Nuclear Technology

Introduction to Nuclear Energy

1. Nuclear Energy is the energy released through changes occurring within the nucleus of an atom, particularly during nuclear fission, nuclear fusion and radioactive decay.
2. The atomic nucleus consists of protons and neutrons, collectively called nucleons, which are held together by nuclear interactions.
   
   
3. Nuclear reactions can release enormous quantities of energy because small differences in nuclear mass correspond to substantial amounts of energy.
4. The relationship between mass and energy is expressed by Einstein’s Mass–Energy Equivalence Equation: E = mc²

   Where:

   • E = Energy.
   • m = Mass converted into an equivalent amount of energy.
   • c = Speed of light in a vacuum, approximately 3 × 10⁸ m/s.
5. Nuclear energy is used in:
   • Electricity generation through nuclear power stations.
   • Medicine, including cancer treatment and diagnostic imaging.
   • Agriculture, particularly crop improvement and food irradiation.
   • Industry, including radiography, sterilisation and material testing.
   • Scientific research, including nuclear physics and isotope studies.
   • Space exploration, including radioisotope power systems and research into nuclear propulsion.

Nuclear Energy and Nuclear Binding Energy

1. Nuclear Binding Energy is the energy required to separate a nucleus completely into its constituent protons and neutrons.
   
   
2. The mass of a bound nucleus is smaller than the combined masses of its free constituent nucleons. This difference is known as the Mass Defect.
3. The binding energy associated with the mass defect is:

   B = Δmc²

4. Binding Energy per Nucleon measures the average binding energy associated with each nucleon and provides an indication of nuclear stability.
5. Nuclei in the region of iron and nickel possess particularly high binding energies per nucleon.
6. Consequently, energy can be released through:
   • Fusion of light nuclei into more tightly bound nuclei.
   • Fission of very heavy nuclei into more tightly bound fragments.

Nuclear Energy and Conventional Energy

Types of Nuclear Reactions: Fission and Fusion

Nuclear Fission

1. Nuclear Fission is a nuclear reaction in which a heavy nucleus splits into two or more lighter nuclei, usually accompanied by the release of neutrons and energy.
2. Fission can occur spontaneously in certain nuclei or can be induced by the absorption of a neutron.
3. Important fissile isotopes include:
   • Uranium-235 (U-235).
   • Uranium-233 (U-233).
   • Plutonium-239 (Pu-239).
4. A representative fission reaction involving uranium-235 is:

   ²³⁵₉₂U + ¹₀n → ¹⁴¹₅₆Ba + ⁹²₃₆Kr + 3¹₀n + Energy

5. In this reaction:
   • Uranium-235 absorbs a neutron.
   • An excited compound nucleus forms.
   • The nucleus splits into lighter fragments.
   • Additional neutrons are released.
   • Approximately 200 MeV of energy is liberated per fission event, with the exact energy distribution depending on the reaction.
     
     
6. The fission products are not always barium and krypton; several combinations of daughter nuclei are possible.

Nuclear Chain Reaction

1. A Nuclear Chain Reaction occurs when neutrons produced by one fission event trigger further fission reactions.
2. A self-sustaining chain reaction is essential for continuous nuclear energy production.
3. The behaviour of a chain reaction is described by the Effective Neutron Multiplication Factor (k_eff).

4. In a nuclear power reactor, the chain reaction is carefully controlled through neutron management and reactor-control systems.
   
   
5. A reactor operating at steady power is generally maintained at or near the critical state.
6. Neutrons that are absorbed without producing further fission, or escape from the reactor core, influence the sustainability of the chain reaction.

Nuclear Fusion

1. Nuclear Fusion occurs when two light atomic nuclei combine to form a heavier nucleus.
2. Fusion may release energy when the resulting nucleus is more tightly bound.
3. Fusion is the principal source of energy in the Sun and other main-sequence stars.
4. Fusion requires conditions that allow nuclei to approach sufficiently closely despite their electrostatic repulsion.
5. Such conditions generally involve extremely high temperatures and, depending on the system, high densities or sufficient confinement time.

Deuterium–Tritium Fusion Reaction

²₁H + ³₁H → ⁴₂He + ¹₀n + 17.6 MeV

6. This reaction involves:
   • Deuterium (²H), a hydrogen isotope containing one proton and one neutron.
   • Tritium (³H), a radioactive hydrogen isotope containing one proton and two neutrons.
   • Production of a helium-4 nucleus and a neutron.
   • Release of approximately 17.6 MeV of energy.
     
     
7. In stars such as the Sun, hydrogen fusion occurs mainly through the Proton–Proton Chain.
8. Deuterium–tritium fusion is particularly important for experimental fusion reactors because of its comparatively favourable reaction characteristics.

Differences Between Nuclear Fission and Nuclear Fusion

Nuclear Fuel

1. Nuclear Fuel is material used in nuclear systems to sustain reactions that release energy.
2. In fission reactors, the fuel commonly contains isotopes capable of undergoing nuclear fission or producing fissile isotopes through neutron absorption.
3. The most important elements associated with nuclear fuel cycles are:
   • Uranium.
   • Plutonium.
   • Thorium.
4. Nuclear fuel materials are broadly distinguished as fissile and fertile.

Fissile and Fertile Materials

Fissile Materials

1. 1. Fissile Material can sustain a nuclear chain reaction using low-energy neutrons under suitable conditions.
   2. Important examples are:
      • Uranium-235.
      • Uranium-233.
      • Plutonium-239.

Fertile Materials

1. 1. Fertile Material is not ordinarily fissile with thermal neutrons but can be transformed into a fissile isotope through neutron absorption and subsequent nuclear transformations.
   2. Important examples are:
      • Uranium-238, which can produce Plutonium-239.
      • Thorium-232, which can produce Uranium-233.

Nuclear Fuel Cycle

1. The Nuclear Fuel Cycle includes the processes required to obtain, prepare, use and manage nuclear fuel.
2. Its main stages are:

   Uranium Exploration → Mining → Milling → Conversion → Enrichment (where required) → Fuel Fabrication → Reactor Use → Spent-Fuel Management → Reprocessing or Disposal
   
   

3. The fuel cycle can be classified into two major approaches.

Open Fuel Cycle

• • Spent nuclear fuel is not reprocessed to recover reusable nuclear material.
  • It is managed for long-term storage and eventual disposal.

Closed Fuel Cycle

• • Spent fuel is reprocessed to recover usable nuclear material, such as uranium and plutonium.
  • Recovered materials may be fabricated into new nuclear fuel.
  • India follows a strategy emphasising a closed nuclear fuel cycle, particularly for its three-stage nuclear power programme.

4. Reprocessing does not eliminate radioactive waste. It changes the composition and quantity of materials requiring different forms of management.
5. The fuel cycle also requires strict safeguards, radiation protection, material accounting and environmental controls.

Uranium

Properties of Uranium

1. Uranium (U) is a naturally occurring radioactive metallic element with atomic number 92.
2. It is one of the most important raw materials for commercial nuclear energy production.
3. Naturally occurring uranium consists predominantly of three isotopes:

4. The low natural abundance of U-235 influences reactor design and, for certain reactor types, creates a requirement for uranium enrichment.
5. Pressurised Heavy Water Reactors (PHWRs) can operate using natural uranium because heavy water provides favourable neutron economy.
6. Many Light Water Reactors (LWRs) use enriched uranium fuel.

Uranium Enrichment

1. Uranium Enrichment is the process of increasing the proportion of U-235 relative to U-238.
2. Enrichment is required for several reactor designs because natural uranium contains only a small proportion of the fissile isotope U-235.
3. The most widely used commercial enrichment method is Gas Centrifugation, which separates uranium isotopes on the basis of small differences in mass.
4. Uranium enrichment is usually discussed in terms of the percentage of U-235.

5. Many conventional commercial LWRs use uranium enriched to approximately 3–5% U-235.
6. Enrichment is a sensitive nuclear-fuel-cycle activity because the same general technological field has peaceful and proliferation-related implications.
7. The International Atomic Energy Agency (IAEA) promotes safeguards and verification arrangements to reduce risks of diversion of nuclear material from peaceful uses.

Uranium Deposits in India

1. India’s uranium resources occur in several geological environments, including:
   • Proterozoic sedimentary and metamorphic terrains.
   • Fracture-controlled mineralised zones.
   • Sandstone-associated deposits.
   • Granitic and other geological formations.
2. Important uranium-bearing regions include:

3. According to a government statement issued in August 2026, the Atomic Minerals Directorate for Exploration and Research (AMD) had established approximately 4,42,800 tonnes of in-situ U₃O₈ resources across identified Indian deposits.
   
   
4. U₃O₈ is triuranium octoxide, a uranium oxide used as a standard reporting basis for uranium resources.
5. Reported geological resources must not be confused with economically recoverable reserves or the quantity of uranium immediately available for reactor fuel.

Uranium Mining in India

1. Uranium mining involves exploration, extraction, processing and recovery of uranium-bearing material.
2. The Uranium Corporation of India Limited (UCIL) is an important public-sector undertaking associated with uranium mining and processing.
3. UCIL operates under the Department of Atomic Energy (DAE).
4. Its mining and processing activities have historically been concentrated in Jharkhand, with uranium-production operations also associated with Tummalapalle in Andhra Pradesh.
5. Uranium extraction may involve underground mining, open-cast mining or other methods depending on geological and technological conditions.

