A nuclear power plant, also called a nuclear power station, nuclear generating station, or atomic power station, is a type of power plant that uses heat from a nuclear reactor to create electricity. Like other power plants that use heat, it uses steam to turn a turbine connected to a generator, which makes electricity. As of October 2025, the International Atomic Energy Agency reported that there were 416 nuclear power reactors operating in 31 countries worldwide, and 62 reactors were being built.

Most nuclear power plants use reactors that rely on enriched uranium in a fuel cycle that is used only once. Fuel is removed from the reactor when the number of atoms that stop nuclear reactions becomes too high to keep the reaction going, usually after about three years. After removal, the fuel is cooled for several years in on-site pools before being moved to long-term storage. This spent fuel is not very large in volume but is highly radioactive. Its radioactivity decreases over time, but it must be kept away from the environment for hundreds of thousands of years. Newer technologies, such as fast reactors, may reduce this time. Since the spent fuel still contains materials that can be used in nuclear reactions, some countries, like France and Russia, reuse parts of the fuel by extracting usable materials to make new fuel. This process is more costly than using newly mined uranium. All reactors create plutonium-239, which is found in spent fuel. Because plutonium-239 can be used to make nuclear weapons, reprocessing spent fuel is considered a risk for weapons development.

Building a nuclear power plant usually takes between five and ten years, which can lead to high costs depending on how the project is funded. Due to these high construction costs and lower costs for running the plant, nuclear power plants are often used to provide electricity continuously, as this helps spread out the cost over many hours of operation.

Nuclear power plants produce about the same amount of carbon emissions as renewable energy sources like solar and wind farms, and much less than fossil fuels like natural gas and coal. Nuclear power is one of the safest ways to generate electricity, with accident and pollution-related deaths per unit of electricity comparable to solar and wind power plants.

History

On December 21, 1951, heat from a nuclear reactor at the Experimental Breeder Reactor I was first used to make electricity, powering four light bulbs.

On June 27, 1954, the Obninsk Nuclear Power Plant in Obninsk, Soviet Union, became the first nuclear power station to supply electricity to a power grid. The first large power station, Calder Hall in the United Kingdom, opened on October 17, 1956. It was also designed to produce plutonium. The first large power station only used for making electricity was the Shippingport Atomic Power Station in Pennsylvania, United States. It was connected to the power grid on December 18, 1957.

Basic components

The process of making electricity in a nuclear power plant works similarly to other power plants that use heat. Inside the nuclear reactor, atoms split apart in a process called fission, which creates heat. This heat warms a coolant, which can be water, gas, or liquid metal, depending on the reactor type. The heated coolant then moves to a steam generator, where it heats water to make steam. In some reactors, like pressurized water reactors (PWRs), the steam is made in a separate part of the plant. In others, like boiling water reactors (BWRs), the steam is made directly inside the reactor. The steam is then sent to a steam turbine, which turns a generator to make electricity. After the steam passes through the turbine, it is cooled back into water in a condenser. This condenser is connected to a cooling system, such as a river or a cooling tower, to remove heat. The cooled water is then pumped back to the steam generator to repeat the process. This cycle is called the Rankine cycle.

The nuclear reactor is the most important part of the power plant. In the center of the reactor, fission creates heat. This heat warms the coolant as it flows through the reactor, removing energy from the reactor. The heat is used to make steam, which moves through turbines to power electrical generators.

Nuclear reactors use uranium as fuel. Uranium is a heavy metal found in Earth’s rocks and seawater. Naturally, uranium exists in two forms: uranium-238 (U-238) and uranium-235 (U-235). U-238 makes up about 99.3% of natural uranium, and U-235 makes up about 0.7%. U-238 has 146 neutrons, while U-235 has 143 neutrons.

Different uranium forms behave differently. U-235 is fissile, meaning it splits easily and releases a lot of energy, making it useful for nuclear power. U-238 does not split as easily. These isotopes also have different half-lives. U-238 decays more slowly than U-235, so it is less radioactive.

