It will remain stable until normal conditions are restored. Most important, even if a local disaster cuts the power to the cooling system and safety systems fail, this reactor will not melt down, spew radioactive material, or become too hot and dangerous to approach. Customers will be able to buy just one, to power a chemical or steel plant, or a few, linked like batteries, to power a city. It will be made in factories for easy shipping and rapid assembly. This reactor will sit in an ordinary building the size of, say, a suburban self-storage facility. Forget about those airport-scale compounds with their fortresslike containment enclosures and 40-story cooling towers belching steam. The scale is unlike that of an existing commercial nuclear plant. The test unit looks surprisingly unimpressive: a shiny cylindrical drum only about 16 feet tall, resembling an oversize water heater. When I glance at a countdown clock behind the receptionist during a visit last May, it says 31 days, 8 hours, 9 minutes, and 22 seconds until the experiment begins. If all goes according to plan, the system-never tried before-will control and regulate a simulated chain reaction. But everything else will be true to life, including the molten fluoride salt that will flow through the device to cool it. In this test run, electricity, not uranium, will furnish the energy graphite-encased fuel pebbles, each about the size of a golf ball, will be dummies containing no radioactive material. There, digital readouts count down the minutes, T-minus style, until power begins flowing to a test unit simulating the blistering heat of a new kind of nuclear reactor. The building looks like a factory or a warehouse nothing about it betrays the moonshot exercise happening within.

Around it, desert stretches toward hazy mountains on the horizon. Kairos Power’s new test facility is on a parched site a few miles south of the Albuquerque, New Mexico, airport. This article was featured in One Story to Read Today, a newsletter in which our editors recommend a single must-read from The Atlantic, Monday through Friday.

Nuclear power plant meltdown