Environmental Concerns Associated with Uranium Mining

1. Uranium mining and processing require careful environmental management because of the presence of uranium and its radioactive decay products.
2. Major concerns include:
   • Groundwater contamination: Potential movement of uranium and other contaminants into water systems.
   • Radon exposure: Release of radioactive radon gas from uranium-bearing rocks and mine workings.
   • Tailings management: Safe containment of processed mineral residues.
   • Dust generation: Possible inhalation of radioactive and non-radioactive particles.
   • Occupational exposure: Radiation and other industrial hazards affecting workers.
   • Land degradation: Physical disturbance associated with mining and waste storage.
3. Radon-222 is an important radioactive gas associated with the uranium-238 decay series.
4. Environmental impacts depend on ore properties, mining practices, hydrology, waste management and exposure pathways.
5. Effective protection requires radiological monitoring, groundwater assessment, engineered waste containment, worker protection and rehabilitation of affected sites.

Thorium

1. Thorium (Th) is a naturally occurring radioactive metallic element with atomic number 90.
2. Its principal naturally occurring isotope is Thorium-232 (Th-232).
3. Thorium-232 is a fertile isotope, not a fissile isotope.
4. It cannot ordinarily sustain a thermal-neutron chain reaction by itself.
5. Through neutron absorption and subsequent radioactive transformations, it can be converted into Uranium-233, which is fissile.

   ²³²₉₀Th + ¹₀n → ²³³₉₀Th

   ²³³₉₀Th → β⁻ → ²³³₉₁Pa → β⁻ → ²³³₉₂U

6. The uranium-233 produced may subsequently be used as nuclear fuel.
7. A thorium-based fuel cycle requires an initial fissile material, such as U-233, U-235 or plutonium, to support the necessary neutron economy.

Distribution of Thorium in India

1. India possesses substantial thorium-bearing mineral resources, especially in coastal placer deposits.
2. The most important thorium-bearing mineral is Monazite, a phosphate mineral containing rare-earth elements and thorium.
3. Other minerals associated with thorium include Thorite and Thorianite.
4. Thorium-bearing deposits are particularly associated with heavy-mineral sands along parts of the Indian coastline.

5. Thorium occurs in mineral deposits rather than as readily usable nuclear fuel.
6. Extraction, processing, fuel fabrication and reactor utilisation require specialised technologies.
7. Large thorium resources therefore represent long-term nuclear fuel potential, not immediately available commercial generating capacity.

Uranium and Thorium: Major Differences

Potential Advantages of Thorium-Based Fuel Cycles

1. Resource Availability
   • Thorium is relatively abundant in Earth’s crust.
   • India’s thorium-bearing mineral resources provide a basis for long-term fuel diversification.
2. Breeding of U-233
   • Thorium-232 can produce fissile uranium-233 through neutron absorption and radioactive transformations.
   • This allows a potential route to using fertile resources for electricity generation.
3. Fuel Utilisation
   • Some thorium fuel-cycle designs offer the potential for efficient utilisation of fertile nuclear material.
   • Actual benefits depend on the reactor type, neutron economy and fuel-processing arrangements.
4. Waste Characteristics
   • Certain thorium cycles may reduce the production of selected long-lived transuranic elements.
   • However, they still produce radioactive fission products and other materials requiring safe management.
5. Reactor Flexibility
   • Thorium may be considered in several reactor concepts, including heavy-water reactors, molten-salt reactors and certain advanced systems.
6. Long-Term Energy Security
   • Thorium-based technologies could diversify India’s nuclear fuel options and reduce reliance on conventional uranium resources.

Challenges in Thorium Utilisation

1. Thorium is not directly fissile, making a driver fuel necessary.
2. Recovery and processing of uranium-233 can involve substantial radiological and engineering challenges.
3. Uranium-232 contamination, arising through certain nuclear reactions, creates intense gamma-radiation protection requirements because of its decay products.
4. Development of suitable reactor designs requires substantial research and capital investment.
5. Fuel fabrication, irradiation testing and reprocessing remain complex.
6. Thorium reactors are not automatically safer or more economical than uranium reactors; their performance depends on detailed engineering design and operating conditions.

Applications of Thorium

1. Nuclear Technology: Fertile material for potential advanced reactor fuel cycles.
2. High-Temperature Ceramics: Thorium dioxide has a very high melting point.
3. Materials Research: Thorium-containing compounds have specialised chemical and material properties.
4. Historical Industrial Applications: Thorium compounds were used in certain gas mantles, welding electrodes, optical materials and specialised alloys.
5. Radiation Detection and Research: Thorium-related materials and decay products may be relevant to scientific investigations.
6. Many older commercial applications have been restricted, replaced or reduced because of radiological safety and availability of safer alternatives.

Nuclear Reactors

1. A Nuclear Reactor is a device designed to initiate, maintain and control nuclear chain reactions under carefully regulated conditions.
2. In most commercial nuclear power stations, reactors generate heat through controlled nuclear fission.
3. The heat is used to produce steam, which drives a turbine connected to an electrical generator.
4. Nuclear reactors are used for:
   • Electricity generation.
   • Scientific research.
   • Radioisotope production.
   • Neutron irradiation and material testing.
   • Naval propulsion, in certain countries.
   • Development and evaluation of advanced nuclear technologies.

Working of a Nuclear Power Reactor

A typical nuclear electricity-generating system operates through the following stages:

1. Nuclear Fission: Fissile nuclei undergo controlled fission inside the reactor core.
2. Heat Production: Energy released through fission heats the fuel and surrounding coolant.
3. Heat Transfer: The coolant transports thermal energy away from the reactor core.
4. Steam Generation: Heat produces steam, either directly in the reactor system or through a separate steam generator.
5. Turbine Operation: High-pressure steam rotates a turbine.
6. Electricity Generation: The turbine drives an electrical generator.
7. Steam Condensation: Exhaust steam is condensed into water.
8. Water Recirculation: The water returns to the steam-generation system.

Energy conversion sequence: Nuclear Energy → Thermal Energy → Mechanical Energy → Electrical Energy

Major Components of a Nuclear Reactor

Moderator

1. A Moderator is a material used in thermal nuclear reactors to reduce the kinetic energy of fast neutrons.
2. Slow or thermal neutrons have a greater probability of inducing fission in certain fissile isotopes, particularly U-235.
3. Important moderators include:
   • Ordinary Water (H₂O).
   • Heavy Water (D₂O).
   • Graphite.
4. A moderator must possess suitable neutron-scattering and neutron-absorption characteristics.
5. Fast Reactors generally operate without a neutron moderator because they use a fast-neutron spectrum.

Control Rods

1. Control Rods contain materials capable of absorbing neutrons.
2. Their main function is to regulate reactor reactivity and the neutron population.
3. Important neutron-absorbing materials include:
   • Boron.
   • Cadmium.
   • Hafnium.
   • Selected alloys containing suitable neutron absorbers.
4. Inserting control rods into the reactor core generally increases neutron absorption and reduces reactivity.
5. Withdrawing control rods may increase reactivity under suitable conditions.
6. Control rods form part of the reactor’s operating and shutdown systems.
7. They work alongside other reactivity-control mechanisms, such as soluble neutron absorbers and changes in reactor temperature.

Coolant

1. A Reactor Coolant transfers heat generated in the core to another part of the reactor system.
2. The coolant must have appropriate thermal and chemical properties for the reactor design.
3. Common or proposed reactor coolants include:
   • Ordinary water.
   • Heavy water.
   • Liquid sodium.
   • Gas, including helium or carbon dioxide.
   • Molten salts.
   • Other liquid metals.
4. The coolant and moderator may be the same substance in some reactors but perform distinct physical functions.
5. For example, heavy water can serve as both the moderator and coolant in particular PHWR designs, although the circuits may be separate.

Major Types of Nuclear Reactors

India’s Reactor Programme

Pressurised Heavy Water Reactor (PHWR)

1. A Pressurised Heavy Water Reactor uses heavy water, or deuterium oxide (D₂O), as a moderator.
2. Indian PHWR designs also use heavy water as the primary coolant.
3. An important advantage of heavy water is its relatively low neutron absorption.
4. This enables PHWRs to operate with natural uranium fuel, without requiring uranium enrichment.
5. PHWRs commonly employ pressure tubes containing fuel bundles rather than the large pressure vessel arrangement used in many PWRs.

Working Principle

1. 1. Uranium fuel undergoes fission.
   2. The primary heavy-water coolant absorbs heat from the fuel.
   3. The heated primary coolant transfers energy to a secondary circuit through steam generators.
   4. Steam drives turbines connected to generators.
   5. The secondary steam is condensed and recirculated.

Advantages and Limitations of PHWRs

Advantages

1. 1. Can utilise natural uranium without enrichment.
   2. Provides favourable neutron economy.
   3. Pressure-tube designs permit refuelling during operation in suitable configurations.
   4. Supports indigenous nuclear fuel-cycle capabilities.
   5. Can be adapted to different fuel-management strategies.

Limitations

1. 1. Heavy water is expensive to produce and requires specialised handling.
   2. Pressure tubes and associated systems require careful inspection and ageing management.
   3. Reactor construction and operation demand sophisticated safety systems.
   4. Spent fuel requires secure management and appropriate safeguards.