Because fission creates radiation, the reactor core is protected by a shield. This shield stops radiation from escaping into the environment. Many reactors also have a thick concrete dome to protect against accidents or outside damage.

The steam turbine changes the heat in steam into mechanical energy. The turbine is usually placed in a separate building from the reactor to keep the reactor safe. This setup prevents damage from the turbine from affecting the reactor or safety systems.

In a pressurized water reactor (PWR), the steam turbine is separated from the reactor. To find leaks in the steam generator early, an activity meter checks the steam leaving the generator. In a boiling water reactor (BWR), radioactive water flows directly through the turbine, so the turbine is part of the area with radiation controls.

An electric generator changes the mechanical energy from the turbine into electricity. Large generators are used to produce enough power. A cooling system removes heat from the reactor and sends it elsewhere in the plant. The hot coolant is often used to heat water in a boiler, which creates steam to power turbines and generators.

If an emergency happens, safety valves can stop pipes from breaking or the reactor from exploding. These valves open automatically to keep pressure within safe limits. In a BWR, steam is sent to a suppression chamber where it cools down. These chambers are connected to a cooling system.

The main condenser is a large heat exchanger that turns wet vapor (a mix of steam and water) from the turbine into liquid water. This water is then pumped back to the reactor. In the condenser, the vapor touches cold tubes filled with water from a river, lake, or cooling tower. The Palo Verde Nuclear Generating Station is unique because it uses treated wastewater from Phoenix instead of natural water for cooling. The water is either returned to its source at a warmer temperature or sent to a cooling tower, where it cools further or evaporates.

The water level in the reactor and steam generator is controlled by the feedwater system. A pump takes water from the condenser, increases its pressure, and sends it to the steam generator (in PWRs) or directly to the reactor (in BWRs).

Keeping the power plant running continuously is essential for safety. Most plants have two separate power sources to back each other up. These are usually connected to multiple transformers and power lines. Some plants can also use the turbine generator to power the plant itself while it is operating, using transformers to get power from the generator before it is sent to the main grid.

World operating status

Nuclear power plants provide about 10% of the world's electricity, produced by around 440 reactors in many countries. These plants are a major source of low-carbon electricity, supplying about one-quarter of the world's low-carbon energy. As of 2020, nuclear power was the second-largest source of low-carbon energy, making up 26% of the total. Nuclear power facilities operate in 32 countries or regions, and their electricity is shared with other nations through power grids, especially in Europe.

In 2022, nuclear power plants generated 2,545 terawatt-hours (TWh) of electricity, slightly less than the 2,653 TWh produced in 2021. Thirteen countries generated at least one-quarter of their electricity from nuclear sources. France uses nuclear energy for about 70% of its electricity needs, while Ukraine, Slovakia, Belgium, and Hungary use about half of their electricity from nuclear sources. Japan, which once used nuclear energy for more than a quarter of its electricity, plans to return to similar levels.

Over the past 15 years, the United States has improved the performance of its nuclear power plants, increasing their efficiency and output as if 19 new 1,000 MWe reactors were added without building them. In 2022, nuclear power plants in France still produced over 60% of the country's electricity. A previous goal to reduce nuclear electricity production to less than 50% by 2025 was delayed to 2035 in 2019 and canceled in 2023. Russia continues to export the most nuclear power plants globally, with 19 of 22 reactors under construction by foreign vendors as of July 2023. However, some projects were canceled due to the Russian invasion of Ukraine. China is building the most nuclear reactors at one time, with 25 under construction by late 2023.

Nuclear decommissioning is the process of taking apart a nuclear power plant and cleaning the site so it no longer needs protection from radiation. Unlike other power plants, nuclear decommissioning requires special steps to handle radioactive materials and safely move them to waste storage.

Decommissioning includes removing all radioactive materials and carefully demolishing the plant. Once a facility is fully decommissioned, there should be no risk of a radioactive accident or harm to visitors. After decommissioning, the site is no longer under government regulation, and the company that operated the plant no longer has responsibility for its safety.

