Nuclear power plants use a process called nuclear fission to produce electricity. In simple terms, fission happens when the nucleus of a uranium atom splits into two smaller parts. This splitting releases a huge amount of energy in the form of heat. The heat then boils water to make steam. The steam turns a turbine, which spins a generator to make electricity. This is the same basic idea as a coal or gas plant, but the source of heat is different. Instead of burning fuel, nuclear reactors get heat from splitting atoms.

This makes them very different from other power plants. They do not produce smoke or carbon dioxide while running. However, they create radioactive waste that must be stored safely for a long time. The heart of a nuclear power plant is the reactor core. It contains fuel rods made from uranium pellets. The uranium used is often enriched so that it contains more of the isotope U-235, which splits easily. When a neutron hits a U-235 nucleus, the nucleus splits and releases more neutrons. These new neutrons then hit other nuclei, causing a chain reaction.

To control this reaction, control rods made of boron or cadmium are placed between the fuel rods. These materials absorb extra neutrons, slowing or stopping the chain reaction. By moving the control rods in or out, operators can control how much heat the reactor produces. This allows them to keep the reaction steady and safe. The heat from fission must be carried away to make steam. This is done using a coolant, which is usually water. In many reactors, the water in the reactor core is kept under high pressure so it stays liquid even at very high temperatures.

The uranium used is often enriched so that it contains more of the isotope U-235, which splits easily.

This hot water then flows through pipes to a steam generator. In the steam generator, the heat from the water turns a separate supply of water into steam. The steam then goes to the turbine. This setup means the radioactive water in the reactor never mixes with the water that makes steam for the turbine. This is called a pressurised water reactor, and it is the most common type used today. Other types use boiling water directly in the core. The steam produced is very hot and under high pressure.

It flows through pipes to a huge turbine, which is like a fan with many blades. The steam pushes against the blades, making the turbine spin very fast. The turbine is connected to a generator, which contains a large magnet that spins inside coils of wire. This spinning creates a flow of electricity, just like a bicycle dynamo. After the steam passes through the turbine, it goes to a condenser where it is cooled back into water. The cooling water often comes from a river, lake, or the sea. The cooled water is then pumped back to the steam generator to be used again.

This cycle keeps repeating. Safety is a major concern in nuclear power plants. They have multiple layers of protection to prevent accidents. The reactor core is inside a thick concrete and steel containment building that can withstand extreme events. There are also emergency cooling systems that can shut down the reactor if something goes wrong. Operators are trained to respond to many possible problems. Despite these measures, accidents like Chernobyl and Fukushima have shown that failures can happen. Modern reactors are designed to be even safer, with passive safety systems that work without human action.

For example, some new designs use gravity to cool the core if power is lost. But no system is perfect, so waste management and regulation are very important. Nuclear power provides about 10 percent of the world's electricity. It has a big advantage: it produces no greenhouse gases while running. This makes it a low-carbon energy source, which is helpful in fighting climate change. However, it also has challenges. The radioactive waste from spent fuel rods must be stored carefully for thousands of years. Building a new nuclear plant costs a lot of money and takes many years.

There are also concerns about the risk of accidents and the spread of nuclear weapons. Some countries are moving away from nuclear power, while others see it as a key part of their future energy mix. As technology improves, new reactor designs may become safer and cheaper.