What Is A Type Of Nuclear Energy?

Nuclear energy is the energy released from the nucleus, or core, of an atom when nuclear fission or fusion occurs (IAEA, 2022). The process involves splitting atoms to produce energy, usually in the form of heat. This heat is used to boil water to produce steam that spins a turbine to generate electricity (National Geographic, 2023).

The concept of nuclear energy began in the early 20th century, when scientists first realized that the nucleus of an atom contains large amounts of usable energy. The first nuclear reactor was created in 1942 during the Manhattan Project. Nuclear power plants began operating commercially in the mid-1950s (NEI, 2018).

Today, nuclear energy provides about 10% of the world’s electricity from about 440 power reactors. Nuclear energy is considered a relatively clean energy source that emits zero greenhouse gases during operation. It provides a steady baseload electricity supply in many countries around the world (IAEA, 2022).

How Nuclear Energy Works

diagram of nuclear fission process

Nuclear energy comes from the process of nuclear fission. This occurs when an atom’s nucleus splits into smaller parts, releasing a large amount of energy. The most common fuel used for nuclear fission is uranium. Uranium atoms can be split by bombarding them with neutrons. When a uranium atom is hit by a neutron, it separates into two smaller atoms and releases neutrons plus energy in the form of heat. This heat is used to boil water into steam that spins a turbine to generate electricity.

Uranium is a radioactive element and its atoms can split apart in a controlled chain reaction. This makes uranium excellent fuel for nuclear reactors. In its natural state, uranium is not rich enough to sustain a chain reaction. It must be enriched to increase the concentration of uranium-235, which is the particular isotope of uranium that undergoes fission. When uranium-235 atoms absorb extra neutrons, they split and release more neutrons, enabling a continuous fission chain reaction that produces heat energy.

The heat generated from splitting uranium atoms is extremely high. Just one uranium fuel pellet the size of a fingertip contains as much energy as 17,000 cubic feet of natural gas, 1,780 pounds of coal, or 149 gallons of oil. The enormous amount of energy produced through nuclear fission is what makes nuclear power plants capable of generating large amounts of electricity.

Types of Nuclear Reactors

There are several different types of nuclear reactors used around the world. The main types are:

Pressurized Water Reactors (PWRs)

PWRs make up the majority of nuclear reactors globally. In a PWR, ordinary water is used as a coolant and neutron moderator. The water is kept under high pressure to prevent it from boiling. The heated water flows through steam generators which produce steam to drive turbines and generate electricity (World Nuclear Association, https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/nuclear-power-reactors.aspx).

Boiling Water Reactors (BWRs)

In a BWR, water is used as both coolant and moderator, and is allowed to boil in the reactor core. The resulting steam drives the turbines directly. BWRs make up around a third of reactors globally (U.S. Energy Information Administration, https://www.eia.gov/energyexplained/nuclear/nuclear-power-plants-types-of-reactors.php).

Light Water Reactors

Light water reactors (LWRs) are the most common type of nuclear reactor. They use normal water (H2O) as opposed to heavy water (D2O). Most LWRs are either PWRs or BWRs (World Nuclear Association, https://www.world-nuclear.org/nuclear-essentials/are-there-different-types-of-reactor.aspx).

Breeder Reactors

Breeder reactors produce more fissile material than they consume, by converting non-fissile isotopes into fissile isotopes. This makes them attractive for fuel production. However, they have raised proliferation concerns due to the production of weaponizable plutonium (World Nuclear Association).

Fast Neutron Reactors

Fast neutron reactors use fast neutrons to cause fission, rather than slow neutrons like most reactors. They can use fuel more efficiently and reduce waste, but fewer have been built compared to thermal reactors (World Nuclear Association).

Nuclear Fuel Cycle

The nuclear fuel cycle represents the progression of nuclear fuel from mining to disposal. There are two main phases: the front end and the back end.

The front end of the fuel cycle involves:

  • Uranium mining – Uranium ore is mined from the ground and then milled into uranium oxide concentrate. Major uranium mining countries include Canada, Australia, and Kazakhstan (https://www.eia.gov/energyexplained/nuclear/the-nuclear-fuel-cycle.php).
  • Enrichment – The uranium oxide is enriched to increase the proportion of fissile uranium-235 and produce low enriched uranium (LEU) suitable for nuclear fuel. Enrichment increases the uranium-235 levels from under 1% to 3-5% (https://www.nrc.gov/materials/fuel-cycle-fac/stages-fuel-cycle.html).
  • Fuel Fabrication – Enriched uranium is converted into uranium dioxide powder and pressed into pellets. The pellets are inserted into long tubes to form fuel rods for nuclear reactors (https://world-nuclear.org/information-library/nuclear-fuel-cycle/introduction/nuclear-fuel-cycle-overview.aspx).

The back end involves:

  • Electricity Generation – The fuel rods are loaded into nuclear reactors where nuclear fission produces heat to generate electricity.
  • Spent Fuel Storage – After 3-6 years, the spent nuclear fuel is removed and stored temporarily at the reactor site in spent fuel pools or dry cask storage.

After temporary storage, options for spent fuel management include permanent disposal deep underground or reprocessing to recover fissile materials for recycling.

Safety and Risks

While nuclear power produces low-carbon electricity, it does come with some health and safety risks that need to be managed carefully.

Radioactive waste management is a major concern. Spent nuclear fuel remains radioactive for thousands of years and must be carefully contained and isolated from the environment. Most waste is stored on-site at power plants in spent fuel pools or dry casks. But there is still no permanent disposal site for high-level radioactive waste in the United States, leading to questions about long-term storage solutions [1].

