Nuclear reactor

A reactor makes heat.

It uses special fuel. This fuel splits apart. When it splits, it makes energy. This energy is very strong.

It can make electricity. It can also move ships. The heat makes steam. The steam turns big wheels. This helps us have power. It is a very big job.

A nuclear reactor is a tool that makes heat. It uses a special way to make energy. This way is called fission.

In fission, a tiny part of an atom splits apart. This happens when an atom absorbs a neutron. When the atom splits, it lets out more neutrons. These neutrons hit other atoms. This starts a nuclear chain reaction.

To keep this safe, we must control the reaction. We use control rods to do this. These rods act like sponges for neutrons. They soak up neutrons to slow the reaction down. If we pull the rods out, the reaction speeds up.

We also use a coolant to move the heat. This is often water. The hot coolant makes steam. That steam turns big wheels to make electricity.

Reactors are very strong. One kilogram of uranium-235 has much more power than coal. It is 120,000 times more energy-dense than coal. Today, there are 417 commercial reactors in the world. They provide 9% of the world's electricity.

A nuclear reactor is a special device used to keep a controlled nuclear chain reaction going. These machines are very important for many different jobs. They provide electricity for homes and businesses. They also power ships and submarines through marine propulsion. Some reactors help scientists with research or make isotopes for medicine.

The energy they produce is incredibly dense. For example, low-enriched uranium has 120,000 times more energy than coal. This makes them a very efficient way to create power.

To understand how they work, we must look at fission. This is when a large nucleus, like uranium-235, absorbs a neutron and splits apart. When it splits, it releases energy and more neutrons. These new neutrons hit other atoms to cause more fission. This creates a nuclear chain reaction.

To keep this safe, reactors use control rods. These rods act as neutron poisons to soak up neutrons and slow the reaction. A coolant, like water, then carries the heat away to make steam.

People have been studying this science for a long time. Scientists discovered fission in 1938. In 1942, the Metallurgical Laboratory built the first artificial critical reactor. They called it Chicago Pile-1.

Later, in 1944, large reactors were used at the Hanford Site for weapons production. In 1953, the US Navy began using a pressurized water reactor design for submarines. By 1954, the Soviet Obninsk plant began making small-scale nuclear electricity.

There are many different types of reactors used today. About 70% of commercial reactors use the pressurized water design. Other types include gas-cooled, molten-salt, and small modular reactors.

Currently, there are 417 commercial reactors operating around the world. There are also 226 research reactors and over 200 marine propulsion reactors. These commercial plants provide about 9% of the global electricity supply. This is a significant part of the world's low-carbon electricity.

While reactors are helpful, they must be managed with great care. Accidents can happen due to design flaws or mistakes by operators. The Three Mile Island accident happened in 1979. The Chernobyl disaster and the Fukushima disaster both occurred later.

These events had major effects on the nuclear industry. Even so, many people work to make new designs safer and more efficient. We can even reprocess spent fuel to recover usable material for the future.

A nuclear reactor is a specialized device designed to sustain a controlled nuclear fission chain reaction. These machines serve several critical roles in modern society. They generate commercial electricity, provide marine propulsion for ships and submarines, and support scientific research. Some reactors are even used for district heating or producing isotopes for medical and industrial use.

Because of their high efficiency, they are a major part of the global energy landscape. For instance, low-enriched uranium is 120,000 times more energy-dense than coal.

The core process relies on nuclear fission. This occurs when a large, fissile nucleus, such as uranium-235 or plutonium-239, absorbs a single neutron. When this happens, the heavy nucleus splits into two or more lighter nuclei, known as fission products. This split releases kinetic energy, gamma radiation, and several free neutrons. If these neutrons are absorbed by other fissile atoms, they trigger further fission events. This sequence creates a nuclear chain reaction.

To prevent this from growing too fast, reactors use specific mechanisms to regulate the number of neutrons available.

Reactors manage this reactivity using control rods and moderators. Control rods are made of neutron poisons, which are materials that absorb neutrons. When operators insert these rods deeper into the core, they soak up more neutrons and reduce the power output. Conversely, pulling the rods out increases the rate of fission. A moderator is also used to help the process. It causes fast neutrons to lose energy and become thermal neutrons. Thermal neutrons are more likely to induce fission, so the moderator helps increase the reactor's power.

Heat management is the next vital step in the process. As fission products collide with nearby atoms, their kinetic energy turns into thermal energy. The reactor also absorbs gamma rays and heat from the radioactive decay of fission products. To capture this, a coolant is circulated past the reactor core. This coolant is often water, but it can also be gas, liquid metal, or molten salt.

The coolant carries the heat away to create steam. In many systems, this steam drives turbines and electrical generator shafts to produce electricity.

The history of nuclear technology began with the discovery of fission in 1938. Following this, many countries began military research programs. In 1942, the Metallurgical Laboratory built Chicago Pile-1, the first artificial critical nuclear reactor.

By 1944, large-scale reactors were operating at the Hanford Site for weapons production. The pressurized water reactor design was later developed for the US Navy in 1953. Small-scale electricity production began in 1954 at the Soviet Obninsk plant. The first commercial power station, Calder Hall, started operation in England in 1956.

Today, the industry includes many different reactor designs. About 70% of commercial reactors use the pressurized water design. Other types include gas-cooled, breeder, heavy-water, molten-salt, and small modular reactors. Each design aims to improve safety, efficiency, or cost. Globally, there are 417 commercial reactors and 226 research reactors in operation. Commercial reactors provide about 9% of the world's electricity. This is a significant portion of the low-carbon electricity used alongside renewables.

Despite their benefits, reactors require extreme care to avoid accidents. Failures can result from design flaws or human error. The 1979 Three Mile Island accident reached INES Level 5. Later, the Chernobyl disaster and the 2011 Fukushima disaster both reached Level 7.

These events significantly impacted the nuclear industry and the anti-nuclear movement. Scientists must also manage complex issues like xenon poisoning. This occurs when the fission product xenon-135 builds up and absorbs neutrons, making it difficult to restart a reactor after a shutdown.