Nuclear energy: From the Manhattan Project to decarbonization

Introduction

Nuclear energy has established itself as a key component in the transition to cleaner and more sustainable energy sources. As the world seeks to reduce carbon emissions and mitigate climate change, nuclear power has emerged as a viable energy alternative to generate electricity on a large scale without producing large amounts of carbon dioxide (CO₂).

This article outlines the basic principles, as well as technological developments and new trends in the field of nuclear energy within the energy sector. It discusses how this energy source is presented as a viable alternative to solve global energy problems in a decarbonizing planet. In addition, it provides a historical overview covering the fundamentals that initiated nuclear power generation, offering a comprehensive understanding of this source as a promising option for the energy future.

History of nuclear energy: Manhattan Project

The development of nuclear energy has its roots in 20th-century physics, with the discovery of radioactivity and the understanding of atomic structure. The Manhattan Project¹, a research and development project carried out during World War II that produced the first nuclear weapons during World War II, was an important milestone, as it led to the development of the atomic bomb. However, it also laid the foundation for civilian applications of nuclear energy.

In the post-war period, nuclear energy began to be used for civilian purposes, mainly for electricity generation. In the 1950s, the first commercial nuclear power plants were built in the common good to save the planet from catastrophic climatic consequences: massive forest fires, disappearing glaciers, and ice caps, among others.

Over time, there have been significant incidents that have shaped the evolution of nuclear energy. The Chernobyl accident in 1986 and the Fukushima disaster in 2011 are two examples that highlighted the risks associated with nuclear power and led to changes in regulations and public perception. Despite these problems, nuclear power has continued to evolve, with technological advances and more stringent safety measures allowing its continued use in electricity generation and other civilian applications.

Principles of nuclear energy

Nuclear energy is based on the release of energy contained in the nuclei of atoms. The two main processes that enable this release are nuclear fission and nuclear fusion. In nuclear fission, the nucleus of a heavy atom, such as uranium or plutonium, splits into smaller nuclei, releasing a large amount of energy. This process is usually induced by neutrons striking the nucleus, causing it to split. The chain reaction occurs when neutrons released by fission hit other nuclei, generating more fission and, consequently, more energy.

Nuclear fusion, on the other hand, involves the combination of light nuclei, such as hydrogen, to form a heavier nucleus. This is the process that occurs in the Sun and other stars, where the pressure and temperature are extremely high. Although fusion has immense potential to generate clean and safe energy, replicating these conditions on Earth is a technological challenge that is still under development.

In both processes, neutrons play a key role: in fission, they are the catalyst for the chain reaction, while in fusion, optimal conditions are sought to achieve the bonding of nuclei. These reactions generate a significant amount of heat, which is then converted into electrical energy by conventional generation systems, such as steam turbines.

Operation of a nuclear power plant

A nuclear power plant consists of several key components that enable the generation of electricity from nuclear fission. The nuclear reactor is where fission occurs. It consists of the core, the control rods and the moderator. The heat generated by fission is transferred to a cooling system, usually water, which is heated and converted into steam. This steam is directed to the turbines, which generate electricity.

The nuclear fuel cycle describes the process of nuclear fuel production and utilization, as well as waste management. It begins with the extraction and enrichment of uranium to obtain fuel suitable for fission. Once used, the spent fuel is stored and processed for safe disposal. The cycle includes recycling and disposal steps to minimize environmental impact².

The following video shows a 3D animation of how a nuclear power plant works. Source: Learn from the base.

What is a nuclear reactor?

