The former site of the K-33 gaseous diffusion enrichment plant in Oak Ridge’s East Tennessee Technology Park is the future site of Hermes and Hermes 2. (Photo: Kairos Power)
Nuclear Regulatory Commission staff has completed its final safety evaluation for Kairos Power’s application to build its Hermes 2 molten salt–cooled reactor test facility in Oak Ridge, Tenn., the agency announced July 22. Earlier, and independently, the NRC’s Advisory Committee on Reactor Safeguards (ACRS) reviewed safety-related aspects of the Kairos application and provided its review to the Commission on July 17. The evaluation concluded that there are no safety aspects that would preclude issuing a construction permit for the facility, but that can’t happen until the NRC staff issues its final environmental assessment later this summer and the Commission assesses the staff’s work (under newly streamlined procedures for mandatory hearings) this fall before voting on whether to authorize a construction permit.
Round 2: If there’s a sense of déjà vu, maybe it’s because Hermes 2 is following a path to a construction permit first traveled by its permitted but yet-to-be-constructed predecessor—known simply as Hermes.
The Hermes 2 test reactor facility would contain twin 35 MWt pebble-bed reactors with ping-pong ball–sized solid fuel pebbles containing HALEU in TRISO particles, with molten fluoride salt coolant. Each Hermes 2 reactor unit would be of similar size and design as Hermes, and Hermes 2 would be built on the same site. The Hermes 2 reactors would have an intermediate molten salt heat transfer loop and share a turbine to demonstrate electricity generation.
Here are a few milestones Hermes and Hermes 2 have already met:
- September and October 2021—Kairos Power submitted its license application for Hermes in two parts.
- May 2023—ACRS completed its review of the construction permit application for Hermes, recommending approval, followed in June 2023 by the completion of the NRC staff’s safety review.
- July 2023—Kairos Power applied for a construction permit for Hermes 2.
- December 2023—Kairos Power received a construction permit for Hermes—the first non–light water reactor approved for construction in the United States in more than 50 years.
NRC celebrates efficiency: Kairos Power’s iterative approach to demonstrating its technology means an iterative review process for the NRC.
“We finished our review of Hermes 2 design nearly four months ahead of schedule, and using about 60 percent fewer resources than expected, using insights from our previous Kairos review,” said Andrea Veil, director of the NRC’s Office of Nuclear Reactor Regulation. “We remain committed to applying these sorts of lessons learned to maintain safety while promptly and efficiently processing applications.”
Kairos Power will have to submit separate applications to operate Hermes and later Hermes 2 in the future.
