06 Oct

Nuclear Energy

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Contents

• Meaning of Nuclear Energy
• India’s three phase nuclear power program
• Features of the Prototype Fast Breeder Reactor
• Advantages of FBR
• Importance of Thorium Based Reactors
• Thermo Nuclear Reactions (Fusion Reactions) – Progress and India’s contribution
• About International Thermonuclear Experimental Reactor

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What is nuclear energy?

• Nuclear energy is the energy in the nucleus of an atom which is released during nuclear fission or fusion reaction.
• During these reactions, a small amount of mass is lost and gets converted into energy according to Einstein’s equation.
  • In nuclear fission, the nucleus of a heavy atom (such as uranium, plutonium or thorium), hen bombarded with low – energy neutrons, can be split apart into lighter nuclei.
  • When this is done tremendous amount of energy is released, if the mass of the original nucleus is just a little more than the sum of the masses of the individual products.

• E.g. of fission reaction

              Pu (239, 94) + n (1,0) ->  Ba (145, 56) + Sr (92,38) + 2 n(1,0)       

• E.g. of fusion reaction

• This is one of the common reactions taking place in sun.

India’s Three-Phase Nuclear Power Program

The three-stage nuclear power production program of India had been conceived by the ‘father of Indian Nuclear Power Program’ Dr Homi J Bhabha, with the ultimate objective of utilizing the country’s vast reserves of thorium-232.

• The first stage comprises setting up of Heavy Water Reactors/Pressurized Heavy Water Reactors (PHWRs) and associated fuel cycle facilities.
• The second stage envisages setting up of Fast Breeder Reactors (FBRs) backed by reprocessing plants and plutonium-based fuels fabrication plants. Plutonium is produced by irradiation of U-238.
• The third stage is based on the thorium-232 -> Uranium 233 Cycle, Uranium-233 is obtained by irradiation of Thorium.

Progress of the 3 Stages

• The first stage of Nuclear Power Programme is already in commercial domain. The Nuclear Power Corporation of India Ltd. (NPCIL), a public sector undertaking of DAE, is responsible for the design, construction, and operation of nuclear reactors. The company presently operates 22 reactors with a capacity of 7 GW. The total operational capacity is expected to go to 22.4 GW by 2031

• The Second Stage of Nuclear power generation programme is geared towards setting up the Fast Breeder Reactors. These reactors produce more fuel than they consume. The fast breeder program is in technology demonstration stage.

Features of the Prototype Fast Breeder Reactor (PFBR)

• Fuel: Plutonium Uranium Oxide (PuO₂ and UO₂)
• Coolant: Liquid Sodium
• Liquid Sodium additional safety requirements
  • Since sodium explodes if it comes in contact with water and burns when in contacts with air, additional safety requirements are needed to isolate the coolant from the environment.
  • Sodium also absorbs neutron to form Radioactive Na²⁴ isotope.

• Advantages of FBR:

  • They can ensure upto 60 times as much energy from the original Uranium compared with normal reactors.
  • Reduction in radioactive waste.
  • Safety -> closed fuel cycle would ensure safety
  • Energy security for India -> India plans third phase of its nuclear energy program on the success of FBR.

• The Third Stage: of the Nuclear Power Programme is in technology development stage.
  • The ongoing development of 300 MWe Advanced Heavy Water Reactor (AHWR) at BARC aims at developing expertise for thorium utilization and demonstrating advanced safety concepts.
  • Thorium-based systems such as AHWR can be set up on commercial scale only after a large capacity based on fast breeder reactors, is built up.

Why Thorium based reactors are important for us

• Abundance: India has the world’s third largest reserve of thorium.
• Less Enrichment requirement: Thorium mining produces a single pure isotope, whereas the mixture of natural uranium isotope must be enriched to function.

• Superior Nuclear Properties: Superior physical and nuclear properties
• Better Nuclear weapon resistant: Better resistance to nuclear weapon proliferation
• • Weapon grade fissionable material (U-233) is harder to retrieve safely from a thorium reactor. It contains U-232, a strong source of gamma radiation that makes it difficult to work with. Further, its daughter product, thallium-208, is equally difficult to handle and easy to detect.
• Reduced plutonium and actinide production
• They have miniscule long lived radioactive waste.

