Nuclear Power Generation

A nuclear power plant works on the same basic idea as a kettle on your stove that boils water into steam. A coal plant burns coal to boil water. A nuclear plant boils water with the heat released when atoms split.

The main fuel is uranium, a heavy metal. When a very small particle called a neutron slowly hits the center of a uranium-235 atom, the atom loses its balance and splits in two. In an instant, it gives off a huge burst of heat. This splitting is called nuclear fission.

The energy from atoms is far larger than anything from the chemical reactions we see every day. One small uranium fuel pellet, about the size of your pinky tip (roughly 5 g), gives off as much energy as burning about 1 ton of coal or about 3 barrels of oil.

With so little fuel, a plant can turn a boiler full of water, as big as a house, into high-temperature, high-pressure steam in one go. That's how it makes a large amount of electricity steadily from a small amount of fuel.

When one uranium atom splits, it releases a lot of heat and also shoots out 2 or 3 more neutrons in all directions. Those neutrons hit other uranium atoms nearby, which split too, and the splitting keeps going. This is called a "chain reaction."

It works like a row of tightly packed dominoes: knock one over, and the rest fall one after another. But if you leave this domino effect alone, heat builds up too fast, and the equipment could melt down.

So plants use rods made of a special material that soaks up neutrons like a sponge. By pushing the rods deep between the fuel or pulling them out, operators adjust the number of neutrons with control rods.

Thanks to the control rods, the chain reaction stays at a steady level, like a calm campfire. Plants also have precise safety systems that can push the control rods all the way in right away to shut the reactor down safely when needed.

Why does splitting an atom release such a staggering amount of energy? Weigh the uranium before the reaction, then weigh all the fragments afterward on an extremely precise scale, and you'll find something strange. Even when you add up every fragment, the total is very slightly lighter than the original uranium.

As the physicist Albert Einstein showed, mass (weight) and energy are the same thing in different forms and can change into each other. During the reaction, an extremely tiny amount of mass vanished without a trace and turned into a huge amount of heat energy, which poured out.

In pressurized water reactors, which are common in Korea, hot water heated in the reactor flows to a steam generator, where it boils the water in a separate set of pipes into steam. There are also boiling water reactors, which boil water directly inside the reactor. This high-temperature, high-pressure steam then pushes hard and fast against a giant pinwheel-shaped turbine inside the plant.

An electromagnet inside the generator, connected to the turbine's shaft, spins around. Through electromagnetic induction, this finally produces the electricity we use every day in our homes and factories.