Pressurised Water Reactor (PWR)

1. A Pressurised Water Reactor is a type of light-water reactor.
2. It uses ordinary water as both the coolant and moderator.
3. The primary coolant is maintained at high pressure to prevent bulk boiling inside the reactor core.
4. Heat is transferred to a separate secondary circuit through steam generators.
5. PWRs typically use enriched uranium fuel.
6. India’s Kudankulam Nuclear Power Plant uses Russian-designed VVER-type pressurised water reactors.

Boiling Water Reactor (BWR)

1. A Boiling Water Reactor uses ordinary water as both the coolant and moderator.
2. Unlike a PWR, water boils inside the reactor vessel under controlled conditions.
3. Steam from the reactor system is used to drive a turbine.
4. The Tarapur Atomic Power Station Units 1 and 2 use boiling water reactors.
5. These were among India’s earliest commercial nuclear power reactors.

Breeder Reactors

1. A Breeder Reactor is designed to produce fissile material from fertile material.
2. Breeding occurs when neutron absorption converts fertile isotopes into fissile isotopes.
3. Important breeding pathways include:
   • U-238 → Pu-239.
   • Th-232 → U-233.
4. A breeder reactor can achieve a breeding ratio greater than 1, meaning it produces more fissile material than it consumes under the relevant accounting convention.
5. Not every fast reactor is necessarily a breeder reactor; its breeding performance depends on the core design and fuel cycle.

Fast Breeder Reactor (FBR)

1. A Fast Breeder Reactor uses fast neutrons rather than relying on a thermal-neutron spectrum.
2. It generally does not require a neutron moderator.
3. Fast reactors can utilise plutonium-bearing fuel and convert fertile material into additional fissile material.
4. Liquid sodium is commonly used as a coolant in several fast reactor designs because of its favourable thermal characteristics and limited neutron moderation.
5. FBR technology is important for India’s strategy of improving nuclear fuel utilisation.

Advantages

• • Potential to improve the utilisation of uranium resources.
  • Can support a closed nuclear fuel cycle.
  • Can produce additional fissile material.
  • Supports advanced fuel-cycle research and technological development.

Challenges

• • Complex reactor engineering.
  • High initial capital requirements.
  • Liquid-metal coolant safety considerations.
  • Sophisticated fuel fabrication and reprocessing.
  • Nuclear safeguards and proliferation-related concerns.

Prototype Fast Breeder Reactor (PFBR), Kalpakkam

1. The Prototype Fast Breeder Reactor (PFBR) is an indigenous 500 MWe sodium-cooled fast reactor at Kalpakkam, Tamil Nadu.
2. It is being implemented by Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI).
3. The reactor technology was developed principally through the research and development work of Indira Gandhi Centre for Atomic Research (IGCAR).
4. It uses uranium–plutonium mixed-oxide (MOX) fuel.
5. Its breeding arrangements enable the conversion of fertile material into fissile material.

Major Development in 2026

1. The PFBR achieved first criticality on 6 April 2026.
2. First criticality means that the reactor achieved a self-sustaining controlled nuclear chain reaction.
3. This milestone marked India’s entry into the second stage of its three-stage nuclear power programme.
4. First criticality must not be confused with commercial electricity generation or full-power operation.
5. The achievement represents a significant step towards advanced fuel-cycle technologies and eventual large-scale thorium utilisation.

Advanced Heavy Water Reactor (AHWR)

1. The Advanced Heavy Water Reactor (AHWR) is an Indian reactor concept developed with the objective of demonstrating greater thorium utilisation.
2. The BARC-developed design incorporates:
   • Heavy-water moderation.
   • Light-water cooling.
   • Thorium-based fuel-cycle options.
   • Selected passive safety features.
3. An important goal is to facilitate the use of thorium alongside suitable fissile materials.
4. Some proposed safety features employ natural circulation and passive heat-removal mechanisms.
5. AHWR remains associated with research and development rather than a fleet of operational commercial power reactors.

Small Modular Reactors (SMRs)

1. Small Modular Reactors are nuclear reactor designs generally having an electrical capacity of up to 300 MWe per module, according to the commonly used IAEA classification.
2. Their designs may allow factory fabrication of major components and modular installation.
3. Potential applications include:
   • Electricity generation for industrial facilities.
   • Replacement of selected fossil-fuel-based generating capacity.
   • Remote-grid applications.
   • Process heat for industries.
   • Integration with other low-carbon energy systems.
4. Potential advantages include flexibility in deployment, smaller individual unit size and certain design-dependent safety features.
5. Challenges include regulatory approval, cost competitiveness, fuel availability, waste management and achieving commercial-scale manufacturing.

Indian Initiatives

1. India has announced the development of indigenous SMR technologies, including the:
   • Bharat Small Modular Reactor (BSMR-200).
   • SMR-55, a proposed 55 MWe reactor.
2. The Union Budget 2025–26 announced a Nuclear Energy Mission supporting research and development in SMR technologies.
3. The mission envisages operationalising at least five indigenously developed SMRs by 2033.
4. These are development targets, not evidence that the proposed designs are already operating commercially.

Nuclear Power in India: Development

1. India’s nuclear energy programme emerged during the early post-independence period.
2. Homi Jehangir Bhabha played a foundational role in establishing India’s nuclear research institutions and long-term nuclear power strategy.
3. The Atomic Energy Commission (AEC) was established in 1948.
4. The Department of Atomic Energy (DAE) was established on 3 August 1954, under the direct charge of the Prime Minister.
5. The first commercial nuclear electricity generation in India began at the Tarapur Atomic Power Station in 1969.
6. India progressively developed capabilities in:
   • Reactor design.
   • Uranium mining.
   • Nuclear fuel fabrication.
   • Heavy-water production.
   • Nuclear power generation.
   • Reprocessing.
   • Waste management.
   • Fast reactor development.

Major Nuclear Power Stations in India

Important Nuclear Power Plants

1. Tarapur Atomic Power Station

1. 1. Located in Maharashtra.
   2. Began commercial nuclear electricity generation in 1969.
   3. Its first two units use Boiling Water Reactor (BWR) technology.
   4. Subsequent units use PHWR technology.

2. Rajasthan Atomic Power Station

1. 1. Located at Rawatbhata, Rajasthan.
   2. One of India’s most important PHWR complexes.
   3. Includes multiple reactor units developed over different periods.
   4. Represents a major centre for the expansion of indigenous PHWR capabilities.

3. Kakrapar Atomic Power Station

1. 1. Located in Gujarat.
   2. The complex includes 220 MWe and 700 MWe PHWR units.
   3. KAPS-3 and KAPS-4 are significant milestones in India’s indigenous 700 MWe PHWR development.
   4. Their deployment demonstrates progress towards larger standardised domestic reactors.

4. Kudankulam Nuclear Power Plant

1. 1. Located in Tirunelveli district, Tamil Nadu.
   2. Developed through India–Russia nuclear cooperation.
   3. Uses VVER pressurised water reactor technology.
   4. Units 1 and 2 have generating capacities of 1,000 MWe each.
   5. Additional units are under construction.

Proposed Jaitapur Nuclear Power Project

1. The Jaitapur Nuclear Power Project is proposed in Ratnagiri district, Maharashtra.
2. It is associated with nuclear cooperation between India and France.
3. The proposed configuration involves six European Pressurised Reactors (EPRs).
4. Each unit is designed for approximately 1,650 MWe.
5. Total proposed capacity:

   6 × 1,650 = 9,900 MWe

6. The project remains subject to commercial, technical, regulatory and implementation processes.
7. It should not be described as an operational nuclear power station.

Proposed and Expanding Nuclear Power Projects

Present Nuclear Power Capacity in India

Installed nuclear capacity: 8,780 MW (Gross capacity)

Operational reactors: 24 

1. India has 24 operational commercial nuclear power reactors, with a combined gross installed capacity of approximately 8,780 MW.
2. It excludes Rajasthan Atomic Power Station Unit 1 (RAPS-1), which has been under long shutdown.
3. Nuclear electricity contributed approximately 3.1% of India’s total electricity generation during FY 2025–26.
4. The government’s announced objective is to reach 100 GW of nuclear power capacity by 2047.
5. The current expansion roadmap envisages approximately 22 GW by 2031–32, depending on the timely completion of projects under implementation.
6. Future capacity projections are targets rather than assured generating capacity.

Advantages of Nuclear Power for India

1. Low-Carbon Electricity: Nuclear power has relatively low lifecycle greenhouse-gas emissions.
2. Reliable Generation: Nuclear plants can deliver continuous electricity with high capacity factors.
3. High Energy Density: Small quantities of nuclear fuel can release large amounts of energy.
4. Energy Diversification: Nuclear energy can reduce dependence on fossil fuels.
5. Grid Stability: Nuclear power can complement variable renewable-energy sources.
6. Technological Development: The nuclear programme supports advanced manufacturing and scientific research.
7. Strategic Capability: Indigenous reactor and fuel-cycle technologies improve long-term energy resilience.

Challenges of Nuclear Power in India

1. High initial capital and financing requirements.
2. Long construction and commissioning periods.
3. Availability of economically recoverable uranium.
4. Management of radioactive waste and spent fuel.
5. Public concern regarding radiation and nuclear accidents.
6. Land acquisition and environmental clearance challenges.
7. Complex regulatory and safety requirements.
8. Dependence on specialised equipment and components.
9. Need for emergency preparedness and long-term decommissioning planning.

