The U.S. Nuclear Regulatory Commission has granted a license to Kairos Power to construct the first nuclear power plant that does not use water for cooling.
Molten salt used for cooling at the CEA Cadarache institute in France. (Photo: AFP).
Kairos Power plans to construct an experimental plant named Hermes, which will utilize molten fluoride salt cooling in Oak Ridge, Tennessee, by 2027, according to Business Insider on December 20. The first version of the plant will not generate electricity, but the subsequent version, Hermes 2, is expected to produce power by 2028. Mike Laufer, CEO of Kairos Power, stated that the molten salt nuclear reactor does not require thick pressure vessels to keep water in a liquid state at high temperatures. It is smaller than traditional water-cooled types and can be built in a wider variety of locations.
Hermes will operate at temperatures of nearly 650 degrees Celsius. However, the coolant, a mixture of lithium fluoride and beryllium fluoride known as FLiBe, boils at 1,430 degrees Celsius, significantly higher than the reactor core temperatures. Therefore, FLiBe remains liquid under high-temperature conditions without the need for additional pressure. The fuel that Kairos Power uses is also different from conventional reactors. The company plans to use tristructural-isotropic (TRISO) fuel, which can withstand extreme temperatures better and has a lower likelihood of releasing radioactive products.
What sets molten salt reactors apart is how they cool the core, using salt instead of water. Nearly all operational reactors today use water as a coolant, with their cores potentially reaching temperatures of 300 degrees Celsius. Preventing water from evaporating and maintaining a liquid state at such high temperatures requires significant pressure, leading to complex technology, extensive space, and high costs. However, some types of salt have much higher boiling points, thus eliminating the need for costly high-pressure environments, according to Nicholas V. Smith, project director of the Molten Chloride Reactor Experiment at Idaho National Laboratory.
For example, the first molten salt reactor was tested in the 1950s and was small enough to fit on an aircraft, while the Diablo Canyon nuclear power plant in California occupies up to 4.9 hectares of land. However, this type of reactor gradually fell into obscurity in the 1970s as the U.S. shifted its preference to water-cooled reactors.
