CANDU Reactor Power Plant and its Advantages and Disadvantages

CANDU Reactor Power Plant and its Advantages and Disadvantages
  1. A reactor developed and designed by Canadian is called as CANDU (Canadian Deutorium Uranium) reactor. It uses pressurized heavy water (PHW) (which is 99.8% deutorium oxide, D2O) a moderator and primary coolant while the fuel used is natural uranium.
  2. A CANDUPHW (Canadian Deutoriam Uranium Pressurized Heavy Water) power plast is shown in Figure.
  3. Natural uranium oxide fuel is in the form of small cylinder pallets. These are packed in a corrosion resistant zirconium alloy tubes 0.5 cm long and 1.3 cm diameter to form a fuel rod.
  4. These short rods are combined in 37 bundles of 37 rods and 12 bundles are placed end to end in each pressure tubes. This type of arrangement helps in refuelling the reactor while in operation.
  5. Reactor vessel is a steel cylinder called calandria. It is placed horizontally. It has pressure tubes penetrating the reactor vessel.
  6. The active core is about 6 m high and 7 to 8 min diameter. In the primary circuit, the D2O coolant enters the array of pressure tubes at 110 bar and 260°C. It flows through the fuel element and leaves the pressure tubes at about 370°C after absorbing the heat generated by fission of fuel material.
  7. The coolant at 110 bar, 370°C leaving the reactor enters the steam generator where the generated steam is used in conventional steam power plant. Control rods are made up of cadmium.
  8. These are used to start and shut down the reactor. In addition there are other absorbing rods which are used to control power output during reactor operation.
CANDU Reactor

Advantages of CANDU reactor :
  1. Heavy water is used as moderator which has low fuel consumption.
  2. Enriched fuel is not required.
  3. Cost and time of construction is less.
  4. It has good neutron economy resulting into good breeding ratio.
Disadvantages of CANDU reactor :
  1. Heavy water used is costly.
  2. It has critical temperature limitations.
  3. Leakage problems may occur.
  4. Size of plant is large.
  5. It requires high standards of design, manufacture and maintenance.

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