India’s Three-Stage Nuclear Power Programme

1. India’s Three-Stage Nuclear Power Programme was conceptualised under the leadership of Dr. Homi Jehangir Bhabha during the 1950s.
2. The strategy was designed to maximise the utilisation of India’s domestic nuclear fuel resources.
3. It reflects two important characteristics of India’s resource base:
   • Relatively limited economically available uranium resources compared with long-term nuclear ambitions.
   • Substantial thorium-bearing mineral resources.
4. The programme seeks to develop nuclear energy through a closed fuel cycle, with the recovery and reuse of fissile materials.
5. Its three stages are:
   • Stage I – Natural Uranium-Based PHWRs.
   • Stage II – Plutonium-Based Fast Breeder Reactors.
   • Stage III – Thorium-Based Nuclear Reactors.

First Stage: Natural Uranium-Based PHWRs

1. The first stage uses natural uranium as fuel in Pressurised Heavy Water Reactors.
2. U-235 undergoes fission and generates electricity.
3. During reactor operation, some U-238 absorbs neutrons and is converted into Pu-239.
4. The plutonium present in spent fuel can be recovered through reprocessing.
5. The recovered fissile material provides an important resource for the second stage.
6. India’s indigenous PHWR programme has established substantial experience in reactor design, construction, operation and associated fuel-cycle activities.

Fuel Transformation :

²³⁸₉₂U + ¹₀n → ²³⁹₉₂U → β⁻ → ²³⁹₉₃Np → β⁻ → ²³⁹₉₄Pu

Second Stage: Plutonium-Based Fast Breeder Reactors

1. The second stage uses plutonium recovered from spent uranium fuel as an important fissile component.
2. Fast Breeder Reactors operate using a fast-neutron spectrum.
3. U-238 can be converted into additional Pu-239 through neutron absorption.
4. Under suitable fuel configurations, breeder reactors may produce more fissile material than they consume.
5. Breeding arrangements may also support the production of U-233 from thorium.
6. The 500 MWe PFBR at Kalpakkam is a major project under this stage.
7. Its achievement of first criticality on 6 April 2026 marked an important technological milestone.

Third Stage: Thorium-Based Reactors

1. The third stage seeks large-scale utilisation of Thorium-232.
2. Thorium-232 is fertile and must be converted into fissile uranium-233.
3. U-233 can undergo fission and release energy.
4. The objective is to develop a sustainable nuclear fuel cycle capable of utilising India’s thorium-bearing resources.
5. Important reactor concepts include:
   • Advanced Heavy Water Reactors.
   • Other thorium-compatible reactor designs.
   • Selected breeder and advanced reactor systems.
6. Successful implementation requires:
   • Adequate fissile material.
   • Advanced reactor technologies.
   • Appropriate fuel fabrication.
   • Efficient neutron utilisation.
   • Safe reprocessing and recycling.
   • Commercial and regulatory viability.
7. The third stage remains a long-term technological objective, not an established large-scale commercial power-generation system.

Comparison of India’s Three Nuclear Stages

Importance of the Three-Stage Programme

1. Long-Term Fuel Security: Seeks to reduce constraints arising from limited domestic uranium resources.
2. Thorium Utilisation: Provides a technological pathway for using India’s substantial thorium-bearing resources.
3. Indigenous Development: Encourages domestic expertise in fuel fabrication, reprocessing and advanced reactors.
4. Fuel Efficiency: Aims to make more effective use of fertile nuclear materials.
5. Energy Diversification: Contributes to long-term low-carbon energy planning.
6. Strategic Research: Supports sophisticated research in nuclear physics, engineering and materials science.

Nuclear Fusion Research

1. Controlled Nuclear Fusion seeks to generate useful energy from fusion reactions within a deliberately confined and regulated system.
2. Unlike stellar fusion, terrestrial reactors must reproduce the required physical conditions using advanced technological systems.
3. One of the principal challenges is maintaining a sufficiently hot and dense plasma for adequate confinement time.
4. Fusion research examines the possibility of using light isotopes, especially deuterium and tritium, as fuels.
5. Major fusion confinement approaches include:
   • Magnetic Confinement Fusion.
   • Inertial Confinement Fusion.

Plasma

1. Plasma is a state of matter containing charged particles, including ions and electrons.
2. It can respond strongly to electric and magnetic fields.
3. Fusion plasmas contain nuclei and electrons at extremely high temperatures.
4. Magnetic confinement systems use magnetic fields to restrict the movement of charged particles and reduce contact with material walls.

International Thermonuclear Experimental Reactor (ITER)

1. ITER is a major international experimental nuclear fusion project.
2. It is located at Cadarache, Saint-Paul-lez-Durance, France.
3. ITER uses a Tokamak design.
4. Its principal objective is to demonstrate the scientific and technological feasibility of large-scale controlled magnetic-confinement fusion.
5. ITER is an experimental fusion device, not a commercial nuclear power station.
6. Its planned deuterium–tritium experiments aim to achieve a fusion gain factor of:

   Q = P_fusion / P_{external heating} = 10

7. This means producing 500 MW of fusion power from 50 MW of external plasma-heating power under the designed operating conditions.
8. A plasma gain factor of 10 does not mean that ITER will deliver net electricity to the power grid.

International Participation in ITER

ITER involves seven members:

1. 1. European Union.
   2. India.
   3. China.
   4. Japan.
   5. Republic of Korea.
   6. Russia.
   7. United States.

The European Union participates as the host member, while the other members supply major components, expertise and project contributions.

Important Components of ITER

Major Challenges in Controlled Fusion

1. Extremely High Temperature: Fusion plasmas must reach temperatures of around 150 million°C for ITER’s intended operating conditions.
2. Plasma Stability: Magnetic fields must control instabilities that can disrupt confinement.
3. Material Durability: Reactor components must withstand heat, radiation and energetic neutron bombardment.
4. Tritium Management: Tritium is radioactive and requires carefully controlled handling.
5. Neutron Damage: High-energy fusion neutrons can damage structural materials.
6. Tritium Breeding: Future commercial D–T fusion systems need reliable methods of producing tritium from lithium.
7. Energy Conversion: Useful fusion energy must be converted into electricity efficiently.
8. Economic Viability: Future power plants must demonstrate acceptable construction, operation and maintenance costs.

ITER Development Timeline

1. ITER’s earlier reference schedule envisaged major experimental milestones sooner than is now planned.
2. Technical challenges, component repairs and project complexity required a revised programme.
3. Under the updated ITER baseline:
   • 2034: Planned start of research operations.
   • 2036: Planned achievement of full magnetic energy.
   • 2039: Planned beginning of deuterium–tritium operations.

India’s Contributions to ITER

1. India participates through ITER-India, with major involvement from the Institute for Plasma Research (IPR).
2. Indian participation involves:
   • Development and manufacturing of assigned components.
   • Cryogenic and vacuum-related technologies.
   • Superconducting magnet-related systems.
   • Power supplies and specialised equipment.
   • Plasma diagnostics.
   • Engineering design and technological support.
3. Indian industries have contributed to the manufacturing of sophisticated ITER components.
4. Participation supports the transfer of expertise to Indian scientific institutions and industries.
5. ITER provides opportunities for Indian researchers and engineers to work on advanced international fusion technologies.

Nuclear Fusion Research in India

Institute for Plasma Research (IPR)

1. The Institute for Plasma Research (IPR) is an autonomous research institution under the Department of Atomic Energy.
2. It is located at Bhat, Gandhinagar, Gujarat.
3. Its major research areas include:
   • Plasma physics.
   • Magnetic confinement fusion.
   • Tokamak technology.
   • Plasma diagnostics.
   • Advanced materials.
   • Plasma-processing technologies.
   • Fusion engineering.
4. IPR is an important Indian institution for experimental fusion research and advanced plasma science.
5. It contributes to India’s international fusion collaborations, including ITER.

ADITYA Tokamak

1. ADITYA was India’s early experimental tokamak programme.
2. It was developed at IPR to investigate plasma behaviour and magnetic confinement.
3. The programme contributed to the development of experimental expertise in:
   • Plasma generation.
   • Magnetic-field control.
   • Plasma diagnostics.
   • Vacuum technology.
   • Fusion-device operation.
4. Its successor and upgraded configurations have supported further research and technology development.

Steady State Superconducting Tokamak (SST-1)

1. SST-1 stands for Steady State Superconducting Tokamak-1.
2. It is an experimental fusion device developed by IPR.
3. It uses superconducting magnets for plasma confinement.
4. Its main objectives include:
   • Investigating long-duration plasma operation.
   • Studying plasma stability.
   • Developing superconducting magnet technologies.
   • Evaluating plasma-heating and control systems.
   • Strengthening the technological basis for advanced fusion reactors.
5. SST-1 contributes to India’s capabilities in superconductivity, cryogenic engineering and plasma research.

Tritium Technology

1. Tritium (³H) is a radioactive isotope of hydrogen.
2. It contains:
   • One proton.
   • Two neutrons.
3. Its half-life is approximately 12.32 years.
4. Tritium is important in experimental deuterium–tritium fusion systems.
5. Technologies associated with tritium involve:
   • Safe storage.
   • Fuel processing.
   • Purification.
   • Monitoring.
   • Containment.
   • Recovery and recycling.
   • Radiation protection.
6. Future fusion plants may require tritium-breeding blankets using lithium-containing materials.

