Context: India's second indigenous 700 MW Nuclear power reactor at Kakrapar Atomic Power Project (KAPP) in Gujarat has achieved its first criticality. It has set the stage for its gradual move towards producing electricity for commercial purposes.
Nuclear Fission
- Most Nuclear Power Plants produce energy using Nuclear Fission mechanism.
- Nuclear fission is the process of disintegrating a heavy atom’s nucleus, such as Uranium or Plutonium, into two or more smaller nuclei.
- When a fissile atom, like uranium-235, absorbs a neutron, it splits into two smaller atoms and releases several more neutrons.
- These neutrons can then go on to cause other fissile atoms to split, creating a chain reaction.
- This process releases a substantial amount of Nuclear energy, which is harnessed and converted into steam to power a turbine that generates electricity.
- Criticality of Nuclear Reactor: A Nuclear reactor is said to be critical when the number of neutrons produced in Nuclear fission reactions equals the number of neutrons lost through absorption, leakage, and other processes. This equilibrium state allows for a sustained and controlled chain reaction.
- Fuel used: U-235 (low-enriched or reactor-grade uranium)
Uranium Enrichment
- Naturally occurring Uranium is composed of three major isotopes:
- Uranium-238 (99.284% natural abundance)
- Uranium-235 (0.711%)
- Uranium-234 (0.005%)
- U-235 atomsis the only nuclide existing in nature (in appreciable amount) that is fissile with thermal neutrons.Since naturally occurring Uranium does not have a high enough concentration of U-235, Uranium enrichment is necessary to create an effective nuclear fuel out of mined Uranium.
- Uranium enrichment is the process of increasing the concentration/percentage of U-235 in Natural uranium beyond through the process of isotope separation.
- U-235 atomsis the only nuclide existing in nature (in appreciable amount) that is fissile with thermal neutrons.Since naturally occurring Uranium does not have a high enough concentration of U-235, Uranium enrichment is necessary to create an effective nuclear fuel out of mined Uranium.
- Uranium enrichment is the process of increasing the concentration/percentage of U-235 in Natural uranium beyond through the process of isotope separation.
Present Installed Nuclear Power Capacity in India
Presently, India operates 22 nuclear reactors across eight sites, with a total capacity of 6,780 MWe. Among these 18 reactors are Pressurised Heavy Water Reactors (PHWRs) and 4 are Light Water Reactors (LWRs).
Pressurised Heavy Water Reactor (PHWR)
- PHWR is a nuclear power reactor, commonly using unenriched natural uranium as its fuel and heavy water (deuterium oxide, D2O) as both coolant and moderator.
- Coolant: Coolant in a nuclear reactor absorbs all the excess heat generated by the ongoing nuclear reactions, preventing the reactor from melting down.
- Moderator: Heavy water acts as a moderator, slowing down neutrons to the right speed making them more likely to collide with other Uranium atoms and trigger fissions. This chain reaction is the very essence of how a PHWR produces energy.
- Control Rods: Boron or cadmium control rods are used to absorb excess neutrons and regulate the nuclear reaction.
- Advantages: PHWRs are known for their ability to use natural uranium fuel, produce less high-level radioactive waste, and operate at lower pressures compared to some other reactor types.
Kakrapar Atomic Power Station
- Kakrapar Atomic Power Station is a nuclear power plant located in Mandvi, Surat district in Gujarat.
- Operated by: Nuclear Power Corporation of India Limited (NPCIL).
- Kakrapar site consists of four pressurised heavy water reactors (PHWRs).
- Two 220 MW units
- Two 700 MW units
- KAPP Unit-3 (first indigenously developed PHWR plants with modern safety features)had started commercial operation in August 2023.