Chapter 8 · Topic 8.2 · Prelims + Mains2 of 3
Nuclear Technology: Three-stage programme and nuclear
Key points
- Three stages, PFBR, thorium, monazite.
- Capacity, targets, SMRs, SHANTI Act, Russia.
Prelims box: facts and traps
| Item | Value |
|---|---|
| Installed capacity | 8,780 MW (24 reactors) |
| Generation 2024-25 | 56,681 million units; 3.1% share |
| Under construction | 18 reactors, 13,600 MW |
| Capacity on completion | 22,380 MW (projected for 2031-32) |
| Nuclear Energy Mission | 100 GW by 2047 |
| Small modular reactors | Rs 20,000 crore; at least 5 operational by 2033. |
- Another 18 reactors of 13,600 MW, including the 500 MW PFBR, are being built; when they are complete, capacity will reach 22,380 MW (PIB, 6 Aug 2025).
- The Nuclear Energy Mission, set out in the Union Budget 2025-26, targets 100 GW by 2047 to support net zero by 2070.
- The 100 GW target is for 2047, under the Nuclear Energy Mission for Viksit Bharat; DAE told Parliament in August 2026 that capacity stood at 8,780 MW from 24 reactors and is expected to reach about 22 GW by 2031-32.
- Trap (UPSC Prelims 2022, India): “Monazite occurs naturally in the entire Indian coastal sands in India” is incorrect.
- Trap (UPSC Prelims 2012): all the statements are correct.
India’s three-stage programme and the PFBR
Homi Bhabha’s three-stage programme links India’s limited uranium to its vast thorium. Stage 1: PHWRs burn natural uranium, and their spent fuel yields plutonium. Stage 2: Fast Breeder Reactors burn that plutonium and produce more fuel than they consume; they will also breed uranium-233 from thorium. Stage 3: thorium-based reactors fuelled by uranium-233 (PIB Factsheet, 7 Apr 2026).
India’s 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam attained first criticality, the start of a controlled fission chain reaction, on 6 April 2026, after clearance from the Atomic Energy Regulatory Board (AERB). Designed by IGCAR and built by BHAVINI, it uses uranium-plutonium mixed oxide (MOX) fuel, a uranium-238 blanket in which fast neutrons breed plutonium-239, and liquid sodium as coolant; it is designed to later use thorium-232 in the blanket (PIB, 7 Apr 2026). With it India entered the second stage; once fully operational, India will be only the second country after Russia to run a commercial fast breeder reactor (PIB Factsheet). Mains 2026 asked: Distinguish between a Fast Breeder Reactor (FBR) and a thermal nuclear reactor, and explain ‘criticality’.
Distinguish between a Fast Breeder Reactor (FBR) and a thermal nuclear reactor. In the context of first indigenously developed prototype FBR at Kalpakkam, explain the term ‘criticality’. What are its implications for clean energy future of our country?
Why thorium? NPCIL lists India’s identified reserves as about 78,000 tonnes of uranium against 3,63,000 tonnes of thorium (NPCIL FAQ, undated), and DAE has since established 4,33,800 tonnes of in-situ U3O8 resource in 47 deposits (PIB, 6 Aug 2025). UPSC’s key accepts that Thorium is far more abundant in nature than uranium, gives more energy per unit mass of mined mineral, and produces less harmful waste (Prelims 2012: answer (d), 1, 2 and 3).
To meet its rapidly growing energy demand, some opine that India should pursue research and development on thorium as the future fuel of nuclear energy. In this context, what advantage does thorium hold over uranium? 1. Thorium is far more abundant in nature than uranium. 2. On the basis of per unit mass of mined mineral, thorium can generate more energy compared to natural uranium. 3. Thorium produces less harmful waste compared to uranium. Which of the statements given above is/are correct?
- 1 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Show answer
Answer: (d) · UPSC official key
Thorium comes from monazite in beach sands. Monazite is a ‘prescribed substance’ under the Atomic Energy Act; apart from thorium, it contains rare earths, and Indian Rare Earths Limited (IREL), a government-owned company under DAE, is the only entity permitted to produce and process monazite and to handle it for domestic use and export (DAE, 2012). So Monazite is a source of rare earths, contains thorium and is handled only by government bodies, but it does not occur in the entire coastline (Prelims 2022: answer (b)).
