Kairos Power has broken ground at Oak Ridge on the first Generation IV reactor to be officially certified in the U.S. and the first non-light water reactor in 50 years. It is being built along with a non-nuclear demonstration unit that will inform the design of the new reactor facility.
Despite being one of the pioneering nations in civilian nuclear power, the United States has fallen far behind even once non-players like China and India. There are many reasons for this, some political, some economic, but the drive to reduce carbon emissions while maintaining a modern industrial society is driving the return of nuclear reactors in more advanced forms.
On July 17, 2024, Kairos Power began construction of the Hernes low-power demonstration reactor in Oak Ridge, Tennessee. It will not generate electricity for the grid. Instead, its function will be to develop Kairos’ molten fluoride salt-cooled pebble bed reactor, an inherently safe design that can shut down in the event of an accident and keep the reactor core safely cool.
Kairos
The company is also building a second facility in Oak Ridge called ETU 3.0, essentially a non-nuclear version of Hermes. This testbed will allow engineers to study the machines in action without worrying about radiation and to find ways to make building and operating such a nuclear station more economical. This is critical because the main cost of nuclear power is not the reactor, but the civil engineering required to house and maintain it.
Construction in Oak Ridge is only half of the project, according to the company. The reactor itself is a modular design. Those modules will be built and tested at a factory in Albuquerque, New Mexico, before being shipped to Tennessee.
Hermes is a pebble bed reactor in which the nuclear fuel is coated in spherical pellets of enriched uranium, carbon and ceramic layers. These TRi-structural ISOtropic (TRISO) particles are about the size of a poppy seed and act like small nuclear pressure vessels. They are formed into large, round pebbles about the size of a cobblestone. The pebbles are placed inside a reactor core that is more like a hopper in design. Fresh fuel enters at the top, the pebbles clump together to start and sustain the reaction, and spent fuel collects at the bottom of the vessel.
Kairos Power
While similar reactors are cooled by helium gas, Hermes is cooled by molten fluoride salts circulating through the reactor. The salts keep the reactor core at 1,085 °F (585 °C) as they carry heat to a heat exchanger. This secondary salt loop is connected to a steam generator, which in turn drives a turbine.
If power to the reactor is cut off for any reason, the fuel pebbles automatically regulate the nuclear reaction according to the laws of physics. As the reactor heats up, fewer neutrons remain to sustain the reaction and the reaction dies out. Within hours, the reactor reaches an equilibrium point. In the meantime, molten salt flows through natural circulation, cooling the core. Even as the reactor temperature rises, the fuel pebbles are extremely durable and will not fail under any predicted scenario.
All of this occurs at ordinary sea level pressure, so no special containment structure or pressure vessel is required. The reactor is also constructed of 316 stainless steel, which is highly resistant to salt corrosion.
Kairos Power
Developed with a $303 million grant from the Department of Energy, Hermes is expected to be completed by 2027. While Bill Gates is working on his own reactor project in Wyoming, he is still waiting for government approval before building the nuclear power plant himself; Kairos already has approval.
“Hermes is an important step toward introducing advanced reactor technology that has the potential to transform our energy landscape,” said Mike Laufer, CEO and co-founder of Kairos Power. “The lessons we learn from building and operating this reactor will be invaluable in enabling continued innovation in our test program and accelerating Kairos Power’s progress toward delivering true cost certainty to our customers.”
Source: Kairos Power