SET:S&T:BSRs/SMRs:ATOMIC ENERGY :NUCLEAR FISSION :notes prepared on 1122025
Topic : ATOMIC ENERGY (for G S
Papers) {Prepared on 1 .12.2025 }
For Study purpose only
NB: For any doubts clarification, please refer to
the recommended text
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TOPIC : ATOMIC ENERGY: for UPSC(CSE)(Prelims)Exams.2026
QUESTIONS & ANSWERS
Nuclear power provides 10 per cent of the world’s electricity, but to stem climate change, far greater amounts of clean and reliable energy are needed.
Thirty countries currently operate nuclear power plants. More than two dozen others are looking at nuclear energy to meet their power and climate needs.
In the western United States, more than 30 towns and cities are also looking to the future. They want to go carbon free, and they are betting on SMRs to get there.
Nuclear Power Corporation of India Ltd.(NPCIL) operates 24 Nuclear Power Reactors at seven sites across the nation with installed capacity of 8180 MW.
In the category of PHWRs of 220MW capacity, there are 15 PHWR reactors of 220 MW capacity being operated currently. Gross generation of power depends on type of turbines, ambient conditions, seasonal changes and type of condenser cooling-closed loop/once through.
Bharat Small Reactors(BSRs):-
220 MWe PHWR Bharat Small Reactors (BSRs) in Brown/Green fields , initiative is being part of NPCIL’s broader commitment to support India’s clean energy transition, leveraging NPCIL’s expertise to drive sustainable industrial growth and to facilitate wider participation in this important initiative,in large interest of the industries for consumption of electricity for their own user.
Small Modular Reactors(SMRs):-
Small modular reactors (SMRs) are advanced nuclear reactors that have a power
capacity of up to 300 MW(e) per unit, which is about one-third of the generating capacity of traditional nuclear power reactors.
Why they are called SMRs?
Ans: SMRs, which can produce a large amount of low-carbon electricity, are:
● Small – physically a fraction of the size of a conventional nuclear power reactor.
● Modular – making it possible for systems and components to be factory-assembled and transported as a unit to a location for installation. ● Reactors – harnessing nuclear fission to generate heat to produce energy.
What are the Advantages of SMRs?
Ans: Many of the benefits of SMRs are inherently linked to the nature of their design – small and modular.
1)Given their smaller footprint, SMRs can be sited on locations not suitable for larger nuclear power plants.
2)Prefabricated units of SMRs can be manufactured and then shipped and installed on site, making them more affordable to build than large power reactors, which are often custom designed for a particular location, sometimes leading to construction delays.
3)SMRs offer savings in cost and construction time, and they can be deployed incrementally to match increasing energy demand.
What are the challenges of SMRs?
Ans: One of the challenges to accelerating access to energy is infrastructure – limited grid coverage in rural areas – and the costs of grid connection for rural electrification.
A single power plant should represent no more than 10 per cent of the total installed grid capacity. In areas lacking sufficient lines of transmission and grid capacity, SMRs can be installed into an existing grid or remotely off-grid, as a function of its smaller electrical output, providing low-carbon power for industry and the population. This is particularly relevant for microreactors, which are a subset of SMRs designed to generate electrical power typically up to 10 MW(e). Microreactors have smaller footprints than other SMRs and will be better suited for regions inaccessible to clean, reliable and affordable energy. Furthermore, microreactors could serve as a backup power supply in emergency situations or replace power generators that are often fuelled by diesel, for example, in rural communities or remote businesses.
2)In comparison to existing reactors, proposed SMR designs are generally simpler, and the safety concept for SMRs often relies more on passive systems and inherent safety characteristics of the reactor, such as low power and operating pressure. This means that in such cases no human intervention or external power or force is required to shut down systems, because passive systems rely on physical phenomena, such as natural circulation, convection, gravity and self-pressurization. These increased safety margins, in some cases, eliminate or significantly lower the potential for unsafe releases of radioactivity to the environment and the public in case of an accident.
Important points:-
1)SMRs have reduced fuel requirements. Power plants based on SMRs may require less frequent refuelling, every 3 to 7 years, in comparison to between 1 and 2 years for conventional plants.
2)Some SMRs are designed to operate for up to 30 years without refuelling.