With reference to India, consider the following statements : 1. Monazite is a source of rare earths. 2. Monazite contains thorium. 3. Monazite occurs naturally in the entire Indian coastal sands in India. 4. In India, Government bodies only can process or export monazite. Which of the statements given above are correct ?
- 1, 2 and 3 only
- 1, 2 and 4 only
- 3 and 4 only
- 1, 2, 3 and 4
Show answer
Answer: (b) · UPSC official key
Mains 2017 asked for an account of nuclear science in India and the advantage of fast breeder reactor programme, and Mains 2013 asked about the availability of raw material required for the generation of atomic energy. Points: limited uranium but large thorium; breeders multiply
fissile material and bridge to thorium; a closed fuel cycle recycles spent fuel and reduces waste (PIB, 2026).
Give an account of the growth and development of nuclear science and technology in India. What is the advantage of fast breeder reactor programme in India?
With growing scarcity of fossil fuels, the atomic energy is gaining more and more significance in India. Discuss the availability of raw material required for the generation of atomic energy in India and in the world.
Nuclear power: capacity, targets and the SHANTI
Act India has 24 reactors with an installed capacity of 8,780 MW, excluding RAPS-1 (100 MW), which is under long-term shutdown. Another 18 reactors of 13,600 MW, including the 500 MW PFBR, are being built; when they are complete, capacity will reach 22,380 MW (PIB, 6 Aug 2025). Nuclear plants generated 56,681 million units in 2024-25, a 3.1% share of India’s electricity (PIB Factsheet, 2026).
| Item | Value | Status |
|---|---|---|
| Installed capacity | 8,780 MW (24 reactors) | measured, Aug 2025 |
| Generation 2024-25 | 56,681 million units; 3.1% share | measured |
| Under construction | 18 reactors, 13,600 MW | in progress |
| Capacity on completion | 22,380 MW (projected for 2031-32) | projection |
| Nuclear Energy Mission | 100 GW by 2047 | target |
| Small modular reactors | Rs 20,000 crore; at least 5 operational by 2033 | allocation; target |
Sources: PIB, 6 Aug 2025 and Factsheet of 7 Apr 2026. Targets and projections are not achievements.
The Nuclear Energy Mission, set out in the Union Budget 2025-26, targets 100 GW by 2047 to support net zero by 2070. It allots Rs 20,000 crore to small modular reactors, and BARC is designing the 200 MWe Bharat Small Modular Reactor (BSMR-200), a 55 MWe SMR and a 5 MWth high-temperature gas-cooled reactor for hydrogen (PIB). The SHANTI Act, 2025 (Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India) lets private firms, under a central licence and AERB safety authorisation, build, own and operate nuclear plants, make fuel and do research, while the Centre keeps exclusive control of enrichment, spent fuel management and heavy water production (PIB, 29 Jan 2026).
Partners help too: India has civil nuclear agreements with 18 countries (PIB Factsheet). During the October 2018 summit, India and Russia signed the Action Plan for Prioritization and Implementation of Cooperation Areas in the Nuclear Field, and noted progress on the remaining units at Kudankulam and talks on a new Russian-designed plant (India-Russia Joint Statement, 5 Oct 2018). So the partner was Russia (Prelims 2019: answer (b)).
Recently, India signed a deal known as ‘Action Plan for Prioritization and Implementation of Cooperation Areas in the Nuclear Field’ with which of the following countries?
- Japan
- Russia
- The United Kingdom
- The United States of America
Show answer
Answer: (b) · UPSC official key
Mains 2018 asked whether, With growing energy needs should India keep on expanding its nuclear energy programme, discussing the facts and fears. Facts: low-carbon baseload power, a 100 GW target and a breeder-thorium path. Fears: safety after accidents like Chernobyl, waste, cost and liability; India’s answers include AERB oversight, PHWR designs that do not use combustible graphite (NPCIL) and recycling of spent fuel.
With growing energy needs should India keep on expanding its nuclear energy programme? Discuss the facts and fears associated with nuclear energy.
Mains box: analysis and answer points
- Homi Bhabha's three-stage programme links India's limited uranium to its vast thorium.
- Points: limited uranium but large thorium; breeders multiply
- Stage 1: PHWRs burn natural uranium, and their spent fuel yields plutonium.