Other Approaches to Fusion Research

1. Magnetic Confinement Fusion: Uses magnetic fields to confine hot plasma.
2. Inertial Confinement Fusion: Compresses small fuel targets for extremely short periods, often using powerful lasers.
3. Alternative Magnetic Configurations: Includes stellarators and other magnetic-confinement designs.
4. Advanced Materials Research: Investigates components capable of operating in high-temperature and radiation-intensive environments.
5. Fusion Diagnostics: Develops methods for measuring plasma parameters and understanding instabilities.

Significance of India’s Fusion Research

1. Strengthens fundamental research in plasma physics.
2. Develops expertise in advanced superconducting and cryogenic technologies.
3. Encourages collaboration between research institutions and industries.
4. Supports international scientific partnerships.
5. Creates opportunities for specialised human-resource development.
6. Contributes to the long-term search for commercially viable low-carbon energy technologies.

Radioactivity & Radioactive Elements

1. Radioactivity is the spontaneous transformation of an unstable atomic nucleus into a different nuclear state or another nucleus, accompanied by the emission of particles, electromagnetic radiation or both.
2. This process occurs because certain nuclei possess unstable arrangements of protons and neutrons or exist in unstable excited states.
3. The original radioactive nucleus is called the Parent Nucleus, while the nucleus formed after decay is called the Daughter Nucleus.
4. Radioactive decay may involve the emission of:
   • Alpha particles.
   • Beta particles.
   • Gamma radiation.
   • Other particles or radiation, depending on the decay process.
5. A particular radioactive nucleus decays probabilistically; the exact moment of its decay cannot generally be predicted.
6. The decay rate of a large population of nuclei follows well-defined statistical laws.
7. Radioactivity is a nuclear phenomenon and is not normally altered by ordinary changes in temperature, pressure or chemical state.

Discovery of Radioactivity

1. Henri Becquerel discovered natural radioactivity in 1896 while investigating uranium compounds.
2. He observed that uranium-containing materials could affect photographic plates without exposure to sunlight.
3. Marie Curie and Pierre Curie subsequently made major contributions to the understanding of radioactive substances.
4. Marie Curie introduced the term Radioactivity.
5. Marie and Pierre Curie discovered polonium and radium in 1898.
6. Ernest Rutherford made important contributions to identifying and explaining alpha and beta radiation.
7. The study of radioactivity contributed to the development of nuclear physics, atomic theory and modern radiation technologies.

Radioactive Elements and Isotopes

1. A Radioactive Isotope, or Radioisotope, is an isotope whose nucleus is unstable and undergoes radioactive decay.
2. Isotopes of an element possess the same atomic number but different neutron numbers.
3. Some elements possess both stable and radioactive isotopes.
4. Other elements, including uranium and thorium, have no stable isotopes.

Radioactive Decay Series

1. Certain radioactive isotopes transform through a succession of daughter nuclei before reaching a stable end product.
2. Such sequences are called Radioactive Decay Series.
3. The major naturally occurring decay series include:

4. These decay series involve multiple alpha and beta decay processes.
5. Radioactive daughter products may have different chemical properties and environmental behaviours from their parent isotopes.

Radioactive Decay and Radiation

Alpha Decay

1. Alpha Decay involves the emission of an alpha particle from an unstable nucleus.
2. An alpha particle consists of:
   • Two protons.
   • Two neutrons.
3. It is equivalent to a helium-4 nucleus.
4. During alpha decay:
   • The mass number decreases by 4.
   • The atomic number decreases by 2.

    Example : ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

5. Alpha particles are relatively massive and carry a positive electric charge.
6. They have strong ionising ability but limited penetration through matter.
7. A sheet of paper or the outer dead layer of skin can stop many alpha particles.
8. However, alpha-emitting materials can be especially hazardous if inhaled or ingested because radiation is then deposited within living tissues.

Beta Decay

Beta-Minus Decay (β⁻)

1. Beta-Minus Decay occurs when a neutron transforms into a proton, emitting an electron and an electron antineutrino.
2. The atomic number increases by one, while the mass number remains unchanged.

    n → p + e⁻ + ν̅_e

Example  : ¹⁴₆C → ¹⁴₇N + e⁻ + ν̅_e

Beta-Plus Decay (β⁺)

1. Beta-Plus Decay, or Positron Emission, occurs when a proton transforms into a neutron while emitting a positron and an electron neutrino.
2. The atomic number decreases by one, while the mass number remains unchanged.

p → n + e⁺ + ν_e

3. Beta radiation is generally more penetrating than alpha radiation but less penetrating than high-energy gamma radiation.
4. Suitable shielding may include plastic or aluminium, with shielding design depending on particle energy.

Gamma Decay

1. Gamma Radiation consists of high-energy electromagnetic photons emitted during certain nuclear transitions.
2. Gamma emission commonly occurs when an excited nucleus releases excess energy.
3. Unlike alpha and beta decay, gamma emission does not ordinarily change the nucleus’s atomic number or mass number.
4. Gamma rays:
   • Possess no electric charge.
   • Have no rest mass.
   • Travel at the speed of light in a vacuum.
   • Can penetrate substantial thicknesses of matter, depending on photon energy.
5. Gamma radiation is attenuated using suitable shielding materials such as lead, concrete or steel.

Comparison of Alpha, Beta and Gamma Radiation

Other Important Nuclear Radiation

1. Neutron Radiation
   • Consists of free neutrons.
   • Has no electric charge.
   • Can penetrate materials and induce nuclear reactions.
   • Requires shielding materials selected for neutron moderation and absorption.
2. X-Rays
   • High-energy electromagnetic radiation.
   • Usually associated with electronic processes or the deceleration of charged particles.
   • Used extensively in medical imaging and industrial testing.
3. Proton and Heavy-Ion Radiation
   • Consists of energetic charged particles.
   • Used in scientific research and selected radiation-therapy technologies.
4. Cosmic Radiation
   • Includes high-energy particles originating from extraterrestrial sources.
   • Produces secondary radiation when interacting with Earth’s atmosphere.

Ionising and Non-Ionising Radiation

1. Radiation is broadly classified according to its ability to remove electrons from atoms or molecules.

Ionising Radiation

• • Possesses sufficient energy to ionise matter.
  • Includes alpha particles, beta particles, gamma rays, X-rays and energetic neutrons through their interactions with matter.
  • May cause changes in biological molecules and cellular structures.

Non-Ionising Radiation

• • Does not normally possess sufficient photon energy to ionise atoms or molecules directly.
  • Includes radio waves, microwaves, infrared radiation and visible light.
  • Much ultraviolet radiation is conventionally classified as non-ionising, although sufficiently energetic ultraviolet photons can cause ionisation.

2. Non-ionising radiation is not necessarily harmless at all exposure levels.
3. High-intensity microwave, infrared, visible or ultraviolet radiation may cause biological effects through heating, photochemical reactions or other mechanisms.
4. Exposure risk depends on the radiation type, intensity, duration and affected tissue.

Radioactive Decay Law and Half-Life 

Radioactive Decay Law

1. Radioactive Decay Law describes the statistical reduction in the number of undecayed radioactive nuclei over time.
2. The number of nuclei remaining after a given period is expressed as:

   N(t) = N₀e^−λt

   Where:

   • N(t) = Number of undecayed radioactive nuclei at time t.
   • N₀ = Initial number of radioactive nuclei.
   • λ = Decay constant.
   • t = Elapsed time.
3. The equation describes exponential radioactive decay.
4. The same law can be applied to radioactive activity when no additional source of the radionuclide is present.

Decay Constant

1. The Decay Constant (λ) represents the probability of decay per unit time for an individual radioactive nucleus.
2. A higher decay constant corresponds to faster decay.
3. The decay constant is characteristic of the radionuclide and its nuclear state.

Half-Life

1. Half-Life (T_1/2) is the time required for the expected number of undecayed nuclei in a sufficiently large sample to decrease to half its initial value.
2. It is related to the decay constant by:

   T_1/2 = ln(2) / λ

   T_1/2 ≈ 0.693 / λ

3. After successive half-lives, the fraction remaining decreases exponentially.

4. Half-life is independent of the initial quantity of the radioactive substance.
5. A short half-life indicates relatively rapid decay, but does not by itself establish the overall biological or environmental danger of a radionuclide.

Mean Life

1. Mean Life (τ) is the average lifetime of radioactive nuclei before decay.
2. It is related to the decay constant by:

   τ = 1 / λ

3. Therefore:

   τ = T_1/2 / ln(2)

4. Mean life is approximately 1.443 times the half-life.

Radioactive Activity

1. Activity is the number of nuclear disintegrations occurring per unit time.
2. It is expressed as:

   A = λN

3. The SI unit of activity is the Becquerel (Bq).
4. One becquerel corresponds to one nuclear disintegration per second.
5. An older unit is the Curie (Ci):

   1 Ci = 3.7 × 10¹⁰ Bq

Units Used in Radiation Measurement

1. 1 Gray = 1 joule of absorbed radiation energy per kilogram.
2. The Sievert is used in radiation protection to express quantities incorporating biological-effect weighting factors.
3. The same absorbed dose may have different biological implications depending on the radiation type and affected tissue.
4. Activity, absorbed dose and effective dose measure different physical quantities and must not be used interchangeably.

