At its core, nuclear energy harnesses the immense power locked within atomic nuclei, primarily through the processes of nuclear fission and fusion. Unlike traditional fossil fuels, which rely on the combustion of hydrocarbons, nuclear reactions release energy by splitting or merging atomic nuclei. This unique mechanism yields prodigious amounts of heat, which can be converted into electricity through turbines and generators.
Importance of Nuclear Energy in the Global Energy Mix
In an era plagued by climate change and dwindling fossil fuel reserves, nuclear energy emerges as a beacon of hope for a sustainable future. Its virtues lie not only in its capacity to generate vast quantities of electricity but also in its low greenhouse gas emissions. As nations grapple with the urgent need to reduce carbon footprints, nuclear power offers a pragmatic solution that complements renewable energy sources like wind and solar.
Moreover, nuclear energy provides a reliable base load power supply, ensuring grid stability even in the face of fluctuating demand. This attribute is particularly crucial in mitigating the intermittency issues inherent in renewables, thereby enhancing energy security and resilience
Foundation and Development of Nuclear Energy Technology
The foundations of nuclear energy were laid in the late 19th and early 20th centuries through groundbreaking discoveries in the field of nuclear physics. Pioneering scientists such as Marie Curie, Ernest Rutherford, and Henri Becquerel made seminal contributions by unraveling the mysteries of radioactivity and atomic structure. Their experiments with radioactive elements and the phenomenon of nuclear decay paved the way for a deeper understanding of the fundamental forces governing the atomic nucleus.
The realization that nuclear reactions could unleash vast amounts of energy sparked intense scientific inquiry and technological innovation in the first half of the 20th century. The crowning achievement came in 1942 with the successful demonstration of controlled nuclear fission by Enrico Fermi and his team at the University of Chicago. This milestone laid the groundwork for the development of nuclear reactors, which utilize controlled chain reactions to generate heat for electricity production.
Throughout the subsequent decades, significant strides were made in reactor design, materials science, and safety engineering, leading to the establishment of the first commercial nuclear power plants in the 1950s and 1960s. Innovations such as Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs) revolutionized the nuclear energy industry, paving the way for widespread adoption across the globe.
The Tarapur Atomic Power Station (TAPS) holds a significant position in the country’s nuclear energy narrative. Commissioned in 1969, TAPS initially comprised two Boiling Water Reactors (BWRs), making it the first nuclear power station in India to achieve criticality and contribute to the electricity grid. Over time, TAPS expanded to include two pressurized heavy water reactors (PHWRs), enhancing its power generation capacity and operational capabilities.
Basics of Nuclear Energy
Understanding the fundamentals of nuclear energy is essential for grasping its potential, challenges, and role in our energy landscape. This section elucidates the core concepts underlying nuclear energy, including atomic structure, nuclear reactions, and the processes driving energy generation in nuclear reactors.
Atomic Structure and Nuclear Reactions: At the heart of nuclear energy lies the structure of the atom, comprising a dense nucleus surrounded by orbiting electrons. The nucleus, composed of protons and neutrons, dictates the atom’s identity and properties. It is the manipulation of these nuclear constituents that forms the basis of nuclear reactions. Nuclear reactions occur when the configuration of atomic nuclei changes, resulting in the emission or absorption of particles and energy.
Fission and Fusion Processes: The two primary types of nuclear reactions are fission and fusion. Fission involves the splitting of heavy atomic nuclei, such as uranium-235 or plutonium-239, into smaller fragments, releasing a tremendous amount of energy in the process. Fusion, on the other hand, entails the merging of light atomic nuclei, such as hydrogen isotopes, to form heavier elements, accompanied by the release of even greater energy.
In nuclear fission, the nucleus of a heavy atom is bombarded with neutrons, causing it to become unstable and split into two or more smaller nuclei, along with the release of additional neutrons and energy. This chain reaction, if properly controlled, can sustain a continuous release of energy, as exemplified in nuclear reactors. (Refer figure 1)
Nuclear fusion, the process powering the sun and stars, involves the collision and fusion of atomic nuclei under extremely high temperatures and pressures. Although fusion holds the promise of virtually limitless energy and produces no long-lived radioactive waste, it remains a formidable scientific and engineering challenge to achieve sustained fusion reactions on earth.
Energy Generation in Nuclear Reactors: Nuclear reactors harness the heat generated by nuclear fission to produce electricity through a series of interconnected processes. In a typical nuclear reactor, fission reactions occur within fuel assemblies, where uranium or plutonium fuel rods are arranged to facilitate a controlled chain reaction. The heat produced by fission reactions is transferred to a coolant, such as water or gas, which circulates through the reactor core, absorbing thermal energy.
The coolant then carries the heat to a steam generator, where it vaporizes water to produce steam. The high-pressure steam drives turbines connected to electrical generators, converting the kinetic energy into electrical power. This electricity is then distributed to homes, businesses, and industries via power grids, providing a reliable and low-carbon source of energy. (Refer figure 2)
Types of Nuclear Reactors
Nuclear reactors come in various designs, each with its unique characteristics, operating principles, and advantages and disadvantages.