Most nuclear power plants were designed to operate for about 30 years, but newer plants are built to last 40 to 60 years. A future type of reactor, called the Centurion Reactor, is being designed to last 100 years.

One major challenge for nuclear plants is the weakening of the reactor's pressure vessel caused by neutron exposure. In 2018, Russia announced a technique called thermal annealing that reduces radiation damage and extends a reactor's lifespan by 15 to 30 years.

Nuclear power plants are often used for base load electricity because their fuel costs are lower than those of coal or gas plants. Since most nuclear costs are upfront (capital costs), running plants at less than full capacity does not save much money.

Nuclear power plants are sometimes used to adjust electricity supply (load following) in France, though this is not ideal for their economics. At the German Biblis Nuclear Power Plant, Unit A could change its power output by 15% per minute between 40% and 100% of its maximum capacity.

Russia has developed floating nuclear power stations that can be moved to different locations and relocated for easier decommissioning. In 2022, the United States Department of Energy funded a three-year study on offshore floating nuclear power. In October 2022, NuScale Power and a Canadian company, Prodigy, announced a joint project to build a small modular reactor-based floating plant in North America.

Economics

The economics of nuclear power plants is a topic that people disagree about, and very expensive investments depend on choosing an energy source. Nuclear power stations usually have high costs for building the plants, but the cost of fuel is low. These costs for fuel extraction, processing, use, and storing spent fuel are included in the total costs. Comparing nuclear power with other ways to generate electricity depends on how long it takes to build nuclear plants and how they are financed. Cost estimates include the costs of taking apart nuclear plants and storing or recycling nuclear waste in the United States because of the Price Anderson Act.

If all spent nuclear fuel could be recycled in the future using new reactors, Generation IV reactors are being designed to fully use all parts of the nuclear fuel process. However, so far, no large amounts of nuclear waste have been recycled from nuclear power plants. Most plants still use temporary storage for waste because of delays in building deep underground storage sites. Only Finland has an operating storage site, so worldwide, the long-term costs of storing nuclear waste are unclear.

Besides the cost of building plants, efforts to reduce global warming, such as a carbon tax or trading carbon emissions, make nuclear power more economically attractive. More advanced reactor designs, like Generation III reactors, are expected to use fuel more efficiently and have lower building costs. Generation IV reactors could improve fuel efficiency even more and reduce nuclear waste.

In Eastern Europe, some long-term nuclear projects are having trouble getting money, such as the Belene project in Bulgaria and additional reactors at Cernavodă in Romania. Some companies that were planning to fund these projects have stopped. When cheap natural gas is available and its supply is stable, this makes it harder for nuclear projects to get support.

When studying the economics of nuclear power, it is important to consider who handles the risks of future problems. Until now, most nuclear power plants were built by government-owned or regulated companies, and many risks, such as construction costs and fuel prices, were passed on to consumers. Now, in many countries, electricity markets are more open, and risks like competition from cheaper energy sources are handled by the companies that build and operate nuclear plants, not consumers. This changes how the economics of new nuclear plants are evaluated.

After the 2011 Fukushima nuclear accident in Japan, the costs of operating and building new nuclear plants are likely to increase because of stricter rules for managing spent fuel and improving safety. However, some new reactor designs, like the AP1000, use passive cooling systems that do not require active systems like those at Fukushima I, which reduced the need for extra safety equipment.

According to the World Nuclear Association, as of March 2020:

• Nuclear power is as affordable as other electricity sources, except when low-cost fossil fuels are available.
• Fuel costs for nuclear plants are a small part of total costs, but building costs are higher than for coal plants and much higher than for gas plants.
• System costs for nuclear power (and coal and gas plants) are much lower than for renewable energy sources that depend on weather conditions.
• Encouraging long-term, expensive investments in electricity markets that focus on short-term prices makes it hard to create a diverse and reliable energy system.
• When evaluating nuclear power’s economics, the costs of dismantling plants and storing waste are fully included.
• Building nuclear power plants is similar to other large infrastructure projects worldwide, where costs and challenges are often underestimated.

