For the first time in 50 years, the U.S. Nuclear Regulatory Commission has issued a construction permit for a new type of nuclear test reactor. The Hermes demonstration reactor will be built in Oak Ridge, Tennessee, by California-based company Kairos Power and will use molten fluoride salt instead of water as a coolant, according to Chemistry World. This change will allow the reactor to operate at a much lower pressure, making it safer and more flexible.