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Nuclear energy supplies 10% of the world’s electricity, making it the second-largest source of low-emission electricity. The United States leads as the top global producer of nuclear electricity. In 2025, nuclear energy provided nearly 18% of total U.S. electricity generation, or 784 million kilowatt-hours (kWh), which is equivalent to the average annual consumption of over 72 million homes. Nuclear energy is very reliable, running at maximum power about 92% of the time, higher than any other energy source. Two countries generate most of their electricity from nuclear power: France (67%) and Slovakia (61%).
Nuclear energy generation has no associated carbon dioxide emissions. In fact, several states, including Illinois and New York, have developed zero-emission credit programs that financially reward nuclear facilities for their role in advancing state emission reduction goals. The process of building a nuclear power plant and mining and refining uranium ore involve fossil fuels, but nuclear plants themselves only emit water vapor. Nuclear energy has saved an estimated 70 gigatonnes of carbon dioxide emissions over the 50-plus years it has been part of the global power supply. While classified as a low-emissions source, it is notably not classified as renewable because its production requires uranium, which exists in limited quantities and must be mined and enriched before being used for energy generation.
Nuclear energy is created when the nuclei of atoms split (fission) or combine (fusion) and release enough energy to heat water into steam that spins turbines and generates electricity. Fission is the only process used for commercially produced nuclear energy because fusion is not currently commercially viable.
Fission Process
In a nuclear fission plant, technicians pack large metal tubes full of pellets containing uranium into reactors. Each reactor, which typically has tens of thousands of such fuel rods, is kept in a pressure vessel with water or another coolant. Then, a small amount of a highly radioactive element that spontaneously releases neutrons, such as Californium-252, is temporarily inserted into the reactor core to fire off neutrons into the surrounding uranium. The uranium atoms become “excited” and split into two halves—called fission products—that shoot out, releasing energy and heat in the process. Additional neutrons are also released in the process, generating a chain reaction. The reaction is regulated by control rods placed alongside the fuel rods and by water surrounding the fuel rods. The control rods, which absorb free neutrons, must be lifted from the reactor for the chain reaction to start. Depending on whether or not the water is pressurized, steam may be produced directly in the reactor pressure vessel or in an adjoining steam generator. This steam then spins a turbine rotor connected to a generator, which transforms the kinetic energy into electrical energy.
Fusion Process
Nuclear energy can also be created through fusion, which is the reaction happening in the core of the sun and other stars. Fusion takes place within plasma (a state of matter that is neither solid nor liquid nor gas), which must be kept very hot. High temperatures in a confined space allow the positively-charged nuclei of “light” elements like hydrogen, which only has one proton, to overcome their natural repulsion and combine to form a “heavier,” bigger nuclei like helium (two protons). The creation of these heavier nuclei releases energy. Though fusion reactors have not yet become commercially viable, scientists proved in 2022 that a human-engineered, energy-positive fusion reaction is possible in practice in laboratory conditions.
As of March 2026, there were 57 commercially operating nuclear power plants in the United States, collectively containing 97 reactors and operating across 28 states. For scale, there were 14,218 operational commercial power plants of all kinds in the United States in 2024. Illinois has the largest nuclear capacity with 11 reactors that are generating 12% of total U.S. nuclear-sourced electricity. Each U.S. nuclear power plant contains between one and four reactors. Plant Vogtle in Georgia is the most powerful U.S. nuclear plant, with four reactors and a generating capacity of around 4.5 GW altogether. The R.E. Ginna plant in New York is the country's smallest nuclear power plant — it has a single 0.6-GW reactor.
Nuclear plants have the highest capacity factor of any form of energy, operating at full power more than twice as often as coal plants do. They run 24/7, produce power regardless of regular weather changes, operate for decades, and require relatively little downtime for maintenance and refueling (typically needed every 18 to 24 months). Scheduled downtime typically occurs during the fall and spring, when electricity demand is lower, to minimize disruption to the grid.
Most currently operating U.S. nuclear plants came online between 1970 and 1990. The latest commercial nuclear reactor to be built in the United States entered service in 2024 in Georgia. As of April 2026, there were 21 nuclear reactors undergoing decommissioning across the country.