Pressurized Water Reactor (PWR): PWRs are the most common type of nuclear reactors in operation worldwide. In a PWR, water serves as both coolant and moderator. Water heated by the reactor core remains under high pressure to prevent boiling, transferring heat to a secondary water loop via a steam generator, which then drives turbines to produce electricity. (Refer figure 3)
Boiling Water Reactor (BWR): BWRs operate similarly to PWRs but with a key difference: the primary coolant water boils directly in the reactor core, producing steam that drives turbines. Unlike PWRs, BWRs do not employ a separate steam generator, simplifying the design but posing challenges related to steam purity. (Refer figure 4)
Pressurized Heavy Water Reactor (PHWR): PHWRs use heavy water (deuterium oxide) as both coolant and moderator, allowing natural uranium or slightly enriched uranium to be used as fuel. Heavy water’s superior neutron-capturing properties enable efficient neutron moderation and sustained nuclear reactions. (Refer figure 5)
Gas-Cooled Reactor (GCR): GCRs utilize gases such as carbon dioxide or helium as coolant, circulating through the reactor core to transfer heat to a secondary gas loop or directly to gas turbines. This design offers enhanced safety features and potential for high-temperature operation but requires robust materials to withstand the harsh reactor environment. (Refer figure 6)
Liquid Metal-Cooled Reactor (LMR): LMRs employ liquid metals such as sodium or lead-bismuth eutectic as coolant, offering superior heat transfer properties compared to water-based reactors. LMRs are well-suited for fast neutron spectra, enabling efficient conversion of fertile isotopes into fissile material. (Refer figure 7)
Advantages and Disadvantages of Nuclear Reactors
Main Advantages
Nuclear reactors provide a reliable source of base load electricity with minimal greenhouse gas emissions, contributing to energy security and climate change mitigation.
Various reactor designs offer flexibility in fuel choices, coolant options, and safety features, catering to diverse energy needs and regulatory requirements.
Nuclear power has a high energy density, enabling large-scale electricity generation with relatively small fuel inputs.
Main Disadvantages
Nuclear reactors pose inherent safety and security risks, including the potential for accidents, radioactive waste generation, and proliferation concerns.
The construction and decommissioning of nuclear facilities entail significant financial costs and regulatory burdens, which can hinder widespread deployment.
Public perception and acceptance of nuclear power remain mixed, influenced by factors such as safety concerns, environmental impacts, and social acceptability.
Nuclear Power Generation Status in India
Nuclear energy is the fifth-largest source of electricity for India that contributes about 2% of the total electricity generation in the country. (Refer table 1)
India has over 23 nuclear reactors in 7 power plants across the country, which produces 8,080 MW of nuclear power. (Refer table 2)
Recent Developments – Joint Ventures with Public Sector Undertakings (PSUs): Government has also allowed Joint Ventures with PSUs to enhance India’s nuclear program. As a result, the Nuclear Power Corporation of India Limited (NPCIL) is now in two joint ventures with the National Thermal Power Corporation Limited (NTPC) and the Indian Oil Corporation Limited (IOCL).
Expansion of Nuclear Installations: In the past, India’s nuclear installations were mostly located in South India or in Maharashtra and Gujarat in the west. However, the government is now promoting its expansion to other parts of the country. As an example, the upcoming nuclear power plant in Gorakhpur town of Haryana, which will become operational in the near future.
Main Processes, Concerns, Policies & Solutions
The nuclear fuel cycle encompasses the series of interconnected processes involved in the production, use, and disposal of nuclear fuel for electricity generation.
Uranium Mining: Uranium, the primary fuel for nuclear reactors, is extracted from underground mines or extracted via in-situ leaching techniques. The mined ore undergoes milling and processing to extract uranium oxide, known as yellowcake.
Uranium Enrichment: Natural uranium consists predominantly of uranium-238 isotopes, with only a small fraction of uranium-235, the fissile isotope used for nuclear fuel. Uranium enrichment processes increase the concentration of uranium-235 to levels suitable for reactor use. Common methods include gas centrifugation, gaseous diffusion, and laser enrichment.
Fuel Fabrication: Once uranium is enriched to the desired level, it undergoes fabrication into nuclear fuel assemblies for use in reactors. This process involves converting enriched uranium into ceramic pellets, typically made of uranium dioxide (UO2), which are then encased in metal cladding, such as zirconium alloy tubes. The fabricated fuel assemblies are carefully inspected and tested before being loaded into reactor cores for electricity generation.
Spent Fuel Storage: After several years of operation in a reactor, nuclear fuel assemblies become depleted of fissile material and are considered ‘spent’. Spent fuel contains a mixture of fission products, transuranic elements, and unburned uranium and plutonium isotopes, some of which remain radioactive for thousands of years. Spent fuel is initially stored in on-site storage pools or dry cask storage facilities to cool and decay heat and radiation levels.
Long-Term Disposal: The ultimate fate of spent nuclear fuel involves long-term disposal in geologic repositories designed to isolate radioactive waste from the environment for thousands of years. Geological disposal repositories, such as the proposed Yucca Mountain repository in the United States, rely on natural barriers, such as stable rock formations and engineered containment systems, to prevent the release of radioactive materials into the biosphere.
To be continued…
Divyanshu Arora is a Final Year Electronics and Communication Engineering student at Bharati Vidyapeeth’s College of Engineering, Delhi. He has a specialization in Renewable Energy from Coursera.com. He also has earned specializations in Data Analytics, Fintech, IT Support and Machine Learning from Coursera.
Dr. Rajesh Kumar Arora obtained the B. Tech. & Master of Engineering (ME) degrees in Electrical Engineering from Delhi College of Engineering, University of Delhi. He completed his PhD in grounding system design from UPES, Dehradun. He is also certified Energy Manager and Auditor. Among others, he has worked in 400kV and 220kV Substations for more than 14 years in Delhi Transco Limited (DTL). Presently he is working in D&E (Design and Engineering) Department of DTL. His research interests include high voltage technology, grounding system, protection system, computer application and power distribution automation.
