Nuclear energy is one of America's greatest technological achievements. In December 1942, scientists achieved the world's first controlled nuclear chain reaction, known as going critical, under the bleachers of the University of Chicago’s old Stagg Field. This small experiment grew into a brand new source of energy that today provides about 18 percent of U.S. electricity and supports Navy operations by powering submarines and aircraft carriers.
Compared to other energy sources, nuclear energy can provide an immense amount of power in a very small footprint. Nuclear power is so energy dense that, on average, powering 1,000,000 homes for a year with nuclear energy requires only about half the area of Central Park in New York City. By comparison, ground-mounted solar panels would require over 60 Central Parks.
Rather than creating heat by burning something, like natural gas or coal power plants, nuclear power plants use the energy stored within uranium atoms themselves. When a uranium atom splits, the two halves shoot out in a burst of energy. That energy is converted to heat as those halves hit other atoms and slow down, much like a rug burn on your knees from a power slide. The hot fuel pellets inside the fuel rods heat the water surrounding it to eventually create steam which turns a turbine to generate electricity.
When uranium atoms split, they produce radioactive materials, which are kept within the fuel rods and the enclosed reactor building. Because the heat generated comes from splitting atoms rather than burning hydrocarbons, there are no carbon emissions from the reaction itself, and the steam from the cooling towers of the reactors is pure water vapor.
Source: Photos from Georgia Power Vogtle Construction Photo Archive
America's commercial reactors are essential energy assets. The 96 operational reactors supply nearly 20 percent of U.S. electricity, providing around-the-clock, carbon-free power with some of the highest reliability of any generating technology.
Today, all U.S. commercial nuclear reactors are light-water reactors (LWRs). LWRs use ordinary water to cool the reactor and produce steam for electricity generation. There are two different types of commercial LWRs used in the U.S.: pressurized water reactors (PWR) and boiling water reactors (BWR). Today, they range from 500 MWe to 1.5 GWe. These reactors were historically built as large as possible to take advantage of economies of scale.
Source: Nuclear Regulatory Commission
America’s reliable, baseload nuclear fleet was mostly built in the 1970s and 80s. The U.S. has decades of operational and maintenance experience running existing reactors safely and efficiently. This experience has led to innovations within the current LWR fleet. Often, the fastest and most cost-effective way to expand nuclear generation in the near-term is getting more electricity from the reactors already operating, using three key tools: license renewals, power uprates and plant restarts.
License Renewals
Most commercial reactors are licensed for an initial period of 40 years, which is the upper limit set by law. The reactors could safely operate for over 100 years with license renewals required by the NRC every 20-years after the initial license. While many reactors once faced premature retirement, industry outlook has shifted dramatically. A 2025 industry survey found that nearly every U.S. reactor plans to seek operation through 80 years, allowing existing facilities to continue producing reliable electricity for decades.
License Uprates
The NRC sets limits on the maximum power output for each plant. Uprates are a fast and cost-effective way to increase power output. Utilities have consistently used them since the 1970s, with 171 uprates being approved by the NRC as of January 2022.
There are three types of power uprates:
Plant Restarts
In recent years, especially with rising electricity demand, several prematurely retired nuclear power plants are seeking to restart. Restarting these reactors allows utilities to reuse existing infrastructure, making restarts a potentially faster and more cost-effective way to add firm, carbon-free generating capacity. Restart projects still require extensive inspections, equipment refurbishment, updated safety analyses, and approval from the Nuclear Regulatory Commission before returning to operation. Three of those prematurely retired reactors are seeking to restart operations: the Palisades Nuclear Plant in Michigan, Duane Arnold in Iowa, and the Crane Clean Energy Center (formerly Three Mile Island Unit 1) in Pennsylvania.
In addition to reliable electricity, the nuclear industry is known for providing long-term jobs. Each large nuclear power plant employs 500-800 people and the industry’s median wage is twice the national median wage.
What's Different About New Reactors?
While today's new reactors build upon decades of operating experience, new designs introduce innovations that can further expand the benefits of nuclear power. American innovators and national laboratories are reimagining a nuclear-powered future. Some of these advancements have resulted in:
Reactor Categories
While there is not yet standard language for categorizing new reactors, these 5 general terms are helpful to understand the landscape: new reactors, new large LWRs, small modular reactors (SMRs), advanced reactors and microreactors.
Nuclear energy has been a cornerstone of American innovation and its role continues to be important as electricity demand accelerates and the nation seeks to strengthen its energy security, manufacturing base and technological leadership. Nuclear energy offers a proven foundation of reliable power with significant room for continued innovation.
In the near term, extending the life of existing reactors, increasing their output through license renewals and uprates and restarting recently retired plants represent the fastest and most cost-effective ways to expand clean, reliable electricity generation. Over the longer term, new nuclear reactors, including small modular reactors, advanced reactors and microreactors, will open entirely new markets by providing electricity, industrial heat and resilient power for defense and remote applications.
No single technology will meet America's growing energy needs alone, but nuclear energy's unique combination of reliability, energy density and clean generation ensures it will remain an essential part of a secure energy system for decades to come.