One of the biggest challenges associated with nuclear energy is the disposal of radioactive nuclear waste. Exposure to high levels of radiation can damage the cells and DNA of living things. In humans, this can cause radiation sickness, cancer, skin burns, and cardiovascular disease.
What Is a Half-Life?
Radioactive materials gradually become less radioactive over time, and the time it takes for a material to reach half of its original radioactivity levels is called its “half-life.” The half-life of radioactive atoms can range anywhere from minutes to thousands of years (Plutonium-239’s half-life is about 24,000 years).
Commercial power plants take precautionary measures to ensure that radioactive materials will only exit the plant site as tightly sealed waste being moved for permanent storage. By volume, most nuclear waste emits relatively low levels of radiation. Items like tools or clothing that come into contact with nuclear radiation at plants or fuel processing facilities are subject to federal regulations for their handling and disposal.
Spent fuel rods are cooled in large concrete cylinders filled with about 40 feet of water and lined with steel, located at the reactor site or a specialized off-site facility. Nuclear waste can then be moved to dry cask storage systems, which are meant to serve as an interim solution to further cool the rods before permanent disposal. However, no permanent nuclear waste disposal solution currently exists in the United States. Attempts to create such a site at Yucca Mountain in Nevada were delayed due to legal and political opposition and now appear to be tabled indefinitely. Finland is the first, and so far only, country to have constructed a permanent nuclear waste storage facility. As of June 2026, the facility is expected to become operational soon.
One partial solution to the problem of storing spent nuclear fuel is reprocessing spent fuel. About 96% of spent nuclear fuel is technically capable of being used again. However, the United States stopped all commercial reprocessing by the early 1980s due to rising costs and national security concerns. The Department of Energy, or DOE, still does some reprocessing on defense sites. In the 118th Congress, the House Appropriations Committee recommended that DOE continue its reprocessing program and technological research, with the goal that commercial reprocessing become feasible again by 2033. Other countries, such as France and Russia, carry out commercial nuclear waste reprocessing.
The most common uranium extraction method in the United States is now in situ leaching, where chemicals are pumped into the ground and used to dissolve uranium embedded in rock. Open pit mining continues to be practiced as well, but at much lower rates since the “uranium boom” ended in the 1980s. In both cases, the resulting uranium ore is refined through another chemical process known as milling, which results in liquid and solid waste. The radioactive waste products are stored in artificial waste ponds called impoundments.
Uranium in underground ore very gradually decays into radium, which further decays into radon gas. While the radon gas from open pit, in situ, and underground mining (with proper ventilation) drifts into the atmosphere with little risk to humans in the area, in the 20th century, mine waste rock was piled outside of mine entrances, creating radioactive radon dust that blew into nearby communities. Elevated radiation levels in the Southwest’s midcentury atomic testing sites and abandoned uranium mines continue to contaminate nearby communities.
Up to two-thirds of U.S. uranium deposits are on tribal lands, and more than 75% of active uranium mines exist within 50 miles of a reservation. Native American communities in the western United States disproportionately made up the uranium mining and milling workforce, which had little or no safety regulations in place until the 1960s. High levels of radiation exposure have been devastating for the health of Southwest tribal communities, causing high levels of multiple chronic diseases. One study conducted from 1969 to 1993 found that 67% of lung cancer cases in Diné (Navajo) men affected former uranium miners. Mine Safety and Health Administration regulations now cover all mines, federal and private. Policy ideas for addressing these environmental injustices include creating tribal community liaison positions within the EPA and mandating community participation from the inception of uranium projects and policies. For some advocates, the ultimate goal is a ban of all uranium-related activity on and around tribal lands.
Most U.S. nuclear plants were built in the 1960s and 1970s, before the impacts of climate change were taken into account. While the infrastructure surrounding nuclear plants (e.g., a reactor’s containment shell) is designed to be extremely resilient, events like extreme heat and storm surges exacerbated by climate change threaten the equipment and cooling capacity of plants, which could reduce a reactor’s productivity or force a shutdown. In response to a request by two senators, the Government Accountability Office (GAO) presented a full geographical analysis of the vulnerability of each operational nuclear plant in the United States to different weather hazards exacerbated by climate change in 2024. GAO noted that the Nuclear Regulatory Commission has not adequately taken future climate data projections into account when evaluating risks to the U.S. nuclear fleet, relying instead on historical weather trends.
