Nuclear Energy: Understanding the Science Behind Nuclear Power

Nuclear Energy: Understanding the Science Behind Nuclear Power

Nuclear energy is a form of energy released from the nucleus, the core of atoms composed of protons and neutrons. This energy can be generated through two processes: fission, where atoms’ nuclei split into smaller parts, or fusion, where nuclei fuse together.

Presently, the global production of nuclear energy for electricity primarily relies on nuclear fission, while fusion technology is still in the research and development phase. This article delves into nuclear fission, leaving the exploration of nuclear fusion for another discussion.

What is Nuclear Fission?

Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei, releasing energy. For instance, when a neutron strikes the nucleus of uranium-235, it splits into smaller nuclei, releasing additional neutrons. These neutrons trigger a chain reaction as they collide with other uranium-235 atoms, generating heat and radiation in a fraction of a second.

Each fission reaction results in the release of energy in the form of heat and radiation. This heat can be harnessed to produce electricity in a manner similar to how fossil fuels generate power.

Oil refinery colored lights at night

How Do Nuclear Power Plants Work?

Within nuclear power plants, reactors and associated equipment manage and control chain reactions, often fueled by uranium-235. The heat generated through fission warms a cooling agent, typically water, producing steam. This steam is directed to spin turbines, activating an electric generator that produces low-carbon electricity.

Mining, Enrichment, and Disposal of Uranium

Uranium, a naturally occurring metal found in rocks worldwide, has isotopes with different properties. Uranium-238 is abundant but cannot sustain a fission chain reaction, while uranium-235, constituting less than 1% of the world’s uranium, is suitable for energy production. To enhance the fission potential of natural uranium, enrichment processes increase the uranium-235 content.

After enrichment, uranium becomes effective nuclear fuel, used for three to five years. The spent fuel, still radioactive, must be disposed of according to strict guidelines to safeguard people and the environment. Alternatively, spent fuel can be recycled for use in special nuclear power plants.

The Nuclear Fuel Cycle

The nuclear fuel cycle encompasses various steps to produce electricity from uranium in nuclear power reactors, starting with mining and concluding with nuclear waste disposal.

Nuclear Waste

Nuclear power plant operations generate waste with varying radioactivity levels, managed based on their radioactivity and purpose. The animation below details how radioactive waste, a small fraction of overall waste, is handled to protect the environment.

Daytime shot of a nuclear power plant at a river with blue sky and some clouds as well as blurred reflection. Tihange, Belgium.

Future nuclear power plants, known as innovative advanced reactors, aim to produce significantly less nuclear waste and are expected to be under construction by 2030.

Nuclear Power and Climate Change

Nuclear power stands as a low-carbon energy source, contributing close to one-third of the world’s carbon-free electricity. In the pursuit of climate change goals, nuclear reactors play a crucial role compared to conventional fossil fuel-based power plants.

To explore further details on nuclear power and its role in the clean energy transition, refer to the IAEA Bulletin.

The Role of the IAEA


The International Atomic Energy Agency (IAEA) establishes and promotes international standards and guidance for the safe and secure use of nuclear energy. The IAEA supports global nuclear programs by providing technical support, knowledge management, and overseeing safeguards to ensure peaceful use. Review missions and advisory services guide countries through the entire lifecycle of nuclear energy production, from mining uranium to decommissioning plants and managing nuclear waste. Additionally, the IAEA administers a reserve of low enriched uranium (LEU) in Kazakhstan for countries in urgent need of LEU for peaceful purposes.

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