Nuclear power startup Kairos Power has received approval from the U.S. Nuclear Regulatory Commission to begin construction of two test reactors in Oak Ridge, Tennessee. The permit marks a significant milestone for Kairos, which in October signed a deal with Google to provide 500 megawatts of power to its data centers.
The fluoride salt-cooled, high-temperature reactor is a scaled-down version of what Kairos ultimately hopes to build to power Google starting in 2030. And while the new reactor is technically a testbed, Kairos intends to connect the plant to the power grid. spokesperson Ashley Lewis told TechCrunch.
Each Hermes 2 reactor can generate 35 megawatts of heat and will be connected to a 20 megawatt turbine to turn that heat into electricity. Kairos' commercial-scale power plant also features two nuclear reactors that can generate a total of 150 megawatts of electricity.
The Kairos design differs from existing nuclear reactors in two important ways. The fuel is made of uranium encased in carbon and a ceramic shell, durable enough to contain fissile material in the event of an accident. And the reactor is cooled not by water but by molten salt.
The small modular reactor (SMR) startup, which received a $303 million award from the U.S. Department of Energy, has been working for years to improve molten salt cooling systems. The boiling point of fluoride salts is very high, allowing the coolant to flow at low pressure. This means that in the event of an accident, if the pumping system fails, there is no high-pressure radioactive material waiting to be spewed out. Additionally, Oak Ridge National Laboratory states that molten salt reactors can rely on passive convection to move salt into the reactor and cool it if power to the pumps is interrupted.
Taken together, these features are enough to qualify the Kairos design as a “generation IV” reactor, a classification system created by an international organization with support from national nuclear agencies. The classification system is vague and extensive, so it's difficult to determine exactly how Hermes 2 will score on the rubric.
Kairos has been slowly working toward approval of its reactor design for the past year and a half. Hermes 2 passed a safety review by the NRC in July and an environmental assessment in August. All told, it took 18 months for the NRC to issue a construction permit. This was a relatively quick schedule compared to previous reactor permits.
Now, the pressure is on for Kairos to deliver on his promise. The company says it hopes to bring the first reactor under its contract with Google online in 2030, with the remaining reactors completed by 2035. In the world of nuclear power, 10 years is not a long time.