Thermo Nuclear Reactions (Fusion Reactions) – Progress and India’s contribution

• Fusion reactions are also called Thermonuclear reactions
• What is the need of extremely high temperature -> to overcome the electrical repulsive force
• So far, fusion devices that show a net energy gain have not been demonstrated in lab

Advantages of Nuclear Fusion:

• Raw material easily available
• Nuclear Fusion is a clean and green route to produce energy, as it doesn’t involve any remnant waste products.
• Long term energy security

USA’s Attempt

• An experiment at the U.S. National Ignition Facility (NIF), within the Livermore National Laboratory, Livermore, California, have successfully conducted a fusion test that produced 153% as much energy as went into triggering it (Dec 2023)

More Details:

• NIF uses powerful lasers to heat and compress hydrogen nuclei. When these nuclei fuse, they release energy. When this heat energy is greater than the heat delivered to the container, the event is called ignition. The ratio of output energy to the input delivered to the container is the Gain. A gain of 1 is called scientific breakeven.
• In 2021, the NIF had reported a gain of 0.72. Now (in Dec 2022), it has reportedly achieved ignition with a gain on 53 with a yield of 3 megajoules.

Inertial Confinement:

• Magnetic confinement and inertial confinement are two popular ways to achieve nuclear fusion.
  • Magnetic confinement uses a torus-shaped reactor called tokamak, in which a hydrogen plasma is heated to a high temperature and the nuclei are guided by strong magnetic fields to fuse. ITER is a famous example of an experiment trying to achieve fusion using magnetic confinement.
    • • Note: ITER is an international collaboration, it is under construction at a site in France and is scheduled to be built by 2025. It is considered to be more technologically mature than what NIF is attempting.

What was done at NIF: Inertial Confinement:

• Understanding Inertial Confinement: In an inertial confinement fusion (ICF) reactor, a tiny pellet of fuel such as deuterium-tritium (D-T) would be compressed to tremendous density and temperature so that fusion power is produced in the few nanoseconds before the pellet blows apart. The compression is achieved by focusing an intense laser beam or a charged particle beam, upon the small pellet.
• In NIF’s set up, 192 high-power lasers fire pulses at a 2 mm wide capsule inside a 1-cm-long cylinder called hohlraum, in less than 10 billionths of a second. The capsule holds deuterium and tritium atoms.
• As the pulse strikes the hohlraum’s inside, the latter heats up and releases x-rays, which heat the nuclei to millions of degrees centigrade and compress them to billions of Earth atmosphere. This technique is called inertial confinement method because the nuclei’s inertia creates a short window between implosion and explosion in which the strong nuclear force dominates, fusing the nuclei.
• Specifically, when two hydrogen-2 nuclei fuse, they yield a helium-4 nucleus, a neutron and 6 MeV of energy.
• Sustainability: For fusion reaction to be sustained the energy released by the initial reaction needs to set the stage for more reactions. To this end, NIF’s goal has been to create a ‘burning plasma’.

Significance:

• Fusion ignition is one of the most impressive feat of the 21^st century and is an engineering marvel beyond belief.

Some Caveats:

• First: NIF experiment is highly sophisticated and required very high precision. Even small changes in the experiment may negatively impact the output. So, for long term use, they will have to reproduce its results again.
• Second: For fusion reaction to be truly gainful, the energy released by the reactions needs to be greater than the energy going into the lasers, about 300 megajoules, and not just the energy delivered to the hohlraum.
• Third: The road to a power plant from the NIF’s current achievement isn’t well understood.

About International Thermonuclear Experimental Reactor (ITER) 

• ITER is an international mega project which is aimed at creating nuclear energy through nuclear fusion reaction.
• 35 countries are collaborating to build the world’s largest tokamak, a magnetic fusion device that has been designed to prove the feasibility of fusion as a large scale and carbon free source of energy.
• The primary objective of the ITER is the investigation and demonstration of burning plasma – plasmas in which the energy of the helium nuclei produced by the fusion reactions is enough to maintain the temperature of plasma, thereby reducing or eliminating the need of external heating.

What will ITER do?

• Achieve a deuterium-tritium plasma in which the fusion conditions are sustained mostly by internal fusion heating (“burning plasma”).
• Generate 500 MW of fusion power in plasma.
• Demonstration of the integrated operation of technologies for a fusion power plant (superconducting magnets, remote maintenance, and systems to exhaust power from the plasma)
• Test tritium breeding – One of the missions for the later stages of ITER operation is to demonstrate the feasibility of producing tritium within the vacuum vessel.
• Demonstrate the safety characteristic of a fusion device.

India is also participating in ITER. PM Modi while participating in the ITER assembly said that the ITER is perfect example of the age-old India belief – Vasudhaiva Kutumbakam – the entire world is working together for the betterment of humankind and that India stands proud with its fair share of contributions to the cooling water, cryogenic and cry-distribution systems, auxiliary heating devices using RF and beam technologies.

Past Year Mains Questions

• [2018]: With growing energy needs should India keep on extending its nuclear energy program? Discuss the facts and fears associated with nuclear energy.
• [2017]: 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?  (250 words, 15 marks)