US Started The Construction Of The Country’s First 4th Generation Nuclear Reactor 

Kairos Power has announced that it has begun construction of the first molten salt, rather than water, nuclear reactor in the United States in 50 years. The demonstrator will be built by 2028 in Oak Ridge, Tennessee. The reactor will not generate electricity, but will serve as the basis for designing a full-fledged fourth-generation nuclear power plant.

Hermes is a pebble-bed reactor, in which the nuclear fuel is encased in spherical pellets made from layers of enriched uranium, carbon, and ceramic. These isotropic particles, called TRISO, are about the size of a poppy seed and act as tiny nuclear pressure vessels. They are formed into large, round pellets about the size of a boulder. The pellets are placed in the core of the reactor, which is designed more like a silo. Fresh fuel is loaded at the top; the pellets pool together to start and maintain the reaction; and the spent fuel is collected at the bottom of the reactor.

Typically, such reactors are cooled by helium, but Hermes is cooled by molten fluoride salts circulating through the reactor. These salts have excellent chemical stability, transfer heat at high temperatures, and contain fission products that might be released from the fuel.

The construction of the Hermes facility was supported by a $303 million grant from the U.S. Department of Energy.