Kairos Power will build the Hermes molten salt-cooled demonstration reactor at the Heritage Center Industrial Park in Oak Ridge, Tennessee. It is the first non-water cooled reactor to be approved for construction in the USA in more than 50 years.

Kairos' vision for the Hermes plant (Image: Kairos Power)

The US Nuclear Regulatory Commission (NRC) voted to issue the permit after reviewing the company's application to construct the non-power test reactor. A mandatory hearing was held in October.

The NRC accepted the Hermes construction permit application for review in November 2021, but Kairos began pre-application engagement with the regulator in 2018. This extensive engagement - which established lines of communication between the two organisations - made it possible for the NRC to complete its review of the application well ahead of schedule, Kairos said.

"Kairos Power is thrilled to have achieved this major regulatory milestone as we make final preparations to start construction at the Hermes site next year. We are excited for this next phase in the deployment of the Hermes reactor, and we remain committed to being a good community partner to our neighbors in Oak Ridge as we bring value to the region and build on its nuclear legacy," said Kairos Power co-founder and CEO Mike Laufer.

Hermes will be a 35 MW (thermal) non-power version of the company's fluoride salt-cooled high temperature reactor, the KP-HFR. Kairos has also submitted a construction permit application for Hermes 2, a proposed two-unit demonstration plant that would build on the learnings from Hermes and would demonstrate the complete architecture of future commercial plants. Hermes 2 will produce electricity. The Hermes demonstration reactors will help mitigate technology, licensing, supply chain, and construction risk to achieve cost certainty for KP-HFR technology, Kairos said. The company is targeting commercial deployments in the early 2030s.

The NRC issued the final environmental impact statement for the site in August and the final safety evaluation for the permit in June. Kairos will have to submit a separate application for an operating licence before starting up the demonstration reactor.

Hermes is one of several new reactor technologies to receive federal support through the US Department of Energy's (DOE) Advanced Reactor Demonstration Program. US Assistant Secretary for Nuclear Energy Kathryn Huff said the NRC approval is a "huge milestone" for the energy sector. "NRC's approval of the first ever CPA granted to a Generation IV reactor charts a path forward for future design applications as we work toward deploying new reactor technologies," she said. "This accomplishment is a testament to the collaborative work among Kairos, the NRC, DOE and all stakeholders involved in the project."

Kairos is currently testing the high-purity fluoride salt coolant - known as Flibe - at its first engineering test unit (ETU) in New Mexico. The company plans to build and operate three ETU iterations before constructing Hermes.

Researched and written by World Nuclear News