Inside a donut-shaped reaction chamber called a tokamak, two types of hydrogen, called deuterium and tritium, will be smashed together until they fuse in a roiling plasma hotter than the surface of the sun, releasing enough clean energy to power tens of thousands of homes—a limitless source of electricity lifted straight from science fiction.
The problem—the white elephant in the room—is that by the time ITER is ready, there might not be enough fuel left to run it.