- Likely next angle: Monazite: IREL only
- Asked: Mains 2026 (GS Paper III, 10 marks): Distinguish between a Fast Breeder Reactor (FBR) and a thermal nuclear reactor. In the context of first indigenously developed prototype FBR at Kalpakkam, explain the term 'criticality'. What are its implications for clean energy future of our country?
Practice
Practice MCQs (8)
With reference to the Nuclear Energy Mission announced in the Union Budget 2025-26, consider the following statements:
1. An outlay of Rs 20,000 crore was provided for research and development of Small Modular Reactors.
2. It aims to have at least five indigenously designed Small Modular Reactors operational by 2033.
3. It aims at an installed nuclear power capacity of 100 GW by 2030.
Which of the statements given above is/are correct?
Answer (d) & explanation
Statements 1 and 2 are correct. The Nuclear Energy Mission in the Union Budget 2025-26 set aside Rs 20,000 crore for research and development of Small Modular Reactors, with the target of at least five indigenously designed and operational SMRs by 2033 (PIB, Feb 2025). The 100 GW target is for 2047, under the Nuclear Energy Mission for Viksit Bharat; DAE told Parliament in August 2026 that capacity stood at 8,780 MW from 24 reactors and is expected to reach about 22 GW by 2031-32. A 100 GW target for 2030 would be impossible from that base.
The Prototype Fast Breeder Reactor at Kalpakkam was designed by which one of the following institutions?
Answer (d) & explanation
The answer is IGCAR. The Indira Gandhi Centre for Atomic Research at Kalpakkam, a DAE research centre set up in 1971, leads India's fast reactor programme: it built and runs the Fast Breeder Test Reactor (1985) and KAMINI, and designed the PFBR. Construction and operation of the PFBR are with BHAVINI, a separate public sector company. NPCIL builds and runs the thermal power reactors (PHWRs and LWRs), the AERB is the safety regulator, and the Heavy Water Board produces heavy water.
KAMINI, a small research reactor at the Indira Gandhi Centre for Atomic Research, Kalpakkam, is notable because it
Answer (a) & explanation
The answer is (a). KAMINI (Kalpakkam Mini reactor) is a 30 kWth research reactor whose fuel is a uranium-233–aluminium alloy; DAE describes it as the only reactor in the world operating with uranium-233 fuel. The U-233 comes from thorium irradiated in Indian reactors, so KAMINI demonstrates the physics needed for the third stage. It is used for neutron radiography and activation analysis. India's first grid-connected power reactors were the Tarapur BWRs (1969), and fusion tokamaks are at the Institute for Plasma Research, Gandhinagar.
Consider the following statements about India's 700 MWe Pressurised Heavy Water Reactor programme:
1. In 2017 the Union Cabinet approved ten indigenous 700 MWe PHWRs to be built in 'fleet mode'.
2. The Mahi Banswara project in Rajasthan is being implemented by ASHVINI, a joint venture of NPCIL and NTPC.
3. The Mahi Banswara project will use imported Russian VVER reactors.
4. Kakrapar units 3 and 4 in Gujarat were the first two indigenous 700 MWe PHWRs to be commissioned.
How many of the statements given above are correct?
Answer (c) & explanation
Three statements (1, 2 and 4) are correct. On 17 May 2017 the Cabinet approved ten 700 MWe PHWRs in fleet mode, with identical design and bulk procurement to cut cost and time. The Mahi Banswara project (4 x 700 MWe) is being built by ASHVINI (Anushakti Vidhyut Nigam Ltd; NPCIL 51%, NTPC 49%); the Prime Minister laid its foundation stone on 25 September 2025, and it is the first nuclear project set up by a joint venture of two central public sector enterprises. Statement 3 is wrong: Mahi Banswara uses the same indigenous IPHWR- 700 design. Kakrapar 3 and 4 were the first two 700 MWe units in operation.
Consider the following pairs: Nuclear facility — Distinction
1. Apsara, Trombay — First research reactor in Asia (1956)
2. Tarapur units 1 and 2 — India's first nuclear power station, using Boiling Water Reactors
3. Kakrapar units 3 and 4 — Russian-designed VVER reactors
4. Kaiga — Site of the Prototype Fast Breeder Reactor
How many of the pairs given above are correctly matched?
