Nuclear power plant
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Nuclear power plants generate electricity through nuclear fission. In a pressurized water reactor (PWR), heat from nuclear fission is used to heat water and produce steam to turn turbines and generate electricity. The steam does not come into contact with radioactive materials. Nuclear power plants produce far more energy from uranium fuel than fossil fuel plants and produce no greenhouse gases, but nuclear waste requires careful storage and disposal.
Nuclear power plant
- 1. Nuclear (Atomic) Power Plant By Mr.B.Ramesh, M.E.,(Ph.D) Research Scholar, CEG, Anna University, Chennai. Associate Professor of Mechanical Engineering, St. Joseph’s College of Engineering, Jeppiaar Trust, Chennai-119
- 2. Nuclear (Atomic) Power Plant Working principle : A nuclear power plant works in a similar way as a thermal power plant. The difference between the two is in the fuel they use to heat the water in the boiler(steam generator). Inside a nuclear power station, energy is released by nuclear fission in the core of the reactor. 1 kg of Uranium U235 can produce as much energy as the burning of 4500 tonnes of high grade variety of coal or 2000 tonnes of oil.
- 3. Nuclear chain reactionNuclear chain reaction Neutrons released in fissionNeutrons released in fission trigger the fissions of other nuclei proton neutron U-235 nucleus
- 4. Nuclear (Atomic) Power Plant… Chain Reaction… Uranium exists as an isotope in the form of U235 which is unstable. When the nucleus of an atom of Uranium is split, the neutrons released hit other atoms and split them in turn. More energy is released each time another atom splits. This is called a chain reaction.
- 5. Nuclear (Atomic) Power Plant… Nuclear fission:
- 6. Nuclear fission…Nuclear fission… Nuclear fission: heavy nuclei split into two smallerheavy nuclei split into two smaller partsparts in order to become more stable proton neutron U-235 nucleus Kr-92 nucleus Ba-141 nucleus energy
- 7. Nuclear Fission… • It is a process of splitting up of nucleus of fissionable material like uranium into two or more fragments with release of enormous amount of energy. •The nucleus of U235 is bombarded with high energy neutrons U235 +0n1 Ba141 +Kr92 +2.50n1 +200 MeV energy. • The neutrons produced are very fast and can be made to fission other nuclei of U235 , thus setting up a chain reaction. • Out of 2.5 neutrons released one neutron is used to sustain the chain reaction. 1 eV = 1.6X10-19 joule. 1 MeV = 106 eV
- 8. Nuclear (Atomic) Power Plant… Nuclear fission… U235 splits into two fragments (Ba141 & K92 ) of approximately equal size. About 2.5 neutrons are released. 1 neutron is used to sustain the chain reaction. 0.9 neutrons is absorbed by U238 and becomes Pu239 . The remaining 0.6 neutrons escapes from the reactor. The neutrons produced move at a very high velocity of 1.5 x 107 m/sec and fission other nucleus of U235 . Thus fission process and release of neutrons take place continuously throughout the remaining material. A large amount of energy(200 Million electron volts, Mev) is produced. Note : Moderators are provided to slow down the neutrons from the high velocities but not to absorb them.
- 9. Nuclear (Atomic) Power Plant… Principal parts of a nuclear reactor: Core : Here the nuclear fission process takes place. Moderator : This reduces the speed of fast moving neutrons. Most moderators are graphite, water or heavy water.
- 10. Nuclear (Atomic) Power Plant… Principal parts of a nuclear reactor… Control rods : Coolant : They carry the intense heat generated. Water is used as a coolant, some reactors use liquid sodium as a coolant. Fuel : The fuel used for nuclear fission is U235 isotope. Radiation shield : To protect the people working from radiation and (thermal shielding) radiation fragments. Control rods limit the number of fuel atoms that can split. They are made of boron or cadmium which absorbs neutrons
- 11. The chain reaction is not slowed down a huge amount of energy is released very quickly the rate of fission increases rapidly Nuclear bombNuclear bomb Uncontrolled nuclear reactionUncontrolled nuclear reaction
- 12. Nuclear reactorsNuclear reactors Nuclear power plant: Rate of fission is controlled by artificial means to generate electricity The Daya Bay Nuclear Power Station
- 13. Nuclear (Atomic) Power Plant… Types of Nuclear power plant: Main two types are : * Pressurised Water Reactor (PWR) * Boiling Water Reactor (BWR)
- 14. Nuclear (Atomic) Power Plant… Pressurised Water Reactor (PWR) Heat is produced in the reactor due to nuclear fission and there is a chain reaction. The heat generated in the reactor is carried away by the coolant (water or heavy water) circulated through the core. The purpose of the pressure equalizer is to maintain a constant pressure of 14 MN/m2 . This enables water to carry more heat from the reactor. The purpose of the coolant pump is to pump coolant water under pressure into the reactor core.
- 15. Nuclear (Atomic) Power Plant… Pressurised Water Reactor (PWR) The steam generator is a heat exchanger where the heat from the coolant is transferred on to the water that circulates through the steam generator. As the water passes through the steam generator it gets converted into steam. The steam produced in the steam generator is sent to the turbine. The turbine blades rotate. The turbine shaft is coupled to a generator and electricity is produced. After the steam performing the work on the turbine blades by expansion, it comes out of the turbine as wet steam. This is converted back into water by circulating The feed pump pumps back the condensed water into the steam generator.
