When is a nuclear reactor ‘in operation’? The US Nuclear Regulatory Commission (US NRC) had to consider its definition of this state, to ensure it applies appropriately to new types of nuclear power plants. Specifically, it has addressed this issue in respect of so-called ‘micro reactors’ – nuclear power plants rated at as little as 2-3 MW, such as that proposed by Hadron Energy (see below). This type of plant will be small enough to be fabricated in a factory and transported on an HGV, to be delivered to its site as a closed unit, operated remotely and removed at the end of its life.
Fuel loading and entering operation is an example of how the mobility of microreactors is a fundamental change in the nuclear industry. The current nuclear model has a small number of fixed sites for reactors and fuel cycle facilities, with occasional movements of new or spent fuel between them. In contrast, microreactors may have a large number of small reactor units, which are mobile and may be moved several times over their lifetimes (during the start and finish).
A containerised reactor is likely to be fabricated at one or more factory sites. Instead of being loaded with fuel at its eventual operating site, there are several other options. The reactor may receive its fuel load at the factory, with radiological implications for the factory and the fuel transport process. The containerised reactor could be moved to a fuel cycle facility to be loaded with fuel. Or one company could co-locate a fuel fabrication plant with its reactor assembly, and provide a fuel service to other microreactor suppliers. The fact that there are different business models available is a big change for the industry.
In a pre-application regulatory engagement plan (REP) for its microreactor standardised design, Hadron Energy said key areas identified for early engagement include the regulatory implications of factory manufacturing and testing, transportability, flexible siting approaches, and remote operations, hoping that “early engagement will identify areas where modernization of regulatory processes might benefit future applications”.
The US Nuclear Regulatory Commission has been working on the policy framework that will underpin a microreactor nuclear industry. Its consideration of how to define a reactor as being ‘in operation’ came in a recent decision-making in connection with its Factory-Built Microreactor Policy.
It decided that a factory-built microreactor loaded with fuel may be excluded from being ‘in operation’ if it has features to prevent a nuclear chain reaction, and operation in these circumstances would begin with removal of those features. In a separate second decision, it said that a microreactor with features to prevent a chain reaction may be loaded with fuel at a factory if it is done under an NRC licence that allows possession of the fuel. The third decision is that the NRC staff may apply regulations for non-power reactors to authorise testing of a microreactor at a factory, before it is shipped to an operating site.
Alongside the decisions, the Commission said staff had to keep the Commission informed as they develop the necessary technology-inclusive guidance on the use of features to preclude criticality, and ensure there are no unintentional contradictions other regulations. It said, “ln developing guidance and policy recommendations for the concept of features to preclude criticality, the staff should consider that the dynamics of transporting manufactured modules should, at minimum, require some form of physical measures to preclude criticality for modules in transit, especially those that have undergone preoperational testing at the factory.” The staff should ensure that the reactor licence clearly does not authorise operation at power when features to preclude criticality are inserted so the reactor can be transported, after operational testing or at the end of the operating cycle.
Regulating for microreactors
In developing a regulatory framework for microreactors, the USNRC is aiming to speed up and smooth the process, ensure the burden of regulation is appropriate, and where possible be proactive.
In that respect, under the ADVANCE Act of 2024 (Accelerating Deployment of Versatile, Advance Nuclear for Clean Energy Act), the Commission is required to “develop risk-informed and performance-based strategies and guidance to license and regulate micro-reactors… including strategies and guidance for…. risk analysis methods, including alternatives to probabilistic risk assessments”. That includes, for example, using existing meteorology and weather data from the National Oceanic and Atmospheric Administration, National Weather Service or other established nearby sources to support analyses and design bases for applications.
The NRC staff is expected to be proactive in developing regulation and licensing options for microreactor manufacturers that combine the activities of a microreactor applicant (factory fabrication, operational testing, fuel loading and transport) in a single licence. That could use licence conditions or technical specifications to address unique technical considerations, such as (above) the need for features to preclude criticality while the microreactor is in transit.
If NRC follows its direction to be ‘proactive’ on microreactors it may have implications for licensing of other reactor classes. The NRC staff have to consider whether proposed licensing and oversight strategies for microreactors, now or in the future, would be applicable to other types of nuclear reactors, including larger power reactors, research reactors and test facilities. Further, the staff have to analyse what changes could or should be made to the Atomic Energy Act “to better accommodate the production and deployment concepts currently under consideration”, and submit its findings as part of papers submitted to the Commission on policy or regulatory
issues.