Answer (b) & explanation
Only pairs 1 and 2 are correct. Apsara at Trombay attained criticality on 4 August 1956 and was the first research reactor in Asia. Tarapur units 1 and 2 (Maharashtra), built with US cooperation, began commercial operation in 1969 as India's first nuclear power station, with BWRs. Pair 3 is wrong: Kakrapar 3 and 4 (Gujarat) are the first two indigenous 700 MWe PHWRs; the Russian VVERs are at Kudankulam, Tamil Nadu. Pair 4 is wrong: the PFBR (and the older Fast Breeder Test Reactor) are at Kalpakkam, Tamil Nadu; Kaiga in Karnataka has 220 MWe PHWRs, with two 700 MWe units under construction.
With reference to Small Modular Reactors (SMRs), consider the following statements:
1. As described by the International Atomic Energy Agency, SMRs are advanced reactors with a power capacity of up to about 300 MW(e) per unit.
2. Their systems and components can be fabricated in factories and transported as modules to the site for installation.
3. By definition, SMRs can be installed only within the premises of existing large nuclear power stations.
Which of the statements given above is/are correct?
Answer (b) & explanation
Statements 1 and 2 are correct. The IAEA describes SMRs as advanced nuclear reactors with a capacity of up to 300 MW(e) per unit, roughly one-third of a conventional large reactor. 'Modular' means that systems are factory-fabricated and shipped as modules, which can cut construction time and cost, and many designs rely on passive safety. Statement 3 is wrong: one of the main attractions of SMRs is siting flexibility, for example at retired coal plant sites, near industries as captive plants or in remote areas.
Consider the following statements regarding small reactors in India's nuclear plans:
1. The 'Bharat Small Reactors' announced for private-sector partnership in the Union Budget 2025-26 are 220 MW pressurised light water reactors of a new design.
2. The Bharat Small Modular Reactor (BSMR-200) being designed by BARC with NPCIL is based on pressurised water reactor technology.
3. The high-temperature gas-cooled reactor being designed by BARC is meant mainly to supply heat for hydrogen production.
Which of the statements given above is/are correct?
Answer (b) & explanation
Statements 2 and 3 are correct. Government material on the Union Budget 2025- 26 says that Bharat Small Reactors are 220 MW Pressurised Heavy Water Reactors, a proven Indian design being adapted to need less land so that industries (steel, aluminium, metals) can host them as captive plants, with NPCIL handling design and operation. The new BSMR-200, designed by BARC and NPCIL, is a pressurised (light) water reactor, and SMR-55 is also PWR- based; both are planned at Tarapur. BARC's high-temperature gas-cooled reactor (up to 5 MWth, sited at BARC Visakhapatnam) is meant to supply process heat for hydrogen through a thermochemical cycle such as copper-chlorine (DAE replies in Parliament, 2026).
In a nuclear power reactor, the chain reaction can be controlled by the relatively slow mechanical movement of control rods mainly because
Answer (b) & explanation
The answer is (b). Most fission neutrons are 'prompt', but a small fraction (about 0.65% for uranium-235) are delayed neutrons, emitted seconds to about a minute later by fission products. Because the chain reaction depends on this lagging fraction when the reactor is just critical (multiplication factor k = 1), power changes over seconds rather than microseconds, giving control rods and automatic systems time to act. Control rods absorb neutrons (boron, cadmium, hafnium); slowing neutrons is the job of the moderator.
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In 150 words, explain the significance of Nuclear Technology with one recent example.
Flashcards (10)
Fuel in an Indian PHWR?
Natural uranium.
India's share of electricity from nuclear in
2024-25? 3.1%.
Stage 2 of India's programme uses which
reactor? Fast Breeder Reactors.
When did PFBR reach first criticality?
6 April 2026.
Who designed and who built the PFBR?
IGCAR designed; BHAVINI built.
Who alone may process and export
monazite? IREL.
India's installed nuclear capacity (Aug
2025)? 8,780 MW in 24 reactors.
Nuclear Energy Mission target?
100 GW by 2047.
SMR allocation and target?
Rs 20,000 crore; at least 5 by 2033.
What does the SHANTI Act allow?
Licensed private firms in nuclear power, under AERB.
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