- 16. Schematic diagram of a nuclear power plant with PWR control rods fuel rods reactor pressure vessel water (cool) water (hot) water (high pressure) water (low pressure) coolant out coolant in steam condenser steam (low pressure) turbine electric power steam generator steam (high pressure) pump primary loop secondary loop generator reactor core pump
- 17. control rods reactor pressure vessel water (cool) water (hot) water (high pressure) water (low pressure) coolant out coolant in steam condenser steam (low pressure) turbine electric power steam generator steam (high pressure) pump primary loop secondary loop fuel rods They contain the nuclear fuel: uranium (U-235) They are surrounded by a moderator (water or graphite)moderator (water or graphite) to slow down the neutrons released.slow down the neutrons released.
- 18. control rods reactor pressure vessel water (cool) water (hot) water (high pressure) water (low pressure) coolant out coolant in steam condenser steam (low pressure) turbine electric power steam generator steam (high pressure) pump primary loop secondary loop fuel rods They control the rate of reaction by moving in and out of the reactor. Move in: rate of reaction Move out: rate of reaction All are moved in: the reactor is shut down They are made of boron or cadmium that can absorb neutrons.absorb neutrons.
- 19. steam generator control rods reactor pressure vessel water (high pressure) water (low pressure) coolant out coolant in steam condenser steam (high pressure) pump primary loop secondary loop fuel rods The steam drives a turbine, whichThe steam drives a turbine, which turns the generator.turns the generator. Electricity is produced by the generator. water (hot) water (cool) steam (low pressure) turbine electric power generator
- 20. control rods fuel rods reactor pressure vessel water (cool) water (hot) water (high pressure) water (low pressure) coolant out coolant in steam condenser steam (low pressure) turbine electric power steam generator steam (high pressure) pump primary loop secondary loop Two separate water systemsTwo separate water systems are used to avoid radioactive substances to reach the turbine.
- 21. control rods reactor pressure vessel water (high pressure) water (low pressure) coolant out coolant in steam condenser steam (low pressure) turbine electric power pump primary loop secondary loop fuel rods The energy released in fissions heats up the water around the reactor. The water in theThe water in the secondary loopsecondary loop is boiled tois boiled to steamsteam. water (hot) water (cool) steam generator steam (high pressure)
- 22. Nuclear (Atomic) Power Plant… Boiling Water Reactor (BWR) The water is circulated through the reactor where it converts to water steam mixture. The steam gets collected above the steam separator. This steam is expanded in the turbine which turns the turbine shaft. The expanded steam coming out of the turbine is condensed and is pumped back as feed water by the feed water pump into the reactor core. Also the down coming recirculation water from the steam separator is fed back to the reactor core.
- 23. Nuclear (Atomic) Power Plant… Steam power plant means any plant that uses steam to produce electricity. E.g. Thermal and Nuclear power plants.
- 24. Nuclear (Atomic) Power Plant… Advantages of Nuclear power plant: Space required is less when compared with other power plants. Nuclear power plant is the only source which can meet the increasing demand of electricity at a reasonable cost. A nuclear power plant uses much less fuel than a fossil-fuel plant. 1 metric tonne of uranium fuel = 3 million metric tonnes of coal = 12 million barrels of oil. Disadvantages of Nuclear power plant: o Radioactive wastes must be disposed carefully, otherwise it will adversely affect the health of workers and the environment as a whole. o Maintenance cost of the plant is high.
- 25. Nuclear wasteNuclear waste They are highly radioactive Many of them have very long half-lives. Radioactive wasteRadioactive waste mustmust be stored carefully.be stored carefully.
- 26. Low level radioactive wasteLow level radioactive waste cooling water pipes, radiation suitscooling water pipes, radiation suits, etc., etc. stored in storage facilitiesstored in storage facilities radioactivity will fall to a safe level afterradioactivity will fall to a safe level after 10 to10 to 50 years50 years..
- 27. used nuclear fuelused nuclear fuel highly radioactivehighly radioactive embedded in concrete andembedded in concrete and storedstored deep undergrounddeep underground forfor several thousand yearsseveral thousand years High level radioactive waste
- 28. Nuclear fusionNuclear fusion Nuclear fusion: light nuclei fuse together to form a heavier nucleus
- 29. Nuclear fusion…Nuclear fusion… Nuclear fusion: light nuclei fuse together to form a heavier nucleus proton neutron helium nucleus neutron energy deuterium nucleus tritium nucleus H-2 + H-3 He-4 + n + energy
- 30. Videos and Animations 1. 8. 2. 9. Nuclear power station 3. 10. How a nuclear power plant works 4. Nuclear Reactor 5. 11.Nuclear power –How it works 6.How a pressurised water nuclear 12. reactor works 7. 13. Nuclear power generator 14. Reactor 1 nuclear fission.swf 2 nuclear reactions.swf 3 nuclear reactor an activity.swf 5 nuclear reactor working.swf 7-Nuclear power plant1.swf 8 nuclear powerplant2.swf 12 Nuclear power plant3.swf
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