Natural Background Radiation

1. Human beings are continuously exposed to small amounts of natural radiation.
2. Important sources include:
   • Cosmic radiation.
   • Terrestrial radionuclides.
   • Radon gas.
   • Naturally occurring radioactive isotopes within the human body.
3. Natural background radiation varies with geology, altitude, building materials and other environmental factors.
4. A commonly quoted global average natural background exposure is approximately 2.4 mSv per year, although actual values vary substantially.
5. Radiation exposure must be assessed by considering its source, magnitude, duration and biological context.

Applications of Radiation Technology

Medical Applications

1. Radioisotopes are used in medical imaging, diagnosis and treatment.
2. Their applications include:
   • Positron Emission Tomography (PET).
   • Single Photon Emission Computed Tomography (SPECT).
   • Thyroid diagnosis and therapy.
   • Radiopharmaceutical treatment.
   • Selected cancer therapies.
3. Medical applications require controlled activity levels, suitable radiopharmaceuticals and radiation-protection procedures.
4. Diagnostic nuclear medicine often uses small quantities of radiotracers to investigate biological function.

Industrial Applications

1. Non-Destructive Testing (NDT)

• • Radiation can be used to inspect materials without destroying the object being tested.
  • Industrial radiography helps identify defects in welds, castings and structural components.
  • Common industrial radiation sources include X-ray equipment and suitable gamma-emitting radionuclides.

2. Thickness Measurement

• • Radiation gauges are used to measure thickness or density in selected industrial processes.
  • Applications include paper, plastics, sheets and other manufactured products.

3. Process Monitoring

• • Radioactive tracers may be used to investigate:
    • Fluid movement.
    • Leakage.
    • Mixing.
    • Industrial flow systems.

4. Sterilisation

• • Gamma radiation, electron beams and certain X-ray systems are used to sterilise medical equipment and selected industrial products.

5. Material Modification

• • Radiation can alter the properties of polymers and other materials.
  • Applications include cross-linking, modification of material characteristics and specialised manufacturing.

Agricultural Applications

1. Mutation Breeding

1. 1. Radiation can induce genetic changes in plants.
   2. Researchers may select useful variations for crop improvement.
   3. Mutation breeding has contributed to the development of crop varieties with desirable characteristics.
   4. Radiation-induced mutations are generally random and require extensive selection and testing.

2. Sterile Insect Technique (SIT)

1. 1. The Sterile Insect Technique involves mass-rearing selected pest insects, sterilising them and releasing them into the environment.
   2. Sterile insects may mate with wild insects, reducing successful reproduction.
   3. SIT can contribute to integrated pest-management programmes.
   4. Its success depends on species biology, population management and field implementation.

3. Food Irradiation

1. 1. Food Irradiation involves exposing food to controlled doses of ionising radiation.
   2. It may be used to:
      • Reduce microorganisms.
      • Control certain insect pests.
      • Delay sprouting.
      • Extend shelf life.
      • Improve food safety.
   3. Properly applied food irradiation does not make food radioactive.
   4. Its use is governed by approved processes, permitted dose ranges and food-safety regulations.

Environmental Applications

1. Radiotracers: Used to study the movement of substances through environmental systems.
2. Hydrological Research: Isotopes can help investigate groundwater movement and recharge.
3. Pollution Studies: Selected isotope techniques help trace contaminant sources and environmental processes.
4. Sediment Research: Radioisotopes can be used to study erosion, deposition and sediment transport.
5. Wastewater Treatment: Radiation technologies have been investigated for treatment and degradation of certain pollutants.

Scientific and Archaeological Applications

1. Radiometric Dating uses radioactive decay to estimate the ages of materials.
2. Different isotopic systems are suited to different time ranges and geological materials.
3. Important examples include:

4. Radiocarbon Dating is especially useful for organic materials up to approximately 50,000 years old, depending on sample quality and analytical conditions.
5. Radiometric dating assumes that the relevant isotopic system can be understood and that contamination or material loss is adequately accounted for.

Space Applications

1. Certain space missions use Radioisotope Power Systems to generate electricity or heat.
2. A Radioisotope Thermoelectric Generator (RTG) converts heat from radioactive decay into electrical energy.
3. RTGs do not operate through a controlled nuclear fission chain reaction.
4. They are particularly useful for missions where solar energy is insufficient or unreliable.
5. RTGs have been used on several deep-space probes and planetary exploration missions.
6. Other nuclear technologies under investigation include nuclear thermal propulsion and space-based fission power systems.

Summary

Nuclear Medicine

1. Nuclear Medicine is a medical specialty that uses radioactive substances, known as Radiopharmaceuticals, for the diagnosis, evaluation and treatment of diseases.
2. Unlike conventional anatomical imaging, many nuclear medicine techniques provide information about the physiological and metabolic functioning of organs and tissues.
3. Nuclear medicine uses carefully selected radioactive isotopes that emit radiation detectable by specialised instruments.
4. Radiopharmaceuticals generally consist of a radionuclide incorporated into a compound designed to reach a particular organ, tissue or biological target.
5. Nuclear medicine is widely used in:
   • Oncology.
   • Cardiology.
   • Neurology.
   • Endocrinology.
   • Bone and skeletal disorders.
   • Renal and urinary disorders.

Major Nuclear Medicine Imaging Techniques

1. Positron Emission Tomography (PET)

1. 1. PET is a functional imaging technique that detects pairs of gamma photons produced following positron annihilation.
   2. It uses positron-emitting radiopharmaceuticals.
   3. A commonly used radiotracer is Fluorine-18 Fluorodeoxyglucose (¹⁸F-FDG).
   4. FDG-PET helps visualise glucose metabolism in tissues.
   5. Important applications include:
      • Cancer detection and staging.
      • Monitoring response to treatment.
      • Investigating selected neurological disorders.
      • Assessment of certain cardiovascular conditions.

2. Single Photon Emission Computed Tomography (SPECT)

1. 1. SPECT uses radiopharmaceuticals that emit gamma photons.
   2. A gamma camera acquires observations from multiple directions.
   3. Computer processing reconstructs three-dimensional information about tracer distribution.
   4. Technetium-99m is among the most widely used radionuclides in SPECT imaging.
   5. Major applications include:
      • Myocardial perfusion imaging.
      • Bone scans.
      • Renal function studies.
      • Selected brain imaging procedures.

3. PET-CT and SPECT-CT

1. 1. PET-CT combines PET functional imaging with CT-based anatomical imaging.
   2. SPECT-CT combines SPECT functional imaging with CT.
   3. These hybrid techniques improve the anatomical localisation of radiotracer uptake.
   4. They are especially valuable in cancer diagnosis, treatment planning and selected organ-function studies.

Nuclear Medicine and Conventional Radiological Imaging

1. CT uses X-rays generated by an imaging device, whereas PET and SPECT use radiation emitted by administered radiopharmaceuticals.
2. MRI uses magnetic fields and radiofrequency signals rather than ionising radiation.
3. Not all medical imaging techniques belong to nuclear medicine.

Applications in Cancer Diagnosis and Treatment

1. Cancer Detection and Staging
   • PET imaging can identify areas of increased metabolic activity.
   • It helps determine the extent of certain cancers.
   • It can support the identification of metastatic disease.
2. Treatment Response Assessment
   • Nuclear imaging helps assess whether selected tumours are responding to therapy.
   • Changes in tracer uptake may provide information before major anatomical changes become apparent.
3. Radiopharmaceutical Therapy
   • Therapeutic radionuclides deliver ionising radiation to selected tissues.
   • Examples include:
     • Iodine-131 for certain thyroid disorders.
     • Lutetium-177 in selected targeted radionuclide therapies.
     • Other specialised radiopharmaceutical treatments.
4. The suitability of nuclear medicine varies according to disease type, diagnostic objective and clinical circumstances.

Applications in Other Medical Fields

Benefits of Nuclear Medicine

1. Early Detection: Functional changes may become detectable before obvious anatomical abnormalities.
2. Functional Assessment: Provides information about organ physiology, metabolism and biological activity.
3. Disease Staging: Helps determine the distribution of certain diseases.
4. Treatment Planning: Supports personalised therapeutic decisions.
5. Treatment Monitoring: Assists in evaluating the effectiveness of selected treatments.
6. Targeted Therapy: Certain radiopharmaceuticals deliver radiation preferentially to specific tissues.

Limitations and Risks

1. Radiation Exposure: Patients receive controlled amounts of ionising radiation.
2. Pregnancy Considerations: Certain procedures require special precautions or may be inappropriate during pregnancy.
3. Breastfeeding Precautions: Some radiopharmaceuticals require temporary restrictions or specific guidance.
4. Allergic or Adverse Reactions: Although uncommon for many radiotracers, reactions and other adverse effects are possible.
5. Limited Availability: Advanced equipment and radiopharmaceutical production may not be accessible everywhere.
6. Cost: Some nuclear medicine procedures are expensive.
7. Interpretation Limitations: Increased tracer uptake does not always indicate malignancy and must be interpreted within the clinical context.