The Russian state nuclear company Rosatom is the biggest player in the international nuclear power market, building plants around the world. While Russian oil and gas faced international sanctions after Russia’s full-scale invasion of Ukraine in February 2022, Rosatom was not affected by sanctions. However, some countries, especially in Europe, delayed or canceled planned nuclear plants that were to be built by Rosatom.

Safety and security

Modern nuclear reactors have many safety improvements compared to older ones. These improvements help prevent serious accidents. A nuclear power plant cannot explode like a nuclear weapon because the uranium fuel used in reactors is not enriched enough. Nuclear weapons require special explosives to force nuclear material into a very small space to cause a reaction. Most reactors need careful temperature control to avoid a core meltdown, which has happened a few times due to accidents or natural disasters. These events released radiation and made nearby areas unsafe for people. Power plants must protect against theft of nuclear material and attacks from enemy planes or missiles.

The most serious accidents in history include the 1979 Three Mile Island accident, the 1986 Chernobyl disaster, and the 2011 Fukushima Daiichi disaster. These events happened when generation II reactors first started operating.

Professor of sociology Charles Perrow explains that many unexpected problems can occur in complex systems like nuclear reactors. These problems are hard to avoid and cannot be fully prevented through design. A team from MIT estimated that, based on nuclear power growth from 2005 to 2055, at least four serious accidents might happen during that time. This study did not consider safety improvements made since 1970.

Regulation and oversight

Nuclear power operates under an insurance system that sets limits or rules for handling the costs of accidents. This system follows international agreements, including the Paris Convention on Third Party Liability in Nuclear Energy, the Brussels Supplementary Convention, and the Vienna Convention on Civil Liability for Nuclear Damage. However, many countries that operate the majority of the world's nuclear power plants, such as the United States, Russia, China, and Japan, are not part of these international agreements.

Controversy

The debate about using nuclear fission reactors to create electricity from nuclear fuel for non-military purposes was most intense during the 1970s and 1980s. In some countries, this discussion became the most intense in the history of technology-related disagreements.

Supporters believe nuclear power is a long-lasting energy source that reduces carbon emissions and can improve energy security if it replaces reliance on imported fuels. They argue that nuclear power produces almost no air pollution, unlike the main alternative, fossil fuels. Supporters also claim nuclear power is the only realistic way for most Western countries to achieve energy independence. They highlight that the risks of storing nuclear waste are small and can be reduced further with modern reactor technology. They also note that nuclear power plants in Western countries have a strong safety record compared to other major types of power plants.

Opponents say nuclear power creates many risks for people and the environment, and that the costs do not justify the benefits. These risks include health dangers and environmental harm from uranium mining, processing, and transport. Other concerns are the possibility of nuclear weapons spreading or sabotage, the challenge of managing radioactive waste, and the release of hot water from power plants into natural water bodies, which can harm marine life. Opponents also argue that nuclear reactors are highly complex and that serious accidents have occurred. They believe new technology cannot fully reduce these risks, even with improvements in safety procedures and waste storage. They also do not consider small modular reactors (SMRs) or thorium reactors as solutions.

Opponents also claim that when all stages of the nuclear fuel process are considered, including uranium mining and decommissioning old plants, nuclear power is not a low-carbon energy source. Countries without uranium mines cannot gain energy independence through current nuclear technologies. Construction costs often exceed initial estimates, and managing spent nuclear fuel is difficult to predict in terms of cost.

On August 1, 2020, the United Arab Emirates (UAE) started the first nuclear energy plant in the Arab region. Unit 1 of the Barakah plant in Abu Dhabi began producing heat on the day of its launch, while the other three units are still being built. However, Paul Dorfman, head of the Nuclear Consulting Group, warned that the UAE’s investment in the plant could increase risks in the already unstable Gulf region, harm the environment, and raise concerns about nuclear weapons spreading.

