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Commerical Operation


The major types of reactors in commercial operation

  1. Pressurised Water Reactor (PWR)
    PWR is a light water reactor using ordinary water as the coolant and moderator. The PWR has a primary cooling circuit with water circulating through the reactor core at high pressure above 150 bars to extract the heat generated by nuclear fission. The water then passes through a steam generator for heat exchanging with the secondary circuit. The steam generator produces steam on the secondary side to drive the turbine and generator. Water in the primary circuit is maintained at a high temperature of over 300oC under high pressure of above 150 bars (1 bar = 100 kPa) to prevent it from boiling.

  2. Boiling Water Reactor (BWR)
    BWR is a light water reactor using ordinary water as coolant and moderator similar to the PWR except it only has a single circuit connecting the reactor and the turbine without a steam generator. Water in the reactor is kept at a lower pressure of about 75 bars such that it will boil at about 285oC. The steam produced from the reactor will directly feed into the turbine after passing through steam separators above the reactor core. The steam leaving the turbine is condensed into liquid water after passing through the condenser and then re-circulated back to the reactor for conversion into steam again.

  3. Pressurised Heavy Water Reactor (CANDU)
    CANDU is a pressurised heavy water reactor operated on natural uranium fuel (U-238) and uses heavy water (D2O) as coolant and moderator. CANDU is an acronym for CANada Deuterium Uranium. The CANDU reactor is capable of on line refuelling during operation.

  4. Light Water Graphite Reactor (RBMK)
    RBMK is a type of reactor designed in the former Soviet Union, which uses ordinary boiling water as the coolant and graphite as the moderator. This type of reactor is capable of on line refuelling. The reactor involved in the Chernobyl accident belongs to this type.
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