Nuclear Energy

Nuclear energy is the energy stored inside the tiny center of an atom. That center is called the nucleus. When the nucleus of certain atoms is split apart or joined together, it releases a huge amount of energy. People use this energy to make electricity, and scientists also study it to understand how stars shine.

There are two ways to release nuclear energy. The first is called fission, which means splitting. The second is called fusion, which means joining. Power plants on Earth today all use fission. Fusion is what powers the Sun and other stars.

In a fission reaction, a heavy atom like uranium is hit by a tiny particle called a neutron. The atom splits into smaller pieces and gives off heat, radiation, and more neutrons. Those new neutrons hit other atoms, which split and release even more neutrons. This is called a chain reaction. Once it starts, it can keep itself going.

A nuclear power plant uses this chain reaction to boil water. The heat from splitting atoms turns water into steam. The steam spins a giant turbine, which spins a generator, which makes electricity. In that way, a nuclear plant is like a coal plant or a gas plant. The difference is the fuel. A small amount of uranium holds an enormous amount of energy. One pound of uranium can produce about the same energy as three million pounds of coal.

Nuclear energy has real advantages. It does not release carbon dioxide, so it does not add to climate change the way burning coal or gas does. It also makes a lot of power from very little fuel. But there are serious problems too. Fission creates radioactive waste, which stays dangerous for thousands of years. Accidents can be terrible. In 1986, a reactor at Chernobyl in Ukraine exploded, and in 2011, an earthquake and tsunami damaged the Fukushima plant in Japan. Both accidents forced people to leave their homes for many years.

People still debate whether nuclear energy is a good choice. Some scientists say it is the fastest way to stop burning fossil fuels. Others argue that the waste and the risk of accidents make it too dangerous. The argument is not settled.

Scientists around the world are also working on fusion power, the kind of reaction that happens in the Sun. Fusion would make far less waste and could not run out of control. So far, no one has built a fusion reactor that produces more energy than it uses. That may change in the coming decades.