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Atomic Reactor

All About Atomic Reactor .

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Atomic Reactor

  1. 1. Nuclear Reactor BY G Mujtaba Ahsan iqbal Zafar Bakhshi (BS.Chem. 012/15)
  3. 3. Nuclear Reactor • Device designed to maintain a chain reaction producing a steady flow of neutrons generated by the fission of heavy nuclei. • It is an apparatus in which heat is produced due to nuclear fission chain reaction for the generation of the electricity
  4. 4. Components of Nuclear Reactor
  5. 5. Pressure Vessel / Tubes  Usually a robust steel vessel containing the reactor core and moderator/coolant.  Or it may be a series of tubes holding the fuel and conveying the coolant through the surrounding moderator
  6. 6. Reactor Core  It consists of fuel elements, control rods, coolant, moderator.  Cores generally have shapes of right circular cylinders with diameters ranging from 0.5 to 15 metres.
  7. 7. Reflector  It is placed round the core, to reflect back some of the neutrons that leak out from core surface.
  8. 8. Fuel  Uranium-235 is the basic fuel.  Usually pellets of uranium oxide (UO2) are arranged in tubes to form fuel rods.
  9. 9. Control Rods  Usually made up of cadmium or boron.  Function:  Slow down the rate of reaction to a controllable limit . Other wise chain reaction blows up like a nuclear bomb.  Raising and lowering the control rods allow operators to control the rate of the nuclear reaction.
  10. 10. Moderator  Function:  To slow down neutrons from high velocities and hence high energy level which they have on being released from fission process so that probability of neutron to hit the fuel rods increases.  Main moderator used: Water H2O Heavy water D2O Graphite Beryllium
  11. 11. Coolant Function: Coolant is used to remove intense heat produced in the reactor and that heat can be transferred to water in a separate vessel which is converted into steam and runs the turbine.  Main coolant used: Water H2O , CO2, Hg, He
  12. 12. Containment The structure around the reactor and associated steam generators which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation in case of any serious malfunction inside. It is typically a meter-thick concrete and steel structure.
  13. 13. For Starting Reactor To start a reactor, a neutron from a source is ejected through thermal means and the control rods are taken upwards so that the control rods can not disturb the reaction.  Hence neutron hits the fuel rods, break it into lighter nuclei, energy is released, number of neutron keeps on increasing since K will be greater than 1 for this time period and hence reaction starts and its rate also increases.  Hence reaction starts and its rate also increases.
  14. 14. Meaning of K K (the effective neutron multiplication factor) is the average number of neutrons from one fission that cause another fission. The remaining neutrons either are absorber in non-fission reactions or leave the system without being absorbed. The value of K determines how a nuclear chain reaction proceeds.
  15. 15. For Maintaining the reaction at constant level  When rate of reaction achieves a permissible value then control rods are inserted between the fuel rods in such away that K becomes equal to 1. Hence the rate of reaction achieves a finite constant value.
  16. 16. For Shutting Down Reactor To shut down the reactor either in normal or emergency conditions, the control rods are inserted in such away that K becomes less than 1. Hence the number of neutrons keeps on decreasing i.e. rate of reaction decreases, so the reaction stops after a certain interval of time.
  17. 17. Classification of Nuclear Reactor: • 1. On the basis of Neutron Energy • a) Fast Reactors • b) Thermal Reactors • 2. On the basis of Fuel used • a) Natural fuel • b) Enriched Uranium • 3. On the basis of Moderator used • a) Water Moderator • b) Heavy water Moderator • c) Graphite Moderator • d) Beryllium Moderator • 4. On the basis of Coolant used • a) Water cooled reactor (Ordinary or Heavy) • b) Gas cooled reactor • c) Liquid metal cooled reactor • d) Organic liquid cooled reactor.
  18. 18. Boiling Water Reactor
  19. 19. 1. Boiling Water Reactor • In the boiling water reactor (BWR), the water which passes over the reactor core act as moderator and coolant. It is also the steam source for the turbine. • A typical operating pressure for BWR is about 70 atm at which the water boils at about 285°C temperature. This operating temperature gives a efficiency of only 42% with a practical operating efficiency of around 32%, somewhat less than the Pressurized Water Reactor(PWR)
  20. 20. Disadvantages • Possibility of radioactive contamination in the turbine mechanism. • Safety precautions are needed which can turn out to be costly. • Wasting of steam and resulting of lower thermal efficiency. • Only 3% - 5% by mass can be converted to steam per pass.
  21. 21. Pressurized Water Reactor
  22. 22. 2. Pressurized Water Reactor • Uranium (Uranium – 235) as fuel. • Chain reaction produces high level of heat. • Heat tubes pass the heat to the primary cooling system water simply by contact. • Primary cooling system is a closed circuit of pressurized water. • Primary water enters the reactor vessel at 296 °C and exit at 327 °C.
  23. 23. Advantages • Water used as coolant, moderator and reflector is cheap and available in plenty. • The reactor is compact and high power density (65 KW/Liter). • Hardly 60 control rods are required in 1000 MW plant. • Inspecting and maintaining of turbine, feed heaters and condenser during operation. • Reducing fuel cost and extracting more energy.
  24. 24. Disadvantages • Requires high pressure vessel and high capital cost. • Thermodynamic efficiency of plant is as low as 20% due to low pressure. • Corrosion problems are more severe. Use of stainless steel for vessel is necessary. • Fuel recharging requires a couple of months time.
  25. 25. Applications • Produce Electricity
  26. 26. References • Abdul Kareem et al. NUCLEAR REACTOR AND ITS WORKING. • Ashvani Shah C&I Reliance. NUCLEAR REACTOR. • General Physical Book. • Nptel Lectures.
  27. 27. Thank You For Your Attention