Environmental impact

Nuclear power plants do not release greenhouse gases while they are operating. Older nuclear power plants, such as those using second-generation reactors, produce about the same amount of carbon dioxide over their entire life cycle as wind power, which is about 11 grams per kilowatt-hour. This is one-third of the amount from solar power and one-forty-fifth of the amount from natural gas, and one-seventy-fifth of the amount from coal. Newer models, like the HPR1000, produce even less carbon dioxide over their lifetime, as little as 1.31 grams per kilowatt-hour, which is one-eighth of the amount from second-generation reactors.

Nuclear power plants also have other environmental effects, such as radioactive waste, ionizing radiation, and waste heat. Large nuclear power plants may release waste heat into natural water bodies, which can harm water-dwelling organisms. Mining nuclear fuel, such as uranium or thorium, can negatively affect the environment near mining sites. While current methods of storing nuclear waste in deep underground locations are generally considered safe, accidents during the transportation of nuclear waste can still cause leaks of radioactive materials.

Large nuclear accidents, such as those at Chernobyl or Fukushima, release large amounts of radioactive material into the environment, harming people and animals. Solutions include improving rules and training for nuclear operations, reducing radiation exposure to surface organisms through deep burial or other treatments of radioactive materials at accident sites, and creating permanent areas where people cannot live near accident locations.

Future development

In March 2024, about 60 nuclear reactors for power plants are being built worldwide, with a total power capacity of 64 gigawatts. An additional 110 reactors are planned. Most of these reactors, whether being built or planned, are located in Asia. In recent years, the number of new reactors starting to operate has been roughly equal to the number of older reactors being shut down. Over the past 20 years, 100 reactors began operating, while 107 reactors were retired.

A group of countries is working together to develop six new types of nuclear reactors called Generation IV. This group, called the Generation IV International Forum (GIF), was started by the U.S. Department of Energy in 2000 and officially formed in 2001. It includes 13 countries where nuclear energy is important for future energy needs. Founding members include Argentina, Brazil, Canada, France, Japan, South Korea, South Africa, the UK, and the USA. Newer members include Switzerland, China, Russia, Australia, and the European Union through Euratom. This group focuses on sharing research and development ideas to create international standards for these new reactor designs, rather than building reactors themselves.

In 2002, GIF chose six reactor designs after reviewing about 100 ideas over two years. These six designs represent the future of nuclear energy. Three of the six are fast neutron reactors, which operate at higher temperatures than current reactors. These reactors are designed to be more sustainable, cost-effective, safe, and reliable. They also help reduce the risk of nuclear weapons being made. Four of the six designs have been thoroughly tested, providing a foundation for further research and possible use in commercial power plants by 2030.

The first and only nuclear power plant in the world to use Generation IV reactors for commercial power is the Shidao Bay Nuclear Power Plant. This reactor is a high-temperature gas-cooled reactor. Construction began on September 21, 2014. It started producing electricity on December 20, 2021, and officially began commercial operations on December 12, 2023.

Another area of development for nuclear power is nuclear fusion. Research on nuclear fusion and plasma physics has made major progress, with over 50 countries involved. Scientists recently achieved the first experiment where fusion produced more energy than was used. Different designs are being tested, including machines that use magnets, such as stellarators and tokamaks, as well as other methods like lasers and advanced fuel approaches. The timeline for using fusion energy depends on global teamwork, how quickly the industry grows, and building the necessary infrastructure to support this energy source.

Construction of ITER, the largest international fusion project, began in 2020 in France. This marks an important step in proving that fusion energy can work. Experiments are expected to start in the second half of this decade, with full-power tests planned for 2036. ITER aims to help create DEMO power plants, which experts believe could be operational by 2050. At the same time, private companies are using publicly funded research to advance fusion technology, which may lead to commercial fusion power before the middle of the 21st century. Many countries involved in ITER are also developing their own fusion reactor designs. In China, researchers are working on a new reactor called the China Fusion Engineering Test Reactor (CFETR), with the goal of building a practical commercial fusion power plant by 2050.