The U.S. Nuclear Regulatory Commission is issuing a construction permit for a new type of nuclear reactor that uses molten salt to cool the reactor core.

The NRC is issuing the permit to Kairos Power for the Hermes test reactor in Oak Ridge, Tennessee, the agency said Tuesday. The reactor won’t generate generate electricity and it will be far smaller than traditional ones.

This is the first construction permit the NRC has issued for a reactor that uses something other than water to cool the reactor core. The United States Atomic Energy Commission, the predecessor to the NRC, did license other types of designs.

Kairos Power is working on fluoride salt-cooled, high-temperature reactor technology. The California-based company received funding from the Department of Energy. The 35-megawatt thermal reactor will test the concept of using molten salt as a coolant and test the type of nuclear fuel, the NRC said.

Kairos Power aims to develop a larger version for commercial electricity that could be used in the early 2030s. It says the construction permit is a big step forward as it works to deploy clean, safe, reliable and affordable energy.

The global nuclear industry launched an initiative at this year’s U.N. climate talks for nations to pledge to triple nuclear energy by 2050. More than 20 have already signed on, including the United States and the host of COP28, the United Arab Emirates.

The NRC has certified one small modular nuclear reactor design for use anywhere in the United States, a light-water reactor by Oregon-based NuScale Power.

Kairos Power took a different approach and asked the NRC for permission to build its test reactor only at the Oak Ridge site. It still needs an operating license. It applied for a second construction permit for a larger version, a two-unit demonstration plant, also at Oak Ridge.

The NRC is expecting at least two more applications next year for construction permits from other companies working on small modular reactors or advanced designs.

Critics say it would be safer to use other low-carbon technologies to address climate change, such as solar and wind power.

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