3)Both public and private institutions are actively participating in efforts to bring SMR technology to fruition within this decade.
4)Russia’s Akademik Lomonosov, the world’s first floating nuclear power plant that began commercial operation in May 2020, is producing energy from two 35 MW(e) SMRs. Other SMRs are under construction or in the licensing stage in Argentina, Canada, China, Russia, South Korea and the United States of America.
5)SMRs in Land based water cooled category include the water cooled SMR designs having different configurations of:-
i) Light Water Reactor (LWR) and
ii)Pressurized Heavy Water Reactor (PHWR) technologies (integral Pressurized Water Reactors (PWRs) and PHWR,
iii)compact PWR, loop-type PWR, Boiling Water Reactors (BWRs) as well as pool type PWR) for on-land applications.
These designs take advantage of mature technology used in most of the LRs in operation
[BWR: Boiling Water Reactor]
What is nuclear energy ?
Ans : Nuclear energy is a form of energy released from the nucleus, the core of atoms, made up of protons and neutrons. This source of energy can be produced in two ways:
(i) fission – when nuclei of atoms split into several parts( using Uranium as fuel) – or
ii)fusion – when nuclei fuse together(using Hydrogen as fuel in Sun and Stars).
Question: What is nuclear fission? What is Chain Reaction?
Ans:Nuclear fission is a reaction where the nucleus of an atom splits into two or more smaller nuclei, while releasing energy.
For instance, when hit by a neutron, the nucleus of an atom of Uranium-235 splits into two smaller nuclei, for example a barium nucleus and a krypton nucleus and two or three neutrons. These extra neutrons will hit other surrounding Uranium-235 atoms, which will also split and generate additional neutrons in a multiplying effect, thus generating a chain reaction in a fraction of a second.
Each time the reaction occurs, there is a release of energy in the form of heat and radiation. The heat can be converted into electricity in a nuclear power plant, similarly to how heat from fossil fuels such as coal, gas and oil is used to generate electricity.
Question : How does a nuclear power plant work?
Ans: Inside nuclear power plants, nuclear reactors and their equipment contain and control the chain reactions, most commonly fuelled by Uranium-235, to produce heat through fission. The heat warms the reactor’s cooling agent, typically water, to produce steam. The steam is then channelled to spin turbines, activating an electric generator to create low-carbon electricity.
Uranium:
Uranium is a metal that can be found in rocks all over the world. Uranium has several naturally occurring isotopes, which are forms of an element differing in mass and physical properties but with the same chemical properties. Uranium
has two primordial isotopes: uranium-238 and uranium-235. Uranium-238 isotope makes up the majority of the uranium in the world but cannot produce a fission chain reaction, while uranium-235 isotope can be used to produce energy by fission but constitutes less than 1 per cent of the world’s uranium.
Question: What is Uranium Enrichment ?
Ans: To make natural uranium more likely to undergo fission, it is necessary to increase the amount of Uranium-235 isotope in a given sample through a special process called uranium enrichment using centrifuges etc. Once the uranium is enriched, it can be used effectively as nuclear fuel in power plants for three to five years, after which it is still radioactive and has to be disposed of following stringent guidelines to protect people and the environment. Used fuel, also referred to as spent fuel, can also be recycled into other types of fuel for use as new fuel in special nuclear power plants.
Question: What is Nuclear Fuel Cycle ?
Ans: The nuclear fuel cycle is an industrial process involving various steps to produce electricity from uranium in nuclear power reactors. The cycle starts with the mining of uranium and ends with the disposal of nuclear waste.
What is Nuclear Waste?
Ans: The operation of nuclear power plants produces waste with varying levels of radioactivity. These waste materials are managed differently depending on their level of radioactivity and purpose.
What is Radioactive waste in other places/applications?
Ans: Radioactive waste makes up a small portion of all waste. It is the by-product of millions of medical procedures each year, industrial and agricultural applications that use radiation
Question: Nuclear Power and Climate Change ?
Ans: Nuclear power is a low-carbon source of energy, because unlike coal, oil or gas power plants, nuclear power plants practically do not produce CO2 during their operation. Nuclear power reactors generate about one quarter of the world’s low-carbon electricity and are crucial in meeting climate change goals.
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