US regulators conclude Hermes safety review

NRC's evaluation concludes that there are no safety aspects that would preclude issuing a construction permit for the reactor and comes after the agency's independent Advisory Committee on Reactor Safeguards provided the results of its review, recommending that the construction permit for the Hermes demonstration reactor be approved.

Kairos submitted its permit application in two parts, in September and October 2021, but the company began extensive pre-application engagement with the NRC in 2018. The NRC accepted the Hermes CPA for review in November 2021, committing to an accelerated 21-month review timeline, and has completed it in 18 months - well ahead of schedule, according to Andrea Veil, director of the NRC's Office of Nuclear Reactor Regulation. "This reflects the NRC's commitment to maintaining safety, by applying risk-informed approaches, while improving efficiency," she said.

"We are pleased to have worked closely with the NRC staff to complete a thorough, efficient, and innovative review, which is encouraging for future deployment of advanced nuclear reactors," said Kairos Vice President of Regulatory Affairs Peter Hastings. "We look forward to continuing our close collaboration with the staff and the Commission to support the Final Environmental Impact Statement and complete the mandatory hearing."

Kairos is taking a "rapid iterative" approach to development, which the company says reduces risk on the path to commercialisation and establishes confidence for build and construction. The company will have to submit a separate application in the future for an operating licence. It said the Hermes construction permit application is laying the groundwork for this application which will, in its turn, generate lessons to inform the license applications for future commercial deployments.

Hermes will be a 35 MW (thermal) non-power version of the company's fluoride salt-cooled high temperature reactor - the KP-FHR, which uses TRISO (TRI-structural ISOtropic) fuel pebbles with a low-pressure fluoride salt coolant. The demonstration reactor has been selected by the US Department of Energy to receive USD629 million in cost-shared risk reduction funding over seven years under the Advanced Reactor Demonstration Program, and is intended to provide operational data to support the development of a larger version for commercial deployment.

A site at the East Tennessee Technology Park in Oak Ridge has been selected for the demonstration reactor, and TRISO fuel pebbles will be produced at the Los Alamos National Laboratory's Low Enriched Fuel Fabrication Facility under an agreement announced in late 2022. The company has also commissioned a plant to produce high-purity fluoride salt coolant - known as Flibe - in partnership with Materion Corporation. The Molten Salt Purification Plant, in Elmore, Ohio, has now shipped its first batch of the coolant to Kairos Power’s testing facility in Albuquerque, New Mexico, to support Engineering Test Unit (ETU) operations, the company said in a separate announcement.