One proactive role for the staff is to engage with Department of Energy (DOE) and Department of Defense (DOD) efforts to build and operate microreactors on the departments’ sites or as part of critical national security infrastructure. This engagement “should include identifying and implementing licensing process efficiencies… to streamline the transition of microreactor technology to the commercial sector”. Among these commercial options are maritime applications, and the NRC staff plans to monitor developments related to commercial maritime applications and assess the need for future Commission direction and coordination with other Federal agencies related to deployment of commercial maritime reactors.
One aspect of the licensing process potentially in question is a requirement under the Atomic Energy Act for an opportunity for a ‘contested hearing’ with regard to a new nuclear plant. The staff “currently have procedures and requirements to address contested hearings, but understand there may be implications related to the rapid deployment concepts,” and actions are TBD (to be determined) based on additional discussion for “a potential path forward”.
The NRC staff will continue to assess further potential enhancements to the regulatory framework for microreactors as technologies and deployment models evolve. The staff said it “continues to be receptive to feedback from stakeholders and other interested parties regarding the licensing and deployment topics listed in the integrated microreactor activities plan”.
On the dashboard
The NRC staff have produced an Integrated Microreactor Activities Plan, which is intended to be a comprehensive view of microreactor licensing and regulatory topics. It includes actions to enhance the flexibility of the regulatory framework to support the variety of technologies and deployment models under consideration by the industry.
The staff’s plan aligns with Section 208 of the ADVANCE Act, which directs the NRC to develop and implement risk-informed and performance-based strategies and guidance to license and regulate microreactors in eight areas: staffing and operations; oversight and inspections; security and safeguards; emergency preparedness; risk analysis methods; decommissioning funding assurance; transportation of fuelled microreactors; and siting. The NRC staff created a dashboard to show the status of these activities.
The plan has been producing deliverables since the start of 2024, such as a risk-informed methodology to be used in developing the safety basis for 10 CFR Part 71 applications for transportable microreactors.
NRC says stakeholders have indicated that additional regulatory clarity is needed in the near term to proceed with deployment models for large numbers of microreactors of standard designs. Among the activities due for completion in spring 2025 were activities in several of the areas covered by the dashboard.
Licensing:
The staff response will include a paper on nth-of-a-kind microreactor licensing and deployment that includes options for Commission considerations for review and approval of standardised operational programmes at the design stage. Among the issues addressed will be a paper on options for aircraft impact assessment for microreactors, including potential criteria for excluding microreactors from the aircraft impact assessment requirements . The NRC staff ultimately plans to develop an online portal for microreactor licensing that would allow applicants to submit electronic applications for nth-of-a-kind microreactors and the NRC staff to conduct their reviews and issue licence documents. This portal is timetabled for action in 2027.
Siting:
The NRC staff is considering a white paper on strategies for siting considerations for licensing mobile microreactors, timetabled for summer 2025. The paper will also include information on alternatives for environmental reviews, maximal design standardisation, grading the level of site characterisation, security, emergency preparedness, streamlined processing of licence applications and construction inspection. It also includes a paper on nth-of-a-kind microreactor licensing that includes information on alternative approaches for environmental reviews and a separate paper on population density-related siting criteria, both specifically for microreactors.
Inspection:
Microreactor developers have indicated that applications for licences for microreactors may be submitted “in the next several years” and information on operational programmes may affect development of their deployment models. In response, the NRC staff will be working on an inspection manual, due to be completed in 2026, and an inspection framework for the operational phase, due to be completed the following year. Further new rulemaking would address security, with “alternative approaches for physical security that would be better suited to microreactor designs”.
Operation:
The microreactor model generally assumes that plant will be operated remotely. In order to review proposed remote and autonomous operational approaches the NRC staff plans to develop draft guidance in the near-term which adapts the “self-reliant-mitigation facility” screening methodology of the 10 CFR Part 53 proposed rule. This will support NRC staff review of licence applications that might be submitted in the next several years. The staff will continue research into remote and autonomous operations, already in progress, to develop a long-term strategy for remote and autonomous operations.
Manufacturing:
The NRC provided a paper to the Commission in January 2024, which included options for licensing fuel loading at a factory. The NRC staff are now waiting for a direction from the Commission, after which the NRC staff will consider the need to develop related guidance. Manufacturers will be licence holders but they may use contractors, so the NRC staff plans to engage with stakeholders on their plans for using such contractors in their microreactor deployment models.
