The Advisory Committee on Reactor Safeguards (ACRS) recently endorsed the NRC Staff’s proposed alternative option for licensing microreactors in a letter submitted to NRC Chairman Christopher Hanson. In brief, the licensing option endorsed by ACRS would allow a factory-fabricated microreactor to be loaded with fuel having features to preclude criticality and undergo operational testing at the factory before being transported to an installation site. If approved by the Commission, such an approach would create a lower regulatory burden commensurate with the anticipated decreased potential safety hazards posed by microreactors.
Background
The NRC considers microreactors to be reactors with power levels in the tens of megawatts thermal (unlike current power reactors, which generate thousands of megawatts) and inherent safety features. Some microreactors are expected to be built in factories and then shipped to sites where they will be installed. Such factory-built microreactors may be “self-contained” and include the reactor, shielding, and balance of plant in one or more containers that would be shipped to a deployment site and later removed.
Other factory-built microreactors may consist of a core module transported to a deployment site and incorporated into a permanent structure that includes power conversion and balance of plant systems. Microreactors could be used for providing power and heat for remote communities, supplying backup power, producing clean hydrogen, desalinization, and providing process heat for industrial applications.
NRC Staff’s Proposed Alternatives
NRC regulations were not crafted with factory-produced microreactors in mind. One particular hurdle is the Commission’s long-standing position that fuel loading be part of reactor operation, which requires an operating license under Part 50 or 52. This presents several regulatory hurdles for factory-produced microreactors and poses a significant regulatory burden on the fabrication of microreactors that may be disproportionate to the reduced risk from the size and design of these types of reactors.
First, the factory operator would need to hold a facility operating license or combined license to load fuel at the factory. Second, the NRC’s regulations do not allow for transporting utilization facilities that are in operation, which would prevent the transport of fueled microreactors from a factory. Third, an operating license would be necessary to test the microreactors at the factory. To address these issues, the NRC Staff proposed alternatives for defining when a microreactor is “in operation” and to allow fuel loading and testing at a factory in a draft white paper and evaluation of licensing considerations for microreactors.
To address the question of when a microreactor is “in operation,” the Staff’s alternative would credit features to preclude criticality. Under this option, a factory-fabricated microreactor with features that preclude criticality would not be considered “in operation” when loaded with fuel. Operations would start only when those features are removed. For fuel loading, the Staff’s alternative would allow fuel loading at the factory under a Part 70 license for possession of special nuclear material rather than requiring the factory to be licensed under Part 50 or 52. This would also rely on the features to prevent criticality. For testing, the Staff’s alternative would apply regulations for nonpower reactors to operational testing at the factory.
ACRS Endorses NRC Staff’s Proposed Alternatives
In its letter to Chairman Hanson, ACRS stated that it favors the Staff’s proposed alternatives for microreactors because using existing licensing requirements for fabricators “would involve a regulatory burden for fabricators that may not comport with the hazard from some micro-reactors.”
Even so, the ACRS noted that more work is needed to fully implement the Staff’s proposals. First, regulatory definitions would be needed to determine which microreactors are eligible. Second, the Staff would need to develop guidance to address the features to preclude criticality, the amount of shutdown margin required, and the robustness required for transportation.
We expect the NRC Staff to begin work on a paper with these proposals to submit to the Commission for approval, the timing of which is currently unknown. We will continue to monitor developments in this area.