What are the main parts of a nuclear reactor?

Almost any reactor comes down to five parts: the fuel that fissions, the moderator that tunes the neutrons, the coolant that carries heat away, the control rods that set the pace, and the power-conversion system that turns heat into electricity. Learn those five and you can read any design on Earth.

The beauty is how much room those five dials leave for innovation — swap water for helium, liquid metal, or molten salt and you get a whole family of advanced reactors, which is exactly why this is such an exciting time for the technology.