Nuclear Accidents, Radiological Hazards and Nuclear Winter

Nuclear and Radiological Accidents

1. A Nuclear Accident involves an event at a nuclear facility or involving nuclear material that may produce radiological consequences.
2. A Radiological Accident may occur in medical, industrial, research or other settings involving radioactive sources.
3. Potential consequences include:
   • Worker or public exposure.
   • Release of radioactive substances.
   • Environmental contamination.
   • Disruption of infrastructure.
   • Long-term cleanup requirements.
4. The magnitude of consequences depends on the released radionuclides, exposure pathways, protective actions and environmental conditions.

International Nuclear and Radiological Event Scale (INES)

1. The International Nuclear and Radiological Event Scale (INES) communicates the safety significance of nuclear and radiological events.
2. It consists of seven numbered levels:
   • Levels 1–3 are classified as Incidents.
   • Levels 4–7 are classified as Accidents.
3. Events without safety significance for the scale may be classified as Below Scale / Level 0.

Major Nuclear Accidents

1. Chernobyl Nuclear Disaster (1986)

1. 1. Occurred on 26 April 1986.
   2. Location: Chernobyl Nuclear Power Plant, near Pripyat, in present-day Ukraine, then part of the Soviet Union.
   3. Classified as an INES Level 7 accident.
   4. A combination of reactor-design deficiencies and unsafe operating conditions contributed to the disaster.
   5. The accident involved a rapid increase in reactor power, explosions and a graphite fire.
   6. Large quantities of radioactive substances entered the environment.
   7. Consequences included:
      • Severe exposure of workers and emergency responders.
      • Evacuations and long-term restrictions.
      • Radioactive contamination of extensive areas.
      • Increased thyroid-cancer incidence among individuals exposed to radioactive iodine during childhood and adolescence.

2. Fukushima Daiichi Nuclear Disaster (2011)

1. 1. Occurred on 11 March 2011.
   2. Location: Fukushima Prefecture, Japan.
   3. Classified as an INES Level 7 accident.
   4. The Great East Japan Earthquake and subsequent tsunami caused severe disruption to electrical power and cooling systems.
   5. Loss of cooling contributed to core damage and meltdowns in multiple reactor units.
   6. Hydrogen explosions damaged reactor buildings.
   7. The accident resulted in radioactive releases, large-scale evacuations and extensive decommissioning requirements.

Other Important Nuclear Accidents and Incidents

Health Effects of Ionising Radiation

1. Radiation can damage biological tissues by depositing energy and causing ionisation.
2. Biological consequences depend on:
   • Radiation type.
   • Absorbed dose.
   • Dose rate.
   • Tissue sensitivity.
   • Exposure duration.
   • Whether the radioactive source is internal or external.

Deterministic or Tissue-Reaction Effects

1. These effects generally occur above a dose threshold.
2. Their severity tends to increase with dose.
3. Examples include:
   • Skin injury.
   • Cataracts.
   • Bone-marrow suppression.
   • Acute Radiation Syndrome.

Stochastic Effects

1. These involve probabilistic outcomes, notably cancer.
2. Radiation protection commonly assumes that the probability of such effects increases with dose.
3. The severity of an individual stochastic effect is not determined by the radiation dose that initiated it.

Environmental Effects of Radioactive Contamination

1. Soil Contamination: Radioactive substances may persist in soils and interact with crops and organisms.
2. Water Contamination: Radionuclides may enter surface water or groundwater.
3. Food-Chain Transfer: Certain radionuclides can move through agricultural and ecological systems.
4. Habitat Impacts: Radiation exposure and associated human activities may affect ecosystems.
5. Long-Term Restrictions: Contamination may require restrictions on land use, food consumption or human occupancy.

Nuclear Winter

1. Nuclear Winter is a hypothetical large-scale climatic disturbance that could follow extensive nuclear warfare.
2. The concept emerged through scientific research during the 1980s.
3. The principal mechanism involves the injection of large amounts of black carbon or soot into the upper atmosphere.
4. This soot may absorb and scatter incoming solar radiation, reducing the sunlight reaching Earth’s surface.
5. Potential consequences include:
   • Global or regional cooling.
   • Reduced photosynthesis.
   • Changes in precipitation patterns.
   • Shortened growing seasons.
   • Agricultural production losses.
   • Disruption of food supply chains.
6. The severity and duration of these effects would depend on the scale of fires, atmospheric transport and other factors.
7. Nuclear winter is distinct from radiation contamination: its principal climatic mechanism involves smoke-induced reduction in solar radiation.

India’s Nuclear Energy Policy

Evolution of India’s Nuclear Programme

1. India’s nuclear programme developed in response to scientific, technological, economic and national-security considerations.
2. Homi Jehangir Bhabha played a central role in establishing its institutional foundations.
3. India’s nuclear policy has involved both:
   • Peaceful nuclear applications, including power generation, medicine and research.
   • Strategic nuclear capabilities related to national defence.

Important Milestones

Pokhran Nuclear Tests

Pokhran-I (1974)

1. 1. Conducted on 18 May 1974.
   2. Location: Pokhran Test Range, Rajasthan.
   3. Known by the code name Smiling Buddha.
   4. Marked India’s first nuclear explosive test.

Pokhran-II (1998)

1. 1. Conducted in May 1998.
   2. Involved a series of five declared nuclear explosive tests on 11 and 13 May.
   3. Commonly associated with Operation Shakti.
   4. The tests marked a major development in India’s declared nuclear weapons capability.

India’s Nuclear Doctrine

1. India’s publicly articulated nuclear doctrine emphasises credible minimum deterrence.
2. The doctrine announced in January 2003 included a commitment to No First Use (NFU) of nuclear weapons, with stated qualifications.
3. It envisages nuclear retaliation in response to specified nuclear attacks.
4. The public statement also retained the option of nuclear retaliation in the event of a major biological or chemical weapons attack.
5. India’s nuclear doctrine emphasises political control over the authorisation of nuclear weapons use.
6. Public nuclear-policy statements distinguish between nuclear weapons for deterrence and civil nuclear energy for peaceful development.

Nuclear Command Authority (NCA)

1. The Nuclear Command Authority is India’s institutional framework for political and operational control of nuclear weapons.
2. It was formally announced on 4 January 2003.
3. It has two principal components.

Political Council

• Chaired by the Prime Minister of India.
• Responsible for authorising nuclear weapons use.

Executive Council

• Chaired by the National Security Adviser (NSA).
• Provides inputs and carries out functions associated with the NCA’s decision-making framework.

Strategic Forces Command

1. The Strategic Forces Command (SFC) was established in 2003.
2. It operates within India’s strategic nuclear command arrangements.
3. Its responsibilities relate to the management and operational readiness of assigned strategic forces, subject to national command structures.

National Security Council

1. The National Security Council (NSC) is an important institutional framework for national-security policy coordination.
2. The Prime Minister chairs the NSC.
3. The National Security Adviser plays a central coordinating role within India’s national-security architecture.
4. Nuclear policy involves coordination among political leadership, strategic institutions, scientific agencies and defence organisations.

Civil Nuclear Law and the SHANTI Act, 2025

1. India’s civil nuclear sector was historically governed primarily by the Atomic Energy Act, 1962, together with other relevant legislation and regulatory arrangements.
2. The Civil Liability for Nuclear Damage Act, 2010 established a framework addressing liability and compensation for specified nuclear incidents.
3. Parliament enacted the Sustainable Harnessing and Advancement of Nuclear Energy for Transforming India (SHANTI) Act, 2025.
4. The Act received presidential assent in December 2025.
5. It modernises India’s legal framework concerning nuclear energy and ionising radiation.

Major Provisions

1. Creates a framework for the peaceful development and utilisation of nuclear energy.
2. Provides for regulated participation by private entities in specified nuclear activities.
3. Strengthens the statutory framework for nuclear safety regulation.
4. Addresses nuclear security, safeguards and liability.
5. Establishes requirements for licensing and safety authorisation.
6. Retains central government control over specified sensitive nuclear activities.

Private-Sector Participation

1. The Act allows eligible private entities to participate in specified nuclear activities under government licensing and regulatory requirements.
2. Areas may include:
   • Establishment and operation of nuclear facilities.
   • Approved nuclear fuel fabrication activities.
   • Research and development.
   • Peaceful non-power applications of ionising radiation.
3. Certain sensitive activities remain under the exclusive control of the Central Government.
4. As reported by the government in July 2026, detailed rules were being prepared and private-sector licensing applications were to be considered under the relevant implementation framework.

Atomic Energy Regulatory Board (AERB)

1. The Atomic Energy Regulatory Board (AERB) was established in 1983.
2. Its principal objective is to regulate specified nuclear and radiation facilities to protect workers, the public and the environment.
3. Important responsibilities include:
   • Development and enforcement of safety requirements.
   • Regulatory authorisation.
   • Safety review and assessment.
   • Inspection of nuclear and radiation facilities.
   • Radiation-protection oversight.
   • Review of emergency preparedness.
   • Regulatory oversight associated with decommissioning and waste management.
4. The SHANTI Act strengthened the statutory basis of India’s nuclear safety regulatory framework.
5. Nuclear safety regulation must be distinguished from nuclear power generation, research and industrial operations.

International Atomic Energy Agency (IAEA)

1. The International Atomic Energy Agency (IAEA) was established in 1957.
2. It is headquartered in Vienna, Austria.
3. It promotes the peaceful, safe and secure use of nuclear science and technology.
4. Major functions include:
   • Nuclear safeguards and verification.
   • Development of international safety standards.
   • Technical cooperation.
   • Promotion of nuclear science applications.
   • Assistance in radiation protection.
   • Nuclear security support.
5. The IAEA is not the global operator of nuclear power plants; the responsibility for nuclear facility safety primarily rests with national authorities and licensed operators.