A nuclear reactor is the main component of a nuclear power plant, designed to carry out nuclear processes, such as fission, in a controlled manner to generate energy. The processes of a nuclear reactor are presented below:

1. Heat generation: The main purpose of a nuclear reactor is to generate heat through nuclear fission. During this process, the nucleus of a heavy atom, such as uranium or plutonium, splits into smaller nuclei, releasing a large amount of energy in the form of heat.
2. Moderation and control of the chain reaction: In fission reactors, it is necessary to control the chain reaction to keep it safe and stable. This is achieved by using moderators, which are materials that slow down neutrons to facilitate the fission process, and control rods, which absorb neutrons to regulate the rate of the reaction. Moderation and control are essential to prevent the reaction from becoming uncontrollable.
3. Heat transfer to generate electricity: The heat generated in the reactor is transferred to a cooling system, usually water or gas, which circulates around the reactor core. This heat is used to convert the water into steam, which in turn drives the turbines to generate electricity. This process is similar to that of conventional thermal power plants but with a different heat source.
4. Fuel and waste management: Another important function is the management of nuclear fuel and radioactive waste generated during the process. Nuclear reactors are designed to maximize the use of fuel and minimize the production of waste. The safe management of this waste is fundamental to the sustainability and acceptance of nuclear energy.

Types of nuclear reactors

There are several types of nuclear reactors, each with unique characteristics and specific applications. The most common are light water reactors, which include boiling water reactors (BWRs) and pressurized water reactors (PWRs).

BWR (Boiling Water Reactor) reactors use water as a moderator and coolant. The water is heated to boiling point inside the reactor, generating steam that drives turbines to produce electricity. A feature of BWRs is that the steam enters directly into the turbines, which simplifies the design but can increase the risk of radioactive contamination. PWR (Pressurised Water Reactor) reactors also use water as a moderator and coolant, but keep the water under high pressure to prevent boiling. The hot water is transferred to a steam generator, where steam is created to drive the turbines. This design provides greater safety by keeping the coolant and steam separate.

There are other types of reactors, such as gas reactors, which use gases such as helium or carbon dioxide as coolants. They offer high thermal efficiency and allow higher operating temperatures. These reactors are less common but have potential for industrial applications. And fast reactors, or fast neutron reactors, do not require a moderator to slow down neutrons, use depleted uranium or plutonium as fuel, and have the ability to “burn” spent nuclear fuels, making them an option for fuel recycling.

Each type of reactor has advantages and disadvantages and is chosen according to factors such as safety, efficiency, and waste management. This diversity in design reflects the broad spectrum of applications and needs in the nuclear energy field.

Nuclear safety and regulations

Safety at nuclear power plants is essential to protect people and the environment from the risks associated with nuclear power. Safety measures include redundancy, containment and control systems to prevent and mitigate incidents. Nuclear reactors are equipped with multiple safety systems, such as control rods to regulate the chain reaction, backup cooling systems and containment structures to prevent leakage of radioactive material.

International and national regulations play a crucial role in nuclear safety. Organisations such as the International Atomic Energy Agency (IAEA) set global standards and provide guidance on safe practices. At the national level, regulatory authorities oversee the design, construction, and operation of nuclear plants to ensure compliance with safety standards.

Disasters such as Chernobyl in 1986 and Fukushima in 2011 have had a significant impact on regulations and public perception of nuclear power. Chernobyl, with its explosion and massive release of radioactive material, highlighted the importance of safe design and staff training. Fukushima, caused by an earthquake and tsunami, underlined the need for robust backup systems and effective emergency plans.

Both disasters led to the implementation of stricter regulations and rigorous scrutiny of safety practices around the world. As a result, today’s nuclear plants have much higher safety standards, with a focus on preventing accidents and minimizing risk to people and the environment.

Advantages and disadvantages of nuclear energy

Nuclear energy has notable advantages that make it attractive as an energy source. One of the main ones is its high energy density. A small volume of nuclear fuel can generate a large amount of energy, much more than fossil fuels such as coal or natural gas. Another advantage is the low emission of carbon dioxide (CO₂). Nuclear plants do not emit greenhouse gases during electricity generation, which makes them a favorable option for reducing climate impact.

In addition, continuous production is a key benefit. Unlike renewable energy sources, such as solar or wind, which are intermittent, nuclear power can produce electricity constantly, which contributes to the stability of the electricity grid.

However, there are also disadvantages. Nuclear waste management is a major challenge. Radioactive waste generated during the fission process requires safe storage and disposal, which entails long-term costs and concerns. Another problem is the risk of nuclear accidents, which, although rare, can have catastrophic consequences, as seen in Chernobyl and Fukushima.