Decommissioning:
The NRC staff plans to engage with stakeholders on considerations related to decommissioning, refurbishment and refuelling of microreactors “to better understand post-operation aspects of microreactor deployment models”, and it seeks to provide flexibility for various potential microreactor decommissioning strategies. But at this point the dashboard says developers have not provided enough information on post-operation aspects of microreactor deployment for the NRC staff to develop new guidance.
Pre-application activity
The NRC is already engaged in pre- application activities with Hadron Energy, Inc, regarding a future Standard Design Approval (SDA) application, and manufacturing and fuel loading license applications.
Hadron Energy, Inc is developing a 2 MWe standardised microreactor for commercial licensing and deployment. The factory-built microreactor would be transportable, using low-enriched uranium fuel and light-water cooled and moderated. It is designed to fit within the dimensional envelope of a standard ISO shipping container to facilitate transport via conventional road, rail, air, or sea logistics. It says fleets of units can be co-located to form modular installations capable of meeting aggregated energy demands of 50 MWe or more.
It will be deployed “in locations where conventional grid power is unavailable, unreliable, or logistically impractical”, such as:
- Replacing diesel generators in remote communities, disaster relief zones, and off-grid industrial operations.
- Power supply for military or scientific installations requiring secure, mobile and independent energy.
- Grid support functions such as peak shaving, renewable firming, or backup power in localized high-demand areas (eg data centres).
Established in 2024 as a privately held Delaware C-corporation, Hadron Energy is focused on the design, manufacturing, licensing, and deployment of the microreactor. It is based on light-water reactor (LWR) technology and Hadron says, “Grounding the design in established LWR principles minimizes technical risk associated with core reactor technology and allows regulatory review to focus efficiently on the novel aspects of our implementation”.
It aims to maximise the benefits of standardisation through factory production and testing to enhance safety, quality, and regulatory efficiency.
The fuel will be loaded into the reactor core at a certified manufacturing facility prior to shipment, when the reactor module will be sealed, tested and shipped as a self-contained unit. It will use the existing LEU supply chain. At the end of its operational life (10 – 30 years, depending on fuel enrichment and burnup analysis), the entire reactor unit, including spent fuel, will be returned to a licensed facility for defueling, inspection, potential refurbishment or decommissioning, although detailed plans have still to be developed and discussed. In the interim there will be no refuelling during deployment at site.
Hadron Energy says, “The inherent novelty of our approach – particularly the factory fueling, transportability of the completed reactor, flexible deployment model, and planned remote operations – presents unique considerations for demonstrating compliance with existing regulatory frameworks. Key areas requiring early engagement include establishing the licensing basis for transporting a fuelled microreactor, developing flexible and/or bounding site parameter envelopes suitable for varied deployment locations, and demonstrating compliance with operational requirements, including staffing, for remotely monitored facilities.
The company’s intended regulatory path involves pursuing a Standard Design Approval (SDA) under 10 CFR Part 52, Subpart E for the standard design, followed by a manufacturing licence application under 10 CFR Part 52, Subpart F, together with a licence for fuel loading under 10 CFR Part 70 that references the approved SDA. Part 70, “Domestic Licensing of Special Nuclear Material” is required for factory fuelling because it allows for possession, use and transfer of special nuclear material and for conducting necessary testing activities (including potential Zero Power Critical tests) at the manufacturing facility. The company says, “We plan to utilize mechanisms such as targeted white papers, topical reports, and potentially a conceptual design assessment to seek early NRC feedback”.
The first step for Hadron Energy will be finding a site for its manufacturing facility (with a manufacturing licence). At this point an Early Site Permit based on a deployment site is not needed. In its model Hadron Energy will not be the primary applicant for Combined Licenses. Its regulatory strategy focuses on obtaining Standard Design Approval (SDA), a manufacturing licence, and a Part 70 licence (as above).
Once it has the SDA and manufacturing licence, Hadron Energy expects it would be its customers or partners that apply for Combined Licences for specific deployment sites.
The pre-application engagement plan was sent to NRC in May. Hadron Energy says that it plans to submit a Preliminary Safety Information Document and request a formal conceptual design assessment from the NRC within a year. Its timetable from that point will be re-examined on a six-monthly basis, but it is hoping for SDA by May 2028, a 10 CFR Part 70 Licence by June-July 2028 and its manufacturing licence by October-December 2028. Meanwhile it hopes a customer or partner will submit a Combined Licence Application for the microreactor’s first site by December 2028, to be accepted by the NRC by February 2029.
Time will show whether the ambitious programme of work by regulators, manufacturers and potential customers will be completed on schedule. But at the moment, all parties are leaning on the accelerator.
