Nuclear reactor: parts and uses
A nuclear reactor runs a controlled chain reaction. Its main parts are the fuel, moderator, control rods, coolant and shielding.
What is a nuclear reactor?
A nuclear reactor is a device in which nuclear fission is carried out as a controlled, self-sustaining chain reaction. The heat it produces turns water into steam, which spins a turbine to generate electricity. The first reactor was built by Enrico Fermi in Chicago, USA, in 1942. India's first reactor, Apsara, started at Trombay near Mumbai in 1956. Homi J. Bhabha led India's nuclear energy programme.
Parts of a nuclear reactor
| Part | Material | Job |
|---|---|---|
| Fuel | Uranium-235 or plutonium-239 (fissile: able to undergo fission) | Undergoes fission and releases heat |
| Neutron source | Beryllium mixed with polonium, radium or plutonium | Gives the first neutrons to start the chain reaction |
| Moderator | Graphite or heavy water (D₂O) | Slows down fast neutrons, because slow neutrons split U-235 more easily |
| Control rods | Boron or cadmium | Absorb extra neutrons to keep the reaction steady; pushed in fully to stop the reactor |
| Coolant | Water, heavy water, liquid sodium, or a gas such as helium, air or carbon dioxide | Carries heat from the core to the heat exchanger to make steam |
| Shielding | Thick concrete walls and lead | Stops harmful radiation from reaching workers and the surroundings |
How to draw a nuclear reactor
- 1Draw a large rectangle for the reactor core with thick outer walls. Label the walls 'concrete shield'.
- 2Inside, draw several vertical bars labelled 'fuel rods (U-235)'. Shade the space around them and label it 'moderator (graphite or heavy water)'.
- 3Draw bars coming down from the top between the fuel rods. Label them 'control rods (cadmium or boron)'.
- 4Draw a pipe loop from the core to a box labelled 'heat exchanger (steam generator)'. Label the loop 'coolant'.
- 5From the heat exchanger, draw steam going to a 'turbine' joined to a 'generator', and a 'condenser' sending water back. Add arrows to show the flow.
Uses of nuclear reactors
- To generate electricity in nuclear power stations.
- To produce radioisotopes for medicine, agriculture, industry and research.
- Breeder reactors turn uranium-238 into plutonium-239, a new fuel. They make more fuel than they use.
- To run nuclear submarines and ships, which can travel for long periods without refuelling.
- For research in nuclear physics and on materials.
Nuclear power in India
- Nuclear power stations include Tarapur (Maharashtra), Rawatbhata (Rajasthan), Kalpakkam and Kudankulam (Tamil Nadu), Narora (Uttar Pradesh), Kakrapar (Gujarat) and Kaiga (Karnataka).
- Kalpakkam also has the Fast Breeder Test Reactor at the Indira Gandhi Centre for Atomic Research.
Kudankulam in Tirunelveli district is one of India's largest nuclear power stations, and Kalpakkam near Chennai has India's fast breeder test reactor. Part of the electricity in Tamil Nadu homes comes from these plants.
1 marks: “The control rods in a nuclear reactor are made of ___.” Boron or cadmium.
2 marks: “What is the role of the moderator in a nuclear reactor? Give an example.” It slows down fast neutrons so that they can cause fission of U-235. Example: graphite or heavy water.
7 marks: “Draw a neat diagram of a nuclear reactor and explain its parts.” Labelled diagram; fuel, neutron source, moderator, control rods, coolant and shielding, each with its material and job; uses.
Reactor parts in order: Fancy New Machines Can Cool Safely: Fuel, Neutron source, Moderator, Control rods, Coolant, Shielding.