Nuclear power’s high capacity and low emissions position it as a major potential player in the future of the energy transition. However, two key factors stand in the way of its potential at present: high cost and lengthy permitting.
The two newest nuclear reactors in the United States, Vogtle 3 and 4, began operation in 2023 and 2024 respectively. Their combined production capacity is 2,430 MW and their combined cost landed at $30 billion, up from an initial estimate of $14 billion. For comparison, 9,585 MW of utility-scale solar, which is comparable to 2,430 MW of nuclear when taking capacity factors into account, would likely cost about $11 billion. Huge cost overruns are more common for nuclear projects than for other types of energy generation projects. Building nuclear reactors has become more expensive over time due to new safety regulations around the construction of shell buildings, decreases in labor productivity, and increases in commodity costs.
A lengthy permitting process adds to these costs. The length of the decision process for nuclear permits and licenses has been criticized on both sides of the Congressional aisle. When the Vogtle 3 reactor was approved, it became the first new reactor design to be successfully licensed by the Nuclear Regulatory Commission (NRC), the government body that regulates the operation of commercial nuclear plants, in the agency’s nearly 50-year history. The Environmental Impact Statement (EIS) process that is required for new nuclear reactor proposals (but not other types of power generation projects, which generally only need a simpler Environmental Assessment) takes an average of 4.5 years to complete. The Fiscal Responsibility Act of 2023 (P.L. 118-5) requires federal agencies to complete each EIS within two years.
The International Atomic Energy Agency defines small modular reactors (SMRs) as “advanced nuclear reactors that have a power capacity of up to 300 MW per unit, which is about one-third of the generating capacity of traditional nuclear power reactors.” SMRs are appealing because they take up less square footage than a traditional plant and are less expensive to build (though they also have less energy-generating capacity). DOE claims that light water-cooled SMRs “are under licensing review by the NRC and will likely be deployed in the late 2020s to early 2030s.” As of April 2026, only one SMR is actually under construction in the United States, in Tennessee.
Microreactors, which are even smaller than SMRs, would be able to generate up to 20 MW of thermal energy. They could be built in factories and transported by truck to speed deployment and minimize costs. Idaho National Laboratory is in the process of researching this technology. Some energy policy experts have argued that the excitement and federal funding for SMRs and microreactors is misplaced and could be better directed towards proven existing renewable technologies
Nuclear Plants and Data Centers
Data centers, many used to run artificial intelligence models, are demanding a tremendous amount of energy from power utilities. The colocation of nuclear plants and data centers has been touted as one way to meet data center energy needs while reducing the amount of grid buildout and maintenance needed (thereby reducing costs for taxpayers). The federal government appears to be supportive of this idea, based on the Federal Energy Regulatory Commission’s December 2025 request that East Coast grid operator PJM Interconnection develop rules for such colocation.
Over the past several years, bipartisan interest in incentivizing or streamlining nuclear deployment has led to legislative action. For instance, the Inflation Reduction Act of 2022 (P.L. 117-169) provided a tax credit for producing electricity at a qualified nuclear power facility. However, the credit has been affected by new “prohibited foreign entity” restrictions under the One Big Beautiful Bill Act (P.L. 119-21), and is also now set to be phased out by 2035. More recently, the ADVANCE Act of 2024 (P.L. 118-67) streamlines NRC nuclear licensing and permitting processes and orders the NRC to develop a regulatory framework for emerging fusion technologies.
Federal Regulatory Bodies and Research Offices
Governing Legislation for Regulatory Agencies, Civilians, Nuclear Waste, and Non-proliferation
For more information, see the NRC’s summary of each governing law.
Recent Executive Orders Affecting Nuclear Energy
In May of 2025, the Trump Administration released four nuclear-related executive orders: 14300, 14301, 14299, and 14302. The stated goals of these executive orders were to speed up nuclear reactor licensing, add 300 gigawatts of new U.S. nuclear capacity by 2050, lay the groundwork for faster reactor testing, deploy U.S. reactors for artificial intelligence data centers and military bases, explore fuel recycling and reprocessing, boost domestic nuclear fuel production, bolster the American nuclear workforce, assess spent nuclear fuel management, and expand U.S. nuclear energy exports.
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