The NRC took less than 12 months to evaluate Hermes 2's environmental impacts, compared with nearly two years for Hermes 1, and could thus reach a faster decision on the construction permit application, Nuclear Innovation Alliance Research Director Patrick White said. "What you're seeing here is progress from the NRC as to how to more efficiently and effectively license advanced nuclear technologies," he said.
Kairos Power will test its fluoride salt-cooled, high-temperature reactor technology in Oak Ridge as it prepares for deployment of its first 140-MWe commercial power plant in the early 2030s.
The reactor runs on ceramic TRISO pebbles, a novel high-assay, low-enriched uranium fuel form that remains stable at very high temperatures. TRISO, or tri-structural isotropic particle fuel, contains a small fuel pellet surrounded by concentric carbon and ceramic layers. Like other advanced reactors, Kairos' design incorporates passive safety systems that "[allow] emergency cooling to be driven by fundamental physics rather than engineered systems," the company says.
Kairos submitted its construction permit application for the Hermes 1 reactor in September 2021 and received NRC approval to begin construction in December 2023, marking the first-ever U.S. approval for a Generation IV reactor -- a family of reactor technologies that generally use coolants other than water, incorporate passive safety systems, and may operate at higher temperatures. Construction on Hermes 1 began in late July, Kairos said.
Kairos applied for the Hermes 2 construction permit in July 2023. The NRC has not yet made a final determination on that application, but the Aug. 30 finding of no significant impact was an important milestone that's likely to speed up the process, White said.
"We're not saying this is a major moment in NRC regulation, but it shows [the NRC's] changing approach to environmental review while continuing to meet statutory requirements," White said.
The landmark Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy Act, which President Biden signed July 9, directs the NRC to consider process reforms that "facilitate efficient, timely and predictable environmental reviews of nuclear reactor applications."
NRC has been working for the past year to reform its environmental review processes independently of the newer Congressional directive, White said.
Though it did not require a full environmental impact statement for Hermes 2, the NRC did conduct an environmental assessment that examined potential impacts unique to the second reactor. Such assessments are less involved than environmental impact statements, which are needed when the NRC determines that a proposed reactor is likely to more substantially affect its surroundings, White said.
The Hermes 2 application is a good test case for the NRC's process reforms, but questions remain as to how the commission will approach future advanced reactor proposals, White said.
"It's always hard to tell what is the right pathway for doing one of these reviews, especially for first-of-a-kind technologies," he said.
The risk of beginning with an environmental assessment rather than a full EIS is that an EIS is required anyway if the EA finds the potential for significant impacts, White said. In that scenario, the more efficient approach may be to go straight to the EIS, he said.
The EA-first approach could make sense for certain small reactors with relatively compact footprints and low power outputs, given that the most substantial environmental impacts from new nuclear projects often come from cooling water demand, power generation and transmission infrastructure, and other non-reactor aspects, he added.