Compared to other energy sources, nuclear energy is among the most efficient in terms of production and emissions but faces challenges in terms of safety and waste management.

Developments and trends in nuclear energy

In recent decades, nuclear energy has seen significant advances and has adapted to the changing demands of the global energy sector. One of the most prominent developments is the evolution of fourth generation reactors, designed to be safer, more efficient and more sustainable than their predecessors. These reactors are designed to use nuclear fuel more efficiently, reduce the amount of radioactive waste and minimise the risk of accidents.

The future of fission energy: the first SMR nuclear reactor

One of the most notable developments today is that of small modular reactors (SMRs). These reactors are more compact and can be mass-produced, which reduces costs and construction times. SMRs also offer flexibility, as they can be installed in smaller locations and are suitable for a variety of applications.

Small modular reactor technology offers a smaller-scale, decentralized option for nuclear power generation. US utilities already have NuScale Power³ SMR nuclear fission reactor technology, with a modular and compact design, designed according to the principles and requirements established for fourth-generation nuclear fission equipment.

In areas lacking sufficient transmission lines and grid capacity SMRs can be installed on an existing grid or in a remote off-grid location, due to their lower electrical output, and provide low-carbon energy for industry and population. This is particularly relevant for micro reactors, which are a subset of SMRs designed to generate electricity generally up to 10 MW(e).

SMRs take up less space and are more suitable for regions that do not have access to clean, reliable and affordable energy. In addition, micro reactors could serve as a backup power supply in emergency situations or replace electricity generators that are often diesel-powered, for example in rural communities or remote businesses.

The ITER nuclear fusion project

Nuclear fusion research is also advancing, with projects such as ITER seeking to replicate the sun’s power generation process, promising a virtually limitless, carbon-free energy source. These trends underline nuclear energy’s potential to play a crucial role in the transition to a cleaner, more resilient energy system.

Nuclear fusion projects such as ITER (International Thermonuclear Experimental Reactor), in France, are expected to achieve significant results in the next decade. This project involves 35 countries to build the world’s largest magnetic fusion device (Tokamak)⁴, designed to demonstrate the viability of fusion as a large-scale, carbon-free energy source, based on the same principle by which the sun and stars generate their energy.

The amount of energy a tokamak can produce is a direct result of the number of fusion reactions taking place in its core. Scientists have shown that the larger the core, the greater the volume of the plasma, and therefore the greater the potential fusion energy.

The integration of nuclear power into the energy transition is another important trend. As nations seek to reduce their carbon emissions, nuclear power is being seen as a complement to renewables. Its ability to generate power continuously makes it a potential source for stabilizing the electricity grid and meeting demand in times of low production from renewable sources.

These developments and trends suggest that nuclear energy will continue to play a relevant role in the energy transition future, with a focus on innovation, safety and sustainability.

Conclusions

Nuclear power presents itself as a valuable option in the transition to cleaner energy; as the world seeks to reduce carbon emissions and move towards sustainability, it represents a key alternative in the energy matrix of the future; however, it also faces significant challenges, such as radioactive waste management and the risk of accidents.

The Manhattan Project and the Chernobyl and Fukushima disasters are reminders of the importance of safety and stringent regulations. Despite these risks, technological advances, such as small modular reactors and nuclear fusion projects, are opening up new possibilities for nuclear energy.

The future of nuclear energy looks promising, provided that safety issues are properly addressed and a focus on sustainability is maintained, helping nations achieve their decarbonization goals. With proper regulation and a commitment to innovation, nuclear energy can become an ally in the fight against climate change.

References

1. Scientific American; “What Was the Manhattan Project?; July 21, 2023; https://www.scientificamerican.com/article/what-was-the-manhattan-project/
2. https://nuclear.engie-electrabel.be/en/nuclear-energy/how-does-nuclear-power-plant-work
3. Nuscalepower; “VOYGR Power Plants”; https://www.nuscalepower.com/en/products/voygr-smr-plants
4. https://www.iter.org/mach/Tokamak