Knowledge Nugget: What are the Small Modular Reactors behind India’s big nuclear dreams?

Take a look at the essential events, concepts, terms, quotes, or phenomena every day and brush up your knowledge. Here’s your UPSC Current Affairs knowledge nugget for today on small modular reactors and SHANTI Act.

The country’s top atomic energy regulator is expected to maintain the same rigorous safety and licensing requirements for small modular reactors (SMRs) as those applicable to large nuclear reactors, The Indian Express has learned. This comes even as SMRs are increasingly being pitched as a safer alternative to conventional reactors. The regulator’s position is also significant given the concerted push in the Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India (SHANTI) Act, 2025 to foster private sector participation in the nuclear sector.

In this context, let’s know about the small modular reactors in detail and the SHANTI Act.

Key Takeaways:

1. India’s nuclear power programme has so far been anchored by indigenous pressurised heavy water reactors (PHWRs), which use heavy water as both coolant and moderator and natural uranium as fuel. Even though PHWRs will continue to form the backbone of the country’s nuclear expansion plans, SMRs are increasingly viewed as technology of promise that could help in industrial decarbonisation.

2. The Government of India is also promoting the indigenous development of SMRs, occasionally calling them Bharat SMRs, with the ₹20,000 crore mission aimed at making a significant impact in this regard.

3. India is pushing for a leadership slot in this small reactor space, both as a way of fulfilling its commitment to clean energy transition, and bundling SMRs as a technology-led foreign policy pitch.

4. SMRs are essentially advanced small nuclear reactors that have a power capacity of 30MWe to 300 MWe (megawatt electrical) per unit. Conventional nuclear reactors, the kind which are currently installed in India and elsewhere, usually have capacities to produce 500 MW of electricity or more.

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5. The relatively simpler and modular design of SMRs—enabling their components to be assembled in a factory instead of being constructed on-site—lowers costs and allows flexible deployment, making them a much more attractive proposition in recent years.

6. SMRs are being viewed as a promising option for decarbonising energy-intensive sectors such as steel, aluminium and cement, owing to their ability to produce large volumes of round-the-clock, low-carbon electricity.

7. While lots of different types of SMRs are being developed, there are currently four main types, each using a different coolant to manage the extreme heat of a nuclear fission reaction — light water, high temperature gas, liquid metal, and molten salt.

8. The most common type, though, are light water reactors, which are very similar to traditional nuclear power plants being built in Russia, France and the US that are all water-cooled. That makes light water SMRs much easier to design.

Do you Know?

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Under the Nuclear Energy mission for Viksit Bharat, India now strives to achieve the target of 100 GW nuclear power capacity by 2047.

What is SHANTI Act?

1. The SHANTI Act, which received the assent of President on December 21, 2025, effectively allows private sector participation for the setting up a nuclear facility, or to carry out activities for the production, use and disposal of nuclear energy under a license from the Central Government and safety authorisation of the country’s nuclear regulator — the Atomic Energy Regulatory Board.

2. The SHANTI Act is an effort to align with norms of global nuclear commerce. It replaces the Atomic Energy Act of 1962 and the Civil Liability for Nuclear Damage Act of 2010 with a single umbrella law.

3. The new law allows public and private companies to set up nuclear power plants and undertake activities related to the transport, storage, import and export of nuclear fuel, technology, equipment and minerals. Until now, these activities were restricted to public sector entities only.

What is India’s Three-stage nuclear programme?

1. India’s nuclear journey began shortly after Independence with the establishment of the Atomic Energy Commission in 1948. In 1956, Asia’s first research reactor, Apsara, was commissioned at the Bhabha Atomic Research Centre (BARC) in Trombay.

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2. India was the second Asian nation to build a nuclear power plant in 1969 at Tarapur, just after Japan and long before China. It also built up an impressive nuclear research and development programme in the 1950s and 1960s with significant assistance from its Western partners.

3. India owes the vision of the three-phase programme of nuclear power to ensure energy security to Dr Homi J Bhabha, the father of India’s nuclear programme, and Dr Vikram Sarabhai, who recognised the need for developing FBRs, as these reactors generate more nuclear fuel than they consume due to the gainful conversion of fertile isotopes into fissile material.

Three-stage nuclear programme

→ STAGE 1: Pressurised Heavy Water Reactors (PHWRs) use natural uranium-based fuels to generate electricity, while producing fissile plutonium (Pu239), which can be extracted by reprocessing the spent fuel. It uses heavy water (deuterium oxide) both as a coolant and moderator. The programme has been supplemented by the construction of imported Light Water Reactors (LWRs).

→ STAGE 2: It involves setting up Fast Breeder Reactors (FBRs) of the kind at Kalpakkam, using plutonium-based fuels, which can enhance nuclear power capacity, and convert fertile thorium into fissile uranium (U233). Reprocessing of the spent fuel is vital for efficient utilisation of the plutonium inventory.

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→ STAGE 3: The third stage will be based on the ThU233 cycle. U233 produced in the second stage can be used for the third stage of the power programme, which consists of advanced thermal and fast breeder reactors, for long-term energy security. The Advanced Heavy Water Reactor (AHWR) is proposed for this. Now, the use of molten salt reactors is also seen as an option.

BEYOND THE NUGGET: Kalpakkam Fast Breeder Reactor Attains Criticality

1. India’s first indigenous Fast Breeder Reactor (FBR) at Kalpakkam in Tamil Nadu recently attained criticality.

2. Attaining criticality, or going critical, means the initiation of a self-sustaining nuclear fission reaction that will eventually lead to the generation of power by the 500-megawatt electric (MWe) FBR.

3. Attaining criticality is a key milestone before full power generation, indicating that the reactor core is functioning as designed and that each fission event in the core now releases a sufficient number of neutrons to sustain an ongoing series of reactions. This is the vital second stage of India’s nuclear programme.

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Post Read Question

With reference to the Small Modular Reactors (SMRs), consider the following statements:

1. They are suitable only for on-grid and not for off-grid applications.

2. These are cost-effective alternatives to conventional large nuclear reactors.

3. SMRs have a power capacity of 30MWe to 300 MWe (megawatt electrical) per unit.

How many of the statements given above are correct?

(a) Only one

(b) Only two

(c) All three

(d) None

Answer Key

(b)

(Sources: Special regulatory relaxations unlikely for small nuclear reactors, Knowledge Nugget: How is Nuclear Energy Mission and Small Modular Reactors relevant for UPSC Exam?)

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