International Cooperation and Nuclear Security

1. Civil nuclear cooperation enables countries to collaborate in fuel supply, reactor technologies, research and safety.
2. India has developed nuclear cooperation with countries including:
   • Russia.
   • France.
   • United States.
   • Canada.
   • Other international partners.
3. Nuclear cooperation must operate within the applicable national legal and international safeguards frameworks.
4. Important global nuclear governance concerns include:
   • Non-proliferation.
   • Nuclear safety.
   • Material security.
   • Safeguards verification.
   • Radioactive waste management.
   • Emergency preparedness.

Important Nuclear Research Institutions in India

Department of Atomic Energy (DAE)

1. The Department of Atomic Energy was established on 3 August 1954.
2. It operates under the direct charge of the Prime Minister of India.
3. It is responsible for coordinating major aspects of India’s civil nuclear programme.
4. Its activities include:
   • Nuclear power technology.
   • Uranium exploration and processing.
   • Nuclear fuel fabrication.
   • Heavy-water production.
   • Nuclear fuel reprocessing.
   • Nuclear waste management.
   • Research in fast reactor technology.
   • Fusion research.
   • Advanced materials, electronics, accelerators and lasers.
   • Peaceful applications of radiation technologies.
5. DAE oversees several research centres, industrial organisations, public-sector undertakings and grant-in-aid institutions.

Bhabha Atomic Research Centre (BARC)

1. The Bhabha Atomic Research Centre (BARC) is located at Trombay, Mumbai, Maharashtra.
2. It was established in 1954 as the Atomic Energy Establishment, Trombay (AEET).
3. It was renamed in 1967 in honour of Dr. Homi Jehangir Bhabha.
4. BARC is one of India’s leading multidisciplinary nuclear research institutions.

Major Research Areas

1. Nuclear Reactor Technology: Reactor design and engineering.
2. Nuclear Fuel Cycle: Fuel development, spent-fuel management and reprocessing.
3. Radiation Technology: Industrial, medical and agricultural applications.
4. Materials Science: Development and testing of advanced materials.
5. Nuclear Chemistry: Research on nuclear materials and radiochemical processes.
6. Accelerator Technology: Development and application of particle-accelerator systems.
7. Waste Management: Research into radioactive waste treatment and immobilisation.

Indira Gandhi Centre for Atomic Research (IGCAR)

1. The Indira Gandhi Centre for Atomic Research (IGCAR) is located at Kalpakkam, Tamil Nadu.
2. It was established in 1971.
3. Its principal research focus is fast reactor technology and the associated nuclear fuel cycle.
4. Important areas of work include:
   • Fast breeder reactor development.
   • Reactor physics.
   • Liquid-metal coolant technologies.
   • Advanced materials.
   • Nuclear fuel behaviour.
   • Nuclear fuel reprocessing.
   • Reactor safety.
   • Radiation protection.
5. IGCAR has played a leading role in developing the technology for India’s 500 MWe Prototype Fast Breeder Reactor.
6. Its work is central to the transition from the first to the second stage of India’s nuclear power programme.

Raja Ramanna Centre for Advanced Technology (RRCAT)

1. The Raja Ramanna Centre for Advanced Technology (RRCAT) is located in Indore, Madhya Pradesh.
2. It was established in 1984 as the Centre for Advanced Technology (CAT).
3. It was subsequently renamed in honour of nuclear scientist Raja Ramanna.
4. Its major research areas include:
   • Particle accelerators.
   • Laser science and technology.
   • Synchrotron radiation.
   • Advanced materials.
   • Cryogenic and associated technologies.
   • Precision scientific instrumentation.
5. RRCAT is associated with the development and operation of major accelerator-based research facilities, including the Indus synchrotron radiation sources.
6. Synchrotron radiation is used in material science, biological research, crystallography and other scientific disciplines.

Variable Energy Cyclotron Centre (VECC)

1. The Variable Energy Cyclotron Centre (VECC) was established in 1977.
2. It is located at Kolkata, West Bengal.
3. VECC conducts research involving:
   • Nuclear physics.
   • Particle accelerators.
   • Nuclear reactions.
   • Detector systems.
   • Accelerator technology.
   • Associated materials and applied research.

Cyclotron

1. A Cyclotron is a particle accelerator that uses electric and magnetic fields to accelerate charged particles.
2. Charged particles move along curved trajectories under a magnetic field.
3. An oscillating electric field accelerates the particles as they repeatedly cross accelerating gaps.
4. Cyclotrons are used in:
   • Nuclear physics research.
   • Radioisotope production.
   • Material science.
   • Selected medical applications.
5. VECC operates accelerator facilities including the K-130 Cyclotron, whose designation reflects its bending capability.

Atomic Minerals Directorate for Exploration and Research (AMD)

1. The Atomic Minerals Directorate for Exploration and Research (AMD) is an important constituent unit of DAE.
2. It is headquartered in Hyderabad, Telangana.
3. Its principal responsibility is to identify, evaluate and assess mineral resources important to India’s nuclear energy programme.
4. Important materials include:
   • Uranium.
   • Thorium-bearing minerals.
   • Other atomic minerals.

Major Functions

1. Geological mapping and mineral exploration.
2. Geophysical and geochemical surveys.
3. Radiometric exploration.
4. Drilling and mineral-resource evaluation.
5. Assessment of uranium and thorium occurrences.
6. Identification of new exploration targets.

5. AMD uses geological, geophysical, geochemical and remote-sensing techniques.
6. Its investigations provide an important scientific basis for nuclear fuel-resource planning.

Nuclear Fuel Complex (NFC)

1. The Nuclear Fuel Complex (NFC) is headquartered in Hyderabad, Telangana.
2. It is an industrial organisation under DAE.
3. NFC is responsible for manufacturing selected nuclear fuel products and reactor components.
4. Its activities include:
   • Nuclear fuel fabrication.
   • Production of reactor-related materials.
   • Fabrication of specialised nuclear components.
   • Development of advanced manufacturing technologies.
5. NFC supports the fuel requirements of India’s nuclear power programme, particularly indigenous reactor systems.

Nuclear Power Corporation of India Limited (NPCIL)

1. The Nuclear Power Corporation of India Limited (NPCIL) was incorporated in 1987.
2. Its headquarters are in Mumbai, Maharashtra.
3. It is a major public-sector undertaking associated with commercial nuclear electricity generation.
4. Its responsibilities include:
   • Nuclear reactor design and engineering.
   • Construction of nuclear power stations.
   • Reactor commissioning.
   • Nuclear power plant operation.
   • Maintenance and technological upgrades.
   • Implementation of prescribed safety systems.
5. As of October 2026, NPCIL operates 24 commercial nuclear reactors, excluding RAPS-1, with a total gross installed capacity of 8,780 MW.

Bharatiya Nabhikiya Vidyut Nigam Limited (BHAVINI)

1. BHAVINI is an Indian public-sector undertaking under DAE.
2. It is associated with the development and operation of fast breeder reactor power projects.
3. Its major project is the 500 MWe Prototype Fast Breeder Reactor at Kalpakkam.
4. BHAVINI plays a major role in implementing the second stage of India’s nuclear power programme.
5. The PFBR’s achievement of first criticality in April 2026 marked a major milestone in its programme.

Uranium Corporation of India Limited (UCIL)

1. UCIL is a public-sector undertaking under DAE.
2. It is associated with uranium mining and processing.
3. Its headquarters are at Jaduguda, Jharkhand.
4. Important activities include:
   • Uranium ore extraction.
   • Mineral processing.
   • Production of uranium concentrates.
   • Management of associated mining facilities.
   • Environmental monitoring and mine-related safety.

Heavy Water Board (HWB)

1. The Heavy Water Board operates under DAE.
2. It is responsible for activities associated with the production and management of heavy water and certain other specialised materials.
3. Heavy Water (D₂O) plays an important role in India’s PHWR programme.
4. Heavy water is used because of its favourable neutron-moderation characteristics.
5. HWB’s capabilities contribute to India’s indigenous nuclear fuel-cycle infrastructure.

Board of Radiation and Isotope Technology (BRIT)

1. The Board of Radiation and Isotope Technology (BRIT) is an industrial organisation under DAE.
2. It supports the development and supply of radioisotope products and radiation technologies.
3. Important application areas include:
   • Nuclear medicine.
   • Industrial irradiation.
   • Radioisotope-based technologies.
   • Radiation-processing applications.
4. BRIT helps translate nuclear research capabilities into practical applications.

Global Centre for Nuclear Energy Partnership (GCNEP)

1. The Global Centre for Nuclear Energy Partnership (GCNEP) is an institution under DAE.
2. It is located at Bahadurgarh, Haryana.
3. Its major objectives include:
   • Promoting nuclear safety.
   • Supporting nuclear security research.
   • Encouraging international cooperation.
   • Developing specialised human resources.
   • Providing education and training in nuclear-related fields.
4. Its research and training areas include:
   • Nuclear safety.
   • Advanced nuclear systems.
   • Nuclear security.
   • Radiation protection.
   • Nuclear-material management.
   • Peaceful nuclear technology applications.