. The mPower program completed pre-application engagement with the Nuclear Regulatory Commission between 2009 and 2014. Applied Atomics says it is restarting that process building on the design certification work already on record. The firm is targeting 2030 for our first commercial operation.

The firm said its team is advancing site selection with a focus on industrial and technology customers whose load profiles match mPower’s modular output. The commercial market for firm, dispatchable, carbon-free power did not exist at scale when the mPower program was archived, but it exists now.

Data centers, semiconductor fabrication, advanced manufacturing, and the electrification of transportation have changed the demand picture in ways that the utilities of 2015 could not have planned for, and the gas plants of today cannot adequately serve.

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Standard Nuclear Announces Launch of its Initial Public Offering 

Standard Nuclear, Inc. a reactor-agnostic producer of TRISO nuclear fuel,announced the launch of its proposed initial public offering of 18,250,000 shares of its Class A common stock. The initial public offering price is expected to be between $18.00 and $21.00 per share or $383 million at the $21/share price prior to fees and closing costs.

The offering is subject to market conditions, and there can be no assurance as to whether or when the offering may be completed, or as to the actual size or other terms of the offering. Standard Nuclear has applied to list its Class A common stock on the New York Stock Exchange under the ticker symbol “STDN.”

The proposed offering of these securities will be made only by means of a prospectus. When available, copies of the preliminary prospectus relating to the proposed offering may be obtained via EDGAR on the SEC’s website at www.sec.gov.

About Standard Nuclear

Standard Nuclear’s mission is to reliably deliver the essential building blocks of nuclear power at scale – enabling cost-effective, safe, and secure energy for the world. Supported by leading U.S. defense technology and critical infrastructure investment firms, Standard Nuclear is focused on the large-scale production of advanced nuclear fuel and radioisotope power systems. It is the nation’s only independent manufacturer of TRISO fuel – a robust, high-performance fuel essential to advanced nuclear reactors for terrestrial, national security, and space applications. Standard Nuclear offers a reactor-agnostic supply of advanced fuels to the next-generation nuclear industry and delivers dependable radioisotope power solutions to the space and defense sectors. Through these efforts, it is helping to eliminate U.S. reliance on geopolitical adversaries for these strategically vital technologies.

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NRC Proposes Comprehensive Modernization of Reactor Licensing 

The Nuclear Regulatory Commission proposed a sweeping package of regulatory reforms aimed at modernizing reactor licensing, safety oversight, and siting practices for nuclear power plants. 

The proposed rule would update requirements across virtually every stage of a plant’s lifecycle—from initial design approvals and construction through operation, license renewal, and decommissioning—by introducing more flexible, risk-informed, and performance-based approaches tailored to both today’s technologies and the next generation of reactors.

The proposal, which spans numerous regulatory areas, represents the NRC’s most comprehensive update to nuclear power plant licensing in decades. It is informed by decades of operating experience, lessons learned from new reactor licensing, and the emergence of advanced reactor designs that challenge the boundaries of existing regulations. The rulemaking also advances the regulatory modernization objectives of the ADVANCE Act of 2024 and Executive Order 14300.

“NRC’s regulations have not kept pace with new technologies and our energy needs,” Chairman Ho Nieh said. “This proposed rule strips out rigid frameworks and unnecessary conservatism to accelerate the safe deployment of new reactors and expand existing capacity across America.”

Among the specific proposed changes:

• Faster, More Efficient Construction: The proposal would streamline the start of construction for new reactors by focusing NRC oversight on the most safety-significant systems and allowing certain early site activities under a general license, once an application is docketed.

• Flexible, Risk-Informed Regulatory Options: Applicants and licensees would have new opportunities to use modern, risk-informed approaches as alternatives to traditional requirements, including for safety analyses and model updates.

• Modernized Emergency Preparedness: The rule would make performance-based emergency planning available to all reactor types and allow for more flexible, risk-informed emergency planning zones tailored to each facility’s design.

• Updated Quality Assurance Standards: Licensees could opt for a new, internationally aligned quality assurance framework, supporting innovation and a more flexible supply chain.

• Greater Licensing and Siting Flexibility: The proposal would extend license renewal terms, update siting criteria to accommodate a broader range of technologies, and allow more tailored decommissioning funding requirements for advanced reactors.

• Supporting Advanced Fuels: The proposal would enable the safe use of innovative fuels, such as higher-enriched and accident-tolerant designs, and modernize safety requirements to focus on credible, risk-significant scenarios.

The NRC will accept comments on the proposed rule for 45 days following its publication in the Federal Register. Comments may be submitted at www.regulations.gov under Docket ID NRC-2025-0975. Additional details will be provided in the Federal Register notice.

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NRC Proposes Modernization of Radiation Protection Rules, Reaffirms Current Safety Standards

The Nuclear Regulatory Commission today proposed an update to its radiation protection regulations that would maintain existing public and worker dose limits while reducing unnecessary regulatory burden and modernizing requirements to reflect current science and decades of operating experience.

The proposal would replace the longstanding “as low as reasonably achievable” (ALARA) principle with clearer, more objective requirements focused on compliance with regulatory precautions and established dose limits, which themselves are set well below levels associated with known health effects. The agency concluded that retaining ALARA as a separate regulatory expectation can lead to additional costs and complexity without a measurable safety benefit.

“We’re raising the standard for regulatory clarity, not lowering the standard for safety,” Chairman Ho K. Nieh said. “Our radiation dose limits remain unchanged—what we’re eliminating is unnecessary ambiguity.”

The proposed rule would establish a more risk-informed and performance-based framework for radiation protection by:

•  Adopting a graded approach to dose management based on risk and operational circumstances.

•  Providing licensees greater flexibility to use modern methods for evaluating radiation doses to workers and the public.

•  Expanding options for managing occupational radiation exposure.

• Allowing caregivers of patients receiving treatments involving radioactive materials to voluntarily receive higher doses, improving patient care while maintaining appropriate protections.

The proposal is part of the NRC’s broader effort to modernize regulations, reduce unnecessary burden, and ensure requirements remain aligned with current science and operational experience while maintaining the agency’s commitment to protecting public health and safety.

The NRC will accept public comments for 45 days following publication in the Federal Register and plans to hold a public meeting during the comment period.

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