There are also risks of radiation exposure to workers and communities near reactors. Exposure at high doses can cause health effects like cancer, while lower doses carry unclear long-term risks [2]. Careful monitoring and safety measures aim to minimize exposure.

Nuclear accidents, while rare, can release significant radiation. Major historical accidents include Chernobyl, Three Mile Island, and Fukushima. Newer reactors have additional safety features to help prevent meltdowns and radiological release. But natural disasters, human errors, and systems failures always pose some risks that must be managed [3].

Finally, nuclear facilities could potentially be targets for terrorist attacks or sabotage. Stringent security protocols aim to minimize these risks.

Environmental Impacts

Nuclear power generates large amounts of low-carbon electricity. Nuclear reactors emit no carbon dioxide (CO2) or air pollutants directly while operating. Over the course of its life cycle, nuclear power emits about the same amount of CO2 equivalent emissions per unit of electricity generated as wind and less than solar. This makes nuclear an important tool in mitigating climate change and reaching net zero emissions.

In terms of land use, nuclear power requires far less area to produce the same amount of electricity as renewables. A 1,000-megawatt nuclear facility in the U.S. needs about 1.3 square miles to operate. In comparison, a wind farm would require over 70 square miles to produce the same amount of electricity.

Nuclear plants require large volumes of water for cooling. Most plants use external water from rivers, lakes, or the ocean to cool the steam. This can cause thermal pollution as the water discharged back into the environment is warmer. The temperature change is regulated to minimize harm to aquatic life.

There is a small risk of radiation exposure from uranium mining, radioactive waste management, and reactor operation. However, radiation emissions from nuclear plants are closely monitored and controlled to be well below safety limits. Studies have found no increased risk of cancer for people living near nuclear facilities.

Source: U.S. Energy Information Administration, Fortum


Nuclear power plants have very high capital costs due to complex reactor systems, multiple backup safety systems, and large infrastructure requirements like an integrated spent fuel reprocessing plant. The typical overnight cost of building a large nuclear reactor is $6,000 per kilowatt of capacity, which means a 1,000 megawatt nuclear plant would cost around $6 billion to build.

However, nuclear has relatively low fuel costs compared to coal or natural gas plants. Uranium is abundant and only small amounts are needed to produce large amounts of energy. Fuel costs account for about 26% of the costs of a nuclear plant, much lower than a coal or gas plant. In 2018, the average total generating cost at nuclear plants in the U.S. was $35.50 per megawatt-hour.

Governments often provide subsidies to support the construction of new nuclear plants given their strategic energy security benefits. In the U.S., new nuclear reactors are eligible for production tax credits, loan guarantees from the Department of Energy, and accelerated depreciation for income tax purposes.

Overall, nuclear power has become less economically competitive compared to renewable energy sources like solar and wind. But nuclear remains one of the cheapest low-carbon energy sources and still plays a role in many countries’ energy mix, generating about 10% of the world’s electricity in 2020.




Future Outlook

Nuclear power will play an important role in the clean energy transition as countries seek to decarbonize their energy systems. According to the World Nuclear Association, nuclear power is expected to increase its contribution to global electricity generation from around 10% in 2021 to at least 15% by 2040 (World Energy Needs and Nuclear Power, 2022).

Next-generation nuclear reactors aim to improve safety, reduce costs, and produce less waste compared to existing designs. Advanced reactor types under development include small modular reactors, high-temperature gas-cooled reactors, and fast neutron reactors. Commercialization of advanced reactors could enable expanded applications of nuclear power beyond electricity into areas like hydrogen production and industrial heat supply (The Future of Nuclear Power, 2022).

However, public perception of nuclear power remains an obstacle in some countries. Concerns around safety and radioactive waste disposal have made nuclear controversial. But proponents argue nuclear power is among the safest forms of energy production and essential for displacing fossil fuels. Improved communication and community engagement will be important for gaining wider public acceptance of nuclear’s role in a low-carbon future.

Pros and Cons

Nuclear energy has some notable advantages and disadvantages that must be considered when evaluating it as an energy source.

On the pro side, nuclear power provides a major source of clean energy, producing large amounts of electricity without greenhouse gas emissions or air pollution. Nuclear power plants are efficient and reliable as a baseload power source, able to operate consistently at high capacity to meet demand needs. Uranium is also an extremely dense source of energy, producing significantly more electricity from each pound compared to other fuel sources 1.

However, nuclear energy also faces some significant challenges. There are concerns about the safe disposal of nuclear waste, which can remain radioactive for thousands of years. Nuclear power plants are very capital intensive, requiring very high upfront and fixed costs. There are also continued worries about the safety and security of nuclear plants and the potential for accidents. And uranium itself is a finite resource, with limits to the long-term availability of nuclear fuel 2.


In summary, nuclear energy has both advantages and disadvantages. On the positive side, nuclear power plants do not emit greenhouse gases or air pollution during operation, and nuclear energy can generate electricity continuously with high capacity factors. Nuclear power also plays an important role as a source of carbon-free electricity to mitigate climate change. However, there are concerns related to accidents, radioactive waste management, and costs. The future prospects for nuclear energy will depend on many factors like safety improvements, waste disposal solutions, costs compared to other low-carbon energy sources, and policy decisions.

Overall, nuclear energy will likely continue serving an important but limited role in the world’s electricity generation mix. Some of the new generation III/III+ reactor designs may provide enhanced safety and be economically competitive with fossil fuels and renewables. However, it seems unlikely that nuclear will be significantly expanded globally unless major innovations reduce costs. Most countries are taking a cautious approach by focusing more on energy efficiency, renewables and emerging storage technologies while maintaining existing nuclear reactors. The main challenge for the nuclear sector is demonstrating it can provide safe, clean and cost-effective electricity compared to other low-carbon options.

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